--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/perl-5.22.2/pp_pack.c	Sat May 14 14:54:38 2016 +0000
@@ -0,0 +1,3137 @@
+/*    pp_pack.c
+ *
+ *    Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
+ *    2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008 by Larry Wall and others
+ *
+ *    You may distribute under the terms of either the GNU General Public
+ *    License or the Artistic License, as specified in the README file.
+ *
+ */
+
+/*
+ * He still hopefully carried some of his gear in his pack: a small tinder-box,
+ * two small shallow pans, the smaller fitting into the larger; inside them a
+ * wooden spoon, a short two-pronged fork and some skewers were stowed; and
+ * hidden at the bottom of the pack in a flat wooden box a dwindling treasure,
+ * some salt.
+ *
+ *     [p.653 of _The Lord of the Rings_, IV/iv: "Of Herbs and Stewed Rabbit"]
+ */
+
+/* This file contains pp ("push/pop") functions that
+ * execute the opcodes that make up a perl program. A typical pp function
+ * expects to find its arguments on the stack, and usually pushes its
+ * results onto the stack, hence the 'pp' terminology. Each OP structure
+ * contains a pointer to the relevant pp_foo() function.
+ *
+ * This particular file just contains pp_pack() and pp_unpack(). See the
+ * other pp*.c files for the rest of the pp_ functions.
+ */
+
+#include "EXTERN.h"
+#define PERL_IN_PP_PACK_C
+#include "perl.h"
+
+/* Types used by pack/unpack */ 
+typedef enum {
+  e_no_len,     /* no length  */
+  e_number,     /* number, [] */
+  e_star        /* asterisk   */
+} howlen_t;
+
+typedef struct tempsym {
+  const char*    patptr;   /* current template char */
+  const char*    patend;   /* one after last char   */
+  const char*    grpbeg;   /* 1st char of ()-group  */
+  const char*    grpend;   /* end of ()-group       */
+  I32      code;     /* template code (!<>)   */
+  I32      length;   /* length/repeat count   */
+  howlen_t howlen;   /* how length is given   */ 
+  int      level;    /* () nesting level      */
+  U32      flags;    /* /=4, comma=2, pack=1  */
+                     /*   and group modifiers */
+  STRLEN   strbeg;   /* offset of group start */
+  struct tempsym *previous; /* previous group */
+} tempsym_t;
+
+#define TEMPSYM_INIT(symptr, p, e, f) \
+    STMT_START {	\
+	(symptr)->patptr   = (p);	\
+	(symptr)->patend   = (e);	\
+	(symptr)->grpbeg   = NULL;	\
+	(symptr)->grpend   = NULL;	\
+	(symptr)->grpend   = NULL;	\
+	(symptr)->code     = 0;		\
+	(symptr)->length   = 0;		\
+	(symptr)->howlen   = e_no_len;	\
+	(symptr)->level    = 0;		\
+	(symptr)->flags    = (f);	\
+	(symptr)->strbeg   = 0;		\
+	(symptr)->previous = NULL;	\
+   } STMT_END
+
+typedef union {
+    NV nv;
+    U8 bytes[sizeof(NV)];
+} NV_bytes;
+
+#if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
+typedef union {
+    long double ld;
+    U8 bytes[sizeof(long double)];
+} ld_bytes;
+#endif
+
+#ifndef CHAR_BIT
+# define CHAR_BIT	8
+#endif
+/* Maximum number of bytes to which a byte can grow due to upgrade */
+#define UTF8_EXPAND	2
+
+/*
+ * Offset for integer pack/unpack.
+ *
+ * On architectures where I16 and I32 aren't really 16 and 32 bits,
+ * which for now are all Crays, pack and unpack have to play games.
+ */
+
+/*
+ * These values are required for portability of pack() output.
+ * If they're not right on your machine, then pack() and unpack()
+ * wouldn't work right anyway; you'll need to apply the Cray hack.
+ * (I'd like to check them with #if, but you can't use sizeof() in
+ * the preprocessor.)  --???
+ */
+/*
+    The appropriate SHORTSIZE, INTSIZE, LONGSIZE, and LONGLONGSIZE
+    defines are now in config.h.  --Andy Dougherty  April 1998
+ */
+#define SIZE16 2
+#define SIZE32 4
+
+/* CROSSCOMPILE and MULTIARCH are going to affect pp_pack() and pp_unpack().
+   --jhi Feb 1999 */
+
+#if U16SIZE > SIZE16 || U32SIZE > SIZE32
+#  if BYTEORDER == 0x1234 || BYTEORDER == 0x12345678    /* little-endian */
+#    define OFF16(p)	((char*)(p))
+#    define OFF32(p)	((char*)(p))
+#  else
+#    if BYTEORDER == 0x4321 || BYTEORDER == 0x87654321  /* big-endian */
+#      define OFF16(p)	((char*)(p) + (sizeof(U16) - SIZE16))
+#      define OFF32(p)	((char*)(p) + (sizeof(U32) - SIZE32))
+#    else
+       ++++ bad cray byte order
+#    endif
+#  endif
+#else
+#  define OFF16(p)     ((char *) (p))
+#  define OFF32(p)     ((char *) (p))
+#endif
+
+#define PUSH16(utf8, cur, p, needs_swap)                        \
+       PUSH_BYTES(utf8, cur, OFF16(p), SIZE16, needs_swap)
+#define PUSH32(utf8, cur, p, needs_swap)                        \
+       PUSH_BYTES(utf8, cur, OFF32(p), SIZE32, needs_swap)
+
+#if BYTEORDER == 0x4321 || BYTEORDER == 0x87654321  /* big-endian */
+#  define NEEDS_SWAP(d)     (TYPE_ENDIANNESS(d) == TYPE_IS_LITTLE_ENDIAN)
+#elif BYTEORDER == 0x1234 || BYTEORDER == 0x12345678  /* little-endian */
+#  define NEEDS_SWAP(d)     (TYPE_ENDIANNESS(d) == TYPE_IS_BIG_ENDIAN)
+#else
+#  error "Unsupported byteorder"
+        /* Need to add code here to re-instate mixed endian support.
+           NEEDS_SWAP would need to hold a flag indicating which action to
+           take, and S_reverse_copy and the code in S_utf8_to_bytes would need
+           logic adding to deal with any mixed-endian transformations needed.
+        */
+#endif
+
+/* Only to be used inside a loop (see the break) */
+#define SHIFT_BYTES(utf8, s, strend, buf, len, datumtype, needs_swap)	\
+STMT_START {						\
+    if (UNLIKELY(utf8)) {                               \
+        if (!S_utf8_to_bytes(aTHX_ &s, strend,		\
+	  (char *) (buf), len, datumtype)) break;	\
+    } else {						\
+        if (UNLIKELY(needs_swap))                       \
+            S_reverse_copy(s, (char *) (buf), len);     \
+        else                                            \
+            Copy(s, (char *) (buf), len, char);		\
+        s += len;					\
+    }							\
+} STMT_END
+
+#define SHIFT16(utf8, s, strend, p, datumtype, needs_swap)              \
+       SHIFT_BYTES(utf8, s, strend, OFF16(p), SIZE16, datumtype, needs_swap)
+
+#define SHIFT32(utf8, s, strend, p, datumtype, needs_swap)              \
+       SHIFT_BYTES(utf8, s, strend, OFF32(p), SIZE32, datumtype, needs_swap)
+
+#define SHIFT_VAR(utf8, s, strend, var, datumtype, needs_swap)          \
+       SHIFT_BYTES(utf8, s, strend, &(var), sizeof(var), datumtype, needs_swap)
+
+#define PUSH_VAR(utf8, aptr, var, needs_swap)           \
+       PUSH_BYTES(utf8, aptr, &(var), sizeof(var), needs_swap)
+
+/* Avoid stack overflow due to pathological templates. 100 should be plenty. */
+#define MAX_SUB_TEMPLATE_LEVEL 100
+
+/* flags (note that type modifiers can also be used as flags!) */
+#define FLAG_WAS_UTF8	      0x40
+#define FLAG_PARSE_UTF8       0x20	/* Parse as utf8 */
+#define FLAG_UNPACK_ONLY_ONE  0x10
+#define FLAG_DO_UTF8          0x08	/* The underlying string is utf8 */
+#define FLAG_SLASH            0x04
+#define FLAG_COMMA            0x02
+#define FLAG_PACK             0x01
+
+STATIC SV *
+S_mul128(pTHX_ SV *sv, U8 m)
+{
+  STRLEN          len;
+  char           *s = SvPV(sv, len);
+  char           *t;
+
+  PERL_ARGS_ASSERT_MUL128;
+
+  if (!strnEQ(s, "0000", 4)) {  /* need to grow sv */
+    SV * const tmpNew = newSVpvs("0000000000");
+
+    sv_catsv(tmpNew, sv);
+    SvREFCNT_dec(sv);		/* free old sv */
+    sv = tmpNew;
+    s = SvPV(sv, len);
+  }
+  t = s + len - 1;
+  while (!*t)                   /* trailing '\0'? */
+    t--;
+  while (t > s) {
+    const U32 i = ((*t - '0') << 7) + m;
+    *(t--) = '0' + (char)(i % 10);
+    m = (char)(i / 10);
+  }
+  return (sv);
+}
+
+/* Explosives and implosives. */
+
+#define ISUUCHAR(ch)    (NATIVE_TO_LATIN1(ch) >= NATIVE_TO_LATIN1(' ')  \
+                      && NATIVE_TO_LATIN1(ch) <  NATIVE_TO_LATIN1('a'))
+
+/* type modifiers */
+#define TYPE_IS_SHRIEKING	0x100
+#define TYPE_IS_BIG_ENDIAN	0x200
+#define TYPE_IS_LITTLE_ENDIAN	0x400
+#define TYPE_IS_PACK		0x800
+#define TYPE_ENDIANNESS_MASK	(TYPE_IS_BIG_ENDIAN|TYPE_IS_LITTLE_ENDIAN)
+#define TYPE_MODIFIERS(t)	((t) & ~0xFF)
+#define TYPE_NO_MODIFIERS(t)	((t) & 0xFF)
+
+# define TYPE_ENDIANNESS(t)	((t) & TYPE_ENDIANNESS_MASK)
+# define TYPE_NO_ENDIANNESS(t)	((t) & ~TYPE_ENDIANNESS_MASK)
+
+# define ENDIANNESS_ALLOWED_TYPES   "sSiIlLqQjJfFdDpP("
+
+#define PACK_SIZE_CANNOT_CSUM		0x80
+#define PACK_SIZE_UNPREDICTABLE		0x40	/* Not a fixed size element */
+#define PACK_SIZE_MASK			0x3F
+
+#include "packsizetables.c"
+
+static void
+S_reverse_copy(const char *src, char *dest, STRLEN len)
+{
+    dest += len;
+    while (len--)
+        *--dest = *src++;
+}
+
+STATIC U8
+utf8_to_byte(pTHX_ const char **s, const char *end, I32 datumtype)
+{
+    STRLEN retlen;
+    UV val = utf8n_to_uvchr((U8 *) *s, end-*s, &retlen,
+			 ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+    /* We try to process malformed UTF-8 as much as possible (preferably with
+       warnings), but these two mean we make no progress in the string and
+       might enter an infinite loop */
+    if (retlen == (STRLEN) -1 || retlen == 0)
+	Perl_croak(aTHX_ "Malformed UTF-8 string in '%c' format in unpack",
+		   (int) TYPE_NO_MODIFIERS(datumtype));
+    if (val >= 0x100) {
+	Perl_ck_warner(aTHX_ packWARN(WARN_UNPACK),
+		       "Character in '%c' format wrapped in unpack",
+		       (int) TYPE_NO_MODIFIERS(datumtype));
+	val &= 0xff;
+    }
+    *s += retlen;
+    return (U8)val;
+}
+
+#define SHIFT_BYTE(utf8, s, strend, datumtype) ((utf8) ? \
+	utf8_to_byte(aTHX_ &(s), (strend), (datumtype)) : \
+	*(U8 *)(s)++)
+
+STATIC bool
+S_utf8_to_bytes(pTHX_ const char **s, const char *end, const char *buf, int buf_len, I32 datumtype)
+{
+    UV val;
+    STRLEN retlen;
+    const char *from = *s;
+    int bad = 0;
+    const U32 flags = ckWARN(WARN_UTF8) ?
+	UTF8_CHECK_ONLY : (UTF8_CHECK_ONLY | UTF8_ALLOW_ANY);
+    const bool needs_swap = NEEDS_SWAP(datumtype);
+
+    if (UNLIKELY(needs_swap))
+        buf += buf_len;
+
+    for (;buf_len > 0; buf_len--) {
+	if (from >= end) return FALSE;
+	val = utf8n_to_uvchr((U8 *) from, end-from, &retlen, flags);
+	if (retlen == (STRLEN) -1 || retlen == 0) {
+	    from += UTF8SKIP(from);
+	    bad |= 1;
+	} else from += retlen;
+	if (val >= 0x100) {
+	    bad |= 2;
+	    val &= 0xff;
+	}
+        if (UNLIKELY(needs_swap))
+            *(U8 *)--buf = (U8)val;
+        else
+            *(U8 *)buf++ = (U8)val;
+    }
+    /* We have enough characters for the buffer. Did we have problems ? */
+    if (bad) {
+	if (bad & 1) {
+	    /* Rewalk the string fragment while warning */
+	    const char *ptr;
+	    const int flags = ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY;
+	    for (ptr = *s; ptr < from; ptr += UTF8SKIP(ptr)) {
+		if (ptr >= end) break;
+		utf8n_to_uvchr((U8 *) ptr, end-ptr, &retlen, flags);
+	    }
+	    if (from > end) from = end;
+	}
+	if ((bad & 2))
+	    Perl_ck_warner(aTHX_ packWARN(datumtype & TYPE_IS_PACK ?
+				       WARN_PACK : WARN_UNPACK),
+			   "Character(s) in '%c' format wrapped in %s",
+			   (int) TYPE_NO_MODIFIERS(datumtype),
+			   datumtype & TYPE_IS_PACK ? "pack" : "unpack");
+    }
+    *s = from;
+    return TRUE;
+}
+
+STATIC char *
+S_my_bytes_to_utf8(const U8 *start, STRLEN len, char *dest, const bool needs_swap) {
+    PERL_ARGS_ASSERT_MY_BYTES_TO_UTF8;
+
+    if (UNLIKELY(needs_swap)) {
+        const U8 *p = start + len;
+        while (p-- > start) {
+            append_utf8_from_native_byte(*p, (U8 **) & dest);
+        }
+    } else {
+        const U8 * const end = start + len;
+        while (start < end) {
+            append_utf8_from_native_byte(*start, (U8 **) & dest);
+            start++;
+        }
+    }
+    return dest;
+}
+
+#define PUSH_BYTES(utf8, cur, buf, len, needs_swap)             \
+STMT_START {							\
+    if (UNLIKELY(utf8))	                                        \
+	(cur) = my_bytes_to_utf8((U8 *) buf, len, (cur), needs_swap);       \
+    else {							\
+        if (UNLIKELY(needs_swap))                               \
+            S_reverse_copy((char *)(buf), cur, len);            \
+        else                                                    \
+            Copy(buf, cur, len, char);				\
+	(cur) += (len);						\
+    }								\
+} STMT_END
+
+#define GROWING(utf8, cat, start, cur, in_len)	\
+STMT_START {					\
+    STRLEN glen = (in_len);			\
+    if (utf8) glen *= UTF8_EXPAND;		\
+    if ((cur) + glen >= (start) + SvLEN(cat)) {	\
+	(start) = sv_exp_grow(cat, glen);	\
+	(cur) = (start) + SvCUR(cat);		\
+    }						\
+} STMT_END
+
+#define PUSH_GROWING_BYTES(utf8, cat, start, cur, buf, in_len) \
+STMT_START {					\
+    const STRLEN glen = (in_len);		\
+    STRLEN gl = glen;				\
+    if (utf8) gl *= UTF8_EXPAND;		\
+    if ((cur) + gl >= (start) + SvLEN(cat)) {	\
+        *cur = '\0';				\
+        SvCUR_set((cat), (cur) - (start));	\
+	(start) = sv_exp_grow(cat, gl);		\
+	(cur) = (start) + SvCUR(cat);		\
+    }						\
+    PUSH_BYTES(utf8, cur, buf, glen, 0);        \
+} STMT_END
+
+#define PUSH_BYTE(utf8, s, byte)		\
+STMT_START {					\
+    if (utf8) {					\
+	const U8 au8 = (byte);			\
+	(s) = my_bytes_to_utf8(&au8, 1, (s), 0);\
+    } else *(U8 *)(s)++ = (byte);		\
+} STMT_END
+
+/* Only to be used inside a loop (see the break) */
+#define NEXT_UNI_VAL(val, cur, str, end, utf8_flags)		\
+STMT_START {							\
+    STRLEN retlen;						\
+    if (str >= end) break;					\
+    val = utf8n_to_uvchr((U8 *) str, end-str, &retlen, utf8_flags);	\
+    if (retlen == (STRLEN) -1 || retlen == 0) {			\
+	*cur = '\0';						\
+	Perl_croak(aTHX_ "Malformed UTF-8 string in pack");	\
+    }								\
+    str += retlen;						\
+} STMT_END
+
+static const char *_action( const tempsym_t* symptr )
+{
+    return (const char *)(( symptr->flags & FLAG_PACK ) ? "pack" : "unpack");
+}
+
+/* Returns the sizeof() struct described by pat */
+STATIC I32
+S_measure_struct(pTHX_ tempsym_t* symptr)
+{
+    I32 total = 0;
+
+    PERL_ARGS_ASSERT_MEASURE_STRUCT;
+
+    while (next_symbol(symptr)) {
+	I32 len;
+	int size;
+
+        switch (symptr->howlen) {
+	  case e_star:
+   	    Perl_croak(aTHX_ "Within []-length '*' not allowed in %s",
+                        _action( symptr ) );
+
+	  default:
+	    /* e_no_len and e_number */
+	    len = symptr->length;
+	    break;
+        }
+
+	size = packprops[TYPE_NO_ENDIANNESS(symptr->code)] & PACK_SIZE_MASK;
+	if (!size) {
+            int star;
+	    /* endianness doesn't influence the size of a type */
+	    switch(TYPE_NO_ENDIANNESS(symptr->code)) {
+	    default:
+		Perl_croak(aTHX_ "Invalid type '%c' in %s",
+			   (int)TYPE_NO_MODIFIERS(symptr->code),
+                           _action( symptr ) );
+	    case '.' | TYPE_IS_SHRIEKING:
+	    case '@' | TYPE_IS_SHRIEKING:
+	    case '@':
+	    case '.':
+	    case '/':
+	    case 'U':			/* XXXX Is it correct? */
+	    case 'w':
+	    case 'u':
+		Perl_croak(aTHX_ "Within []-length '%c' not allowed in %s",
+			   (int) TYPE_NO_MODIFIERS(symptr->code),
+                           _action( symptr ) );
+	    case '%':
+		size = 0;
+		break;
+	    case '(':
+	    {
+		tempsym_t savsym = *symptr;
+		symptr->patptr = savsym.grpbeg;
+		symptr->patend = savsym.grpend;
+		/* XXXX Theoretically, we need to measure many times at
+		   different positions, since the subexpression may contain
+		   alignment commands, but be not of aligned length.
+		   Need to detect this and croak().  */
+		size = measure_struct(symptr);
+		*symptr = savsym;
+		break;
+	    }
+	    case 'X' | TYPE_IS_SHRIEKING:
+		/* XXXX Is this useful?  Then need to treat MEASURE_BACKWARDS.
+		 */
+		if (!len)		/* Avoid division by 0 */
+		    len = 1;
+		len = total % len;	/* Assumed: the start is aligned. */
+		/* FALLTHROUGH */
+	    case 'X':
+		size = -1;
+		if (total < len)
+                    Perl_croak(aTHX_ "'X' outside of string in %s", _action( symptr ) );
+		break;
+	    case 'x' | TYPE_IS_SHRIEKING:
+		if (!len)		/* Avoid division by 0 */
+		    len = 1;
+		star = total % len;	/* Assumed: the start is aligned. */
+		if (star)		/* Other portable ways? */
+		    len = len - star;
+		else
+		    len = 0;
+		/* FALLTHROUGH */
+	    case 'x':
+	    case 'A':
+	    case 'Z':
+	    case 'a':
+		size = 1;
+		break;
+	    case 'B':
+	    case 'b':
+		len = (len + 7)/8;
+		size = 1;
+		break;
+	    case 'H':
+	    case 'h':
+		len = (len + 1)/2;
+		size = 1;
+		break;
+
+	    case 'P':
+		len = 1;
+		size = sizeof(char*);
+		break;
+	    }
+	}
+	total += len * size;
+    }
+    return total;
+}
+
+
+/* locate matching closing parenthesis or bracket
+ * returns char pointer to char after match, or NULL
+ */
+STATIC const char *
+S_group_end(pTHX_ const char *patptr, const char *patend, char ender)
+{
+    PERL_ARGS_ASSERT_GROUP_END;
+
+    while (patptr < patend) {
+	const char c = *patptr++;
+
+	if (isSPACE(c))
+	    continue;
+	else if (c == ender)
+	    return patptr-1;
+	else if (c == '#') {
+	    while (patptr < patend && *patptr != '\n')
+		patptr++;
+	    continue;
+	} else if (c == '(')
+	    patptr = group_end(patptr, patend, ')') + 1;
+	else if (c == '[')
+	    patptr = group_end(patptr, patend, ']') + 1;
+    }
+    Perl_croak(aTHX_ "No group ending character '%c' found in template",
+               ender);
+    NOT_REACHED; /* NOTREACHED */
+}
+
+
+/* Convert unsigned decimal number to binary.
+ * Expects a pointer to the first digit and address of length variable
+ * Advances char pointer to 1st non-digit char and returns number
+ */
+STATIC const char *
+S_get_num(pTHX_ const char *patptr, I32 *lenptr )
+{
+  I32 len = *patptr++ - '0';
+
+  PERL_ARGS_ASSERT_GET_NUM;
+
+  while (isDIGIT(*patptr)) {
+    if (len >= 0x7FFFFFFF/10)
+      Perl_croak(aTHX_ "pack/unpack repeat count overflow");
+    len = (len * 10) + (*patptr++ - '0');
+  }
+  *lenptr = len;
+  return patptr;
+}
+
+/* The marvellous template parsing routine: Using state stored in *symptr,
+ * locates next template code and count
+ */
+STATIC bool
+S_next_symbol(pTHX_ tempsym_t* symptr )
+{
+  const char* patptr = symptr->patptr;
+  const char* const patend = symptr->patend;
+
+  PERL_ARGS_ASSERT_NEXT_SYMBOL;
+
+  symptr->flags &= ~FLAG_SLASH;
+
+  while (patptr < patend) {
+    if (isSPACE(*patptr))
+      patptr++;
+    else if (*patptr == '#') {
+      patptr++;
+      while (patptr < patend && *patptr != '\n')
+	patptr++;
+      if (patptr < patend)
+	patptr++;
+    } else {
+      /* We should have found a template code */
+      I32 code = *patptr++ & 0xFF;
+      U32 inherited_modifiers = 0;
+
+      if (code == ','){ /* grandfather in commas but with a warning */
+	if (((symptr->flags & FLAG_COMMA) == 0) && ckWARN(WARN_UNPACK)){
+          symptr->flags |= FLAG_COMMA;
+	  Perl_warner(aTHX_ packWARN(WARN_UNPACK),
+	 	      "Invalid type ',' in %s", _action( symptr ) );
+        }
+	continue;
+      }
+
+      /* for '(', skip to ')' */
+      if (code == '(') {
+        if( isDIGIT(*patptr) || *patptr == '*' || *patptr == '[' )
+          Perl_croak(aTHX_ "()-group starts with a count in %s",
+                        _action( symptr ) );
+        symptr->grpbeg = patptr;
+        patptr = 1 + ( symptr->grpend = group_end(patptr, patend, ')') );
+        if( symptr->level >= MAX_SUB_TEMPLATE_LEVEL )
+	  Perl_croak(aTHX_ "Too deeply nested ()-groups in %s",
+                        _action( symptr ) );
+      }
+
+      /* look for group modifiers to inherit */
+      if (TYPE_ENDIANNESS(symptr->flags)) {
+        if (strchr(ENDIANNESS_ALLOWED_TYPES, TYPE_NO_MODIFIERS(code)))
+          inherited_modifiers |= TYPE_ENDIANNESS(symptr->flags);
+      }
+
+      /* look for modifiers */
+      while (patptr < patend) {
+        const char *allowed;
+        I32 modifier;
+        switch (*patptr) {
+          case '!':
+            modifier = TYPE_IS_SHRIEKING;
+            allowed = "sSiIlLxXnNvV@.";
+            break;
+          case '>':
+            modifier = TYPE_IS_BIG_ENDIAN;
+            allowed = ENDIANNESS_ALLOWED_TYPES;
+            break;
+          case '<':
+            modifier = TYPE_IS_LITTLE_ENDIAN;
+            allowed = ENDIANNESS_ALLOWED_TYPES;
+            break;
+          default:
+            allowed = "";
+            modifier = 0;
+            break;
+        }
+
+        if (modifier == 0)
+          break;
+
+        if (!strchr(allowed, TYPE_NO_MODIFIERS(code)))
+          Perl_croak(aTHX_ "'%c' allowed only after types %s in %s", *patptr,
+                        allowed, _action( symptr ) );
+
+        if (TYPE_ENDIANNESS(code | modifier) == TYPE_ENDIANNESS_MASK)
+          Perl_croak(aTHX_ "Can't use both '<' and '>' after type '%c' in %s",
+                     (int) TYPE_NO_MODIFIERS(code), _action( symptr ) );
+        else if (TYPE_ENDIANNESS(code | modifier | inherited_modifiers) ==
+                 TYPE_ENDIANNESS_MASK)
+          Perl_croak(aTHX_ "Can't use '%c' in a group with different byte-order in %s",
+                     *patptr, _action( symptr ) );
+
+        if ((code & modifier)) {
+	    Perl_ck_warner(aTHX_ packWARN(WARN_UNPACK),
+			   "Duplicate modifier '%c' after '%c' in %s",
+			   *patptr, (int) TYPE_NO_MODIFIERS(code),
+			   _action( symptr ) );
+        }
+
+        code |= modifier;
+        patptr++;
+      }
+
+      /* inherit modifiers */
+      code |= inherited_modifiers;
+
+      /* look for count and/or / */
+      if (patptr < patend) {
+	if (isDIGIT(*patptr)) {
+ 	  patptr = get_num( patptr, &symptr->length );
+          symptr->howlen = e_number;
+
+        } else if (*patptr == '*') {
+          patptr++;
+          symptr->howlen = e_star;
+
+        } else if (*patptr == '[') {
+          const char* lenptr = ++patptr;
+          symptr->howlen = e_number;
+          patptr = group_end( patptr, patend, ']' ) + 1;
+          /* what kind of [] is it? */
+          if (isDIGIT(*lenptr)) {
+            lenptr = get_num( lenptr, &symptr->length );
+            if( *lenptr != ']' )
+              Perl_croak(aTHX_ "Malformed integer in [] in %s",
+                            _action( symptr ) );
+          } else {
+            tempsym_t savsym = *symptr;
+            symptr->patend = patptr-1;
+            symptr->patptr = lenptr;
+            savsym.length = measure_struct(symptr);
+            *symptr = savsym;
+          }
+        } else {
+          symptr->howlen = e_no_len;
+          symptr->length = 1;
+        }
+
+        /* try to find / */
+        while (patptr < patend) {
+          if (isSPACE(*patptr))
+            patptr++;
+          else if (*patptr == '#') {
+            patptr++;
+            while (patptr < patend && *patptr != '\n')
+	      patptr++;
+            if (patptr < patend)
+	      patptr++;
+          } else {
+            if (*patptr == '/') {
+              symptr->flags |= FLAG_SLASH;
+              patptr++;
+              if (patptr < patend &&
+                  (isDIGIT(*patptr) || *patptr == '*' || *patptr == '['))
+                Perl_croak(aTHX_ "'/' does not take a repeat count in %s",
+                            _action( symptr ) );
+            }
+            break;
+	  }
+	}
+      } else {
+        /* at end - no count, no / */
+        symptr->howlen = e_no_len;
+        symptr->length = 1;
+      }
+
+      symptr->code = code;
+      symptr->patptr = patptr;
+      return TRUE;
+    }
+  }
+  symptr->patptr = patptr;
+  return FALSE;
+}
+
+/*
+   There is no way to cleanly handle the case where we should process the
+   string per byte in its upgraded form while it's really in downgraded form
+   (e.g. estimates like strend-s as an upper bound for the number of
+   characters left wouldn't work). So if we foresee the need of this
+   (pattern starts with U or contains U0), we want to work on the encoded
+   version of the string. Users are advised to upgrade their pack string
+   themselves if they need to do a lot of unpacks like this on it
+*/
+STATIC bool
+need_utf8(const char *pat, const char *patend)
+{
+    bool first = TRUE;
+
+    PERL_ARGS_ASSERT_NEED_UTF8;
+
+    while (pat < patend) {
+	if (pat[0] == '#') {
+	    pat++;
+	    pat = (const char *) memchr(pat, '\n', patend-pat);
+	    if (!pat) return FALSE;
+	} else if (pat[0] == 'U') {
+	    if (first || pat[1] == '0') return TRUE;
+	} else first = FALSE;
+	pat++;
+    }
+    return FALSE;
+}
+
+STATIC char
+first_symbol(const char *pat, const char *patend) {
+    PERL_ARGS_ASSERT_FIRST_SYMBOL;
+
+    while (pat < patend) {
+	if (pat[0] != '#') return pat[0];
+	pat++;
+	pat = (const char *) memchr(pat, '\n', patend-pat);
+	if (!pat) return 0;
+	pat++;
+    }
+    return 0;
+}
+
+/*
+
+=head1 Pack and Unpack
+
+=for apidoc unpackstring
+
+The engine implementing the unpack() Perl function.
+
+Using the template pat..patend, this function unpacks the string
+s..strend into a number of mortal SVs, which it pushes onto the perl
+argument (@_) stack (so you will need to issue a C<PUTBACK> before and
+C<SPAGAIN> after the call to this function).  It returns the number of
+pushed elements.
+
+The strend and patend pointers should point to the byte following the last
+character of each string.
+
+Although this function returns its values on the perl argument stack, it
+doesn't take any parameters from that stack (and thus in particular
+there's no need to do a PUSHMARK before calling it, unlike L</call_pv> for
+example).
+
+=cut */
+
+I32
+Perl_unpackstring(pTHX_ const char *pat, const char *patend, const char *s, const char *strend, U32 flags)
+{
+    tempsym_t sym;
+
+    PERL_ARGS_ASSERT_UNPACKSTRING;
+
+    if (flags & FLAG_DO_UTF8) flags |= FLAG_WAS_UTF8;
+    else if (need_utf8(pat, patend)) {
+	/* We probably should try to avoid this in case a scalar context call
+	   wouldn't get to the "U0" */
+	STRLEN len = strend - s;
+	s = (char *) bytes_to_utf8((U8 *) s, &len);
+	SAVEFREEPV(s);
+	strend = s + len;
+	flags |= FLAG_DO_UTF8;
+    }
+
+    if (first_symbol(pat, patend) != 'U' && (flags & FLAG_DO_UTF8))
+	flags |= FLAG_PARSE_UTF8;
+
+    TEMPSYM_INIT(&sym, pat, patend, flags);
+
+    return unpack_rec(&sym, s, s, strend, NULL );
+}
+
+STATIC I32
+S_unpack_rec(pTHX_ tempsym_t* symptr, const char *s, const char *strbeg, const char *strend, const char **new_s )
+{
+    dSP;
+    SV *sv = NULL;
+    const I32 start_sp_offset = SP - PL_stack_base;
+    howlen_t howlen;
+    I32 checksum = 0;
+    UV cuv = 0;
+    NV cdouble = 0.0;
+    const int bits_in_uv = CHAR_BIT * sizeof(cuv);
+    bool beyond = FALSE;
+    bool explicit_length;
+    const bool unpack_only_one = (symptr->flags & FLAG_UNPACK_ONLY_ONE) != 0;
+    bool utf8 = (symptr->flags & FLAG_PARSE_UTF8) ? 1 : 0;
+
+    PERL_ARGS_ASSERT_UNPACK_REC;
+
+    symptr->strbeg = s - strbeg;
+
+    while (next_symbol(symptr)) {
+	packprops_t props;
+	I32 len;
+        I32 datumtype = symptr->code;
+        bool needs_swap;
+	/* do first one only unless in list context
+	   / is implemented by unpacking the count, then popping it from the
+	   stack, so must check that we're not in the middle of a /  */
+        if ( unpack_only_one
+	     && (SP - PL_stack_base == start_sp_offset + 1)
+	     && (datumtype != '/') )   /* XXX can this be omitted */
+            break;
+
+        switch (howlen = symptr->howlen) {
+	  case e_star:
+	    len = strend - strbeg;	/* long enough */
+	    break;
+	  default:
+	    /* e_no_len and e_number */
+	    len = symptr->length;
+	    break;
+        }
+
+        explicit_length = TRUE;
+      redo_switch:
+        beyond = s >= strend;
+
+	props = packprops[TYPE_NO_ENDIANNESS(datumtype)];
+	if (props) {
+	    /* props nonzero means we can process this letter. */
+            const long size = props & PACK_SIZE_MASK;
+            const long howmany = (strend - s) / size;
+	    if (len > howmany)
+		len = howmany;
+
+	    if (!checksum || (props & PACK_SIZE_CANNOT_CSUM)) {
+		if (len && unpack_only_one) len = 1;
+		EXTEND(SP, len);
+		EXTEND_MORTAL(len);
+	    }
+	}
+
+        needs_swap = NEEDS_SWAP(datumtype);
+
+	switch(TYPE_NO_ENDIANNESS(datumtype)) {
+	default:
+	    Perl_croak(aTHX_ "Invalid type '%c' in unpack", (int)TYPE_NO_MODIFIERS(datumtype) );
+
+	case '%':
+	    if (howlen == e_no_len)
+		len = 16;		/* len is not specified */
+	    checksum = len;
+	    cuv = 0;
+	    cdouble = 0;
+	    continue;
+
+	case '(':
+	{
+            tempsym_t savsym = *symptr;
+            const U32 group_modifiers = TYPE_MODIFIERS(datumtype & ~symptr->flags);
+	    symptr->flags |= group_modifiers;
+            symptr->patend = savsym.grpend;
+	    symptr->previous = &savsym;
+            symptr->level++;
+	    PUTBACK;
+	    if (len && unpack_only_one) len = 1;
+	    while (len--) {
+  	        symptr->patptr = savsym.grpbeg;
+		if (utf8) symptr->flags |=  FLAG_PARSE_UTF8;
+		else      symptr->flags &= ~FLAG_PARSE_UTF8;
+ 	        unpack_rec(symptr, s, strbeg, strend, &s);
+                if (s == strend && savsym.howlen == e_star)
+		    break; /* No way to continue */
+	    }
+	    SPAGAIN;
+            savsym.flags = symptr->flags & ~group_modifiers;
+            *symptr = savsym;
+	    break;
+	}
+	case '.' | TYPE_IS_SHRIEKING:
+	case '.': {
+	    const char *from;
+	    SV *sv;
+	    const bool u8 = utf8 && !(datumtype & TYPE_IS_SHRIEKING);
+	    if (howlen == e_star) from = strbeg;
+	    else if (len <= 0) from = s;
+	    else {
+		tempsym_t *group = symptr;
+
+		while (--len && group) group = group->previous;
+		from = group ? strbeg + group->strbeg : strbeg;
+	    }
+	    sv = from <= s ?
+		newSVuv(  u8 ? (UV) utf8_length((const U8*)from, (const U8*)s) : (UV) (s-from)) :
+		newSViv(-(u8 ? (IV) utf8_length((const U8*)s, (const U8*)from) : (IV) (from-s)));
+	    mXPUSHs(sv);
+	    break;
+	}
+	case '@' | TYPE_IS_SHRIEKING:
+	case '@':
+	    s = strbeg + symptr->strbeg;
+	    if (utf8  && !(datumtype & TYPE_IS_SHRIEKING))
+	    {
+		while (len > 0) {
+		    if (s >= strend)
+			Perl_croak(aTHX_ "'@' outside of string in unpack");
+		    s += UTF8SKIP(s);
+		    len--;
+		}
+		if (s > strend)
+		    Perl_croak(aTHX_ "'@' outside of string with malformed UTF-8 in unpack");
+	    } else {
+		if (strend-s < len)
+		    Perl_croak(aTHX_ "'@' outside of string in unpack");
+		s += len;
+	    }
+	    break;
+ 	case 'X' | TYPE_IS_SHRIEKING:
+ 	    if (!len)			/* Avoid division by 0 */
+ 		len = 1;
+	    if (utf8) {
+		const char *hop, *last;
+		I32 l = len;
+		hop = last = strbeg;
+		while (hop < s) {
+		    hop += UTF8SKIP(hop);
+		    if (--l == 0) {
+			last = hop;
+			l = len;
+		    }
+		}
+		if (last > s)
+		    Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		s = last;
+		break;
+	    }
+	    len = (s - strbeg) % len;
+ 	    /* FALLTHROUGH */
+	case 'X':
+	    if (utf8) {
+		while (len > 0) {
+		    if (s <= strbeg)
+			Perl_croak(aTHX_ "'X' outside of string in unpack");
+		    while (--s, UTF8_IS_CONTINUATION(*s)) {
+			if (s <= strbeg)
+			    Perl_croak(aTHX_ "'X' outside of string in unpack");
+		    }
+		    len--;
+		}
+	    } else {
+		if (len > s - strbeg)
+		    Perl_croak(aTHX_ "'X' outside of string in unpack" );
+		s -= len;
+	    }
+	    break;
+ 	case 'x' | TYPE_IS_SHRIEKING: {
+            I32 ai32;
+ 	    if (!len)			/* Avoid division by 0 */
+ 		len = 1;
+	    if (utf8) ai32 = utf8_length((U8 *) strbeg, (U8 *) s) % len;
+	    else      ai32 = (s - strbeg)                         % len;
+	    if (ai32 == 0) break;
+	    len -= ai32;
+            }
+ 	    /* FALLTHROUGH */
+	case 'x':
+	    if (utf8) {
+		while (len>0) {
+		    if (s >= strend)
+			Perl_croak(aTHX_ "'x' outside of string in unpack");
+		    s += UTF8SKIP(s);
+		    len--;
+		}
+	    } else {
+		if (len > strend - s)
+		    Perl_croak(aTHX_ "'x' outside of string in unpack");
+		s += len;
+	    }
+	    break;
+	case '/':
+	    Perl_croak(aTHX_ "'/' must follow a numeric type in unpack");
+
+	case 'A':
+	case 'Z':
+	case 'a':
+	    if (checksum) {
+		/* Preliminary length estimate is assumed done in 'W' */
+		if (len > strend - s) len = strend - s;
+		goto W_checksum;
+	    }
+	    if (utf8) {
+		I32 l;
+		const char *hop;
+		for (l=len, hop=s; l>0; l--, hop += UTF8SKIP(hop)) {
+		    if (hop >= strend) {
+			if (hop > strend)
+			    Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+			break;
+		    }
+		}
+		if (hop > strend)
+		    Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		len = hop - s;
+	    } else if (len > strend - s)
+		len = strend - s;
+
+	    if (datumtype == 'Z') {
+		/* 'Z' strips stuff after first null */
+		const char *ptr, *end;
+		end = s + len;
+		for (ptr = s; ptr < end; ptr++) if (*ptr == 0) break;
+		sv = newSVpvn(s, ptr-s);
+		if (howlen == e_star) /* exact for 'Z*' */
+		    len = ptr-s + (ptr != strend ? 1 : 0);
+	    } else if (datumtype == 'A') {
+		/* 'A' strips both nulls and spaces */
+		const char *ptr;
+		if (utf8 && (symptr->flags & FLAG_WAS_UTF8)) {
+		    for (ptr = s+len-1; ptr >= s; ptr--)
+			if (*ptr != 0 && !UTF8_IS_CONTINUATION(*ptr) &&
+			    !isSPACE_utf8(ptr)) break;
+		    if (ptr >= s) ptr += UTF8SKIP(ptr);
+		    else ptr++;
+		    if (ptr > s+len)
+			Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		} else {
+		    for (ptr = s+len-1; ptr >= s; ptr--)
+			if (*ptr != 0 && !isSPACE(*ptr)) break;
+		    ptr++;
+		}
+		sv = newSVpvn(s, ptr-s);
+	    } else sv = newSVpvn(s, len);
+
+	    if (utf8) {
+		SvUTF8_on(sv);
+		/* Undo any upgrade done due to need_utf8() */
+		if (!(symptr->flags & FLAG_WAS_UTF8))
+		    sv_utf8_downgrade(sv, 0);
+	    }
+	    mXPUSHs(sv);
+	    s += len;
+	    break;
+	case 'B':
+	case 'b': {
+	    char *str;
+	    if (howlen == e_star || len > (strend - s) * 8)
+		len = (strend - s) * 8;
+	    if (checksum) {
+		if (utf8)
+		    while (len >= 8 && s < strend) {
+			cuv += PL_bitcount[utf8_to_byte(aTHX_ &s, strend, datumtype)];
+			len -= 8;
+		    }
+		else
+		    while (len >= 8) {
+			cuv += PL_bitcount[*(U8 *)s++];
+			len -= 8;
+		    }
+		if (len && s < strend) {
+		    U8 bits;
+		    bits = SHIFT_BYTE(utf8, s, strend, datumtype);
+		    if (datumtype == 'b')
+			while (len-- > 0) {
+			    if (bits & 1) cuv++;
+			    bits >>= 1;
+			}
+		    else
+			while (len-- > 0) {
+			    if (bits & 0x80) cuv++;
+			    bits <<= 1;
+			}
+		}
+		break;
+	    }
+
+	    sv = sv_2mortal(newSV(len ? len : 1));
+	    SvPOK_on(sv);
+	    str = SvPVX(sv);
+	    if (datumtype == 'b') {
+		U8 bits = 0;
+		const I32 ai32 = len;
+		for (len = 0; len < ai32; len++) {
+		    if (len & 7) bits >>= 1;
+		    else if (utf8) {
+			if (s >= strend) break;
+			bits = utf8_to_byte(aTHX_ &s, strend, datumtype);
+		    } else bits = *(U8 *) s++;
+		    *str++ = bits & 1 ? '1' : '0';
+		}
+	    } else {
+		U8 bits = 0;
+		const I32 ai32 = len;
+		for (len = 0; len < ai32; len++) {
+		    if (len & 7) bits <<= 1;
+		    else if (utf8) {
+			if (s >= strend) break;
+			bits = utf8_to_byte(aTHX_ &s, strend, datumtype);
+		    } else bits = *(U8 *) s++;
+		    *str++ = bits & 0x80 ? '1' : '0';
+		}
+	    }
+	    *str = '\0';
+	    SvCUR_set(sv, str - SvPVX_const(sv));
+	    XPUSHs(sv);
+	    break;
+	}
+	case 'H':
+	case 'h': {
+	    char *str = NULL;
+	    /* Preliminary length estimate, acceptable for utf8 too */
+	    if (howlen == e_star || len > (strend - s) * 2)
+		len = (strend - s) * 2;
+	    if (!checksum) {
+		sv = sv_2mortal(newSV(len ? len : 1));
+		SvPOK_on(sv);
+		str = SvPVX(sv);
+	    }
+	    if (datumtype == 'h') {
+		U8 bits = 0;
+		I32 ai32 = len;
+		for (len = 0; len < ai32; len++) {
+		    if (len & 1) bits >>= 4;
+		    else if (utf8) {
+			if (s >= strend) break;
+			bits = utf8_to_byte(aTHX_ &s, strend, datumtype);
+		    } else bits = * (U8 *) s++;
+		    if (!checksum)
+			*str++ = PL_hexdigit[bits & 15];
+		}
+	    } else {
+		U8 bits = 0;
+		const I32 ai32 = len;
+		for (len = 0; len < ai32; len++) {
+		    if (len & 1) bits <<= 4;
+		    else if (utf8) {
+			if (s >= strend) break;
+			bits = utf8_to_byte(aTHX_ &s, strend, datumtype);
+		    } else bits = *(U8 *) s++;
+		    if (!checksum)
+			*str++ = PL_hexdigit[(bits >> 4) & 15];
+		}
+	    }
+	    if (!checksum) {
+		*str = '\0';
+		SvCUR_set(sv, str - SvPVX_const(sv));
+		XPUSHs(sv);
+	    }
+	    break;
+	}
+	case 'C':
+            if (len == 0) {
+                if (explicit_length)
+		    /* Switch to "character" mode */
+		    utf8 = (symptr->flags & FLAG_DO_UTF8) ? 1 : 0;
+		break;
+	    }
+	    /* FALLTHROUGH */
+	case 'c':
+	    while (len-- > 0 && s < strend) {
+		int aint;
+		if (utf8)
+		  {
+		    STRLEN retlen;
+		    aint = utf8n_to_uvchr((U8 *) s, strend-s, &retlen,
+				 ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+		    if (retlen == (STRLEN) -1 || retlen == 0)
+			Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		    s += retlen;
+		  }
+		else
+		  aint = *(U8 *)(s)++;
+		if (aint >= 128 && datumtype != 'C')	/* fake up signed chars */
+		    aint -= 256;
+		if (!checksum)
+		    mPUSHi(aint);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aint;
+		else
+		    cuv += aint;
+	    }
+	    break;
+	case 'W':
+	  W_checksum:
+	    if (utf8) {
+		while (len-- > 0 && s < strend) {
+		    STRLEN retlen;
+		    const UV val = utf8n_to_uvchr((U8 *) s, strend-s, &retlen,
+					 ckWARN(WARN_UTF8) ? 0 : UTF8_ALLOW_ANY);
+		    if (retlen == (STRLEN) -1 || retlen == 0)
+			Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		    s += retlen;
+		    if (!checksum)
+			mPUSHu(val);
+		    else if (checksum > bits_in_uv)
+			cdouble += (NV) val;
+		    else
+			cuv += val;
+		}
+	    } else if (!checksum)
+		while (len-- > 0) {
+		    const U8 ch = *(U8 *) s++;
+		    mPUSHu(ch);
+	    }
+	    else if (checksum > bits_in_uv)
+		while (len-- > 0) cdouble += (NV) *(U8 *) s++;
+	    else
+		while (len-- > 0) cuv += *(U8 *) s++;
+	    break;
+	case 'U':
+	    if (len == 0) {
+                if (explicit_length && howlen != e_star) {
+		    /* Switch to "bytes in UTF-8" mode */
+		    if (symptr->flags & FLAG_DO_UTF8) utf8 = 0;
+		    else
+			/* Should be impossible due to the need_utf8() test */
+			Perl_croak(aTHX_ "U0 mode on a byte string");
+		}
+		break;
+	    }
+	    if (len > strend - s) len = strend - s;
+	    if (!checksum) {
+		if (len && unpack_only_one) len = 1;
+		EXTEND(SP, len);
+		EXTEND_MORTAL(len);
+	    }
+	    while (len-- > 0 && s < strend) {
+		STRLEN retlen;
+		UV auv;
+		if (utf8) {
+		    U8 result[UTF8_MAXLEN];
+		    const char *ptr = s;
+		    STRLEN len;
+		    /* Bug: warns about bad utf8 even if we are short on bytes
+		       and will break out of the loop */
+		    if (!S_utf8_to_bytes(aTHX_ &ptr, strend, (char *) result, 1,
+				      'U'))
+			break;
+		    len = UTF8SKIP(result);
+		    if (!S_utf8_to_bytes(aTHX_ &ptr, strend,
+				      (char *) &result[1], len-1, 'U')) break;
+		    auv = NATIVE_TO_UNI(utf8n_to_uvchr(result,
+                                                       len,
+                                                       &retlen,
+                                                       UTF8_ALLOW_DEFAULT));
+		    s = ptr;
+		} else {
+		    auv = NATIVE_TO_UNI(utf8n_to_uvchr((U8*)s,
+                                                       strend - s,
+                                                       &retlen,
+                                                       UTF8_ALLOW_DEFAULT));
+		    if (retlen == (STRLEN) -1 || retlen == 0)
+			Perl_croak(aTHX_ "Malformed UTF-8 string in unpack");
+		    s += retlen;
+		}
+		if (!checksum)
+		    mPUSHu(auv);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV) auv;
+		else
+		    cuv += auv;
+	    }
+	    break;
+	case 's' | TYPE_IS_SHRIEKING:
+#if SHORTSIZE != SIZE16
+	    while (len-- > 0) {
+		short ashort;
+                SHIFT_VAR(utf8, s, strend, ashort, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHi(ashort);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)ashort;
+		else
+		    cuv += ashort;
+	    }
+	    break;
+#else
+	    /* FALLTHROUGH */
+#endif
+	case 's':
+	    while (len-- > 0) {
+		I16 ai16;
+
+#if U16SIZE > SIZE16
+		ai16 = 0;
+#endif
+                SHIFT16(utf8, s, strend, &ai16, datumtype, needs_swap);
+#if U16SIZE > SIZE16
+		if (ai16 > 32767)
+		    ai16 -= 65536;
+#endif
+		if (!checksum)
+		    mPUSHi(ai16);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)ai16;
+		else
+		    cuv += ai16;
+	    }
+	    break;
+	case 'S' | TYPE_IS_SHRIEKING:
+#if SHORTSIZE != SIZE16
+	    while (len-- > 0) {
+		unsigned short aushort;
+                SHIFT_VAR(utf8, s, strend, aushort, datumtype, needs_swap,
+                          needs_swap);
+		if (!checksum)
+		    mPUSHu(aushort);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aushort;
+		else
+		    cuv += aushort;
+	    }
+	    break;
+#else
+            /* FALLTHROUGH */
+#endif
+	case 'v':
+	case 'n':
+	case 'S':
+	    while (len-- > 0) {
+		U16 au16;
+#if U16SIZE > SIZE16
+		au16 = 0;
+#endif
+                SHIFT16(utf8, s, strend, &au16, datumtype, needs_swap);
+		if (datumtype == 'n')
+		    au16 = PerlSock_ntohs(au16);
+		if (datumtype == 'v')
+		    au16 = vtohs(au16);
+		if (!checksum)
+		    mPUSHu(au16);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV) au16;
+		else
+		    cuv += au16;
+	    }
+	    break;
+	case 'v' | TYPE_IS_SHRIEKING:
+	case 'n' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		I16 ai16;
+# if U16SIZE > SIZE16
+		ai16 = 0;
+# endif
+                SHIFT16(utf8, s, strend, &ai16, datumtype, needs_swap);
+                /* There should never be any byte-swapping here.  */
+                assert(!TYPE_ENDIANNESS(datumtype));
+		if (datumtype == ('n' | TYPE_IS_SHRIEKING))
+		    ai16 = (I16) PerlSock_ntohs((U16) ai16);
+		if (datumtype == ('v' | TYPE_IS_SHRIEKING))
+		    ai16 = (I16) vtohs((U16) ai16);
+		if (!checksum)
+		    mPUSHi(ai16);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV) ai16;
+		else
+		    cuv += ai16;
+	    }
+	    break;
+	case 'i':
+	case 'i' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		int aint;
+                SHIFT_VAR(utf8, s, strend, aint, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHi(aint);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aint;
+		else
+		    cuv += aint;
+	    }
+	    break;
+	case 'I':
+	case 'I' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		unsigned int auint;
+                SHIFT_VAR(utf8, s, strend, auint, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHu(auint);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)auint;
+		else
+		    cuv += auint;
+	    }
+	    break;
+	case 'j':
+	    while (len-- > 0) {
+		IV aiv;
+                SHIFT_VAR(utf8, s, strend, aiv, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHi(aiv);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aiv;
+		else
+		    cuv += aiv;
+	    }
+	    break;
+	case 'J':
+	    while (len-- > 0) {
+		UV auv;
+                SHIFT_VAR(utf8, s, strend, auv, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHu(auv);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)auv;
+		else
+		    cuv += auv;
+	    }
+	    break;
+	case 'l' | TYPE_IS_SHRIEKING:
+#if LONGSIZE != SIZE32
+	    while (len-- > 0) {
+		long along;
+                SHIFT_VAR(utf8, s, strend, along, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHi(along);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)along;
+		else
+		    cuv += along;
+	    }
+	    break;
+#else
+	    /* FALLTHROUGH */
+#endif
+	case 'l':
+	    while (len-- > 0) {
+		I32 ai32;
+#if U32SIZE > SIZE32
+		ai32 = 0;
+#endif
+                SHIFT32(utf8, s, strend, &ai32, datumtype, needs_swap);
+#if U32SIZE > SIZE32
+		if (ai32 > 2147483647) ai32 -= 4294967296;
+#endif
+		if (!checksum)
+		    mPUSHi(ai32);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)ai32;
+		else
+		    cuv += ai32;
+	    }
+	    break;
+	case 'L' | TYPE_IS_SHRIEKING:
+#if LONGSIZE != SIZE32
+	    while (len-- > 0) {
+		unsigned long aulong;
+                SHIFT_VAR(utf8, s, strend, aulong, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHu(aulong);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aulong;
+		else
+		    cuv += aulong;
+	    }
+	    break;
+#else
+            /* FALLTHROUGH */
+#endif
+	case 'V':
+	case 'N':
+	case 'L':
+	    while (len-- > 0) {
+		U32 au32;
+#if U32SIZE > SIZE32
+		au32 = 0;
+#endif
+                SHIFT32(utf8, s, strend, &au32, datumtype, needs_swap);
+		if (datumtype == 'N')
+		    au32 = PerlSock_ntohl(au32);
+		if (datumtype == 'V')
+		    au32 = vtohl(au32);
+		if (!checksum)
+		    mPUSHu(au32);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)au32;
+		else
+		    cuv += au32;
+	    }
+	    break;
+	case 'V' | TYPE_IS_SHRIEKING:
+	case 'N' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		I32 ai32;
+#if U32SIZE > SIZE32
+		ai32 = 0;
+#endif
+                SHIFT32(utf8, s, strend, &ai32, datumtype, needs_swap);
+                /* There should never be any byte swapping here.  */
+                assert(!TYPE_ENDIANNESS(datumtype));
+		if (datumtype == ('N' | TYPE_IS_SHRIEKING))
+		    ai32 = (I32)PerlSock_ntohl((U32)ai32);
+		if (datumtype == ('V' | TYPE_IS_SHRIEKING))
+		    ai32 = (I32)vtohl((U32)ai32);
+		if (!checksum)
+		    mPUSHi(ai32);
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)ai32;
+		else
+		    cuv += ai32;
+	    }
+	    break;
+	case 'p':
+	    while (len-- > 0) {
+		const char *aptr;
+                SHIFT_VAR(utf8, s, strend, aptr, datumtype, needs_swap);
+		/* newSVpv generates undef if aptr is NULL */
+		mPUSHs(newSVpv(aptr, 0));
+	    }
+	    break;
+	case 'w':
+	    {
+		UV auv = 0;
+		U32 bytes = 0;
+
+		while (len > 0 && s < strend) {
+		    U8 ch;
+		    ch = SHIFT_BYTE(utf8, s, strend, datumtype);
+		    auv = (auv << 7) | (ch & 0x7f);
+		    /* UTF8_IS_XXXXX not right here - using constant 0x80 */
+		    if (ch < 0x80) {
+			bytes = 0;
+			mPUSHu(auv);
+			len--;
+			auv = 0;
+			continue;
+		    }
+		    if (++bytes >= sizeof(UV)) {	/* promote to string */
+			const char *t;
+
+			sv = Perl_newSVpvf(aTHX_ "%.*"UVuf, (int)TYPE_DIGITS(UV), auv);
+			while (s < strend) {
+			    ch = SHIFT_BYTE(utf8, s, strend, datumtype);
+			    sv = mul128(sv, (U8)(ch & 0x7f));
+			    if (!(ch & 0x80)) {
+				bytes = 0;
+				break;
+			    }
+			}
+			t = SvPV_nolen_const(sv);
+			while (*t == '0')
+			    t++;
+			sv_chop(sv, t);
+			mPUSHs(sv);
+			len--;
+			auv = 0;
+		    }
+		}
+		if ((s >= strend) && bytes)
+		    Perl_croak(aTHX_ "Unterminated compressed integer in unpack");
+	    }
+	    break;
+	case 'P':
+	    if (symptr->howlen == e_star)
+	        Perl_croak(aTHX_ "'P' must have an explicit size in unpack");
+	    EXTEND(SP, 1);
+	    if (s + sizeof(char*) <= strend) {
+		char *aptr;
+                SHIFT_VAR(utf8, s, strend, aptr, datumtype, needs_swap);
+		/* newSVpvn generates undef if aptr is NULL */
+		PUSHs(newSVpvn_flags(aptr, len, SVs_TEMP));
+	    }
+	    break;
+#if defined(HAS_QUAD) && IVSIZE >= 8
+	case 'q':
+	    while (len-- > 0) {
+		Quad_t aquad;
+                SHIFT_VAR(utf8, s, strend, aquad, datumtype, needs_swap);
+		if (!checksum)
+                    mPUSHs(newSViv((IV)aquad));
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)aquad;
+		else
+		    cuv += aquad;
+	    }
+	    break;
+	case 'Q':
+	    while (len-- > 0) {
+		Uquad_t auquad;
+                SHIFT_VAR(utf8, s, strend, auquad, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHs(newSVuv((UV)auquad));
+		else if (checksum > bits_in_uv)
+		    cdouble += (NV)auquad;
+		else
+		    cuv += auquad;
+	    }
+	    break;
+#endif
+	/* float and double added gnb@melba.bby.oz.au 22/11/89 */
+	case 'f':
+	    while (len-- > 0) {
+		float afloat;
+                SHIFT_VAR(utf8, s, strend, afloat, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHn(afloat);
+		else
+		    cdouble += afloat;
+	    }
+	    break;
+	case 'd':
+	    while (len-- > 0) {
+		double adouble;
+                SHIFT_VAR(utf8, s, strend, adouble, datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHn(adouble);
+		else
+		    cdouble += adouble;
+	    }
+	    break;
+	case 'F':
+	    while (len-- > 0) {
+		NV_bytes anv;
+                SHIFT_BYTES(utf8, s, strend, anv.bytes, sizeof(anv.bytes),
+                            datumtype, needs_swap);
+		if (!checksum)
+		    mPUSHn(anv.nv);
+		else
+		    cdouble += anv.nv;
+	    }
+	    break;
+#if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
+	case 'D':
+	    while (len-- > 0) {
+		ld_bytes aldouble;
+                SHIFT_BYTES(utf8, s, strend, aldouble.bytes,
+                            sizeof(aldouble.bytes), datumtype, needs_swap);
+                /* The most common long double format, the x86 80-bit
+                 * extended precision, has either 2 or 6 unused bytes,
+                 * which may contain garbage, which may contain
+                 * unintentional data.  While we do zero the bytes of
+                 * the long double data in pack(), here in unpack() we
+                 * don't, because it's really hard to envision that
+                 * reading the long double off aldouble would be
+                 * affected by the unused bytes.
+                 *
+                 * Note that trying to unpack 'long doubles' of 'long
+                 * doubles' packed in another system is in the general
+                 * case doomed without having more detail. */
+		if (!checksum)
+		    mPUSHn(aldouble.ld);
+		else
+		    cdouble += aldouble.ld;
+	    }
+	    break;
+#endif
+	case 'u':
+	    if (!checksum) {
+                const STRLEN l = (STRLEN) (strend - s) * 3 / 4;
+		sv = sv_2mortal(newSV(l));
+		if (l) SvPOK_on(sv);
+	    }
+
+            /* Note that all legal uuencoded strings are ASCII printables, so
+             * have the same representation under UTF-8 vs not.  This means we
+             * can ignore UTF8ness on legal input.  For illegal we stop at the
+             * first failure, and don't report where/what that is, so again we
+             * can ignore UTF8ness */
+
+            while (s < strend && *s != ' ' && ISUUCHAR(*s)) {
+                I32 a, b, c, d;
+                char hunk[3];
+
+                len = PL_uudmap[*(U8*)s++] & 077;
+                while (len > 0) {
+                    if (s < strend && ISUUCHAR(*s))
+                        a = PL_uudmap[*(U8*)s++] & 077;
+                    else
+                        a = 0;
+                    if (s < strend && ISUUCHAR(*s))
+                        b = PL_uudmap[*(U8*)s++] & 077;
+                    else
+                        b = 0;
+                    if (s < strend && ISUUCHAR(*s))
+                        c = PL_uudmap[*(U8*)s++] & 077;
+                    else
+                        c = 0;
+                    if (s < strend && ISUUCHAR(*s))
+                        d = PL_uudmap[*(U8*)s++] & 077;
+                    else
+                        d = 0;
+                    hunk[0] = (char)((a << 2) | (b >> 4));
+                    hunk[1] = (char)((b << 4) | (c >> 2));
+                    hunk[2] = (char)((c << 6) | d);
+                    if (!checksum)
+                        sv_catpvn(sv, hunk, (len > 3) ? 3 : len);
+                    len -= 3;
+                }
+                if (*s == '\n')
+                    s++;
+                else	/* possible checksum byte */
+                    if (s + 1 < strend && s[1] == '\n')
+                        s += 2;
+            }
+	    if (!checksum)
+		XPUSHs(sv);
+	    break;
+	} /* End of switch */
+
+	if (checksum) {
+	    if (strchr("fFdD", TYPE_NO_MODIFIERS(datumtype)) ||
+	      (checksum > bits_in_uv &&
+	       strchr("cCsSiIlLnNUWvVqQjJ", TYPE_NO_MODIFIERS(datumtype))) ) {
+		NV trouble, anv;
+
+                anv = (NV) (1 << (checksum & 15));
+		while (checksum >= 16) {
+		    checksum -= 16;
+		    anv *= 65536.0;
+		}
+		while (cdouble < 0.0)
+		    cdouble += anv;
+		cdouble = Perl_modf(cdouble / anv, &trouble);
+#ifdef LONGDOUBLE_DOUBLEDOUBLE
+                /* Workaround for powerpc doubledouble modfl bug:
+                 * close to 1.0L and -1.0L cdouble is 0, and trouble
+                 * is cdouble / anv. */
+                if (trouble != Perl_ceil(trouble)) {
+                  cdouble = trouble;
+                  if (cdouble >  1.0L) cdouble -= 1.0L;
+                  if (cdouble < -1.0L) cdouble += 1.0L;
+                }
+#endif
+                cdouble *= anv;
+		sv = newSVnv(cdouble);
+	    }
+	    else {
+		if (checksum < bits_in_uv) {
+		    UV mask = ((UV)1 << checksum) - 1;
+		    cuv &= mask;
+		}
+		sv = newSVuv(cuv);
+	    }
+	    mXPUSHs(sv);
+	    checksum = 0;
+	}
+
+        if (symptr->flags & FLAG_SLASH){
+            if (SP - PL_stack_base - start_sp_offset <= 0)
+		break;
+            if( next_symbol(symptr) ){
+              if( symptr->howlen == e_number )
+		Perl_croak(aTHX_ "Count after length/code in unpack" );
+              if( beyond ){
+         	/* ...end of char buffer then no decent length available */
+		Perl_croak(aTHX_ "length/code after end of string in unpack" );
+              } else {
+         	/* take top of stack (hope it's numeric) */
+                len = POPi;
+                if( len < 0 )
+                    Perl_croak(aTHX_ "Negative '/' count in unpack" );
+              }
+            } else {
+		Perl_croak(aTHX_ "Code missing after '/' in unpack" );
+            }
+            datumtype = symptr->code;
+            explicit_length = FALSE;
+	    goto redo_switch;
+        }
+    }
+
+    if (new_s)
+	*new_s = s;
+    PUTBACK;
+    return SP - PL_stack_base - start_sp_offset;
+}
+
+PP(pp_unpack)
+{
+    dSP;
+    dPOPPOPssrl;
+    I32 gimme = GIMME_V;
+    STRLEN llen;
+    STRLEN rlen;
+    const char *pat = SvPV_const(left,  llen);
+    const char *s   = SvPV_const(right, rlen);
+    const char *strend = s + rlen;
+    const char *patend = pat + llen;
+    I32 cnt;
+
+    PUTBACK;
+    cnt = unpackstring(pat, patend, s, strend,
+		     ((gimme == G_SCALAR) ? FLAG_UNPACK_ONLY_ONE : 0)
+		     | (DO_UTF8(right) ? FLAG_DO_UTF8 : 0));
+
+    SPAGAIN;
+    if ( !cnt && gimme == G_SCALAR )
+       PUSHs(&PL_sv_undef);
+    RETURN;
+}
+
+STATIC U8 *
+doencodes(U8 *h, const U8 *s, I32 len)
+{
+    *h++ = PL_uuemap[len];
+    while (len > 2) {
+	*h++ = PL_uuemap[(077 & (s[0] >> 2))];
+	*h++ = PL_uuemap[(077 & (((s[0] << 4) & 060) | ((s[1] >> 4) & 017)))];
+	*h++ = PL_uuemap[(077 & (((s[1] << 2) & 074) | ((s[2] >> 6) & 03)))];
+	*h++ = PL_uuemap[(077 & (s[2] & 077))];
+	s += 3;
+	len -= 3;
+    }
+    if (len > 0) {
+        const U8 r = (len > 1 ? s[1] : '\0');
+	*h++ = PL_uuemap[(077 & (s[0] >> 2))];
+	*h++ = PL_uuemap[(077 & (((s[0] << 4) & 060) | ((r >> 4) & 017)))];
+	*h++ = PL_uuemap[(077 & ((r << 2) & 074))];
+	*h++ = PL_uuemap[0];
+    }
+    *h++ = '\n';
+    return h;
+}
+
+STATIC SV *
+S_is_an_int(pTHX_ const char *s, STRLEN l)
+{
+  SV *result = newSVpvn(s, l);
+  char *const result_c = SvPV_nolen(result);	/* convenience */
+  char *out = result_c;
+  bool skip = 1;
+  bool ignore = 0;
+
+  PERL_ARGS_ASSERT_IS_AN_INT;
+
+  while (*s) {
+    switch (*s) {
+    case ' ':
+      break;
+    case '+':
+      if (!skip) {
+	SvREFCNT_dec(result);
+	return (NULL);
+      }
+      break;
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
+    case '7':
+    case '8':
+    case '9':
+      skip = 0;
+      if (!ignore) {
+	*(out++) = *s;
+      }
+      break;
+    case '.':
+      ignore = 1;
+      break;
+    default:
+      SvREFCNT_dec(result);
+      return (NULL);
+    }
+    s++;
+  }
+  *(out++) = '\0';
+  SvCUR_set(result, out - result_c);
+  return (result);
+}
+
+/* pnum must be '\0' terminated */
+STATIC int
+S_div128(pTHX_ SV *pnum, bool *done)
+{
+    STRLEN len;
+    char * const s = SvPV(pnum, len);
+    char *t = s;
+    int m = 0;
+
+    PERL_ARGS_ASSERT_DIV128;
+
+    *done = 1;
+    while (*t) {
+	const int i = m * 10 + (*t - '0');
+	const int r = (i >> 7); /* r < 10 */
+	m = i & 0x7F;
+	if (r) {
+	    *done = 0;
+	}
+	*(t++) = '0' + r;
+    }
+    *(t++) = '\0';
+    SvCUR_set(pnum, (STRLEN) (t - s));
+    return (m);
+}
+
+/*
+=for apidoc packlist
+
+The engine implementing pack() Perl function.
+
+=cut
+*/
+
+void
+Perl_packlist(pTHX_ SV *cat, const char *pat, const char *patend, SV **beglist, SV **endlist )
+{
+    tempsym_t sym;
+
+    PERL_ARGS_ASSERT_PACKLIST;
+
+    TEMPSYM_INIT(&sym, pat, patend, FLAG_PACK);
+
+    /* We're going to do changes through SvPVX(cat). Make sure it's valid.
+       Also make sure any UTF8 flag is loaded */
+    SvPV_force_nolen(cat);
+    if (DO_UTF8(cat))
+	sym.flags |= FLAG_PARSE_UTF8 | FLAG_DO_UTF8;
+
+    (void)pack_rec( cat, &sym, beglist, endlist );
+}
+
+/* like sv_utf8_upgrade, but also repoint the group start markers */
+STATIC void
+marked_upgrade(pTHX_ SV *sv, tempsym_t *sym_ptr) {
+    STRLEN len;
+    tempsym_t *group;
+    const char *from_ptr, *from_start, *from_end, **marks, **m;
+    char *to_start, *to_ptr;
+
+    if (SvUTF8(sv)) return;
+
+    from_start = SvPVX_const(sv);
+    from_end = from_start + SvCUR(sv);
+    for (from_ptr = from_start; from_ptr < from_end; from_ptr++)
+	if (!NATIVE_BYTE_IS_INVARIANT(*from_ptr)) break;
+    if (from_ptr == from_end) {
+	/* Simple case: no character needs to be changed */
+	SvUTF8_on(sv);
+	return;
+    }
+
+    len = (from_end-from_ptr)*UTF8_EXPAND+(from_ptr-from_start)+1;
+    Newx(to_start, len, char);
+    Copy(from_start, to_start, from_ptr-from_start, char);
+    to_ptr = to_start + (from_ptr-from_start);
+
+    Newx(marks, sym_ptr->level+2, const char *);
+    for (group=sym_ptr; group; group = group->previous)
+	marks[group->level] = from_start + group->strbeg;
+    marks[sym_ptr->level+1] = from_end+1;
+    for (m = marks; *m < from_ptr; m++)
+	*m = to_start + (*m-from_start);
+
+    for (;from_ptr < from_end; from_ptr++) {
+	while (*m == from_ptr) *m++ = to_ptr;
+	to_ptr = (char *) uvchr_to_utf8((U8 *) to_ptr, *(U8 *) from_ptr);
+    }
+    *to_ptr = 0;
+
+    while (*m == from_ptr) *m++ = to_ptr;
+    if (m != marks + sym_ptr->level+1) {
+	Safefree(marks);
+	Safefree(to_start);
+	Perl_croak(aTHX_ "panic: marks beyond string end, m=%p, marks=%p, "
+		   "level=%d", m, marks, sym_ptr->level);
+    }
+    for (group=sym_ptr; group; group = group->previous)
+	group->strbeg = marks[group->level] - to_start;
+    Safefree(marks);
+
+    if (SvOOK(sv)) {
+	if (SvIVX(sv)) {
+	    SvLEN_set(sv, SvLEN(sv) + SvIVX(sv));
+	    from_start -= SvIVX(sv);
+	    SvIV_set(sv, 0);
+	}
+	SvFLAGS(sv) &= ~SVf_OOK;
+    }
+    if (SvLEN(sv) != 0)
+	Safefree(from_start);
+    SvPV_set(sv, to_start);
+    SvCUR_set(sv, to_ptr - to_start);
+    SvLEN_set(sv, len);
+    SvUTF8_on(sv);
+}
+
+/* Exponential string grower. Makes string extension effectively O(n)
+   needed says how many extra bytes we need (not counting the final '\0')
+   Only grows the string if there is an actual lack of space
+*/
+STATIC char *
+S_sv_exp_grow(pTHX_ SV *sv, STRLEN needed) {
+    const STRLEN cur = SvCUR(sv);
+    const STRLEN len = SvLEN(sv);
+    STRLEN extend;
+
+    PERL_ARGS_ASSERT_SV_EXP_GROW;
+
+    if (len - cur > needed) return SvPVX(sv);
+    extend = needed > len ? needed : len;
+    return SvGROW(sv, len+extend+1);
+}
+
+static SV *
+S_sv_check_infnan(pTHX_ SV *sv, I32 datumtype)
+{
+    SvGETMAGIC(sv);
+    if (UNLIKELY(SvAMAGIC(sv)))
+	sv = sv_2num(sv);
+    if (UNLIKELY(isinfnansv(sv))) {
+	const I32 c = TYPE_NO_MODIFIERS(datumtype);
+	const NV nv = SvNV_nomg(sv);
+	if (c == 'w')
+	    Perl_croak(aTHX_ "Cannot compress %"NVgf" in pack", nv);
+	else
+	    Perl_croak(aTHX_ "Cannot pack %"NVgf" with '%c'", nv, (int) c);
+    }
+    return sv;
+}
+
+#define SvIV_no_inf(sv,d) \
+	((sv) = S_sv_check_infnan(aTHX_ sv,d), SvIV_nomg(sv))
+#define SvUV_no_inf(sv,d) \
+	((sv) = S_sv_check_infnan(aTHX_ sv,d), SvUV_nomg(sv))
+
+STATIC
+SV **
+S_pack_rec(pTHX_ SV *cat, tempsym_t* symptr, SV **beglist, SV **endlist )
+{
+    tempsym_t lookahead;
+    I32 items  = endlist - beglist;
+    bool found = next_symbol(symptr);
+    bool utf8 = (symptr->flags & FLAG_PARSE_UTF8) ? 1 : 0;
+    bool warn_utf8 = ckWARN(WARN_UTF8);
+    char* from;
+
+    PERL_ARGS_ASSERT_PACK_REC;
+
+    if (symptr->level == 0 && found && symptr->code == 'U') {
+	marked_upgrade(aTHX_ cat, symptr);
+	symptr->flags |= FLAG_DO_UTF8;
+	utf8 = 0;
+    }
+    symptr->strbeg = SvCUR(cat);
+
+    while (found) {
+	SV *fromstr;
+	STRLEN fromlen;
+	I32 len;
+	SV *lengthcode = NULL;
+        I32 datumtype = symptr->code;
+        howlen_t howlen = symptr->howlen;
+	char *start = SvPVX(cat);
+	char *cur   = start + SvCUR(cat);
+        bool needs_swap;
+
+#define NEXTFROM (lengthcode ? lengthcode : items > 0 ? (--items, *beglist++) : &PL_sv_no)
+#define PEEKFROM (lengthcode ? lengthcode : items > 0 ? *beglist : &PL_sv_no)
+
+        switch (howlen) {
+	  case e_star:
+	    len = strchr("@Xxu", TYPE_NO_MODIFIERS(datumtype)) ?
+		0 : items;
+	    break;
+	  default:
+	    /* e_no_len and e_number */
+	    len = symptr->length;
+	    break;
+        }
+
+	if (len) {
+	    packprops_t props = packprops[TYPE_NO_ENDIANNESS(datumtype)];
+
+	    if (props && !(props & PACK_SIZE_UNPREDICTABLE)) {
+		/* We can process this letter. */
+		STRLEN size = props & PACK_SIZE_MASK;
+		GROWING(utf8, cat, start, cur, (STRLEN) len * size);
+	    }
+        }
+
+        /* Look ahead for next symbol. Do we have code/code? */
+        lookahead = *symptr;
+        found = next_symbol(&lookahead);
+	if (symptr->flags & FLAG_SLASH) {
+	    IV count;
+	    if (!found) Perl_croak(aTHX_ "Code missing after '/' in pack");
+	    if (strchr("aAZ", lookahead.code)) {
+		if (lookahead.howlen == e_number) count = lookahead.length;
+		else {
+		    if (items > 0) {
+			count = sv_len_utf8(*beglist);
+		    }
+		    else count = 0;
+		    if (lookahead.code == 'Z') count++;
+		}
+	    } else {
+		if (lookahead.howlen == e_number && lookahead.length < items)
+		    count = lookahead.length;
+		else count = items;
+	    }
+	    lookahead.howlen = e_number;
+	    lookahead.length = count;
+	    lengthcode = sv_2mortal(newSViv(count));
+	}
+
+        needs_swap = NEEDS_SWAP(datumtype);
+
+	/* Code inside the switch must take care to properly update
+	   cat (CUR length and '\0' termination) if it updated *cur and
+	   doesn't simply leave using break */
+	switch (TYPE_NO_ENDIANNESS(datumtype)) {
+	default:
+	    Perl_croak(aTHX_ "Invalid type '%c' in pack",
+		       (int) TYPE_NO_MODIFIERS(datumtype));
+	case '%':
+	    Perl_croak(aTHX_ "'%%' may not be used in pack");
+
+	case '.' | TYPE_IS_SHRIEKING:
+	case '.':
+	    if (howlen == e_star) from = start;
+	    else if (len == 0) from = cur;
+	    else {
+		tempsym_t *group = symptr;
+
+		while (--len && group) group = group->previous;
+		from = group ? start + group->strbeg : start;
+	    }
+	    fromstr = NEXTFROM;
+	    len = SvIV_no_inf(fromstr, datumtype);
+	    goto resize;
+	case '@' | TYPE_IS_SHRIEKING:
+	case '@':
+	    from = start + symptr->strbeg;
+	  resize:
+	    if (utf8  && !(datumtype & TYPE_IS_SHRIEKING))
+		if (len >= 0) {
+		    while (len && from < cur) {
+			from += UTF8SKIP(from);
+			len--;
+		    }
+		    if (from > cur)
+			Perl_croak(aTHX_ "Malformed UTF-8 string in pack");
+		    if (len) {
+			/* Here we know from == cur */
+		      grow:
+			GROWING(0, cat, start, cur, len);
+			Zero(cur, len, char);
+			cur += len;
+		    } else if (from < cur) {
+			len = cur - from;
+			goto shrink;
+		    } else goto no_change;
+		} else {
+		    cur = from;
+		    len = -len;
+		    goto utf8_shrink;
+		}
+	    else {
+		len -= cur - from;
+		if (len > 0) goto grow;
+		if (len == 0) goto no_change;
+		len = -len;
+		goto shrink;
+	    }
+	    break;
+
+	case '(': {
+            tempsym_t savsym = *symptr;
+	    U32 group_modifiers = TYPE_MODIFIERS(datumtype & ~symptr->flags);
+	    symptr->flags |= group_modifiers;
+            symptr->patend = savsym.grpend;
+            symptr->level++;
+	    symptr->previous = &lookahead;
+	    while (len--) {
+		U32 was_utf8;
+		if (utf8) symptr->flags |=  FLAG_PARSE_UTF8;
+		else      symptr->flags &= ~FLAG_PARSE_UTF8;
+		was_utf8 = SvUTF8(cat);
+  	        symptr->patptr = savsym.grpbeg;
+		beglist = pack_rec(cat, symptr, beglist, endlist);
+		if (SvUTF8(cat) != was_utf8)
+		    /* This had better be an upgrade while in utf8==0 mode */
+		    utf8 = 1;
+
+		if (savsym.howlen == e_star && beglist == endlist)
+		    break;		/* No way to continue */
+	    }
+	    items = endlist - beglist;
+	    lookahead.flags  = symptr->flags & ~group_modifiers;
+	    goto no_change;
+	}
+	case 'X' | TYPE_IS_SHRIEKING:
+	    if (!len)			/* Avoid division by 0 */
+		len = 1;
+	    if (utf8) {
+		char *hop, *last;
+		I32 l = len;
+		hop = last = start;
+		while (hop < cur) {
+		    hop += UTF8SKIP(hop);
+		    if (--l == 0) {
+			last = hop;
+			l = len;
+		    }
+		}
+		if (last > cur)
+		    Perl_croak(aTHX_ "Malformed UTF-8 string in pack");
+		cur = last;
+		break;
+	    }
+	    len = (cur-start) % len;
+	    /* FALLTHROUGH */
+	case 'X':
+	    if (utf8) {
+		if (len < 1) goto no_change;
+	      utf8_shrink:
+		while (len > 0) {
+		    if (cur <= start)
+			Perl_croak(aTHX_ "'%c' outside of string in pack",
+				   (int) TYPE_NO_MODIFIERS(datumtype));
+		    while (--cur, UTF8_IS_CONTINUATION(*cur)) {
+			if (cur <= start)
+			    Perl_croak(aTHX_ "'%c' outside of string in pack",
+				       (int) TYPE_NO_MODIFIERS(datumtype));
+		    }
+		    len--;
+		}
+	    } else {
+	      shrink:
+		if (cur - start < len)
+		    Perl_croak(aTHX_ "'%c' outside of string in pack",
+			       (int) TYPE_NO_MODIFIERS(datumtype));
+		cur -= len;
+	    }
+	    if (cur < start+symptr->strbeg) {
+		/* Make sure group starts don't point into the void */
+		tempsym_t *group;
+		const STRLEN length = cur-start;
+		for (group = symptr;
+		     group && length < group->strbeg;
+		     group = group->previous) group->strbeg = length;
+		lookahead.strbeg = length;
+	    }
+	    break;
+	case 'x' | TYPE_IS_SHRIEKING: {
+	    I32 ai32;
+	    if (!len)			/* Avoid division by 0 */
+		len = 1;
+	    if (utf8) ai32 = utf8_length((U8 *) start, (U8 *) cur) % len;
+	    else      ai32 = (cur - start) % len;
+	    if (ai32 == 0) goto no_change;
+	    len -= ai32;
+	}
+	/* FALLTHROUGH */
+	case 'x':
+	    goto grow;
+	case 'A':
+	case 'Z':
+	case 'a': {
+	    const char *aptr;
+
+	    fromstr = NEXTFROM;
+	    aptr = SvPV_const(fromstr, fromlen);
+	    if (DO_UTF8(fromstr)) {
+                const char *end, *s;
+
+		if (!utf8 && !SvUTF8(cat)) {
+		    marked_upgrade(aTHX_ cat, symptr);
+		    lookahead.flags |= FLAG_DO_UTF8;
+		    lookahead.strbeg = symptr->strbeg;
+		    utf8 = 1;
+		    start = SvPVX(cat);
+		    cur = start + SvCUR(cat);
+		}
+		if (howlen == e_star) {
+		    if (utf8) goto string_copy;
+		    len = fromlen+1;
+		}
+		s = aptr;
+		end = aptr + fromlen;
+		fromlen = datumtype == 'Z' ? len-1 : len;
+		while ((I32) fromlen > 0 && s < end) {
+		    s += UTF8SKIP(s);
+		    fromlen--;
+		}
+		if (s > end)
+		    Perl_croak(aTHX_ "Malformed UTF-8 string in pack");
+		if (utf8) {
+		    len = fromlen;
+		    if (datumtype == 'Z') len++;
+		    fromlen = s-aptr;
+		    len += fromlen;
+
+		    goto string_copy;
+		}
+		fromlen = len - fromlen;
+		if (datumtype == 'Z') fromlen--;
+		if (howlen == e_star) {
+		    len = fromlen;
+		    if (datumtype == 'Z') len++;
+		}
+		GROWING(0, cat, start, cur, len);
+		if (!S_utf8_to_bytes(aTHX_ &aptr, end, cur, fromlen,
+				  datumtype | TYPE_IS_PACK))
+		    Perl_croak(aTHX_ "panic: predicted utf8 length not available, "
+			       "for '%c', aptr=%p end=%p cur=%p, fromlen=%"UVuf,
+			       (int)datumtype, aptr, end, cur, (UV)fromlen);
+		cur += fromlen;
+		len -= fromlen;
+	    } else if (utf8) {
+		if (howlen == e_star) {
+		    len = fromlen;
+		    if (datumtype == 'Z') len++;
+		}
+		if (len <= (I32) fromlen) {
+		    fromlen = len;
+		    if (datumtype == 'Z' && fromlen > 0) fromlen--;
+		}
+		/* assumes a byte expands to at most UTF8_EXPAND bytes on
+		   upgrade, so:
+		   expected_length <= from_len*UTF8_EXPAND + (len-from_len) */
+		GROWING(0, cat, start, cur, fromlen*(UTF8_EXPAND-1)+len);
+		len -= fromlen;
+		while (fromlen > 0) {
+		    cur = (char *) uvchr_to_utf8((U8 *) cur, * (U8 *) aptr);
+		    aptr++;
+		    fromlen--;
+		}
+	    } else {
+	      string_copy:
+		if (howlen == e_star) {
+		    len = fromlen;
+		    if (datumtype == 'Z') len++;
+		}
+		if (len <= (I32) fromlen) {
+		    fromlen = len;
+		    if (datumtype == 'Z' && fromlen > 0) fromlen--;
+		}
+		GROWING(0, cat, start, cur, len);
+		Copy(aptr, cur, fromlen, char);
+		cur += fromlen;
+		len -= fromlen;
+	    }
+	    memset(cur, datumtype == 'A' ? ' ' : '\0', len);
+	    cur += len;
+	    SvTAINT(cat);
+	    break;
+	}
+	case 'B':
+	case 'b': {
+	    const char *str, *end;
+	    I32 l, field_len;
+	    U8 bits;
+	    bool utf8_source;
+	    U32 utf8_flags;
+
+	    fromstr = NEXTFROM;
+	    str = SvPV_const(fromstr, fromlen);
+	    end = str + fromlen;
+	    if (DO_UTF8(fromstr)) {
+		utf8_source = TRUE;
+		utf8_flags  = warn_utf8 ? 0 : UTF8_ALLOW_ANY;
+	    } else {
+		utf8_source = FALSE;
+		utf8_flags  = 0; /* Unused, but keep compilers happy */
+	    }
+	    if (howlen == e_star) len = fromlen;
+	    field_len = (len+7)/8;
+	    GROWING(utf8, cat, start, cur, field_len);
+	    if (len > (I32)fromlen) len = fromlen;
+	    bits = 0;
+	    l = 0;
+	    if (datumtype == 'B')
+		while (l++ < len) {
+		    if (utf8_source) {
+			UV val = 0;
+			NEXT_UNI_VAL(val, cur, str, end, utf8_flags);
+			bits |= val & 1;
+		    } else bits |= *str++ & 1;
+		    if (l & 7) bits <<= 1;
+		    else {
+			PUSH_BYTE(utf8, cur, bits);
+			bits = 0;
+		    }
+		}
+	    else
+		/* datumtype == 'b' */
+		while (l++ < len) {
+		    if (utf8_source) {
+			UV val = 0;
+			NEXT_UNI_VAL(val, cur, str, end, utf8_flags);
+			if (val & 1) bits |= 0x80;
+		    } else if (*str++ & 1)
+			bits |= 0x80;
+		    if (l & 7) bits >>= 1;
+		    else {
+			PUSH_BYTE(utf8, cur, bits);
+			bits = 0;
+		    }
+		}
+	    l--;
+	    if (l & 7) {
+		if (datumtype == 'B')
+		    bits <<= 7 - (l & 7);
+		else
+		    bits >>= 7 - (l & 7);
+		PUSH_BYTE(utf8, cur, bits);
+		l += 7;
+	    }
+	    /* Determine how many chars are left in the requested field */
+	    l /= 8;
+	    if (howlen == e_star) field_len = 0;
+	    else field_len -= l;
+	    Zero(cur, field_len, char);
+	    cur += field_len;
+	    break;
+	}
+	case 'H':
+	case 'h': {
+	    const char *str, *end;
+	    I32 l, field_len;
+	    U8 bits;
+	    bool utf8_source;
+	    U32 utf8_flags;
+
+	    fromstr = NEXTFROM;
+	    str = SvPV_const(fromstr, fromlen);
+	    end = str + fromlen;
+	    if (DO_UTF8(fromstr)) {
+		utf8_source = TRUE;
+		utf8_flags  = warn_utf8 ? 0 : UTF8_ALLOW_ANY;
+	    } else {
+		utf8_source = FALSE;
+		utf8_flags  = 0; /* Unused, but keep compilers happy */
+	    }
+	    if (howlen == e_star) len = fromlen;
+	    field_len = (len+1)/2;
+	    GROWING(utf8, cat, start, cur, field_len);
+	    if (!utf8_source && len > (I32)fromlen) len = fromlen;
+	    bits = 0;
+	    l = 0;
+	    if (datumtype == 'H')
+		while (l++ < len) {
+		    if (utf8_source) {
+			UV val = 0;
+			NEXT_UNI_VAL(val, cur, str, end, utf8_flags);
+			if (val < 256 && isALPHA(val))
+			    bits |= (val + 9) & 0xf;
+			else
+			    bits |= val & 0xf;
+		    } else if (isALPHA(*str))
+			bits |= (*str++ + 9) & 0xf;
+		    else
+			bits |= *str++ & 0xf;
+		    if (l & 1) bits <<= 4;
+		    else {
+			PUSH_BYTE(utf8, cur, bits);
+			bits = 0;
+		    }
+		}
+	    else
+		while (l++ < len) {
+		    if (utf8_source) {
+			UV val = 0;
+			NEXT_UNI_VAL(val, cur, str, end, utf8_flags);
+			if (val < 256 && isALPHA(val))
+			    bits |= ((val + 9) & 0xf) << 4;
+			else
+			    bits |= (val & 0xf) << 4;
+		    } else if (isALPHA(*str))
+			bits |= ((*str++ + 9) & 0xf) << 4;
+		    else
+			bits |= (*str++ & 0xf) << 4;
+		    if (l & 1) bits >>= 4;
+		    else {
+			PUSH_BYTE(utf8, cur, bits);
+			bits = 0;
+		    }
+		}
+	    l--;
+	    if (l & 1) {
+		PUSH_BYTE(utf8, cur, bits);
+		l++;
+	    }
+	    /* Determine how many chars are left in the requested field */
+	    l /= 2;
+	    if (howlen == e_star) field_len = 0;
+	    else field_len -= l;
+	    Zero(cur, field_len, char);
+	    cur += field_len;
+	    break;
+	}
+	case 'c':
+	    while (len-- > 0) {
+		IV aiv;
+		fromstr = NEXTFROM;
+                aiv = SvIV_no_inf(fromstr, datumtype);
+		if ((-128 > aiv || aiv > 127))
+		    Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
+				   "Character in 'c' format wrapped in pack");
+		PUSH_BYTE(utf8, cur, (U8)(aiv & 0xff));
+	    }
+	    break;
+	case 'C':
+	    if (len == 0) {
+		utf8 = (symptr->flags & FLAG_DO_UTF8) ? 1 : 0;
+		break;
+	    }
+	    while (len-- > 0) {
+		IV aiv;
+		fromstr = NEXTFROM;
+                aiv = SvIV_no_inf(fromstr, datumtype);
+		if ((0 > aiv || aiv > 0xff))
+		    Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
+				   "Character in 'C' format wrapped in pack");
+		PUSH_BYTE(utf8, cur, (U8)(aiv & 0xff));
+	    }
+	    break;
+	case 'W': {
+	    char *end;
+	    U8 in_bytes = (U8)IN_BYTES;
+
+	    end = start+SvLEN(cat)-1;
+	    if (utf8) end -= UTF8_MAXLEN-1;
+	    while (len-- > 0) {
+		UV auv;
+		fromstr = NEXTFROM;
+		auv = SvUV_no_inf(fromstr, datumtype);
+		if (in_bytes) auv = auv % 0x100;
+		if (utf8) {
+		  W_utf8:
+		    if (cur > end) {
+			*cur = '\0';
+			SvCUR_set(cat, cur - start);
+
+			GROWING(0, cat, start, cur, len+UTF8_MAXLEN);
+			end = start+SvLEN(cat)-UTF8_MAXLEN;
+		    }
+		    cur = (char *) uvchr_to_utf8_flags((U8 *) cur,
+						       auv,
+						       warn_utf8 ?
+						       0 : UNICODE_ALLOW_ANY);
+		} else {
+		    if (auv >= 0x100) {
+			if (!SvUTF8(cat)) {
+			    *cur = '\0';
+			    SvCUR_set(cat, cur - start);
+			    marked_upgrade(aTHX_ cat, symptr);
+			    lookahead.flags |= FLAG_DO_UTF8;
+			    lookahead.strbeg = symptr->strbeg;
+			    utf8 = 1;
+			    start = SvPVX(cat);
+			    cur = start + SvCUR(cat);
+			    end = start+SvLEN(cat)-UTF8_MAXLEN;
+			    goto W_utf8;
+			}
+			Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
+				       "Character in 'W' format wrapped in pack");
+			auv &= 0xff;
+		    }
+		    if (cur >= end) {
+			*cur = '\0';
+			SvCUR_set(cat, cur - start);
+			GROWING(0, cat, start, cur, len+1);
+			end = start+SvLEN(cat)-1;
+		    }
+		    *(U8 *) cur++ = (U8)auv;
+		}
+	    }
+	    break;
+	}
+	case 'U': {
+	    char *end;
+
+	    if (len == 0) {
+		if (!(symptr->flags & FLAG_DO_UTF8)) {
+		    marked_upgrade(aTHX_ cat, symptr);
+		    lookahead.flags |= FLAG_DO_UTF8;
+		    lookahead.strbeg = symptr->strbeg;
+		}
+		utf8 = 0;
+		goto no_change;
+	    }
+
+	    end = start+SvLEN(cat);
+	    if (!utf8) end -= UTF8_MAXLEN;
+	    while (len-- > 0) {
+		UV auv;
+		fromstr = NEXTFROM;
+		auv = SvUV_no_inf(fromstr, datumtype);
+		if (utf8) {
+		    U8 buffer[UTF8_MAXLEN], *endb;
+		    endb = uvchr_to_utf8_flags(buffer, UNI_TO_NATIVE(auv),
+					       warn_utf8 ?
+					       0 : UNICODE_ALLOW_ANY);
+		    if (cur+(endb-buffer)*UTF8_EXPAND >= end) {
+			*cur = '\0';
+			SvCUR_set(cat, cur - start);
+			GROWING(0, cat, start, cur,
+				len+(endb-buffer)*UTF8_EXPAND);
+			end = start+SvLEN(cat);
+		    }
+                    cur = my_bytes_to_utf8(buffer, endb-buffer, cur, 0);
+		} else {
+		    if (cur >= end) {
+			*cur = '\0';
+			SvCUR_set(cat, cur - start);
+			GROWING(0, cat, start, cur, len+UTF8_MAXLEN);
+			end = start+SvLEN(cat)-UTF8_MAXLEN;
+		    }
+		    cur = (char *) uvchr_to_utf8_flags((U8 *) cur, UNI_TO_NATIVE(auv),
+						       warn_utf8 ?
+						       0 : UNICODE_ALLOW_ANY);
+		}
+	    }
+	    break;
+	}
+	/* Float and double added by gnb@melba.bby.oz.au  22/11/89 */
+	case 'f':
+	    while (len-- > 0) {
+		float afloat;
+		NV anv;
+		fromstr = NEXTFROM;
+		anv = SvNV(fromstr);
+# if defined(VMS) && !defined(_IEEE_FP)
+		/* IEEE fp overflow shenanigans are unavailable on VAX and optional
+		 * on Alpha; fake it if we don't have them.
+		 */
+		if (anv > FLT_MAX)
+		    afloat = FLT_MAX;
+		else if (anv < -FLT_MAX)
+		    afloat = -FLT_MAX;
+		else afloat = (float)anv;
+# else
+#if defined(NAN_COMPARE_BROKEN) && defined(Perl_isnan)
+		if(Perl_isnan(anv))
+		    afloat = (float)NV_NAN;
+		else
+#endif
+                /* a simple cast to float is undefined if outside
+                 * the range of values that can be represented */
+		afloat = (float)(anv >  FLT_MAX ?  NV_INF :
+                                 anv < -FLT_MAX ? -NV_INF : anv);
+# endif
+                PUSH_VAR(utf8, cur, afloat, needs_swap);
+	    }
+	    break;
+	case 'd':
+	    while (len-- > 0) {
+		double adouble;
+		NV anv;
+		fromstr = NEXTFROM;
+		anv = SvNV(fromstr);
+# if defined(VMS) && !defined(_IEEE_FP)
+		/* IEEE fp overflow shenanigans are unavailable on VAX and optional
+		 * on Alpha; fake it if we don't have them.
+		 */
+		if (anv > DBL_MAX)
+		    adouble = DBL_MAX;
+		else if (anv < -DBL_MAX)
+		    adouble = -DBL_MAX;
+		else adouble = (double)anv;
+# else
+		adouble = (double)anv;
+# endif
+                PUSH_VAR(utf8, cur, adouble, needs_swap);
+	    }
+	    break;
+	case 'F': {
+	    NV_bytes anv;
+	    Zero(&anv, 1, NV); /* can be long double with unused bits */
+	    while (len-- > 0) {
+		fromstr = NEXTFROM;
+#ifdef __GNUC__
+		/* to work round a gcc/x86 bug; don't use SvNV */
+		anv.nv = sv_2nv(fromstr);
+#    if defined(LONGDOUBLE_X86_80_BIT) && defined(USE_LONG_DOUBLE) \
+         && LONG_DOUBLESIZE > 10
+                /* GCC sometimes overwrites the padding in the
+                   assignment above */
+                Zero(anv.bytes+10, sizeof(anv.bytes) - 10, U8);
+#    endif
+#else
+		anv.nv = SvNV(fromstr);
+#endif
+                PUSH_BYTES(utf8, cur, anv.bytes, sizeof(anv.bytes), needs_swap);
+	    }
+	    break;
+	}
+#if defined(HAS_LONG_DOUBLE) && defined(USE_LONG_DOUBLE)
+	case 'D': {
+	    ld_bytes aldouble;
+	    /* long doubles can have unused bits, which may be nonzero */
+	    Zero(&aldouble, 1, long double);
+	    while (len-- > 0) {
+		fromstr = NEXTFROM;
+#  ifdef __GNUC__
+		/* to work round a gcc/x86 bug; don't use SvNV */
+		aldouble.ld = (long double)sv_2nv(fromstr);
+#    if defined(LONGDOUBLE_X86_80_BIT) && LONG_DOUBLESIZE > 10
+                /* GCC sometimes overwrites the padding in the
+                   assignment above */
+                Zero(aldouble.bytes+10, sizeof(aldouble.bytes) - 10, U8);
+#    endif
+#  else
+		aldouble.ld = (long double)SvNV(fromstr);
+#  endif
+                PUSH_BYTES(utf8, cur, aldouble.bytes, sizeof(aldouble.bytes),
+                           needs_swap);
+	    }
+	    break;
+	}
+#endif
+	case 'n' | TYPE_IS_SHRIEKING:
+	case 'n':
+	    while (len-- > 0) {
+		I16 ai16;
+		fromstr = NEXTFROM;
+		ai16 = (I16)SvIV_no_inf(fromstr, datumtype);
+		ai16 = PerlSock_htons(ai16);
+                PUSH16(utf8, cur, &ai16, FALSE);
+	    }
+	    break;
+	case 'v' | TYPE_IS_SHRIEKING:
+	case 'v':
+	    while (len-- > 0) {
+		I16 ai16;
+		fromstr = NEXTFROM;
+		ai16 = (I16)SvIV_no_inf(fromstr, datumtype);
+		ai16 = htovs(ai16);
+                PUSH16(utf8, cur, &ai16, FALSE);
+	    }
+	    break;
+        case 'S' | TYPE_IS_SHRIEKING:
+#if SHORTSIZE != SIZE16
+	    while (len-- > 0) {
+		unsigned short aushort;
+		fromstr = NEXTFROM;
+		aushort = SvUV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, aushort, needs_swap);
+	    }
+            break;
+#else
+            /* FALLTHROUGH */
+#endif
+	case 'S':
+	    while (len-- > 0) {
+		U16 au16;
+		fromstr = NEXTFROM;
+		au16 = (U16)SvUV_no_inf(fromstr, datumtype);
+                PUSH16(utf8, cur, &au16, needs_swap);
+	    }
+	    break;
+	case 's' | TYPE_IS_SHRIEKING:
+#if SHORTSIZE != SIZE16
+	    while (len-- > 0) {
+		short ashort;
+		fromstr = NEXTFROM;
+		ashort = SvIV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, ashort, needs_swap);
+	    }
+            break;
+#else
+            /* FALLTHROUGH */
+#endif
+	case 's':
+	    while (len-- > 0) {
+		I16 ai16;
+		fromstr = NEXTFROM;
+		ai16 = (I16)SvIV_no_inf(fromstr, datumtype);
+                PUSH16(utf8, cur, &ai16, needs_swap);
+	    }
+	    break;
+	case 'I':
+	case 'I' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		unsigned int auint;
+		fromstr = NEXTFROM;
+		auint = SvUV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, auint, needs_swap);
+	    }
+	    break;
+	case 'j':
+	    while (len-- > 0) {
+		IV aiv;
+		fromstr = NEXTFROM;
+		aiv = SvIV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, aiv, needs_swap);
+	    }
+	    break;
+	case 'J':
+	    while (len-- > 0) {
+		UV auv;
+		fromstr = NEXTFROM;
+		auv = SvUV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, auv, needs_swap);
+	    }
+	    break;
+	case 'w':
+            while (len-- > 0) {
+		NV anv;
+		fromstr = NEXTFROM;
+		S_sv_check_infnan(aTHX_ fromstr, datumtype);
+		anv = SvNV_nomg(fromstr);
+
+		if (anv < 0) {
+		    *cur = '\0';
+		    SvCUR_set(cat, cur - start);
+		    Perl_croak(aTHX_ "Cannot compress negative numbers in pack");
+		}
+
+                /* 0xFFFFFFFFFFFFFFFF may cast to 18446744073709551616.0,
+                   which is == UV_MAX_P1. IOK is fine (instead of UV_only), as
+                   any negative IVs will have already been got by the croak()
+                   above. IOK is untrue for fractions, so we test them
+                   against UV_MAX_P1.  */
+		if (SvIOK(fromstr) || anv < UV_MAX_P1) {
+		    char   buf[(sizeof(UV)*CHAR_BIT)/7+1];
+		    char  *in = buf + sizeof(buf);
+		    UV     auv = SvUV_nomg(fromstr);
+
+		    do {
+			*--in = (char)((auv & 0x7f) | 0x80);
+			auv >>= 7;
+		    } while (auv);
+		    buf[sizeof(buf) - 1] &= 0x7f; /* clear continue bit */
+		    PUSH_GROWING_BYTES(utf8, cat, start, cur,
+				       in, (buf + sizeof(buf)) - in);
+		} else if (SvPOKp(fromstr))
+		    goto w_string;
+		else if (SvNOKp(fromstr)) {
+		    /* 10**NV_MAX_10_EXP is the largest power of 10
+		       so 10**(NV_MAX_10_EXP+1) is definitely unrepresentable
+		       given 10**(NV_MAX_10_EXP+1) == 128 ** x solve for x:
+		       x = (NV_MAX_10_EXP+1) * log (10) / log (128)
+		       And with that many bytes only Inf can overflow.
+		       Some C compilers are strict about integral constant
+		       expressions so we conservatively divide by a slightly
+		       smaller integer instead of multiplying by the exact
+		       floating-point value.
+		    */
+#ifdef NV_MAX_10_EXP
+		    /* char   buf[1 + (int)((NV_MAX_10_EXP + 1) * 0.47456)]; -- invalid C */
+		    char   buf[1 + (int)((NV_MAX_10_EXP + 1) / 2)]; /* valid C */
+#else
+		    /* char   buf[1 + (int)((308 + 1) * 0.47456)]; -- invalid C */
+		    char   buf[1 + (int)((308 + 1) / 2)]; /* valid C */
+#endif
+		    char  *in = buf + sizeof(buf);
+
+		    anv = Perl_floor(anv);
+		    do {
+			const NV next = Perl_floor(anv / 128);
+			if (in <= buf)  /* this cannot happen ;-) */
+			    Perl_croak(aTHX_ "Cannot compress integer in pack");
+			*--in = (unsigned char)(anv - (next * 128)) | 0x80;
+			anv = next;
+		    } while (anv > 0);
+		    buf[sizeof(buf) - 1] &= 0x7f; /* clear continue bit */
+		    PUSH_GROWING_BYTES(utf8, cat, start, cur,
+				       in, (buf + sizeof(buf)) - in);
+		} else {
+		    const char     *from;
+		    char           *result, *in;
+		    SV             *norm;
+		    STRLEN          len;
+		    bool            done;
+
+		  w_string:
+		    /* Copy string and check for compliance */
+		    from = SvPV_nomg_const(fromstr, len);
+		    if ((norm = is_an_int(from, len)) == NULL)
+			Perl_croak(aTHX_ "Can only compress unsigned integers in pack");
+
+		    Newx(result, len, char);
+		    in = result + len;
+		    done = FALSE;
+		    while (!done) *--in = div128(norm, &done) | 0x80;
+		    result[len - 1] &= 0x7F; /* clear continue bit */
+		    PUSH_GROWING_BYTES(utf8, cat, start, cur,
+				       in, (result + len) - in);
+		    Safefree(result);
+		    SvREFCNT_dec(norm);	/* free norm */
+		}
+	    }
+            break;
+	case 'i':
+	case 'i' | TYPE_IS_SHRIEKING:
+	    while (len-- > 0) {
+		int aint;
+		fromstr = NEXTFROM;
+		aint = SvIV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, aint, needs_swap);
+	    }
+	    break;
+	case 'N' | TYPE_IS_SHRIEKING:
+	case 'N':
+	    while (len-- > 0) {
+		U32 au32;
+		fromstr = NEXTFROM;
+		au32 = SvUV_no_inf(fromstr, datumtype);
+		au32 = PerlSock_htonl(au32);
+                PUSH32(utf8, cur, &au32, FALSE);
+	    }
+	    break;
+	case 'V' | TYPE_IS_SHRIEKING:
+	case 'V':
+	    while (len-- > 0) {
+		U32 au32;
+		fromstr = NEXTFROM;
+		au32 = SvUV_no_inf(fromstr, datumtype);
+		au32 = htovl(au32);
+                PUSH32(utf8, cur, &au32, FALSE);
+	    }
+	    break;
+	case 'L' | TYPE_IS_SHRIEKING:
+#if LONGSIZE != SIZE32
+	    while (len-- > 0) {
+		unsigned long aulong;
+		fromstr = NEXTFROM;
+		aulong = SvUV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, aulong, needs_swap);
+	    }
+	    break;
+#else
+            /* Fall though! */
+#endif
+	case 'L':
+	    while (len-- > 0) {
+		U32 au32;
+		fromstr = NEXTFROM;
+		au32 = SvUV_no_inf(fromstr, datumtype);
+                PUSH32(utf8, cur, &au32, needs_swap);
+	    }
+	    break;
+	case 'l' | TYPE_IS_SHRIEKING:
+#if LONGSIZE != SIZE32
+	    while (len-- > 0) {
+		long along;
+		fromstr = NEXTFROM;
+		along = SvIV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, along, needs_swap);
+	    }
+	    break;
+#else
+            /* Fall though! */
+#endif
+	case 'l':
+            while (len-- > 0) {
+		I32 ai32;
+		fromstr = NEXTFROM;
+		ai32 = SvIV_no_inf(fromstr, datumtype);
+                PUSH32(utf8, cur, &ai32, needs_swap);
+	    }
+	    break;
+#if defined(HAS_QUAD) && IVSIZE >= 8
+	case 'Q':
+	    while (len-- > 0) {
+		Uquad_t auquad;
+		fromstr = NEXTFROM;
+		auquad = (Uquad_t) SvUV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, auquad, needs_swap);
+	    }
+	    break;
+	case 'q':
+	    while (len-- > 0) {
+		Quad_t aquad;
+		fromstr = NEXTFROM;
+		aquad = (Quad_t)SvIV_no_inf(fromstr, datumtype);
+                PUSH_VAR(utf8, cur, aquad, needs_swap);
+	    }
+	    break;
+#endif
+	case 'P':
+	    len = 1;		/* assume SV is correct length */
+	    GROWING(utf8, cat, start, cur, sizeof(char *));
+	    /* FALLTHROUGH */
+	case 'p':
+	    while (len-- > 0) {
+		const char *aptr;
+
+		fromstr = NEXTFROM;
+		SvGETMAGIC(fromstr);
+		if (!SvOK(fromstr)) aptr = NULL;
+		else {
+		    /* XXX better yet, could spirit away the string to
+		     * a safe spot and hang on to it until the result
+		     * of pack() (and all copies of the result) are
+		     * gone.
+		     */
+		    if ((SvTEMP(fromstr) || (SvPADTMP(fromstr) &&
+			     !SvREADONLY(fromstr)))) {
+			Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
+				       "Attempt to pack pointer to temporary value");
+		    }
+		    if (SvPOK(fromstr) || SvNIOK(fromstr))
+			aptr = SvPV_nomg_const_nolen(fromstr);
+		    else
+			aptr = SvPV_force_flags_nolen(fromstr, 0);
+		}
+                PUSH_VAR(utf8, cur, aptr, needs_swap);
+	    }
+	    break;
+	case 'u': {
+	    const char *aptr, *aend;
+	    bool from_utf8;
+
+	    fromstr = NEXTFROM;
+	    if (len <= 2) len = 45;
+	    else len = len / 3 * 3;
+	    if (len >= 64) {
+		Perl_ck_warner(aTHX_ packWARN(WARN_PACK),
+			       "Field too wide in 'u' format in pack");
+		len = 63;
+	    }
+	    aptr = SvPV_const(fromstr, fromlen);
+	    from_utf8 = DO_UTF8(fromstr);
+	    if (from_utf8) {
+		aend = aptr + fromlen;
+		fromlen = sv_len_utf8_nomg(fromstr);
+	    } else aend = NULL; /* Unused, but keep compilers happy */
+	    GROWING(utf8, cat, start, cur, (fromlen+2) / 3 * 4 + (fromlen+len-1)/len * 2);
+	    while (fromlen > 0) {
+		U8 *end;
+		I32 todo;
+		U8 hunk[1+63/3*4+1];
+
+		if ((I32)fromlen > len)
+		    todo = len;
+		else
+		    todo = fromlen;
+		if (from_utf8) {
+		    char buffer[64];
+		    if (!S_utf8_to_bytes(aTHX_ &aptr, aend, buffer, todo,
+				      'u' | TYPE_IS_PACK)) {
+			*cur = '\0';
+			SvCUR_set(cat, cur - start);
+			Perl_croak(aTHX_ "panic: string is shorter than advertised, "
+				   "aptr=%p, aend=%p, buffer=%p, todo=%ld",
+				   aptr, aend, buffer, (long) todo);
+		    }
+		    end = doencodes(hunk, (const U8 *)buffer, todo);
+		} else {
+		    end = doencodes(hunk, (const U8 *)aptr, todo);
+		    aptr += todo;
+		}
+		PUSH_BYTES(utf8, cur, hunk, end-hunk, 0);
+		fromlen -= todo;
+	    }
+	    break;
+	}
+	}
+	*cur = '\0';
+	SvCUR_set(cat, cur - start);
+      no_change:
+	*symptr = lookahead;
+    }
+    return beglist;
+}
+#undef NEXTFROM
+
+
+PP(pp_pack)
+{
+    dSP; dMARK; dORIGMARK; dTARGET;
+    SV *cat = TARG;
+    STRLEN fromlen;
+    SV *pat_sv = *++MARK;
+    const char *pat = SvPV_const(pat_sv, fromlen);
+    const char *patend = pat + fromlen;
+
+    MARK++;
+    sv_setpvs(cat, "");
+    SvUTF8_off(cat);
+
+    packlist(cat, pat, patend, MARK, SP + 1);
+
+    SvSETMAGIC(cat);
+    SP = ORIGMARK;
+    PUSHs(cat);
+    RETURN;
+}
+
+/*
+ * ex: set ts=8 sts=4 sw=4 et:
+ */