413 lines
10 KiB
C
413 lines
10 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#define circ(buffer, offset) ((buffer)[(offset) % sizeof(buffer)])
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const int lookup_size = 2;
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const int thresh_n = 3;
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const int max_n = 18; // Four bits of lookup
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/**************************************************************
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LZSS.C -- A Data Compression Program
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***************************************************************
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4/6/1989 Haruhiko Okumura
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Use, distribute, and modify this program freely.
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Please send me your improved versions.
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PC-VAN SCIENCE
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NIFTY-Serve PAF01022
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CompuServe 74050,1022
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**************************************************************/
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#define N 4096 /* size of ring buffer - must be power of 2 */
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#define F 18 /* upper limit for match_length */
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#define THRESHOLD 2 /* encode string into position and length
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if match_length is greater than this */
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#define NIL N /* index for root of binary search trees */
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struct encode_state {
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/*
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* left & right children & parent. These constitute binary search trees.
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*/
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int lchild[N + 1], rchild[N + 257], parent[N + 1];
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/* ring buffer of size N, with extra F-1 bytes to aid string comparison */
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uint8_t text_buf[N + F - 1];
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/*
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* match_length of longest match.
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* These are set by the insert_node() procedure.
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*/
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int match_position, match_length;
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};
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int
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decompress_lzss(uint8_t *dst, uint8_t *src, uint32_t srclen)
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{
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/* ring buffer of size N, with extra F-1 bytes to aid string comparison */
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uint8_t text_buf[N + F - 1];
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uint8_t *dststart = dst;
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uint8_t *srcend = src + srclen;
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int i, j, k, r, c;
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unsigned int flags;
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dst = dststart;
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srcend = src + srclen;
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for (i = 0; i < N - F; i++)
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text_buf[i] = ' ';
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r = N - F;
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flags = 0;
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for ( ; ; ) {
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if (((flags >>= 1) & 0x100) == 0) {
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if (src < srcend) c = *src++; else break;
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flags = c | 0xFF00; /* uses higher byte cleverly */
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} /* to count eight */
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if (flags & 1) {
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if (src < srcend) c = *src++; else break;
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*dst++ = c;
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text_buf[r++] = c;
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r &= (N - 1);
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} else {
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if (src < srcend) i = *src++; else break;
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if (src < srcend) j = *src++; else break;
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i |= ((j & 0xF0) << 4);
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j = (j & 0x0F) + THRESHOLD;
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for (k = 0; k <= j; k++) {
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c = text_buf[(i + k) & (N - 1)];
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*dst++ = c;
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text_buf[r++] = c;
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r &= (N - 1);
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}
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}
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}
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return dst - dststart;
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}
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/*
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* initialize state, mostly the trees
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*
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* For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
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* children of node i. These nodes need not be initialized. Also, parent[i]
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* is the parent of node i. These are initialized to NIL (= N), which stands
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* for 'not used.' For i = 0 to 255, rchild[N + i + 1] is the root of the
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* tree for strings that begin with character i. These are initialized to NIL.
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* Note there are 256 trees. */
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static void init_state(struct encode_state *sp)
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{
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int i;
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memset(sp, 0, sizeof(*sp));
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for (i = 0; i < N - F; i++)
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sp->text_buf[i] = ' ';
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for (i = N + 1; i <= N + 256; i++)
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sp->rchild[i] = NIL;
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for (i = 0; i < N; i++)
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sp->parent[i] = NIL;
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}
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/*
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* Inserts string of length F, text_buf[r..r+F-1], into one of the trees
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* (text_buf[r]'th tree) and returns the longest-match position and length
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* via the global variables match_position and match_length.
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* If match_length = F, then removes the old node in favor of the new one,
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* because the old one will be deleted sooner. Note r plays double role,
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* as tree node and position in buffer.
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*/
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static void insert_node(struct encode_state *sp, int r)
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{
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int i, p, cmp;
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uint8_t *key;
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cmp = 1;
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key = &sp->text_buf[r];
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p = N + 1 + key[0];
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sp->rchild[r] = sp->lchild[r] = NIL;
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sp->match_length = 0;
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for ( ; ; ) {
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if (cmp >= 0) {
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if (sp->rchild[p] != NIL)
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p = sp->rchild[p];
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else {
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sp->rchild[p] = r;
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sp->parent[r] = p;
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return;
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}
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} else {
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if (sp->lchild[p] != NIL)
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p = sp->lchild[p];
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else {
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sp->lchild[p] = r;
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sp->parent[r] = p;
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return;
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}
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}
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for (i = 1; i < F; i++) {
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if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
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break;
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}
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if (i > sp->match_length) {
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sp->match_position = p;
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if ((sp->match_length = i) >= F)
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break;
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}
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}
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sp->parent[r] = sp->parent[p];
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sp->lchild[r] = sp->lchild[p];
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sp->rchild[r] = sp->rchild[p];
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sp->parent[sp->lchild[p]] = r;
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sp->parent[sp->rchild[p]] = r;
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if (sp->rchild[sp->parent[p]] == p)
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sp->rchild[sp->parent[p]] = r;
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else
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sp->lchild[sp->parent[p]] = r;
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sp->parent[p] = NIL; /* remove p */
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}
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/* deletes node p from tree */
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static void delete_node(struct encode_state *sp, int p)
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{
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int q;
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if (sp->parent[p] == NIL)
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return; /* not in tree */
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if (sp->rchild[p] == NIL)
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q = sp->lchild[p];
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else if (sp->lchild[p] == NIL)
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q = sp->rchild[p];
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else {
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q = sp->lchild[p];
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if (sp->rchild[q] != NIL) {
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do {
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q = sp->rchild[q];
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} while (sp->rchild[q] != NIL);
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sp->rchild[sp->parent[q]] = sp->lchild[q];
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sp->parent[sp->lchild[q]] = sp->parent[q];
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sp->lchild[q] = sp->lchild[p];
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sp->parent[sp->lchild[p]] = q;
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}
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sp->rchild[q] = sp->rchild[p];
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sp->parent[sp->rchild[p]] = q;
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}
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sp->parent[q] = sp->parent[p];
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if (sp->rchild[sp->parent[p]] == p)
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sp->rchild[sp->parent[p]] = q;
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else
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sp->lchild[sp->parent[p]] = q;
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sp->parent[p] = NIL;
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}
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uint8_t *
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compress_lzss(uint8_t *dst, uint32_t dstlen, uint8_t *src, uint32_t srcLen)
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{
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/* Encoding state, mostly tree but some current match stuff */
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struct encode_state *sp;
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int i, c, len, r, s, last_match_length, code_buf_ptr;
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uint8_t code_buf[17], mask;
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uint8_t *srcend = src + srcLen;
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uint8_t *dstend = dst + dstlen;
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/* initialize trees */
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sp = (struct encode_state *) malloc(sizeof(*sp));
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init_state(sp);
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/*
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* code_buf[1..16] saves eight units of code, and code_buf[0] works
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* as eight flags, "1" representing that the unit is an unencoded
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* letter (1 byte), "" a position-and-length pair (2 bytes).
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* Thus, eight units require at most 16 bytes of code.
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*/
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code_buf[0] = 0;
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code_buf_ptr = mask = 1;
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/* Clear the buffer with any character that will appear often. */
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s = 0; r = N - F;
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/* Read F bytes into the last F bytes of the buffer */
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for (len = 0; len < F && src < srcend; len++)
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sp->text_buf[r + len] = *src++;
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if (!len) {
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free(sp);
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return (void *) 0; /* text of size zero */
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}
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/*
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* Insert the F strings, each of which begins with one or more
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* 'space' characters. Note the order in which these strings are
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* inserted. This way, degenerate trees will be less likely to occur.
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*/
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for (i = 1; i <= F; i++)
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insert_node(sp, r - i);
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/*
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* Finally, insert the whole string just read.
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* The global variables match_length and match_position are set.
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*/
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insert_node(sp, r);
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do {
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/* match_length may be spuriously long near the end of text. */
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if (sp->match_length > len)
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sp->match_length = len;
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if (sp->match_length <= THRESHOLD) {
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sp->match_length = 1; /* Not long enough match. Send one byte. */
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code_buf[0] |= mask; /* 'send one byte' flag */
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code_buf[code_buf_ptr++] = sp->text_buf[r]; /* Send uncoded. */
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} else {
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/* Send position and length pair. Note match_length > THRESHOLD. */
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code_buf[code_buf_ptr++] = (uint8_t) sp->match_position;
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code_buf[code_buf_ptr++] = (uint8_t)
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( ((sp->match_position >> 4) & 0xF0)
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| (sp->match_length - (THRESHOLD + 1)) );
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}
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if ((mask <<= 1) == 0) { /* Shift mask left one bit. */
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/* Send at most 8 units of code together */
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for (i = 0; i < code_buf_ptr; i++)
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if (dst < dstend)
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*dst++ = code_buf[i];
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else {
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free(sp);
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return (void *) 0;
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}
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code_buf[0] = 0;
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code_buf_ptr = mask = 1;
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}
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last_match_length = sp->match_length;
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for (i = 0; i < last_match_length && src < srcend; i++) {
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delete_node(sp, s); /* Delete old strings and */
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c = *src++;
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sp->text_buf[s] = c; /* read new bytes */
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/*
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* If the position is near the end of buffer, extend the buffer
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* to make string comparison easier.
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*/
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if (s < F - 1)
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sp->text_buf[s + N] = c;
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/* Since this is a ring buffer, increment the position modulo N. */
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s = (s + 1) & (N - 1);
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r = (r + 1) & (N - 1);
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/* Register the string in text_buf[r..r+F-1] */
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insert_node(sp, r);
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}
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while (i++ < last_match_length) {
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delete_node(sp, s);
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/* After the end of text, no need to read, */
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s = (s + 1) & (N - 1);
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r = (r + 1) & (N - 1);
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/* but buffer may not be empty. */
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if (--len)
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insert_node(sp, r);
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}
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} while (len > 0); /* until length of string to be processed is zero */
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if (code_buf_ptr > 1) { /* Send remaining code. */
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for (i = 0; i < code_buf_ptr; i++)
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if (dst < dstend)
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*dst++ = code_buf[i];
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else {
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free(sp);
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return (void *) 0;
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}
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}
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free(sp);
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return dst;
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}
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/* my nasty stuff */
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// Yes, I know it's a mess. Feel free to clean it up,
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// but please don't change the command-line interface.
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int main(int argc, char *argv[])
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{
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freopen(NULL, "rb", stdin);
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freopen(NULL, "wb", stderr);
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unsigned char dict[0x1000];
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unsigned int dict_i = 0xFEE;
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if(argc == 2 && strcmp(argv[1], "x") == 0)
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{
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int head_char, lit, offset, len;
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while(1)
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{
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head_char = getchar();
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if(head_char == EOF) return 0;
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head_char |= 0xFF00; //neat little hack, this
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while(head_char != 0xFF)
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{
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if(head_char & 1)
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{ // Literal read (1 char)
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lit = getchar();
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if(lit == EOF) return 0;
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circ(dict, dict_i++) = lit;
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putchar(lit);
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}
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else
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{ // Dictionary read (2 bytes, offset and thingo)
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offset = getchar();
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len = getchar();
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if(offset == EOF) return 0;
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offset |= (len & 0xF0) << 4;
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len &= 0x0F;
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len += 3;
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for(int i=0; i<len; i++)
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{
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int copy = circ(dict, offset + i);
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circ(dict, dict_i++) = copy;
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putchar(copy);
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}
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}
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head_char >>= 1;
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}
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}
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}
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else if(argc == 2 && strcmp(argv[1], "c") == 0)
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{
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uint8_t *a, *b, *ret;
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uint32_t alen;
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a = malloc(0x400000);
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b = malloc(0x400000);
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if(!a || !b) return 1;
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alen = fread(a, 1, 0x400000, stdin);
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ret = compress_lzss(b, 0x400000, a, alen);
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if(!ret) return 1;
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if(fwrite(b, ret-b, 1, stdout) != 1) return 1;
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if(fclose(stdout)) return 1;
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return 0;
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}
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else
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{
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fprintf(stderr, "USAGE: lzss [x|c]\n");
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return 1;
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}
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}
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#define BUF_SIZE 512
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#define BUF_MIN 128
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