/* trees.c -- output deflated data using Huffman coding * Copyright (C) 1995-2024 Jean-loup Gailly * detect_data_type() function provided freely by Cosmin Truta, 2006 * For conditions of distribution and use, see copyright notice in zlib.h */ /* *  ALGORITHM * *      The "deflation" process uses several Huffman trees. The more *      common source values are represented by shorter bit sequences. * *      Each code tree is stored in a compressed form which is itself * a Huffman encoding of the lengths of all the code strings (in * ascending order by source values).  The actual code strings are * reconstructed from the lengths in the inflate process, as described * in the deflate specification. * *  REFERENCES * *      Deutsch, L.P.,"'Deflate' Compressed Data Format Specification". *      Available in ftp.uu.net:/pub/archiving/zip/doc/deflate-1.1.doc * *      Storer, James A. *          Data Compression:  Methods and Theory, pp. 49-50. *          Computer Science Press, 1988.  ISBN 0-7167-8156-5. * *      Sedgewick, R. *          Algorithms, p290. *          Addison-Wesley, 1983. ISBN 0-201-06672-6. */ /* @(#) $Id$ */ /* #define GEN_TREES_H */ #include "deflate.h" #ifdef ZLIB_DEBUG#  include <ctype.h>#endif /* =========================================================================== * Constants */ #define MAX_BL_BITS 7/* Bit length codes must not exceed MAX_BL_BITS bits */ #define END_BLOCK 256/* end of block literal code */ #define REP_3_6      16/* repeat previous bit length 3-6 times (2 bits of repeat count) */ #define REPZ_3_10    17/* repeat a zero length 3-10 times  (3 bits of repeat count) */ #define REPZ_11_138  18/* repeat a zero length 11-138 times  (7 bits of repeat count) */ local const int extra_lbits[LENGTH_CODES] /* extra bits for each length code */   = {0,0,0,0,0,0,0,0,1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,0}; local const int extra_dbits[D_CODES] /* extra bits for each distance code */   = {0,0,0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13}; local const int extra_blbits[BL_CODES]/* extra bits for each bit length code */   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7}; local const uch bl_order[BL_CODES]   = {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};/* The lengths of the bit length codes are sent in order of decreasing * probability, to avoid transmitting the lengths for unused bit length codes. */ /* =========================================================================== * Local data. These are initialized only once. */ #define DIST_CODE_LEN  512 /* see definition of array dist_code below */ #if defined(GEN_TREES_H) || !defined(STDC)/* non ANSI compilers may not accept trees.h */ local ct_data static_ltree[L_CODES+2];/* The static literal tree. Since the bit lengths are imposed, there is no * need for the L_CODES extra codes used during heap construction. However * The codes 286 and 287 are needed to build a canonical tree (see _tr_init * below). */ local ct_data static_dtree[D_CODES];/* The static distance tree. (Actually a trivial tree since all codes use * 5 bits.) */ uch _dist_code[DIST_CODE_LEN];/* Distance codes. The first 256 values correspond to the distances * 3 .. 258, the last 256 values correspond to the top 8 bits of * the 15 bit distances. */ uch _length_code[MAX_MATCH-MIN_MATCH+1];/* length code for each normalized match length (0 == MIN_MATCH) */ local int base_length[LENGTH_CODES];/* First normalized length for each code (0 = MIN_MATCH) */ local int base_dist[D_CODES];/* First normalized distance for each code (0 = distance of 1) */ #else#  include "trees.h"#endif /* GEN_TREES_H */ struct static_tree_desc_s {    const ct_data *static_tree;  /* static tree or NULL */    const intf *extra_bits;      /* extra bits for each code or NULL */    int     extra_base;          /* base index for extra_bits */    int     elems;               /* max number of elements in the tree */    int     max_length;          /* max bit length for the codes */}; #ifdef NO_INIT_GLOBAL_POINTERS#  define TCONST#else#  define TCONST const#endif local TCONST static_tree_desc static_l_desc ={static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS}; local TCONST static_tree_desc static_d_desc ={static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS}; local TCONST static_tree_desc static_bl_desc ={(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS}; /* =========================================================================== * Output a short LSB first on the stream. * IN assertion: there is enough room in pendingBuf. */#define put_short(s, w) { \    put_byte(s, (uch)((w) & 0xff)); \    put_byte(s, (uch)((ush)(w) >> 8)); \} /* =========================================================================== * Reverse the first len bits of a code, using straightforward code (a faster * method would use a table) * IN assertion: 1 <= len <= 15 */local unsigned bi_reverse(unsigned code, int len) {    register unsigned res = 0;    do {        res |= code & 1;        code >>= 1, res <<= 1;    } while (--len > 0);    return res >> 1;} /* =========================================================================== * Flush the bit buffer, keeping at most 7 bits in it. */local void bi_flush(deflate_state *s) {    if (s->bi_valid == 16) {        put_short(s, s->bi_buf);        s->bi_buf = 0;        s->bi_valid = 0;    } else if (s->bi_valid >= 8) {        put_byte(s, (Byte)s->bi_buf);        s->bi_buf >>= 8;        s->bi_valid -= 8;    }} /* =========================================================================== * Flush the bit buffer and align the output on a byte boundary */local void bi_windup(deflate_state *s) {    if (s->bi_valid > 8) {        put_short(s, s->bi_buf);    } else if (s->bi_valid > 0) {        put_byte(s, (Byte)s->bi_buf);    }    s->bi_buf = 0;    s->bi_valid = 0;#ifdef ZLIB_DEBUG    s->bits_sent = (s->bits_sent + 7) & ~7;#endif} /* =========================================================================== * Generate the codes for a given tree and bit counts (which need not be * optimal). * IN assertion: the array bl_count contains the bit length statistics for * the given tree and the field len is set for all tree elements. * OUT assertion: the field code is set for all tree elements of non *     zero code length. */local void gen_codes(ct_data *tree, int max_code, ushf *bl_count) {    ush next_code[MAX_BITS+1]; /* next code value for each bit length */    unsigned code = 0;         /* running code value */    int bits;                  /* bit index */    int n;                     /* code index */     /* The distribution counts are first used to generate the code values     * without bit reversal.     */    for (bits = 1; bits <= MAX_BITS; bits++) {        code = (code + bl_count[bits - 1]) << 1;        next_code[bits] = (ush)code;    }    /* Check that the bit counts in bl_count are consistent. The last code     * must be all ones.     */    Assert (code + bl_count[MAX_BITS] - 1 == (1 << MAX_BITS) - 1,            "inconsistent bit counts");    Tracev((stderr,"\ngen_codes: max_code %d ", max_code));     for (n = 0;  n <= max_code; n++) {        int len = tree[n].Len;        if (len == 0) continue;        /* Now reverse the bits */        tree[n].Code = (ush)bi_reverse(next_code[len]++, len);         Tracecv(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",            n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len] - 1));    }} #ifdef GEN_TREES_Hlocal void gen_trees_header(void);#endif #ifndef ZLIB_DEBUG#  define send_code(s, c, tree) send_bits(s, tree[c].Code, tree[c].Len)   /* Send a code of the given tree. c and tree must not have side effects */ #else /* !ZLIB_DEBUG */#  define send_code(s, c, tree) \     { if (z_verbose>2) fprintf(stderr,"\ncd %3d ",(c)); \       send_bits(s, tree[c].Code, tree[c].Len); }#endif /* =========================================================================== * Send a value on a given number of bits. * IN assertion: length <= 16 and value fits in length bits. */#ifdef ZLIB_DEBUGlocal void send_bits(deflate_state *s, int value, int length) {    Tracevv((stderr," l %2d v %4x ", length, value));    Assert(length > 0 && length <= 15, "invalid length");    s->bits_sent += (ulg)length;     /* If not enough room in bi_buf, use (valid) bits from bi_buf and     * (16 - bi_valid) bits from value, leaving (width - (16 - bi_valid))     * unused bits in value.     */    if (s->bi_valid > (int)Buf_size - length) {        s->bi_buf |= (ush)value << s->bi_valid;        put_short(s, s->bi_buf);        s->bi_buf = (ush)value >> (Buf_size - s->bi_valid);        s->bi_valid += length - Buf_size;    } else {        s->bi_buf |= (ush)value << s->bi_valid;        s->bi_valid += length;    }}#else /* !ZLIB_DEBUG */ #define send_bits(s, value, length) \{ int len = length;\  if (s->bi_valid > (int)Buf_size - len) {\    int val = (int)value;\    s->bi_buf |= (ush)val << s->bi_valid;\    put_short(s, s->bi_buf);\    s->bi_buf = (ush)val >> (Buf_size - s->bi_valid);\    s->bi_valid += len - Buf_size;\  } else {\    s->bi_buf |= (ush)(value) << s->bi_valid;\    s->bi_valid += len;\  }\}#endif /* ZLIB_DEBUG */  /* the arguments must not have side effects */ /* =========================================================================== * Initialize the various 'constant' tables. */local void tr_static_init(void) {#if defined(GEN_TREES_H) || !defined(STDC)    static int static_init_done = 0;    int n;        /* iterates over tree elements */    int bits;     /* bit counter */    int length;   /* length value */    int code;     /* code value */    int dist;     /* distance index */    ush bl_count[MAX_BITS+1];    /* number of codes at each bit length for an optimal tree */     if (static_init_done) return;     /* For some embedded targets, global variables are not initialized: */#ifdef NO_INIT_GLOBAL_POINTERS    static_l_desc.static_tree = static_ltree;    static_l_desc.extra_bits = extra_lbits;    static_d_desc.static_tree = static_dtree;    static_d_desc.extra_bits = extra_dbits;    static_bl_desc.extra_bits = extra_blbits;#endif     /* Initialize the mapping length (0..255) -> length code (0..28) */    length = 0;    for (code = 0; code < LENGTH_CODES-1; code++) {        base_length[code] = length;        for (n = 0; n < (1 << extra_lbits[code]); n++) {            _length_code[length++] = (uch)code;        }    }    Assert (length == 256, "tr_static_init: length != 256");    /* Note that the length 255 (match length 258) can be represented     * in two different ways: code 284 + 5 bits or code 285, so we     * overwrite length_code[255] to use the best encoding:     */    _length_code[length - 1] = (uch)code;     /* Initialize the mapping dist (0..32K) -> dist code (0..29) */    dist = 0;    for (code = 0 ; code < 16; code++) {        base_dist[code] = dist;        for (n = 0; n < (1 << extra_dbits[code]); n++) {            _dist_code[dist++] = (uch)code;        }    }    Assert (dist == 256, "tr_static_init: dist != 256");    dist >>= 7; /* from now on, all distances are divided by 128 */    for ( ; code < D_CODES; code++) {        base_dist[code] = dist << 7;        for (n = 0; n < (1 << (extra_dbits[code] - 7)); n++) {            _dist_code[256 + dist++] = (uch)code;        }    }    Assert (dist == 256, "tr_static_init: 256 + dist != 512");     /* Construct the codes of the static literal tree */    for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;    n = 0;    while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;    while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;    while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;    while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;    /* Codes 286 and 287 do not exist, but we must include them in the     * tree construction to get a canonical Huffman tree (longest code     * all ones)     */    gen_codes((ct_data *)static_ltree, L_CODES+1, bl_count);     /* The static distance tree is trivial: */    for (n = 0; n < D_CODES; n++) {        static_dtree[n].Len = 5;        static_dtree[n].Code = bi_reverse((unsigned)n, 5);    }    static_init_done = 1; #  ifdef GEN_TREES_H    gen_trees_header();#  endif#endif /* defined(GEN_TREES_H) || !defined(STDC) */} /* =========================================================================== * Generate the file trees.h describing the static trees. */#ifdef GEN_TREES_H#  ifndef ZLIB_DEBUG#    include <stdio.h>#  endif #  define SEPARATOR(i, last, width) \      ((i) == (last)? "\n};\n\n" :    \       ((i) % (width) == (width) - 1 ? ",\n" : ", ")) void gen_trees_header(void) {    FILE *header = fopen("trees.h", "w");    int i;     Assert (header != NULL, "Can't open trees.h");    fprintf(header,            "/* header created automatically with -DGEN_TREES_H */\n\n");     fprintf(header, "local const ct_data static_ltree[L_CODES+2] = {\n");    for (i = 0; i < L_CODES+2; i++) {        fprintf(header, "{{%3u},{%3u}}%s", static_ltree[i].Code,                static_ltree[i].Len, SEPARATOR(i, L_CODES+1, 5));    }     fprintf(header, "local const ct_data static_dtree[D_CODES] = {\n");    for (i = 0; i < D_CODES; i++) {        fprintf(header, "{{%2u},{%2u}}%s", static_dtree[i].Code,                static_dtree[i].Len, SEPARATOR(i, D_CODES-1, 5));    }     fprintf(header, "const uch ZLIB_INTERNAL _dist_code[DIST_CODE_LEN] = {\n");    for (i = 0; i < DIST_CODE_LEN; i++) {        fprintf(header, "%2u%s", _dist_code[i],                SEPARATOR(i, DIST_CODE_LEN-1, 20));    }     fprintf(header,        "const uch ZLIB_INTERNAL _length_code[MAX_MATCH-MIN_MATCH+1]= {\n");    for (i = 0; i < MAX_MATCH-MIN_MATCH+1; i++) {        fprintf(header, "%2u%s", _length_code[i],                SEPARATOR(i, MAX_MATCH-MIN_MATCH, 20));    }     fprintf(header, "local const int base_length[LENGTH_CODES] = {\n");    for (i = 0; i < LENGTH_CODES; i++) {        fprintf(header, "%1u%s", base_length[i],                SEPARATOR(i, LENGTH_CODES-1, 20));    }     fprintf(header, "local const int base_dist[D_CODES] = {\n");    for (i = 0; i < D_CODES; i++) {        fprintf(header, "%5u%s", base_dist[i],                SEPARATOR(i, D_CODES-1, 10));    }     fclose(header);}#endif /* GEN_TREES_H */ /* =========================================================================== * Initialize a new block. */local void init_block(deflate_state *s) {    int n; /* iterates over tree elements */     /* Initialize the trees. */    for (n = 0; n < L_CODES;  n++) s->dyn_ltree[n].Freq = 0;    for (n = 0; n < D_CODES;  n++) s->dyn_dtree[n].Freq = 0;    for (n = 0; n < BL_CODES; n++) s->bl_tree[n].Freq = 0;     s->dyn_ltree[END_BLOCK].Freq = 1;    s->opt_len = s->static_len = 0L;    s->sym_next = s->matches = 0;} /* =========================================================================== * Initialize the tree data structures for a new zlib stream. */void ZLIB_INTERNAL _tr_init(deflate_state *s) {    tr_static_init();     s->l_desc.dyn_tree = s->dyn_ltree;    s->l_desc.stat_desc = &static_l_desc;     s->d_desc.dyn_tree = s->dyn_dtree;    s->d_desc.stat_desc = &static_d_desc;     s->bl_desc.dyn_tree = s->bl_tree;    s->bl_desc.stat_desc = &static_bl_desc;     s->bi_buf = 0;    s->bi_valid = 0;#ifdef ZLIB_DEBUG    s->compressed_len = 0L;    s->bits_sent = 0L;#endif     /* Initialize the first block of the first file: */    init_block(s);} #define SMALLEST 1/* Index within the heap array of least frequent node in the Huffman tree */  /* =========================================================================== * Remove the smallest element from the heap and recreate the heap with * one less element. Updates heap and heap_len. */#define pqremove(s, tree, top) \{\    top = s->heap[SMALLEST]; \    s->heap[SMALLEST] = s->heap[s->heap_len--]; \    pqdownheap(s, tree, SMALLEST); \} /* =========================================================================== * Compares to subtrees, using the tree depth as tie breaker when * the subtrees have equal frequency. This minimizes the worst case length. */#define smaller(tree, n, m, depth) \   (tree[n].Freq < tree[m].Freq || \   (tree[n].Freq == tree[m].Freq && depth[n] <= depth[m])) 

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