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| 1 | +/* LZSS encoder-decoder (Haruhiko Okumura; public domain) */ |
| 2 | + |
| 3 | +#include <stdio.h> |
| 4 | +#include <stdlib.h> |
| 5 | + |
| 6 | +#define EI 11 /* typically 10..13 */ |
| 7 | +#define EJ 4 /* typically 4..5 */ |
| 8 | +#define P 1 /* If match length <= P then output one character */ |
| 9 | +#define N (1 << EI) /* buffer size */ |
| 10 | +#define F ((1 << EJ) + 1) /* lookahead buffer size */ |
| 11 | + |
| 12 | +int bit_buffer = 0, bit_mask = 128; |
| 13 | +unsigned long codecount = 0, textcount = 0; |
| 14 | +unsigned char buffer[N * 2]; |
| 15 | +FILE *infile, *outfile; |
| 16 | + |
| 17 | +void error(void) |
| 18 | +{ |
| 19 | + printf("Output error\n"); exit(1); |
| 20 | +} |
| 21 | + |
| 22 | +void putbit1(void) |
| 23 | +{ |
| 24 | + bit_buffer |= bit_mask; |
| 25 | + if ((bit_mask >>= 1) == 0) { |
| 26 | + if (fputc(bit_buffer, outfile) == EOF) error(); |
| 27 | + bit_buffer = 0; bit_mask = 128; codecount++; |
| 28 | + } |
| 29 | +} |
| 30 | + |
| 31 | +void putbit0(void) |
| 32 | +{ |
| 33 | + if ((bit_mask >>= 1) == 0) { |
| 34 | + if (fputc(bit_buffer, outfile) == EOF) error(); |
| 35 | + bit_buffer = 0; bit_mask = 128; codecount++; |
| 36 | + } |
| 37 | +} |
| 38 | + |
| 39 | +void flush_bit_buffer(void) |
| 40 | +{ |
| 41 | + if (bit_mask != 128) { |
| 42 | + if (fputc(bit_buffer, outfile) == EOF) error(); |
| 43 | + codecount++; |
| 44 | + } |
| 45 | +} |
| 46 | + |
| 47 | +void output1(int c) |
| 48 | +{ |
| 49 | + int mask; |
| 50 | + |
| 51 | + putbit1(); |
| 52 | + mask = 256; |
| 53 | + while (mask >>= 1) { |
| 54 | + if (c & mask) putbit1(); |
| 55 | + else putbit0(); |
| 56 | + } |
| 57 | +} |
| 58 | + |
| 59 | +void output2(int x, int y) |
| 60 | +{ |
| 61 | + int mask; |
| 62 | + |
| 63 | + putbit0(); |
| 64 | + mask = N; |
| 65 | + while (mask >>= 1) { |
| 66 | + if (x & mask) putbit1(); |
| 67 | + else putbit0(); |
| 68 | + } |
| 69 | + mask = (1 << EJ); |
| 70 | + while (mask >>= 1) { |
| 71 | + if (y & mask) putbit1(); |
| 72 | + else putbit0(); |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +void encode(void) |
| 77 | +{ |
| 78 | + int i, j, f1, x, y, r, s, bufferend, c; |
| 79 | + |
| 80 | + for (i = 0; i < N - F; i++) buffer[i] = ' '; |
| 81 | + for (i = N - F; i < N * 2; i++) { |
| 82 | + if ((c = fgetc(infile)) == EOF) break; |
| 83 | + buffer[i] = c; textcount++; |
| 84 | + } |
| 85 | + bufferend = i; r = N - F; s = 0; |
| 86 | + while (r < bufferend) { |
| 87 | + f1 = (F <= bufferend - r) ? F : bufferend - r; |
| 88 | + x = 0; y = 1; c = buffer[r]; |
| 89 | + for (i = r - 1; i >= s; i--) |
| 90 | + if (buffer[i] == c) { |
| 91 | + for (j = 1; j < f1; j++) |
| 92 | + if (buffer[i + j] != buffer[r + j]) break; |
| 93 | + if (j > y) { |
| 94 | + x = i; y = j; |
| 95 | + } |
| 96 | + } |
| 97 | + if (y <= P) { y = 1; output1(c); } |
| 98 | + else output2(x & (N - 1), y - 2); |
| 99 | + r += y; s += y; |
| 100 | + if (r >= N * 2 - F) { |
| 101 | + for (i = 0; i < N; i++) buffer[i] = buffer[i + N]; |
| 102 | + bufferend -= N; r -= N; s -= N; |
| 103 | + while (bufferend < N * 2) { |
| 104 | + if ((c = fgetc(infile)) == EOF) break; |
| 105 | + buffer[bufferend++] = c; textcount++; |
| 106 | + } |
| 107 | + } |
| 108 | + } |
| 109 | + flush_bit_buffer(); |
| 110 | +// printf("text: %ld bytes\n", textcount); |
| 111 | +// printf("code: %ld bytes (%ld%%)\n", |
| 112 | +// codecount, (codecount * 100) / textcount); |
| 113 | +} |
| 114 | + |
| 115 | +int getbit(int n) /* get n bits */ |
| 116 | +{ |
| 117 | + int i, x; |
| 118 | + static int buf, mask = 0; |
| 119 | + |
| 120 | + x = 0; |
| 121 | + for (i = 0; i < n; i++) { |
| 122 | + if (mask == 0) { |
| 123 | + if ((buf = fgetc(infile)) == EOF) return EOF; |
| 124 | + mask = 128; |
| 125 | + } |
| 126 | + x <<= 1; |
| 127 | + if (buf & mask) x++; |
| 128 | + mask >>= 1; |
| 129 | + } |
| 130 | + return x; |
| 131 | +} |
| 132 | + |
| 133 | +void decode(void) |
| 134 | +{ |
| 135 | + int i, j, k, r, c; |
| 136 | + |
| 137 | + for (i = 0; i < N - F; i++) buffer[i] = ' '; |
| 138 | + r = N - F; |
| 139 | + while ((c = getbit(1)) != EOF) { |
| 140 | + if (c) { |
| 141 | + if ((c = getbit(8)) == EOF) break; |
| 142 | + fputc(c, outfile); |
| 143 | + buffer[r++] = c; r &= (N - 1); |
| 144 | + } else { |
| 145 | + if ((i = getbit(EI)) == EOF) break; |
| 146 | + if ((j = getbit(EJ)) == EOF) break; |
| 147 | + for (k = 0; k <= j + 1; k++) { |
| 148 | + c = buffer[(i + k) & (N - 1)]; |
| 149 | + fputc(c, outfile); |
| 150 | + buffer[r++] = c; r &= (N - 1); |
| 151 | + } |
| 152 | + } |
| 153 | + } |
| 154 | +} |
| 155 | + |
| 156 | +int encode_file(char const * in, char const * out) |
| 157 | +{ |
| 158 | + // reset counters |
| 159 | + bit_buffer = 0, bit_mask = 128; |
| 160 | + codecount = 0, textcount = 0; |
| 161 | + |
| 162 | + infile = fopen(in, "rb"); |
| 163 | + if (infile == NULL) return 0; |
| 164 | + |
| 165 | + outfile = fopen(out, "wb"); |
| 166 | + if (outfile == NULL) return 0; |
| 167 | + |
| 168 | + encode(); |
| 169 | + |
| 170 | + fclose(infile); |
| 171 | + fclose(outfile); |
| 172 | + |
| 173 | + return 0; |
| 174 | +} |
| 175 | + |
| 176 | +int decode_file(char const * in, char const * out) |
| 177 | +{ |
| 178 | + // reset counters |
| 179 | + bit_buffer = 0, bit_mask = 128; |
| 180 | + codecount = 0, textcount = 0; |
| 181 | + |
| 182 | + infile = fopen(in, "rb"); |
| 183 | + if (infile == NULL) return 0; |
| 184 | + |
| 185 | + outfile = fopen(out, "wb"); |
| 186 | + if (outfile == NULL) return 0; |
| 187 | + |
| 188 | + decode(); |
| 189 | + |
| 190 | + fclose(infile); |
| 191 | + fclose(outfile); |
| 192 | + |
| 193 | + return 0; |
| 194 | +} |
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