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996
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1 #include <stdio.h>
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2 #include <stdlib.h>
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3
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4 unsigned char prog[1048576];
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5 unsigned char swtch[256];
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6
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7 int main(int argc, char **argv)
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8 {
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9 int pc = 0, max;
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10 FILE *in;
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11 if (argc<2) {
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12 fprintf(stderr, "Usage: %s program\n", argv[0]);
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13 exit(1);
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14 }
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15 in = fopen(argv[1], "r");
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16 if (!in) {
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17 fprintf(stderr, "Could not open '%s'.", argv[1]);
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18 exit(1);
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19 }
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20 max = fread(prog, 1, sizeof(prog), in);
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21 fclose(in);
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22 if (max == sizeof(prog)) {
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23 fprintf(stderr, "Warning: only the first %d bytes of the program "
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24 "were read.", sizeof(prog));
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25 }
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26 while (pc<max) {
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27 if (pc<max-1 && prog[pc] == prog[pc+1]) {
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28 if (pc<max-3 && prog[pc] == prog[pc+2] && prog[pc] == prog[pc+3]) {
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29 int i, v=0;
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30 if (pc>max-20) {
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31 fprintf(stderr, "incomplete instruction at end\n");
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32 exit(1);
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33 }
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34 for (i=0; i<16; i++) {
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35 v <<= 1;
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36 v += swtch[prog[pc+4+i]];
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37 }
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38 if (v) {
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39 /* output */
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40 putchar(v);
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41 } else {
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42 /* input */
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43 v = getchar();
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44 for (i=16; i--; ) {
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45 swtch[prog[pc+4+i]] = v&1;
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46 v >>= 1;
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47 }
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48 }
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49 pc += 20;
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50 } else {
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51 /* NAND */
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52 if (pc>max-5) {
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53 fprintf(stderr, "incomplete instruction at end\n");
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54 exit(1);
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55 }
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56 swtch[prog[pc]] = (swtch[prog[pc+2]] & swtch[prog[pc+3]])^1;
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57 if (!swtch[prog[pc]]) {
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58 /* JUMP */
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59 int nxt = pc+5;
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60 int prv = pc-1;
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61 for ( ; ; nxt++, prv--) {
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62 if (nxt < max && prog[pc+4] == prog[nxt]) {
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63 pc = nxt+1;
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64 break;
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65 }
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66 if (prv >= 0 && prog[pc+4] == prog[prv]) {
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67 pc = prv+1;
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68 break;
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69 }
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70 if (nxt >= max && prv < 0) {
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71 exit(0);
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72 }
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73 }
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74 } else {
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75 pc += 5;
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76 }
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77 }
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78 } else {
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79 /* SWITCH */
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80 swtch[prog[pc]] ^= 1;
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81 pc++;
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82 }
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83 }
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84 return 0;
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85 }
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