| |
| |
|
|
| #include <stdio.h> |
|
|
| #define BUFFER_SIZE 65536 |
|
|
| #define LMIN 4 |
| #define LMAX 32767 |
|
|
| int main(int argc, char **argv) { |
| if (argc != 3) { |
| fprintf(stderr, "Usage: compress [input file] [output file]\n"); |
| return 1; |
| } |
| |
| FILE *infile = fopen(argv[1], "rb"); |
| if (!infile) { |
| fprintf(stderr, "Could not open input file for reading.\n"); |
| return 2; |
| } |
| |
| unsigned char buf[BUFFER_SIZE] = { 0 }; |
| int fsize = fread(buf, 1, BUFFER_SIZE, infile); |
| |
| if (fsize >= BUFFER_SIZE) { |
| fprintf(stderr, "The input file is too large for compressing!\n"); |
| return 3; |
| } else if (fsize <= 0) { |
| fprintf(stderr, "The input file is empty.\n"); |
| return 3; |
| } |
| |
| fclose(infile); |
| |
| FILE *outfile = fopen(argv[2], "wb"); |
| if (!outfile) { |
| fprintf(stderr, "Could not open output file for writing.\n"); |
| return 2; |
| } |
| |
| unsigned char bytes[BUFFER_SIZE] = { 0 }; |
| int bi = 0; |
| |
| int pos = 0; |
| while (pos < fsize) { |
| unsigned short l = 0, ml = 0; |
| int p = 0, mp = 0; |
| |
| for (; p < pos; p++) { |
| if (buf[p] == buf[pos+l] && l < LMAX) { |
| l++; |
| } else { |
| if (l >= ml && (pos - p + l) < 32768) { |
| ml = l; |
| mp = p; |
| } |
| |
| p -= l; |
| l = 0; |
| } |
| } |
|
|
| if (l >= ml && (pos - p + l) < 32768) { |
| ml = l; |
| mp = p; |
| } |
|
|
| if (ml >= LMIN) { |
| int bs = 0; |
| while (bi > 0) { |
| int bx = bi; |
| if (bx > 128) bx = 128; |
|
|
| unsigned char b = (1 << 7) | (bx-1); |
|
|
| fwrite(&b, 1, 1, outfile); |
| fwrite(bytes + bs, 1, bx, outfile); |
|
|
| bi -= bx; |
| bs += bx; |
| } |
| |
| unsigned short mp2 = (pos - mp + ml); |
| |
| if (ml < 64) { |
| char ml2 = ml; |
| fwrite(&ml2, 1, 1, outfile); |
| } else { |
| unsigned short ml2 = 0x4000 | ml; |
| ml2 = (ml2 >> 8) | (ml2 << 8); |
| fwrite(&ml2, 2, 1, outfile); |
| } |
| |
| fwrite(&mp2, 2, 1, outfile); |
| |
| pos += ml; |
| } else { |
| bytes[bi++] = buf[pos++]; |
| } |
| |
| printf("Position: %d/%d\n", pos, fsize); |
| } |
|
|
| int bs = 0; |
| while (bi > 0) { |
| int bx = bi; |
| if (bx > 128) bx = 128; |
|
|
| unsigned char b = (1 << 7) | (bx - 1); |
|
|
| fwrite(&b, 1, 1, outfile); |
| fwrite(bytes + bs, 1, bx, outfile); |
|
|
| bi -= bx; |
| bs += bx; |
| } |
| |
| fclose(outfile); |
| |
| return 0; |
| } |
|
|
