#include #if KERNEL #include #include #else #include #include #endif KERNEL __private_extern__ u_int32_t local_adler32(u_int8_t *buffer, int32_t length) { int32_t cnt; u_int32_t result, lowHalf, highHalf; lowHalf = 1; highHalf = 0; for (cnt = 0; cnt < length; cnt++) { if ((cnt % 5000) == 0) { lowHalf %= 65521L; highHalf %= 65521L; } lowHalf += buffer[cnt]; highHalf += lowHalf; } lowHalf %= 65521L; highHalf %= 65521L; result = (highHalf << 16) | lowHalf; return result; } /************************************************************** LZSS.C -- A Data Compression Program *************************************************************** 4/6/1989 Haruhiko Okumura Use, distribute, and modify this program freely. Please send me your improved versions. PC-VAN SCIENCE NIFTY-Serve PAF01022 CompuServe 74050,1022 **************************************************************/ #define N 4096 /* size of ring buffer - must be power of 2 */ #define F 18 /* upper limit for match_length */ #define THRESHOLD 2 /* encode string into position and length if match_length is greater than this */ #define NIL N /* index for root of binary search trees */ struct encode_state { /* * left & right children & parent. These constitute binary search trees. */ int lchild[N + 1], rchild[N + 257], parent[N + 1]; /* ring buffer of size N, with extra F-1 bytes to aid string comparison */ u_int8_t text_buf[N + F - 1]; /* * match_length of longest match. * These are set by the insert_node() procedure. */ int match_position, match_length; }; __private_extern__ int decompress_lzss(u_int8_t *dst, u_int8_t *src, u_int32_t srclen) { /* ring buffer of size N, with extra F-1 bytes to aid string comparison */ u_int8_t text_buf[N + F - 1]; u_int8_t *dststart = dst; u_int8_t *srcend = src + srclen; int i, j, k, r, c; unsigned int flags; dst = dststart; srcend = src + srclen; for (i = 0; i < N - F; i++) text_buf[i] = ' '; r = N - F; flags = 0; for ( ; ; ) { if (((flags >>= 1) & 0x100) == 0) { if (src < srcend) c = *src++; else break; flags = c | 0xFF00; /* uses higher byte cleverly */ } /* to count eight */ if (flags & 1) { if (src < srcend) c = *src++; else break; *dst++ = c; text_buf[r++] = c; r &= (N - 1); } else { if (src < srcend) i = *src++; else break; if (src < srcend) j = *src++; else break; i |= ((j & 0xF0) << 4); j = (j & 0x0F) + THRESHOLD; for (k = 0; k <= j; k++) { c = text_buf[(i + k) & (N - 1)]; *dst++ = c; text_buf[r++] = c; r &= (N - 1); } } } return dst - dststart; } #if !KERNEL /* * initialize state, mostly the trees * * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left * children of node i. These nodes need not be initialized. Also, parent[i] * is the parent of node i. These are initialized to NIL (= N), which stands * for 'not used.' For i = 0 to 255, rchild[N + i + 1] is the root of the * tree for strings that begin with character i. These are initialized to NIL. * Note there are 256 trees. */ static void init_state(struct encode_state *sp) { int i; bzero(sp, sizeof(*sp)); for (i = 0; i < N - F; i++) sp->text_buf[i] = ' '; for (i = N + 1; i <= N + 256; i++) sp->rchild[i] = NIL; for (i = 0; i < N; i++) sp->parent[i] = NIL; } /* * Inserts string of length F, text_buf[r..r+F-1], into one of the trees * (text_buf[r]'th tree) and returns the longest-match position and length * via the global variables match_position and match_length. * If match_length = F, then removes the old node in favor of the new one, * because the old one will be deleted sooner. Note r plays double role, * as tree node and position in buffer. */ static void insert_node(struct encode_state *sp, int r) { int i, p, cmp; u_int8_t *key; cmp = 1; key = &sp->text_buf[r]; p = N + 1 + key[0]; sp->rchild[r] = sp->lchild[r] = NIL; sp->match_length = 0; for ( ; ; ) { if (cmp >= 0) { if (sp->rchild[p] != NIL) p = sp->rchild[p]; else { sp->rchild[p] = r; sp->parent[r] = p; return; } } else { if (sp->lchild[p] != NIL) p = sp->lchild[p]; else { sp->lchild[p] = r; sp->parent[r] = p; return; } } for (i = 1; i < F; i++) { if ((cmp = key[i] - sp->text_buf[p + i]) != 0) break; } if (i > sp->match_length) { sp->match_position = p; if ((sp->match_length = i) >= F) break; } } sp->parent[r] = sp->parent[p]; sp->lchild[r] = sp->lchild[p]; sp->rchild[r] = sp->rchild[p]; sp->parent[sp->lchild[p]] = r; sp->parent[sp->rchild[p]] = r; if (sp->rchild[sp->parent[p]] == p) sp->rchild[sp->parent[p]] = r; else sp->lchild[sp->parent[p]] = r; sp->parent[p] = NIL; /* remove p */ } /* deletes node p from tree */ static void delete_node(struct encode_state *sp, int p) { int q; if (sp->parent[p] == NIL) return; /* not in tree */ if (sp->rchild[p] == NIL) q = sp->lchild[p]; else if (sp->lchild[p] == NIL) q = sp->rchild[p]; else { q = sp->lchild[p]; if (sp->rchild[q] != NIL) { do { q = sp->rchild[q]; } while (sp->rchild[q] != NIL); sp->rchild[sp->parent[q]] = sp->lchild[q]; sp->parent[sp->lchild[q]] = sp->parent[q]; sp->lchild[q] = sp->lchild[p]; sp->parent[sp->lchild[p]] = q; } sp->rchild[q] = sp->rchild[p]; sp->parent[sp->rchild[p]] = q; } sp->parent[q] = sp->parent[p]; if (sp->rchild[sp->parent[p]] == p) sp->rchild[sp->parent[p]] = q; else sp->lchild[sp->parent[p]] = q; sp->parent[p] = NIL; } __private_extern__ u_int8_t * compress_lzss(u_int8_t *dst, u_int32_t dstlen, u_int8_t *src, u_int32_t srcLen) { /* Encoding state, mostly tree but some current match stuff */ struct encode_state *sp; int i, c, len, r, s, last_match_length, code_buf_ptr; u_int8_t code_buf[17], mask; u_int8_t *srcend = src + srcLen; u_int8_t *dstend = dst + dstlen; /* initialize trees */ sp = (struct encode_state *) malloc(sizeof(*sp)); init_state(sp); /* * code_buf[1..16] saves eight units of code, and code_buf[0] works * as eight flags, "1" representing that the unit is an unencoded * letter (1 byte), "0" a position-and-length pair (2 bytes). * Thus, eight units require at most 16 bytes of code. */ code_buf[0] = 0; code_buf_ptr = mask = 1; /* Clear the buffer with any character that will appear often. */ s = 0; r = N - F; /* Read F bytes into the last F bytes of the buffer */ for (len = 0; len < F && src < srcend; len++) sp->text_buf[r + len] = *src++; if (!len) return (void *) 0; /* text of size zero */ /* * Insert the F strings, each of which begins with one or more * 'space' characters. Note the order in which these strings are * inserted. This way, degenerate trees will be less likely to occur. */ for (i = 1; i <= F; i++) insert_node(sp, r - i); /* * Finally, insert the whole string just read. * The global variables match_length and match_position are set. */ insert_node(sp, r); do { /* match_length may be spuriously long near the end of text. */ if (sp->match_length > len) sp->match_length = len; if (sp->match_length <= THRESHOLD) { sp->match_length = 1; /* Not long enough match. Send one byte. */ code_buf[0] |= mask; /* 'send one byte' flag */ code_buf[code_buf_ptr++] = sp->text_buf[r]; /* Send uncoded. */ } else { /* Send position and length pair. Note match_length > THRESHOLD. */ code_buf[code_buf_ptr++] = (u_int8_t) sp->match_position; code_buf[code_buf_ptr++] = (u_int8_t) ( ((sp->match_position >> 4) & 0xF0) | (sp->match_length - (THRESHOLD + 1)) ); } if ((mask <<= 1) == 0) { /* Shift mask left one bit. */ /* Send at most 8 units of code together */ for (i = 0; i < code_buf_ptr; i++) if (dst < dstend) *dst++ = code_buf[i]; else return (void *) 0; code_buf[0] = 0; code_buf_ptr = mask = 1; } last_match_length = sp->match_length; for (i = 0; i < last_match_length && src < srcend; i++) { delete_node(sp, s); /* Delete old strings and */ c = *src++; sp->text_buf[s] = c; /* read new bytes */ /* * If the position is near the end of buffer, extend the buffer * to make string comparison easier. */ if (s < F - 1) sp->text_buf[s + N] = c; /* Since this is a ring buffer, increment the position modulo N. */ s = (s + 1) & (N - 1); r = (r + 1) & (N - 1); /* Register the string in text_buf[r..r+F-1] */ insert_node(sp, r); } while (i++ < last_match_length) { delete_node(sp, s); /* After the end of text, no need to read, */ s = (s + 1) & (N - 1); r = (r + 1) & (N - 1); /* but buffer may not be empty. */ if (--len) insert_node(sp, r); } } while (len > 0); /* until length of string to be processed is zero */ if (code_buf_ptr > 1) { /* Send remaining code. */ for (i = 0; i < code_buf_ptr; i++) if (dst < dstend) *dst++ = code_buf[i]; else return (void *) 0; } return dst; } #endif /* !KERNEL */