Annotation of embedaddon/rsync/zlib/deflate.h, revision 1.1
1.1 ! misho 1: /* deflate.h -- internal compression state
! 2: * Copyright (C) 1995-2004 Jean-loup Gailly
! 3: * For conditions of distribution and use, see copyright notice in zlib.h
! 4: */
! 5:
! 6: /* WARNING: this file should *not* be used by applications. It is
! 7: part of the implementation of the compression library and is
! 8: subject to change. Applications should only use zlib.h.
! 9: */
! 10:
! 11: /* @(#) $Id$ */
! 12:
! 13: #ifndef DEFLATE_H
! 14: #define DEFLATE_H
! 15:
! 16: #include "zutil.h"
! 17:
! 18: /* define NO_GZIP when compiling if you want to disable gzip header and
! 19: trailer creation by deflate(). NO_GZIP would be used to avoid linking in
! 20: the crc code when it is not needed. For shared libraries, gzip encoding
! 21: should be left enabled. */
! 22: #ifndef NO_GZIP
! 23: # define GZIP
! 24: #endif
! 25:
! 26: /* ===========================================================================
! 27: * Internal compression state.
! 28: */
! 29:
! 30: #define LENGTH_CODES 29
! 31: /* number of length codes, not counting the special END_BLOCK code */
! 32:
! 33: #define LITERALS 256
! 34: /* number of literal bytes 0..255 */
! 35:
! 36: #define L_CODES (LITERALS+1+LENGTH_CODES)
! 37: /* number of Literal or Length codes, including the END_BLOCK code */
! 38:
! 39: #define D_CODES 30
! 40: /* number of distance codes */
! 41:
! 42: #define BL_CODES 19
! 43: /* number of codes used to transfer the bit lengths */
! 44:
! 45: #define HEAP_SIZE (2*L_CODES+1)
! 46: /* maximum heap size */
! 47:
! 48: #define MAX_BITS 15
! 49: /* All codes must not exceed MAX_BITS bits */
! 50:
! 51: #define INIT_STATE 42
! 52: #define EXTRA_STATE 69
! 53: #define NAME_STATE 73
! 54: #define COMMENT_STATE 91
! 55: #define HCRC_STATE 103
! 56: #define BUSY_STATE 113
! 57: #define FINISH_STATE 666
! 58: /* Stream status */
! 59:
! 60:
! 61: /* Data structure describing a single value and its code string. */
! 62: typedef struct ct_data_s {
! 63: union {
! 64: ush freq; /* frequency count */
! 65: ush code; /* bit string */
! 66: } fc;
! 67: union {
! 68: ush dad; /* father node in Huffman tree */
! 69: ush len; /* length of bit string */
! 70: } dl;
! 71: } FAR ct_data;
! 72:
! 73: #define Freq fc.freq
! 74: #define Code fc.code
! 75: #define Dad dl.dad
! 76: #define Len dl.len
! 77:
! 78: typedef struct static_tree_desc_s static_tree_desc;
! 79:
! 80: typedef struct tree_desc_s {
! 81: ct_data *dyn_tree; /* the dynamic tree */
! 82: int max_code; /* largest code with non zero frequency */
! 83: static_tree_desc *stat_desc; /* the corresponding static tree */
! 84: } FAR tree_desc;
! 85:
! 86: typedef ush Pos;
! 87: typedef Pos FAR Posf;
! 88: typedef unsigned IPos;
! 89:
! 90: /* A Pos is an index in the character window. We use short instead of int to
! 91: * save space in the various tables. IPos is used only for parameter passing.
! 92: */
! 93:
! 94: typedef struct internal_state {
! 95: z_streamp strm; /* pointer back to this zlib stream */
! 96: int status; /* as the name implies */
! 97: Bytef *pending_buf; /* output still pending */
! 98: ulg pending_buf_size; /* size of pending_buf */
! 99: Bytef *pending_out; /* next pending byte to output to the stream */
! 100: uInt pending; /* nb of bytes in the pending buffer */
! 101: int wrap; /* bit 0 true for zlib, bit 1 true for gzip */
! 102: gz_headerp gzhead; /* gzip header information to write */
! 103: uInt gzindex; /* where in extra, name, or comment */
! 104: Byte method; /* STORED (for zip only) or DEFLATED */
! 105: int last_flush; /* value of flush param for previous deflate call */
! 106:
! 107: /* used by deflate.c: */
! 108:
! 109: uInt w_size; /* LZ77 window size (32K by default) */
! 110: uInt w_bits; /* log2(w_size) (8..16) */
! 111: uInt w_mask; /* w_size - 1 */
! 112:
! 113: Bytef *window;
! 114: /* Sliding window. Input bytes are read into the second half of the window,
! 115: * and move to the first half later to keep a dictionary of at least wSize
! 116: * bytes. With this organization, matches are limited to a distance of
! 117: * wSize-MAX_MATCH bytes, but this ensures that IO is always
! 118: * performed with a length multiple of the block size. Also, it limits
! 119: * the window size to 64K, which is quite useful on MSDOS.
! 120: * To do: use the user input buffer as sliding window.
! 121: */
! 122:
! 123: ulg window_size;
! 124: /* Actual size of window: 2*wSize, except when the user input buffer
! 125: * is directly used as sliding window.
! 126: */
! 127:
! 128: Posf *prev;
! 129: /* Link to older string with same hash index. To limit the size of this
! 130: * array to 64K, this link is maintained only for the last 32K strings.
! 131: * An index in this array is thus a window index modulo 32K.
! 132: */
! 133:
! 134: Posf *head; /* Heads of the hash chains or NIL. */
! 135:
! 136: uInt ins_h; /* hash index of string to be inserted */
! 137: uInt hash_size; /* number of elements in hash table */
! 138: uInt hash_bits; /* log2(hash_size) */
! 139: uInt hash_mask; /* hash_size-1 */
! 140:
! 141: uInt hash_shift;
! 142: /* Number of bits by which ins_h must be shifted at each input
! 143: * step. It must be such that after MIN_MATCH steps, the oldest
! 144: * byte no longer takes part in the hash key, that is:
! 145: * hash_shift * MIN_MATCH >= hash_bits
! 146: */
! 147:
! 148: long block_start;
! 149: /* Window position at the beginning of the current output block. Gets
! 150: * negative when the window is moved backwards.
! 151: */
! 152:
! 153: uInt match_length; /* length of best match */
! 154: IPos prev_match; /* previous match */
! 155: int match_available; /* set if previous match exists */
! 156: uInt strstart; /* start of string to insert */
! 157: uInt match_start; /* start of matching string */
! 158: uInt lookahead; /* number of valid bytes ahead in window */
! 159:
! 160: uInt prev_length;
! 161: /* Length of the best match at previous step. Matches not greater than this
! 162: * are discarded. This is used in the lazy match evaluation.
! 163: */
! 164:
! 165: uInt max_chain_length;
! 166: /* To speed up deflation, hash chains are never searched beyond this
! 167: * length. A higher limit improves compression ratio but degrades the
! 168: * speed.
! 169: */
! 170:
! 171: uInt max_lazy_match;
! 172: /* Attempt to find a better match only when the current match is strictly
! 173: * smaller than this value. This mechanism is used only for compression
! 174: * levels >= 4.
! 175: */
! 176: # define max_insert_length max_lazy_match
! 177: /* Insert new strings in the hash table only if the match length is not
! 178: * greater than this length. This saves time but degrades compression.
! 179: * max_insert_length is used only for compression levels <= 3.
! 180: */
! 181:
! 182: int level; /* compression level (1..9) */
! 183: int strategy; /* favor or force Huffman coding*/
! 184:
! 185: uInt good_match;
! 186: /* Use a faster search when the previous match is longer than this */
! 187:
! 188: int nice_match; /* Stop searching when current match exceeds this */
! 189:
! 190: /* used by trees.c: */
! 191: /* Didn't use ct_data typedef below to supress compiler warning */
! 192: struct ct_data_s dyn_ltree[HEAP_SIZE]; /* literal and length tree */
! 193: struct ct_data_s dyn_dtree[2*D_CODES+1]; /* distance tree */
! 194: struct ct_data_s bl_tree[2*BL_CODES+1]; /* Huffman tree for bit lengths */
! 195:
! 196: struct tree_desc_s l_desc; /* desc. for literal tree */
! 197: struct tree_desc_s d_desc; /* desc. for distance tree */
! 198: struct tree_desc_s bl_desc; /* desc. for bit length tree */
! 199:
! 200: ush bl_count[MAX_BITS+1];
! 201: /* number of codes at each bit length for an optimal tree */
! 202:
! 203: int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */
! 204: int heap_len; /* number of elements in the heap */
! 205: int heap_max; /* element of largest frequency */
! 206: /* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
! 207: * The same heap array is used to build all trees.
! 208: */
! 209:
! 210: uch depth[2*L_CODES+1];
! 211: /* Depth of each subtree used as tie breaker for trees of equal frequency
! 212: */
! 213:
! 214: uchf *l_buf; /* buffer for literals or lengths */
! 215:
! 216: uInt lit_bufsize;
! 217: /* Size of match buffer for literals/lengths. There are 4 reasons for
! 218: * limiting lit_bufsize to 64K:
! 219: * - frequencies can be kept in 16 bit counters
! 220: * - if compression is not successful for the first block, all input
! 221: * data is still in the window so we can still emit a stored block even
! 222: * when input comes from standard input. (This can also be done for
! 223: * all blocks if lit_bufsize is not greater than 32K.)
! 224: * - if compression is not successful for a file smaller than 64K, we can
! 225: * even emit a stored file instead of a stored block (saving 5 bytes).
! 226: * This is applicable only for zip (not gzip or zlib).
! 227: * - creating new Huffman trees less frequently may not provide fast
! 228: * adaptation to changes in the input data statistics. (Take for
! 229: * example a binary file with poorly compressible code followed by
! 230: * a highly compressible string table.) Smaller buffer sizes give
! 231: * fast adaptation but have of course the overhead of transmitting
! 232: * trees more frequently.
! 233: * - I can't count above 4
! 234: */
! 235:
! 236: uInt last_lit; /* running index in l_buf */
! 237:
! 238: ushf *d_buf;
! 239: /* Buffer for distances. To simplify the code, d_buf and l_buf have
! 240: * the same number of elements. To use different lengths, an extra flag
! 241: * array would be necessary.
! 242: */
! 243:
! 244: ulg opt_len; /* bit length of current block with optimal trees */
! 245: ulg static_len; /* bit length of current block with static trees */
! 246: uInt matches; /* number of string matches in current block */
! 247: int last_eob_len; /* bit length of EOB code for last block */
! 248:
! 249: #ifdef DEBUG
! 250: ulg compressed_len; /* total bit length of compressed file mod 2^32 */
! 251: ulg bits_sent; /* bit length of compressed data sent mod 2^32 */
! 252: #endif
! 253:
! 254: ush bi_buf;
! 255: /* Output buffer. bits are inserted starting at the bottom (least
! 256: * significant bits).
! 257: */
! 258: int bi_valid;
! 259: /* Number of valid bits in bi_buf. All bits above the last valid bit
! 260: * are always zero.
! 261: */
! 262:
! 263: } FAR deflate_state;
! 264:
! 265: /* Output a byte on the stream.
! 266: * IN assertion: there is enough room in pending_buf.
! 267: */
! 268: #define put_byte(s, c) {s->pending_buf[s->pending++] = (c);}
! 269:
! 270:
! 271: #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1)
! 272: /* Minimum amount of lookahead, except at the end of the input file.
! 273: * See deflate.c for comments about the MIN_MATCH+1.
! 274: */
! 275:
! 276: #define MAX_DIST(s) ((s)->w_size-MIN_LOOKAHEAD)
! 277: /* In order to simplify the code, particularly on 16 bit machines, match
! 278: * distances are limited to MAX_DIST instead of WSIZE.
! 279: */
! 280:
! 281: /* in trees.c */
! 282: void _tr_init OF((deflate_state *s));
! 283: int _tr_tally OF((deflate_state *s, unsigned dist, unsigned lc));
! 284: void _tr_flush_block OF((deflate_state *s, charf *buf, ulg stored_len,
! 285: int eof));
! 286: void _tr_align OF((deflate_state *s));
! 287: void _tr_stored_block OF((deflate_state *s, charf *buf, ulg stored_len,
! 288: int eof));
! 289:
! 290: #define d_code(dist) \
! 291: ((dist) < 256 ? _dist_code[dist] : _dist_code[256+((dist)>>7)])
! 292: /* Mapping from a distance to a distance code. dist is the distance - 1 and
! 293: * must not have side effects. _dist_code[256] and _dist_code[257] are never
! 294: * used.
! 295: */
! 296:
! 297: #ifndef DEBUG
! 298: /* Inline versions of _tr_tally for speed: */
! 299:
! 300: #if defined(GEN_TREES_H) || !defined(STDC)
! 301: extern uch _length_code[];
! 302: extern uch _dist_code[];
! 303: #else
! 304: extern const uch _length_code[];
! 305: extern const uch _dist_code[];
! 306: #endif
! 307:
! 308: # define _tr_tally_lit(s, c, flush) \
! 309: { uch cc = (c); \
! 310: s->d_buf[s->last_lit] = 0; \
! 311: s->l_buf[s->last_lit++] = cc; \
! 312: s->dyn_ltree[cc].Freq++; \
! 313: flush = (s->last_lit == s->lit_bufsize-1); \
! 314: }
! 315: # define _tr_tally_dist(s, distance, length, flush) \
! 316: { uch len = (length); \
! 317: ush dist = (distance); \
! 318: s->d_buf[s->last_lit] = dist; \
! 319: s->l_buf[s->last_lit++] = len; \
! 320: dist--; \
! 321: s->dyn_ltree[_length_code[len]+LITERALS+1].Freq++; \
! 322: s->dyn_dtree[d_code(dist)].Freq++; \
! 323: flush = (s->last_lit == s->lit_bufsize-1); \
! 324: }
! 325: #else
! 326: # define _tr_tally_lit(s, c, flush) flush = _tr_tally(s, 0, c)
! 327: # define _tr_tally_dist(s, distance, length, flush) \
! 328: flush = _tr_tally(s, distance, length)
! 329: #endif
! 330:
! 331: #endif /* DEFLATE_H */
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