| /* deflate.c -- compress data using the deflation algorithm |
| * Copyright (C) 1995-2002 Jean-loup Gailly. |
| * For conditions of distribution and use, see copyright notice in zlib.h |
| */ |
| |
| /* |
| * ALGORITHM |
| * |
| * The "deflation" process depends on being able to identify portions |
| * of the input text which are identical to earlier input (within a |
| * sliding window trailing behind the input currently being processed). |
| * |
| * The most straightforward technique turns out to be the fastest for |
| * most input files: try all possible matches and select the longest. |
| * The key feature of this algorithm is that insertions into the string |
| * dictionary are very simple and thus fast, and deletions are avoided |
| * completely. Insertions are performed at each input character, whereas |
| * string matches are performed only when the previous match ends. So it |
| * is preferable to spend more time in matches to allow very fast string |
| * insertions and avoid deletions. The matching algorithm for small |
| * strings is inspired from that of Rabin & Karp. A brute force approach |
| * is used to find longer strings when a small match has been found. |
| * A similar algorithm is used in comic (by Jan-Mark Wams) and freeze |
| * (by Leonid Broukhis). |
| * A previous version of this file used a more sophisticated algorithm |
| * (by Fiala and Greene) which is guaranteed to run in linear amortized |
| * time, but has a larger average cost, uses more memory and is patented. |
| * However the F&G algorithm may be faster for some highly redundant |
| * files if the parameter max_chain_length (described below) is too large. |
| * |
| * ACKNOWLEDGEMENTS |
| * |
| * The idea of lazy evaluation of matches is due to Jan-Mark Wams, and |
| * I found it in 'freeze' written by Leonid Broukhis. |
| * Thanks to many people for bug reports and testing. |
| * |
| * REFERENCES |
| * |
| * Deutsch, L.P.,"DEFLATE Compressed Data Format Specification". |
| * Available in ftp://ds.internic.net/rfc/rfc1951.txt |
| * |
| * A description of the Rabin and Karp algorithm is given in the book |
| * "Algorithms" by R. Sedgewick, Addison-Wesley, p252. |
| * |
| * Fiala,E.R., and Greene,D.H. |
| * Data Compression with Finite Windows, Comm.ACM, 32,4 (1989) 490-595 |
| * |
| */ |
| |
| /* @(#) $Id: deflate.c,v 1.1.1.2 2002/03/11 21:53:23 tromey Exp $ */ |
| |
| #include "deflate.h" |
| |
| const char deflate_copyright[] = |
| " deflate 1.1.4 Copyright 1995-2002 Jean-loup Gailly "; |
| /* |
| If you use the zlib library in a product, an acknowledgment is welcome |
| in the documentation of your product. If for some reason you cannot |
| include such an acknowledgment, I would appreciate that you keep this |
| copyright string in the executable of your product. |
| */ |
| |
| /* =========================================================================== |
| * Function prototypes. |
| */ |
| typedef enum { |
| need_more, /* block not completed, need more input or more output */ |
| block_done, /* block flush performed */ |
| finish_started, /* finish started, need only more output at next deflate */ |
| finish_done /* finish done, accept no more input or output */ |
| } block_state; |
| |
| typedef block_state (*compress_func) OF((deflate_state *s, int flush)); |
| /* Compression function. Returns the block state after the call. */ |
| |
| local void fill_window OF((deflate_state *s)); |
| local block_state deflate_stored OF((deflate_state *s, int flush)); |
| local block_state deflate_fast OF((deflate_state *s, int flush)); |
| local block_state deflate_slow OF((deflate_state *s, int flush)); |
| local void lm_init OF((deflate_state *s)); |
| local void putShortMSB OF((deflate_state *s, uInt b)); |
| local void flush_pending OF((z_streamp strm)); |
| local int read_buf OF((z_streamp strm, Bytef *buf, unsigned size)); |
| #ifdef ASMV |
| void match_init OF((void)); /* asm code initialization */ |
| uInt longest_match OF((deflate_state *s, IPos cur_match)); |
| #else |
| local uInt longest_match OF((deflate_state *s, IPos cur_match)); |
| #endif |
| |
| #ifdef DEBUG |
| local void check_match OF((deflate_state *s, IPos start, IPos match, |
| int length)); |
| #endif |
| |
| /* =========================================================================== |
| * Local data |
| */ |
| |
| #define NIL 0 |
| /* Tail of hash chains */ |
| |
| #ifndef TOO_FAR |
| # define TOO_FAR 4096 |
| #endif |
| /* Matches of length 3 are discarded if their distance exceeds TOO_FAR */ |
| |
| #define MIN_LOOKAHEAD (MAX_MATCH+MIN_MATCH+1) |
| /* Minimum amount of lookahead, except at the end of the input file. |
| * See deflate.c for comments about the MIN_MATCH+1. |
| */ |
| |
| /* Values for max_lazy_match, good_match and max_chain_length, depending on |
| * the desired pack level (0..9). The values given below have been tuned to |
| * exclude worst case performance for pathological files. Better values may be |
| * found for specific files. |
| */ |
| typedef struct config_s { |
| ush good_length; /* reduce lazy search above this match length */ |
| ush max_lazy; /* do not perform lazy search above this match length */ |
| ush nice_length; /* quit search above this match length */ |
| ush max_chain; |
| compress_func func; |
| } config; |
| |
| local const config configuration_table[10] = { |
| /* good lazy nice chain */ |
| /* 0 */ {0, 0, 0, 0, deflate_stored}, /* store only */ |
| /* 1 */ {4, 4, 8, 4, deflate_fast}, /* maximum speed, no lazy matches */ |
| /* 2 */ {4, 5, 16, 8, deflate_fast}, |
| /* 3 */ {4, 6, 32, 32, deflate_fast}, |
| |
| /* 4 */ {4, 4, 16, 16, deflate_slow}, /* lazy matches */ |
| /* 5 */ {8, 16, 32, 32, deflate_slow}, |
| /* 6 */ {8, 16, 128, 128, deflate_slow}, |
| /* 7 */ {8, 32, 128, 256, deflate_slow}, |
| /* 8 */ {32, 128, 258, 1024, deflate_slow}, |
| /* 9 */ {32, 258, 258, 4096, deflate_slow}}; /* maximum compression */ |
| |
| /* Note: the deflate() code requires max_lazy >= MIN_MATCH and max_chain >= 4 |
| * For deflate_fast() (levels <= 3) good is ignored and lazy has a different |
| * meaning. |
| */ |
| |
| #define EQUAL 0 |
| /* result of memcmp for equal strings */ |
| |
| struct static_tree_desc_s {int dummy;}; /* for buggy compilers */ |
| |
| /* =========================================================================== |
| * Update a hash value with the given input byte |
| * IN assertion: all calls to to UPDATE_HASH are made with consecutive |
| * input characters, so that a running hash key can be computed from the |
| * previous key instead of complete recalculation each time. |
| */ |
| #define UPDATE_HASH(s,h,c) (h = (((h)<<s->hash_shift) ^ (c)) & s->hash_mask) |
| |
| |
| /* =========================================================================== |
| * Insert string str in the dictionary and set match_head to the previous head |
| * of the hash chain (the most recent string with same hash key). Return |
| * the previous length of the hash chain. |
| * If this file is compiled with -DFASTEST, the compression level is forced |
| * to 1, and no hash chains are maintained. |
| * IN assertion: all calls to to INSERT_STRING are made with consecutive |
| * input characters and the first MIN_MATCH bytes of str are valid |
| * (except for the last MIN_MATCH-1 bytes of the input file). |
| */ |
| #ifdef FASTEST |
| #define INSERT_STRING(s, str, match_head) \ |
| (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ |
| match_head = s->head[s->ins_h], \ |
| s->head[s->ins_h] = (Pos)(str)) |
| #else |
| #define INSERT_STRING(s, str, match_head) \ |
| (UPDATE_HASH(s, s->ins_h, s->window[(str) + (MIN_MATCH-1)]), \ |
| s->prev[(str) & s->w_mask] = match_head = s->head[s->ins_h], \ |
| s->head[s->ins_h] = (Pos)(str)) |
| #endif |
| |
| /* =========================================================================== |
| * Initialize the hash table (avoiding 64K overflow for 16 bit systems). |
| * prev[] will be initialized on the fly. |
| */ |
| #define CLEAR_HASH(s) \ |
| s->head[s->hash_size-1] = NIL; \ |
| zmemzero((Bytef *)s->head, (unsigned)(s->hash_size-1)*sizeof(*s->head)); |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateInit_(strm, level, version, stream_size) |
| z_streamp strm; |
| int level; |
| const char *version; |
| int stream_size; |
| { |
| return deflateInit2_(strm, level, Z_DEFLATED, MAX_WBITS, DEF_MEM_LEVEL, |
| Z_DEFAULT_STRATEGY, version, stream_size); |
| /* To do: ignore strm->next_in if we use it as window */ |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy, |
| version, stream_size) |
| z_streamp strm; |
| int level; |
| int method; |
| int windowBits; |
| int memLevel; |
| int strategy; |
| const char *version; |
| int stream_size; |
| { |
| deflate_state *s; |
| int noheader = 0; |
| static const char* my_version = ZLIB_VERSION; |
| |
| ushf *overlay; |
| /* We overlay pending_buf and d_buf+l_buf. This works since the average |
| * output size for (length,distance) codes is <= 24 bits. |
| */ |
| |
| if (version == Z_NULL || version[0] != my_version[0] || |
| stream_size != sizeof(z_stream)) { |
| return Z_VERSION_ERROR; |
| } |
| if (strm == Z_NULL) return Z_STREAM_ERROR; |
| |
| strm->msg = Z_NULL; |
| if (strm->zalloc == Z_NULL) { |
| strm->zalloc = zcalloc; |
| strm->opaque = (voidpf)0; |
| } |
| if (strm->zfree == Z_NULL) strm->zfree = zcfree; |
| |
| if (level == Z_DEFAULT_COMPRESSION) level = 6; |
| #ifdef FASTEST |
| level = 1; |
| #endif |
| |
| if (windowBits < 0) { /* undocumented feature: suppress zlib header */ |
| noheader = 1; |
| windowBits = -windowBits; |
| } |
| if (memLevel < 1 || memLevel > MAX_MEM_LEVEL || method != Z_DEFLATED || |
| windowBits < 9 || windowBits > 15 || level < 0 || level > 9 || |
| strategy < 0 || strategy > Z_HUFFMAN_ONLY) { |
| return Z_STREAM_ERROR; |
| } |
| s = (deflate_state *) ZALLOC(strm, 1, sizeof(deflate_state)); |
| if (s == Z_NULL) return Z_MEM_ERROR; |
| strm->state = (struct internal_state FAR *)s; |
| s->strm = strm; |
| |
| s->noheader = noheader; |
| s->w_bits = windowBits; |
| s->w_size = 1 << s->w_bits; |
| s->w_mask = s->w_size - 1; |
| |
| s->hash_bits = memLevel + 7; |
| s->hash_size = 1 << s->hash_bits; |
| s->hash_mask = s->hash_size - 1; |
| s->hash_shift = ((s->hash_bits+MIN_MATCH-1)/MIN_MATCH); |
| |
| s->window = (Bytef *) ZALLOC(strm, s->w_size, 2*sizeof(Byte)); |
| s->prev = (Posf *) ZALLOC(strm, s->w_size, sizeof(Pos)); |
| s->head = (Posf *) ZALLOC(strm, s->hash_size, sizeof(Pos)); |
| |
| s->lit_bufsize = 1 << (memLevel + 6); /* 16K elements by default */ |
| |
| overlay = (ushf *) ZALLOC(strm, s->lit_bufsize, sizeof(ush)+2); |
| s->pending_buf = (uchf *) overlay; |
| s->pending_buf_size = (ulg)s->lit_bufsize * (sizeof(ush)+2L); |
| |
| if (s->window == Z_NULL || s->prev == Z_NULL || s->head == Z_NULL || |
| s->pending_buf == Z_NULL) { |
| strm->msg = (char*)ERR_MSG(Z_MEM_ERROR); |
| deflateEnd (strm); |
| return Z_MEM_ERROR; |
| } |
| s->d_buf = overlay + s->lit_bufsize/sizeof(ush); |
| s->l_buf = s->pending_buf + (1+sizeof(ush))*s->lit_bufsize; |
| |
| s->level = level; |
| s->strategy = strategy; |
| s->method = (Byte)method; |
| |
| return deflateReset(strm); |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength) |
| z_streamp strm; |
| const Bytef *dictionary; |
| uInt dictLength; |
| { |
| deflate_state *s; |
| uInt length = dictLength; |
| uInt n; |
| IPos hash_head = 0; |
| |
| if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL || |
| strm->state->status != INIT_STATE) return Z_STREAM_ERROR; |
| |
| s = strm->state; |
| strm->adler = adler32(strm->adler, dictionary, dictLength); |
| |
| if (length < MIN_MATCH) return Z_OK; |
| if (length > MAX_DIST(s)) { |
| length = MAX_DIST(s); |
| #ifndef USE_DICT_HEAD |
| dictionary += dictLength - length; /* use the tail of the dictionary */ |
| #endif |
| } |
| zmemcpy(s->window, dictionary, length); |
| s->strstart = length; |
| s->block_start = (long)length; |
| |
| /* Insert all strings in the hash table (except for the last two bytes). |
| * s->lookahead stays null, so s->ins_h will be recomputed at the next |
| * call of fill_window. |
| */ |
| s->ins_h = s->window[0]; |
| UPDATE_HASH(s, s->ins_h, s->window[1]); |
| for (n = 0; n <= length - MIN_MATCH; n++) { |
| INSERT_STRING(s, n, hash_head); |
| } |
| if (hash_head) hash_head = 0; /* to make compiler happy */ |
| return Z_OK; |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateReset (strm) |
| z_streamp strm; |
| { |
| deflate_state *s; |
| |
| if (strm == Z_NULL || strm->state == Z_NULL || |
| strm->zalloc == Z_NULL || strm->zfree == Z_NULL) return Z_STREAM_ERROR; |
| |
| strm->total_in = strm->total_out = 0; |
| strm->msg = Z_NULL; /* use zfree if we ever allocate msg dynamically */ |
| strm->data_type = Z_UNKNOWN; |
| |
| s = (deflate_state *)strm->state; |
| s->pending = 0; |
| s->pending_out = s->pending_buf; |
| |
| if (s->noheader < 0) { |
| s->noheader = 0; /* was set to -1 by deflate(..., Z_FINISH); */ |
| } |
| s->status = s->noheader ? BUSY_STATE : INIT_STATE; |
| strm->adler = 1; |
| s->last_flush = Z_NO_FLUSH; |
| |
| _tr_init(s); |
| lm_init(s); |
| |
| return Z_OK; |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateParams(strm, level, strategy) |
| z_streamp strm; |
| int level; |
| int strategy; |
| { |
| deflate_state *s; |
| compress_func func; |
| int err = Z_OK; |
| |
| if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR; |
| s = strm->state; |
| |
| if (level == Z_DEFAULT_COMPRESSION) { |
| level = 6; |
| } |
| if (level < 0 || level > 9 || strategy < 0 || strategy > Z_HUFFMAN_ONLY) { |
| return Z_STREAM_ERROR; |
| } |
| func = configuration_table[s->level].func; |
| |
| if (func != configuration_table[level].func && strm->total_in != 0) { |
| /* Flush the last buffer: */ |
| err = deflate(strm, Z_PARTIAL_FLUSH); |
| } |
| if (s->level != level) { |
| s->level = level; |
| s->max_lazy_match = configuration_table[level].max_lazy; |
| s->good_match = configuration_table[level].good_length; |
| s->nice_match = configuration_table[level].nice_length; |
| s->max_chain_length = configuration_table[level].max_chain; |
| } |
| s->strategy = strategy; |
| return err; |
| } |
| |
| /* ========================================================================= |
| * Put a short in the pending buffer. The 16-bit value is put in MSB order. |
| * IN assertion: the stream state is correct and there is enough room in |
| * pending_buf. |
| */ |
| local void putShortMSB (s, b) |
| deflate_state *s; |
| uInt b; |
| { |
| put_byte(s, (Byte)(b >> 8)); |
| put_byte(s, (Byte)(b & 0xff)); |
| } |
| |
| /* ========================================================================= |
| * Flush as much pending output as possible. All deflate() output goes |
| * through this function so some applications may wish to modify it |
| * to avoid allocating a large strm->next_out buffer and copying into it. |
| * (See also read_buf()). |
| */ |
| local void flush_pending(strm) |
| z_streamp strm; |
| { |
| unsigned len = strm->state->pending; |
| |
| if (len > strm->avail_out) len = strm->avail_out; |
| if (len == 0) return; |
| |
| zmemcpy(strm->next_out, strm->state->pending_out, len); |
| strm->next_out += len; |
| strm->state->pending_out += len; |
| strm->total_out += len; |
| strm->avail_out -= len; |
| strm->state->pending -= len; |
| if (strm->state->pending == 0) { |
| strm->state->pending_out = strm->state->pending_buf; |
| } |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflate (strm, flush) |
| z_streamp strm; |
| int flush; |
| { |
| int old_flush; /* value of flush param for previous deflate call */ |
| deflate_state *s; |
| |
| if (strm == Z_NULL || strm->state == Z_NULL || |
| flush > Z_FINISH || flush < 0) { |
| return Z_STREAM_ERROR; |
| } |
| s = strm->state; |
| |
| if (strm->next_out == Z_NULL || |
| (strm->next_in == Z_NULL && strm->avail_in != 0) || |
| (s->status == FINISH_STATE && flush != Z_FINISH)) { |
| ERR_RETURN(strm, Z_STREAM_ERROR); |
| } |
| if (strm->avail_out == 0) ERR_RETURN(strm, Z_BUF_ERROR); |
| |
| s->strm = strm; /* just in case */ |
| old_flush = s->last_flush; |
| s->last_flush = flush; |
| |
| /* Write the zlib header */ |
| if (s->status == INIT_STATE) { |
| |
| uInt header = (Z_DEFLATED + ((s->w_bits-8)<<4)) << 8; |
| uInt level_flags = (s->level-1) >> 1; |
| |
| if (level_flags > 3) level_flags = 3; |
| header |= (level_flags << 6); |
| if (s->strstart != 0) header |= PRESET_DICT; |
| header += 31 - (header % 31); |
| |
| s->status = BUSY_STATE; |
| putShortMSB(s, header); |
| |
| /* Save the adler32 of the preset dictionary: */ |
| if (s->strstart != 0) { |
| putShortMSB(s, (uInt)(strm->adler >> 16)); |
| putShortMSB(s, (uInt)(strm->adler & 0xffff)); |
| } |
| strm->adler = 1L; |
| } |
| |
| /* Flush as much pending output as possible */ |
| if (s->pending != 0) { |
| flush_pending(strm); |
| if (strm->avail_out == 0) { |
| /* Since avail_out is 0, deflate will be called again with |
| * more output space, but possibly with both pending and |
| * avail_in equal to zero. There won't be anything to do, |
| * but this is not an error situation so make sure we |
| * return OK instead of BUF_ERROR at next call of deflate: |
| */ |
| s->last_flush = -1; |
| return Z_OK; |
| } |
| |
| /* Make sure there is something to do and avoid duplicate consecutive |
| * flushes. For repeated and useless calls with Z_FINISH, we keep |
| * returning Z_STREAM_END instead of Z_BUFF_ERROR. |
| */ |
| } else if (strm->avail_in == 0 && flush <= old_flush && |
| flush != Z_FINISH) { |
| ERR_RETURN(strm, Z_BUF_ERROR); |
| } |
| |
| /* User must not provide more input after the first FINISH: */ |
| if (s->status == FINISH_STATE && strm->avail_in != 0) { |
| ERR_RETURN(strm, Z_BUF_ERROR); |
| } |
| |
| /* Start a new block or continue the current one. |
| */ |
| if (strm->avail_in != 0 || s->lookahead != 0 || |
| (flush != Z_NO_FLUSH && s->status != FINISH_STATE)) { |
| block_state bstate; |
| |
| bstate = (*(configuration_table[s->level].func))(s, flush); |
| |
| if (bstate == finish_started || bstate == finish_done) { |
| s->status = FINISH_STATE; |
| } |
| if (bstate == need_more || bstate == finish_started) { |
| if (strm->avail_out == 0) { |
| s->last_flush = -1; /* avoid BUF_ERROR next call, see above */ |
| } |
| return Z_OK; |
| /* If flush != Z_NO_FLUSH && avail_out == 0, the next call |
| * of deflate should use the same flush parameter to make sure |
| * that the flush is complete. So we don't have to output an |
| * empty block here, this will be done at next call. This also |
| * ensures that for a very small output buffer, we emit at most |
| * one empty block. |
| */ |
| } |
| if (bstate == block_done) { |
| if (flush == Z_PARTIAL_FLUSH) { |
| _tr_align(s); |
| } else { /* FULL_FLUSH or SYNC_FLUSH */ |
| _tr_stored_block(s, (char*)0, 0L, 0); |
| /* For a full flush, this empty block will be recognized |
| * as a special marker by inflate_sync(). |
| */ |
| if (flush == Z_FULL_FLUSH) { |
| CLEAR_HASH(s); /* forget history */ |
| } |
| } |
| flush_pending(strm); |
| if (strm->avail_out == 0) { |
| s->last_flush = -1; /* avoid BUF_ERROR at next call, see above */ |
| return Z_OK; |
| } |
| } |
| } |
| Assert(strm->avail_out > 0, "bug2"); |
| |
| if (flush != Z_FINISH) return Z_OK; |
| if (s->noheader) return Z_STREAM_END; |
| |
| /* Write the zlib trailer (adler32) */ |
| putShortMSB(s, (uInt)(strm->adler >> 16)); |
| putShortMSB(s, (uInt)(strm->adler & 0xffff)); |
| flush_pending(strm); |
| /* If avail_out is zero, the application will call deflate again |
| * to flush the rest. |
| */ |
| s->noheader = -1; /* write the trailer only once! */ |
| return s->pending != 0 ? Z_OK : Z_STREAM_END; |
| } |
| |
| /* ========================================================================= */ |
| int ZEXPORT deflateEnd (strm) |
| z_streamp strm; |
| { |
| int status; |
| |
| if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR; |
| |
| status = strm->state->status; |
| if (status != INIT_STATE && status != BUSY_STATE && |
| status != FINISH_STATE) { |
| return Z_STREAM_ERROR; |
| } |
| |
| /* Deallocate in reverse order of allocations: */ |
| TRY_FREE(strm, strm->state->pending_buf); |
| TRY_FREE(strm, strm->state->head); |
| TRY_FREE(strm, strm->state->prev); |
| TRY_FREE(strm, strm->state->window); |
| |
| ZFREE(strm, strm->state); |
| strm->state = Z_NULL; |
| |
| return status == BUSY_STATE ? Z_DATA_ERROR : Z_OK; |
| } |
| |
| /* ========================================================================= |
| * Copy the source state to the destination state. |
| * To simplify the source, this is not supported for 16-bit MSDOS (which |
| * doesn't have enough memory anyway to duplicate compression states). |
| */ |
| int ZEXPORT deflateCopy (dest, source) |
| z_streamp dest; |
| z_streamp source; |
| { |
| #ifdef MAXSEG_64K |
| return Z_STREAM_ERROR; |
| #else |
| deflate_state *ds; |
| deflate_state *ss; |
| ushf *overlay; |
| |
| |
| if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) { |
| return Z_STREAM_ERROR; |
| } |
| |
| ss = source->state; |
| |
| *dest = *source; |
| |
| ds = (deflate_state *) ZALLOC(dest, 1, sizeof(deflate_state)); |
| if (ds == Z_NULL) return Z_MEM_ERROR; |
| dest->state = (struct internal_state FAR *) ds; |
| *ds = *ss; |
| ds->strm = dest; |
| |
| ds->window = (Bytef *) ZALLOC(dest, ds->w_size, 2*sizeof(Byte)); |
| ds->prev = (Posf *) ZALLOC(dest, ds->w_size, sizeof(Pos)); |
| ds->head = (Posf *) ZALLOC(dest, ds->hash_size, sizeof(Pos)); |
| overlay = (ushf *) ZALLOC(dest, ds->lit_bufsize, sizeof(ush)+2); |
| ds->pending_buf = (uchf *) overlay; |
| |
| if (ds->window == Z_NULL || ds->prev == Z_NULL || ds->head == Z_NULL || |
| ds->pending_buf == Z_NULL) { |
| deflateEnd (dest); |
| return Z_MEM_ERROR; |
| } |
| /* following zmemcpy do not work for 16-bit MSDOS */ |
| zmemcpy(ds->window, ss->window, ds->w_size * 2 * sizeof(Byte)); |
| zmemcpy(ds->prev, ss->prev, ds->w_size * sizeof(Pos)); |
| zmemcpy(ds->head, ss->head, ds->hash_size * sizeof(Pos)); |
| zmemcpy(ds->pending_buf, ss->pending_buf, (uInt)ds->pending_buf_size); |
| |
| ds->pending_out = ds->pending_buf + (ss->pending_out - ss->pending_buf); |
| ds->d_buf = overlay + ds->lit_bufsize/sizeof(ush); |
| ds->l_buf = ds->pending_buf + (1+sizeof(ush))*ds->lit_bufsize; |
| |
| ds->l_desc.dyn_tree = ds->dyn_ltree; |
| ds->d_desc.dyn_tree = ds->dyn_dtree; |
| ds->bl_desc.dyn_tree = ds->bl_tree; |
| |
| return Z_OK; |
| #endif |
| } |
| |
| /* =========================================================================== |
| * Read a new buffer from the current input stream, update the adler32 |
| * and total number of bytes read. All deflate() input goes through |
| * this function so some applications may wish to modify it to avoid |
| * allocating a large strm->next_in buffer and copying from it. |
| * (See also flush_pending()). |
| */ |
| local int read_buf(strm, buf, size) |
| z_streamp strm; |
| Bytef *buf; |
| unsigned size; |
| { |
| unsigned len = strm->avail_in; |
| |
| if (len > size) len = size; |
| if (len == 0) return 0; |
| |
| strm->avail_in -= len; |
| |
| if (!strm->state->noheader) { |
| strm->adler = adler32(strm->adler, strm->next_in, len); |
| } |
| zmemcpy(buf, strm->next_in, len); |
| strm->next_in += len; |
| strm->total_in += len; |
| |
| return (int)len; |
| } |
| |
| /* =========================================================================== |
| * Initialize the "longest match" routines for a new zlib stream |
| */ |
| local void lm_init (s) |
| deflate_state *s; |
| { |
| s->window_size = (ulg)2L*s->w_size; |
| |
| CLEAR_HASH(s); |
| |
| /* Set the default configuration parameters: |
| */ |
| s->max_lazy_match = configuration_table[s->level].max_lazy; |
| s->good_match = configuration_table[s->level].good_length; |
| s->nice_match = configuration_table[s->level].nice_length; |
| s->max_chain_length = configuration_table[s->level].max_chain; |
| |
| s->strstart = 0; |
| s->block_start = 0L; |
| s->lookahead = 0; |
| s->match_length = s->prev_length = MIN_MATCH-1; |
| s->match_available = 0; |
| s->ins_h = 0; |
| #ifdef ASMV |
| match_init(); /* initialize the asm code */ |
| #endif |
| } |
| |
| /* =========================================================================== |
| * Set match_start to the longest match starting at the given string and |
| * return its length. Matches shorter or equal to prev_length are discarded, |
| * in which case the result is equal to prev_length and match_start is |
| * garbage. |
| * IN assertions: cur_match is the head of the hash chain for the current |
| * string (strstart) and its distance is <= MAX_DIST, and prev_length >= 1 |
| * OUT assertion: the match length is not greater than s->lookahead. |
| */ |
| #ifndef ASMV |
| /* For 80x86 and 680x0, an optimized version will be provided in match.asm or |
| * match.S. The code will be functionally equivalent. |
| */ |
| #ifndef FASTEST |
| local uInt longest_match(s, cur_match) |
| deflate_state *s; |
| IPos cur_match; /* current match */ |
| { |
| unsigned chain_length = s->max_chain_length;/* max hash chain length */ |
| register Bytef *scan = s->window + s->strstart; /* current string */ |
| register Bytef *match; /* matched string */ |
| register int len; /* length of current match */ |
| int best_len = s->prev_length; /* best match length so far */ |
| int nice_match = s->nice_match; /* stop if match long enough */ |
| IPos limit = s->strstart > (IPos)MAX_DIST(s) ? |
| s->strstart - (IPos)MAX_DIST(s) : NIL; |
| /* Stop when cur_match becomes <= limit. To simplify the code, |
| * we prevent matches with the string of window index 0. |
| */ |
| Posf *prev = s->prev; |
| uInt wmask = s->w_mask; |
| |
| #ifdef UNALIGNED_OK |
| /* Compare two bytes at a time. Note: this is not always beneficial. |
| * Try with and without -DUNALIGNED_OK to check. |
| */ |
| register Bytef *strend = s->window + s->strstart + MAX_MATCH - 1; |
| register ush scan_start = *(ushf*)scan; |
| register ush scan_end = *(ushf*)(scan+best_len-1); |
| #else |
| register Bytef *strend = s->window + s->strstart + MAX_MATCH; |
| register Byte scan_end1 = scan[best_len-1]; |
| register Byte scan_end = scan[best_len]; |
| #endif |
| |
| /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. |
| * It is easy to get rid of this optimization if necessary. |
| */ |
| Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); |
| |
| /* Do not waste too much time if we already have a good match: */ |
| if (s->prev_length >= s->good_match) { |
| chain_length >>= 2; |
| } |
| /* Do not look for matches beyond the end of the input. This is necessary |
| * to make deflate deterministic. |
| */ |
| if ((uInt)nice_match > s->lookahead) nice_match = s->lookahead; |
| |
| Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); |
| |
| do { |
| Assert(cur_match < s->strstart, "no future"); |
| match = s->window + cur_match; |
| |
| /* Skip to next match if the match length cannot increase |
| * or if the match length is less than 2: |
| */ |
| #if (defined(UNALIGNED_OK) && MAX_MATCH == 258) |
| /* This code assumes sizeof(unsigned short) == 2. Do not use |
| * UNALIGNED_OK if your compiler uses a different size. |
| */ |
| if (*(ushf*)(match+best_len-1) != scan_end || |
| *(ushf*)match != scan_start) continue; |
| |
| /* It is not necessary to compare scan[2] and match[2] since they are |
| * always equal when the other bytes match, given that the hash keys |
| * are equal and that HASH_BITS >= 8. Compare 2 bytes at a time at |
| * strstart+3, +5, ... up to strstart+257. We check for insufficient |
| * lookahead only every 4th comparison; the 128th check will be made |
| * at strstart+257. If MAX_MATCH-2 is not a multiple of 8, it is |
| * necessary to put more guard bytes at the end of the window, or |
| * to check more often for insufficient lookahead. |
| */ |
| Assert(scan[2] == match[2], "scan[2]?"); |
| scan++, match++; |
| do { |
| } while (*(ushf*)(scan+=2) == *(ushf*)(match+=2) && |
| *(ushf*)(scan+=2) == *(ushf*)(match+=2) && |
| *(ushf*)(scan+=2) == *(ushf*)(match+=2) && |
| *(ushf*)(scan+=2) == *(ushf*)(match+=2) && |
| scan < strend); |
| /* The funny "do {}" generates better code on most compilers */ |
| |
| /* Here, scan <= window+strstart+257 */ |
| Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); |
| if (*scan == *match) scan++; |
| |
| len = (MAX_MATCH - 1) - (int)(strend-scan); |
| scan = strend - (MAX_MATCH-1); |
| |
| #else /* UNALIGNED_OK */ |
| |
| if (match[best_len] != scan_end || |
| match[best_len-1] != scan_end1 || |
| *match != *scan || |
| *++match != scan[1]) continue; |
| |
| /* The check at best_len-1 can be removed because it will be made |
| * again later. (This heuristic is not always a win.) |
| * It is not necessary to compare scan[2] and match[2] since they |
| * are always equal when the other bytes match, given that |
| * the hash keys are equal and that HASH_BITS >= 8. |
| */ |
| scan += 2, match++; |
| Assert(*scan == *match, "match[2]?"); |
| |
| /* We check for insufficient lookahead only every 8th comparison; |
| * the 256th check will be made at strstart+258. |
| */ |
| do { |
| } while (*++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| scan < strend); |
| |
| Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); |
| |
| len = MAX_MATCH - (int)(strend - scan); |
| scan = strend - MAX_MATCH; |
| |
| #endif /* UNALIGNED_OK */ |
| |
| if (len > best_len) { |
| s->match_start = cur_match; |
| best_len = len; |
| if (len >= nice_match) break; |
| #ifdef UNALIGNED_OK |
| scan_end = *(ushf*)(scan+best_len-1); |
| #else |
| scan_end1 = scan[best_len-1]; |
| scan_end = scan[best_len]; |
| #endif |
| } |
| } while ((cur_match = prev[cur_match & wmask]) > limit |
| && --chain_length != 0); |
| |
| if ((uInt)best_len <= s->lookahead) return (uInt)best_len; |
| return s->lookahead; |
| } |
| |
| #else /* FASTEST */ |
| /* --------------------------------------------------------------------------- |
| * Optimized version for level == 1 only |
| */ |
| local uInt longest_match(s, cur_match) |
| deflate_state *s; |
| IPos cur_match; /* current match */ |
| { |
| register Bytef *scan = s->window + s->strstart; /* current string */ |
| register Bytef *match; /* matched string */ |
| register int len; /* length of current match */ |
| register Bytef *strend = s->window + s->strstart + MAX_MATCH; |
| |
| /* The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16. |
| * It is easy to get rid of this optimization if necessary. |
| */ |
| Assert(s->hash_bits >= 8 && MAX_MATCH == 258, "Code too clever"); |
| |
| Assert((ulg)s->strstart <= s->window_size-MIN_LOOKAHEAD, "need lookahead"); |
| |
| Assert(cur_match < s->strstart, "no future"); |
| |
| match = s->window + cur_match; |
| |
| /* Return failure if the match length is less than 2: |
| */ |
| if (match[0] != scan[0] || match[1] != scan[1]) return MIN_MATCH-1; |
| |
| /* The check at best_len-1 can be removed because it will be made |
| * again later. (This heuristic is not always a win.) |
| * It is not necessary to compare scan[2] and match[2] since they |
| * are always equal when the other bytes match, given that |
| * the hash keys are equal and that HASH_BITS >= 8. |
| */ |
| scan += 2, match += 2; |
| Assert(*scan == *match, "match[2]?"); |
| |
| /* We check for insufficient lookahead only every 8th comparison; |
| * the 256th check will be made at strstart+258. |
| */ |
| do { |
| } while (*++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| *++scan == *++match && *++scan == *++match && |
| scan < strend); |
| |
| Assert(scan <= s->window+(unsigned)(s->window_size-1), "wild scan"); |
| |
| len = MAX_MATCH - (int)(strend - scan); |
| |
| if (len < MIN_MATCH) return MIN_MATCH - 1; |
| |
| s->match_start = cur_match; |
| return len <= s->lookahead ? len : s->lookahead; |
| } |
| #endif /* FASTEST */ |
| #endif /* ASMV */ |
| |
| #ifdef DEBUG |
| /* =========================================================================== |
| * Check that the match at match_start is indeed a match. |
| */ |
| local void check_match(s, start, match, length) |
| deflate_state *s; |
| IPos start, match; |
| int length; |
| { |
| /* check that the match is indeed a match */ |
| if (zmemcmp(s->window + match, |
| s->window + start, length) != EQUAL) { |
| fprintf(stderr, " start %u, match %u, length %d\n", |
| start, match, length); |
| do { |
| fprintf(stderr, "%c%c", s->window[match++], s->window[start++]); |
| } while (--length != 0); |
| z_error("invalid match"); |
| } |
| if (z_verbose > 1) { |
| fprintf(stderr,"\\[%d,%d]", start-match, length); |
| do { putc(s->window[start++], stderr); } while (--length != 0); |
| } |
| } |
| #else |
| # define check_match(s, start, match, length) |
| #endif |
| |
| /* =========================================================================== |
| * Fill the window when the lookahead becomes insufficient. |
| * Updates strstart and lookahead. |
| * |
| * IN assertion: lookahead < MIN_LOOKAHEAD |
| * OUT assertions: strstart <= window_size-MIN_LOOKAHEAD |
| * At least one byte has been read, or avail_in == 0; reads are |
| * performed for at least two bytes (required for the zip translate_eol |
| * option -- not supported here). |
| */ |
| local void fill_window(s) |
| deflate_state *s; |
| { |
| register unsigned n, m; |
| register Posf *p; |
| unsigned more; /* Amount of free space at the end of the window. */ |
| uInt wsize = s->w_size; |
| |
| do { |
| more = (unsigned)(s->window_size -(ulg)s->lookahead -(ulg)s->strstart); |
| |
| /* Deal with !@#$% 64K limit: */ |
| if (more == 0 && s->strstart == 0 && s->lookahead == 0) { |
| more = wsize; |
| |
| } else if (more == (unsigned)(-1)) { |
| /* Very unlikely, but possible on 16 bit machine if strstart == 0 |
| * and lookahead == 1 (input done one byte at time) |
| */ |
| more--; |
| |
| /* If the window is almost full and there is insufficient lookahead, |
| * move the upper half to the lower one to make room in the upper half. |
| */ |
| } else if (s->strstart >= wsize+MAX_DIST(s)) { |
| |
| zmemcpy(s->window, s->window+wsize, (unsigned)wsize); |
| s->match_start -= wsize; |
| s->strstart -= wsize; /* we now have strstart >= MAX_DIST */ |
| s->block_start -= (long) wsize; |
| |
| /* Slide the hash table (could be avoided with 32 bit values |
| at the expense of memory usage). We slide even when level == 0 |
| to keep the hash table consistent if we switch back to level > 0 |
| later. (Using level 0 permanently is not an optimal usage of |
| zlib, so we don't care about this pathological case.) |
| */ |
| n = s->hash_size; |
| p = &s->head[n]; |
| do { |
| m = *--p; |
| *p = (Pos)(m >= wsize ? m-wsize : NIL); |
| } while (--n); |
| |
| n = wsize; |
| #ifndef FASTEST |
| p = &s->prev[n]; |
| do { |
| m = *--p; |
| *p = (Pos)(m >= wsize ? m-wsize : NIL); |
| /* If n is not on any hash chain, prev[n] is garbage but |
| * its value will never be used. |
| */ |
| } while (--n); |
| #endif |
| more += wsize; |
| } |
| if (s->strm->avail_in == 0) return; |
| |
| /* If there was no sliding: |
| * strstart <= WSIZE+MAX_DIST-1 && lookahead <= MIN_LOOKAHEAD - 1 && |
| * more == window_size - lookahead - strstart |
| * => more >= window_size - (MIN_LOOKAHEAD-1 + WSIZE + MAX_DIST-1) |
| * => more >= window_size - 2*WSIZE + 2 |
| * In the BIG_MEM or MMAP case (not yet supported), |
| * window_size == input_size + MIN_LOOKAHEAD && |
| * strstart + s->lookahead <= input_size => more >= MIN_LOOKAHEAD. |
| * Otherwise, window_size == 2*WSIZE so more >= 2. |
| * If there was sliding, more >= WSIZE. So in all cases, more >= 2. |
| */ |
| Assert(more >= 2, "more < 2"); |
| |
| n = read_buf(s->strm, s->window + s->strstart + s->lookahead, more); |
| s->lookahead += n; |
| |
| /* Initialize the hash value now that we have some input: */ |
| if (s->lookahead >= MIN_MATCH) { |
| s->ins_h = s->window[s->strstart]; |
| UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); |
| #if MIN_MATCH != 3 |
| Call UPDATE_HASH() MIN_MATCH-3 more times |
| #endif |
| } |
| /* If the whole input has less than MIN_MATCH bytes, ins_h is garbage, |
| * but this is not important since only literal bytes will be emitted. |
| */ |
| |
| } while (s->lookahead < MIN_LOOKAHEAD && s->strm->avail_in != 0); |
| } |
| |
| /* =========================================================================== |
| * Flush the current block, with given end-of-file flag. |
| * IN assertion: strstart is set to the end of the current match. |
| */ |
| #define FLUSH_BLOCK_ONLY(s, eof) { \ |
| _tr_flush_block(s, (s->block_start >= 0L ? \ |
| (charf *)&s->window[(unsigned)s->block_start] : \ |
| (charf *)Z_NULL), \ |
| (ulg)((long)s->strstart - s->block_start), \ |
| (eof)); \ |
| s->block_start = s->strstart; \ |
| flush_pending(s->strm); \ |
| Tracev((stderr,"[FLUSH]")); \ |
| } |
| |
| /* Same but force premature exit if necessary. */ |
| #define FLUSH_BLOCK(s, eof) { \ |
| FLUSH_BLOCK_ONLY(s, eof); \ |
| if (s->strm->avail_out == 0) return (eof) ? finish_started : need_more; \ |
| } |
| |
| /* =========================================================================== |
| * Copy without compression as much as possible from the input stream, return |
| * the current block state. |
| * This function does not insert new strings in the dictionary since |
| * uncompressible data is probably not useful. This function is used |
| * only for the level=0 compression option. |
| * NOTE: this function should be optimized to avoid extra copying from |
| * window to pending_buf. |
| */ |
| local block_state deflate_stored(s, flush) |
| deflate_state *s; |
| int flush; |
| { |
| /* Stored blocks are limited to 0xffff bytes, pending_buf is limited |
| * to pending_buf_size, and each stored block has a 5 byte header: |
| */ |
| ulg max_block_size = 0xffff; |
| ulg max_start; |
| |
| if (max_block_size > s->pending_buf_size - 5) { |
| max_block_size = s->pending_buf_size - 5; |
| } |
| |
| /* Copy as much as possible from input to output: */ |
| for (;;) { |
| /* Fill the window as much as possible: */ |
| if (s->lookahead <= 1) { |
| |
| Assert(s->strstart < s->w_size+MAX_DIST(s) || |
| s->block_start >= (long)s->w_size, "slide too late"); |
| |
| fill_window(s); |
| if (s->lookahead == 0 && flush == Z_NO_FLUSH) return need_more; |
| |
| if (s->lookahead == 0) break; /* flush the current block */ |
| } |
| Assert(s->block_start >= 0L, "block gone"); |
| |
| s->strstart += s->lookahead; |
| s->lookahead = 0; |
| |
| /* Emit a stored block if pending_buf will be full: */ |
| max_start = s->block_start + max_block_size; |
| if (s->strstart == 0 || (ulg)s->strstart >= max_start) { |
| /* strstart == 0 is possible when wraparound on 16-bit machine */ |
| s->lookahead = (uInt)(s->strstart - max_start); |
| s->strstart = (uInt)max_start; |
| FLUSH_BLOCK(s, 0); |
| } |
| /* Flush if we may have to slide, otherwise block_start may become |
| * negative and the data will be gone: |
| */ |
| if (s->strstart - (uInt)s->block_start >= MAX_DIST(s)) { |
| FLUSH_BLOCK(s, 0); |
| } |
| } |
| FLUSH_BLOCK(s, flush == Z_FINISH); |
| return flush == Z_FINISH ? finish_done : block_done; |
| } |
| |
| /* =========================================================================== |
| * Compress as much as possible from the input stream, return the current |
| * block state. |
| * This function does not perform lazy evaluation of matches and inserts |
| * new strings in the dictionary only for unmatched strings or for short |
| * matches. It is used only for the fast compression options. |
| */ |
| local block_state deflate_fast(s, flush) |
| deflate_state *s; |
| int flush; |
| { |
| IPos hash_head = NIL; /* head of the hash chain */ |
| int bflush; /* set if current block must be flushed */ |
| |
| for (;;) { |
| /* Make sure that we always have enough lookahead, except |
| * at the end of the input file. We need MAX_MATCH bytes |
| * for the next match, plus MIN_MATCH bytes to insert the |
| * string following the next match. |
| */ |
| if (s->lookahead < MIN_LOOKAHEAD) { |
| fill_window(s); |
| if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { |
| return need_more; |
| } |
| if (s->lookahead == 0) break; /* flush the current block */ |
| } |
| |
| /* Insert the string window[strstart .. strstart+2] in the |
| * dictionary, and set hash_head to the head of the hash chain: |
| */ |
| if (s->lookahead >= MIN_MATCH) { |
| INSERT_STRING(s, s->strstart, hash_head); |
| } |
| |
| /* Find the longest match, discarding those <= prev_length. |
| * At this point we have always match_length < MIN_MATCH |
| */ |
| if (hash_head != NIL && s->strstart - hash_head <= MAX_DIST(s)) { |
| /* To simplify the code, we prevent matches with the string |
| * of window index 0 (in particular we have to avoid a match |
| * of the string with itself at the start of the input file). |
| */ |
| if (s->strategy != Z_HUFFMAN_ONLY) { |
| s->match_length = longest_match (s, hash_head); |
| } |
| /* longest_match() sets match_start */ |
| } |
| if (s->match_length >= MIN_MATCH) { |
| check_match(s, s->strstart, s->match_start, s->match_length); |
| |
| _tr_tally_dist(s, s->strstart - s->match_start, |
| s->match_length - MIN_MATCH, bflush); |
| |
| s->lookahead -= s->match_length; |
| |
| /* Insert new strings in the hash table only if the match length |
| * is not too large. This saves time but degrades compression. |
| */ |
| #ifndef FASTEST |
| if (s->match_length <= s->max_insert_length && |
| s->lookahead >= MIN_MATCH) { |
| s->match_length--; /* string at strstart already in hash table */ |
| do { |
| s->strstart++; |
| INSERT_STRING(s, s->strstart, hash_head); |
| /* strstart never exceeds WSIZE-MAX_MATCH, so there are |
| * always MIN_MATCH bytes ahead. |
| */ |
| } while (--s->match_length != 0); |
| s->strstart++; |
| } else |
| #endif |
| { |
| s->strstart += s->match_length; |
| s->match_length = 0; |
| s->ins_h = s->window[s->strstart]; |
| UPDATE_HASH(s, s->ins_h, s->window[s->strstart+1]); |
| #if MIN_MATCH != 3 |
| Call UPDATE_HASH() MIN_MATCH-3 more times |
| #endif |
| /* If lookahead < MIN_MATCH, ins_h is garbage, but it does not |
| * matter since it will be recomputed at next deflate call. |
| */ |
| } |
| } else { |
| /* No match, output a literal byte */ |
| Tracevv((stderr,"%c", s->window[s->strstart])); |
| _tr_tally_lit (s, s->window[s->strstart], bflush); |
| s->lookahead--; |
| s->strstart++; |
| } |
| if (bflush) FLUSH_BLOCK(s, 0); |
| } |
| FLUSH_BLOCK(s, flush == Z_FINISH); |
| return flush == Z_FINISH ? finish_done : block_done; |
| } |
| |
| /* =========================================================================== |
| * Same as above, but achieves better compression. We use a lazy |
| * evaluation for matches: a match is finally adopted only if there is |
| * no better match at the next window position. |
| */ |
| local block_state deflate_slow(s, flush) |
| deflate_state *s; |
| int flush; |
| { |
| IPos hash_head = NIL; /* head of hash chain */ |
| int bflush; /* set if current block must be flushed */ |
| |
| /* Process the input block. */ |
| for (;;) { |
| /* Make sure that we always have enough lookahead, except |
| * at the end of the input file. We need MAX_MATCH bytes |
| * for the next match, plus MIN_MATCH bytes to insert the |
| * string following the next match. |
| */ |
| if (s->lookahead < MIN_LOOKAHEAD) { |
| fill_window(s); |
| if (s->lookahead < MIN_LOOKAHEAD && flush == Z_NO_FLUSH) { |
| return need_more; |
| } |
| if (s->lookahead == 0) break; /* flush the current block */ |
| } |
| |
| /* Insert the string window[strstart .. strstart+2] in the |
| * dictionary, and set hash_head to the head of the hash chain: |
| */ |
| if (s->lookahead >= MIN_MATCH) { |
| INSERT_STRING(s, s->strstart, hash_head); |
| } |
| |
| /* Find the longest match, discarding those <= prev_length. |
| */ |
| s->prev_length = s->match_length, s->prev_match = s->match_start; |
| s->match_length = MIN_MATCH-1; |
| |
| if (hash_head != NIL && s->prev_length < s->max_lazy_match && |
| s->strstart - hash_head <= MAX_DIST(s)) { |
| /* To simplify the code, we prevent matches with the string |
| * of window index 0 (in particular we have to avoid a match |
| * of the string with itself at the start of the input file). |
| */ |
| if (s->strategy != Z_HUFFMAN_ONLY) { |
| s->match_length = longest_match (s, hash_head); |
| } |
| /* longest_match() sets match_start */ |
| |
| if (s->match_length <= 5 && (s->strategy == Z_FILTERED || |
| (s->match_length == MIN_MATCH && |
| s->strstart - s->match_start > TOO_FAR))) { |
| |
| /* If prev_match is also MIN_MATCH, match_start is garbage |
| * but we will ignore the current match anyway. |
| */ |
| s->match_length = MIN_MATCH-1; |
| } |
| } |
| /* If there was a match at the previous step and the current |
| * match is not better, output the previous match: |
| */ |
| if (s->prev_length >= MIN_MATCH && s->match_length <= s->prev_length) { |
| uInt max_insert = s->strstart + s->lookahead - MIN_MATCH; |
| /* Do not insert strings in hash table beyond this. */ |
| |
| check_match(s, s->strstart-1, s->prev_match, s->prev_length); |
| |
| _tr_tally_dist(s, s->strstart -1 - s->prev_match, |
| s->prev_length - MIN_MATCH, bflush); |
| |
| /* Insert in hash table all strings up to the end of the match. |
| * strstart-1 and strstart are already inserted. If there is not |
| * enough lookahead, the last two strings are not inserted in |
| * the hash table. |
| */ |
| s->lookahead -= s->prev_length-1; |
| s->prev_length -= 2; |
| do { |
| if (++s->strstart <= max_insert) { |
| INSERT_STRING(s, s->strstart, hash_head); |
| } |
| } while (--s->prev_length != 0); |
| s->match_available = 0; |
| s->match_length = MIN_MATCH-1; |
| s->strstart++; |
| |
| if (bflush) FLUSH_BLOCK(s, 0); |
| |
| } else if (s->match_available) { |
| /* If there was no match at the previous position, output a |
| * single literal. If there was a match but the current match |
| * is longer, truncate the previous match to a single literal. |
| */ |
| Tracevv((stderr,"%c", s->window[s->strstart-1])); |
| _tr_tally_lit(s, s->window[s->strstart-1], bflush); |
| if (bflush) { |
| FLUSH_BLOCK_ONLY(s, 0); |
| } |
| s->strstart++; |
| s->lookahead--; |
| if (s->strm->avail_out == 0) return need_more; |
| } else { |
| /* There is no previous match to compare with, wait for |
| * the next step to decide. |
| */ |
| s->match_available = 1; |
| s->strstart++; |
| s->lookahead--; |
| } |
| } |
| Assert (flush != Z_NO_FLUSH, "no flush?"); |
| if (s->match_available) { |
| Tracevv((stderr,"%c", s->window[s->strstart-1])); |
| _tr_tally_lit(s, s->window[s->strstart-1], bflush); |
| s->match_available = 0; |
| } |
| FLUSH_BLOCK(s, flush == Z_FINISH); |
| return flush == Z_FINISH ? finish_done : block_done; |
| } |