cregit-Linux how code gets into the kernel

Release 4.9 lib/zlib_deflate/deftree.c

Directory: lib/zlib_deflate
/* +++ trees.c */
/* trees.c -- output deflated data using Huffman coding
 * Copyright (C) 1995-1996 Jean-loup Gailly
 * 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.
 */

/* From: trees.c,v 1.11 1996/07/24 13:41:06 me Exp $ */

/* #include "deflate.h" */

#include <linux/zutil.h>
#include <linux/bitrev.h>
#include "defutil.h"

#ifdef DEBUG_ZLIB
#  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) */


static 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};


static 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};


static 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};


static 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.
 */


#define Buf_size (8 * 2*sizeof(char))
/* Number of bits used within bi_buf. (bi_buf might be implemented on
 * more than 16 bits on some systems.)
 */

/* ===========================================================================
 * Local data. These are initialized only once.
 */


static 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 zlib_tr_init
 * below).
 */


static ct_data static_dtree[D_CODES];
/* The static distance tree. (Actually a trivial tree since all codes use
 * 5 bits.)
 */


static uch dist_code[512];
/* 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.
 */


static uch length_code[MAX_MATCH-MIN_MATCH+1];
/* length code for each normalized match length (0 == MIN_MATCH) */


static int base_length[LENGTH_CODES];
/* First normalized length for each code (0 = MIN_MATCH) */


static int base_dist[D_CODES];
/* First normalized distance for each code (0 = distance of 1) */


struct static_tree_desc_s {
    
const ct_data *static_tree;  /* static tree or NULL */
    
const int *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 */
};


static static_tree_desc  static_l_desc =
{static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS};


static static_tree_desc  static_d_desc =
{static_dtree, extra_dbits, 0,          D_CODES, MAX_BITS};


static static_tree_desc  static_bl_desc =
{(const ct_data *)0, extra_blbits, 0,   BL_CODES, MAX_BL_BITS};

/* ===========================================================================
 * Local (static) routines in this file.
 */

static void tr_static_init (void);
static void init_block     (deflate_state *s);
static void pqdownheap     (deflate_state *s, ct_data *tree, int k);
static void gen_bitlen     (deflate_state *s, tree_desc *desc);
static void gen_codes      (ct_data *tree, int max_code, ush *bl_count);
static void build_tree     (deflate_state *s, tree_desc *desc);
static void scan_tree      (deflate_state *s, ct_data *tree, int max_code);
static void send_tree      (deflate_state *s, ct_data *tree, int max_code);
static int  build_bl_tree  (deflate_state *s);
static void send_all_trees (deflate_state *s, int lcodes, int dcodes,
                           int blcodes);
static void compress_block (deflate_state *s, ct_data *ltree,
                           ct_data *dtree);
static void set_data_type  (deflate_state *s);
static void bi_windup      (deflate_state *s);
static void bi_flush       (deflate_state *s);
static void copy_block     (deflate_state *s, char *buf, unsigned len,
                           int header);

#ifndef DEBUG_ZLIB

#  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 /* DEBUG_ZLIB */

#  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


#define d_code(dist) \
   ((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])
/* Mapping from a distance to a distance code. dist is the distance - 1 and
 * must not have side effects. dist_code[256] and dist_code[257] are never
 * used.
 */

/* ===========================================================================
 * Send a value on a given number of bits.
 * IN assertion: length <= 16 and value fits in length bits.
 */
#ifdef DEBUG_ZLIB
static void send_bits      (deflate_state *s, int value, int length);


static void send_bits( deflate_state *s, int value, /* value to send */ int length /* number of bits */ ) { 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 |= (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 |= value << s->bi_valid; s->bi_valid += length; } }

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Total134100.00%3100.00%

#else /* !DEBUG_ZLIB */ #define send_bits(s, value, length) \ { int len = length;\ if (s->bi_valid > (int)Buf_size - len) {\ int val = value;\ s->bi_buf |= (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 |= (value) << s->bi_valid;\ s->bi_valid += len;\ }\ } #endif /* DEBUG_ZLIB */ /* =========================================================================== * Initialize the various 'constant' tables. In a multi-threaded environment, * this function may be called by two threads concurrently, but this is * harmless since both invocations do exactly the same thing. */
static void tr_static_init(void) { static int static_init_done; 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; /* 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 = bitrev32((u32)n) >> (32 - 5); } static_init_done = 1; }

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joern engeljoern engel10.22%125.00%
Total452100.00%4100.00%

/* =========================================================================== * Initialize the tree data structures for a new zlib stream. */
void zlib_tr_init( deflate_state *s ) { tr_static_init(); s->compressed_len = 0L; 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; s->last_eob_len = 8; /* enough lookahead for inflate */ #ifdef DEBUG_ZLIB s->bits_sent = 0L; #endif /* Initialize the first block of the first file: */ init_block(s); }

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/* =========================================================================== * Initialize a new block. */
static 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->last_lit = s->matches = 0; }

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Total118100.00%3100.00%

#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])) /* =========================================================================== * Restore the heap property by moving down the tree starting at node k, * exchanging a node with the smallest of its two sons if necessary, stopping * when the heap property is re-established (each father smaller than its * two sons). */
static void pqdownheap( deflate_state *s, ct_data *tree, /* the tree to restore */ int k /* node to move down */ ) { int v = s->heap[k]; int j = k << 1; /* left son of k */ while (j <= s->heap_len) { /* Set j to the smallest of the two sons: */ if (j < s->heap_len && smaller(tree, s->heap[j+1], s->heap[j], s->depth)) { j++; } /* Exit if v is smaller than both sons */ if (smaller(tree, v, s->heap[j], s->depth)) break; /* Exchange v with the smallest son */ s->heap[k] = s->heap[j]; k = j; /* And continue down the tree, setting j to the left son of k */ j <<= 1; } s->heap[k] = v; }

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Total141100.00%3100.00%

/* =========================================================================== * Compute the optimal bit lengths for a tree and update the total bit length * for the current block. * IN assertion: the fields freq and dad are set, heap[heap_max] and * above are the tree nodes sorted by increasing frequency. * OUT assertions: the field len is set to the optimal bit length, the * array bl_count contains the frequencies for each bit length. * The length opt_len is updated; static_len is also updated if stree is * not null. */
static void gen_bitlen( deflate_state *s, tree_desc *desc /* the tree descriptor */ ) { ct_data *tree = desc->dyn_tree; int max_code = desc->max_code; const ct_data *stree = desc->stat_desc->static_tree; const int *extra = desc->stat_desc->extra_bits; int base = desc->stat_desc->extra_base; int max_length = desc->stat_desc->max_length; int h; /* heap index */ int n, m; /* iterate over the tree elements */ int bits; /* bit length */ int xbits; /* extra bits */ ush f; /* frequency */ int overflow = 0; /* number of elements with bit length too large */ for (bits = 0; bits <= MAX_BITS; bits++) s->bl_count[bits] = 0; /* In a first pass, compute the optimal bit lengths (which may * overflow in the case of the bit length tree). */ tree[s->heap[s->heap_max]].Len = 0; /* root of the heap */ for (h = s->heap_max+1; h < HEAP_SIZE; h++) { n = s->heap[h]; bits = tree[tree[n].Dad].Len + 1; if (bits > max_length) bits = max_length, overflow++; tree[n].Len = (ush)bits; /* We overwrite tree[n].Dad which is no longer needed */ if (n > max_code) continue; /* not a leaf node */ s->bl_count[bits]++; xbits = 0; if (n >= base) xbits = extra[n-base]; f = tree[n].Freq; s->opt_len += (ulg)f * (bits + xbits); if (stree) s->static_len += (ulg)f * (stree[n].Len + xbits); } if (overflow == 0) return; Trace((stderr,"\nbit length overflow\n")); /* This happens for example on obj2 and pic of the Calgary corpus */ /* Find the first bit length which could increase: */ do { bits = max_length-1; while (s->bl_count[bits] == 0) bits--; s->bl_count[bits]--; /* move one leaf down the tree */ s->bl_count[bits+1] += 2; /* move one overflow item as its brother */ s->bl_count[max_length]--; /* The brother of the overflow item also moves one step up, * but this does not affect bl_count[max_length] */ overflow -= 2; } while (overflow > 0); /* Now recompute all bit lengths, scanning in increasing frequency. * h is still equal to HEAP_SIZE. (It is simpler to reconstruct all * lengths instead of fixing only the wrong ones. This idea is taken * from 'ar' written by Haruhiko Okumura.) */ for (bits = max_length; bits != 0; bits--) { n = s->bl_count[bits]; while (n != 0) { m = s->heap[--h]; if (m > max_code) continue; if (tree[m].Len != (unsigned) bits) { Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits)); s->opt_len += ((long)bits - (long)tree[m].Len) *(long)tree[m].Freq; tree[m].Len = (ush)bits; } n--; } } }

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Total505100.00%4100.00%

/* =========================================================================== * 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. */
static void gen_codes( ct_data *tree, /* the tree to decorate */ int max_code, /* largest code with non zero frequency */ ush *bl_count /* number of codes at each bit length */ ) { ush next_code[MAX_BITS+1]; /* next code value for each bit length */ ush 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++) { next_code[bits] = code = (code + bl_count[bits-1]) << 1; } /* 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 = bitrev32((u32)(next_code[len]++)) >> (32 - 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)); } }

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steven colesteven cole31.40%120.00%
joern engeljoern engel20.93%240.00%
Total215100.00%5100.00%

/* =========================================================================== * Construct one Huffman tree and assigns the code bit strings and lengths. * Update the total bit length for the current block. * IN assertion: the field freq is set for all tree elements. * OUT assertions: the fields len and code are set to the optimal bit length * and corresponding code. The length opt_len is updated; static_len is * also updated if stree is not null. The field max_code is set. */
static void build_tree( deflate_state *s, tree_desc *desc /* the tree descriptor */ ) { ct_data *tree = desc->dyn_tree; const ct_data *stree = desc->stat_desc->static_tree; int elems = desc->stat_desc->elems; int n, m; /* iterate over heap elements */ int max_code = -1; /* largest code with non zero frequency */ int node; /* new node being created */ /* Construct the initial heap, with least frequent element in * heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1]. * heap[0] is not used. */ s->heap_len = 0, s->heap_max = HEAP_SIZE; for (n = 0; n < elems; n++) { if (tree[n].Freq != 0) { s->heap[++(s->heap_len)] = max_code = n; s->depth[n] = 0; } else { tree[n].Len = 0; } } /* The pkzip format requires that at least one distance code exists, * and that at least one bit should be sent even if there is only one * possible code. So to avoid special checks later on we force at least * two codes of non zero frequency. */ while (s->heap_len < 2) { node = s->heap[++(s->heap_len)] = (max_code < 2 ? ++max_code : 0); tree[node].Freq = 1; s->depth[node] = 0; s->opt_len--; if (stree) s->static_len -= stree[node].Len; /* node is 0 or 1 so it does not have extra bits */ } desc->max_code = max_code; /* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree, * establish sub-heaps of increasing lengths: */ for (n = s->heap_len/2; n >= 1; n--) pqdownheap(s, tree, n); /* Construct the Huffman tree by repeatedly combining the least two * frequent nodes. */ node = elems; /* next internal node of the tree */ do { pqremove(s, tree, n); /* n = node of least frequency */ m = s->heap[SMALLEST]; /* m = node of next least frequency */ s->heap[--(s->heap_max)] = n; /* keep the nodes sorted by frequency */ s->heap[--(s->heap_max)] = m; /* Create a new node father of n and m */ tree[node].Freq = tree[n].Freq + tree[m].Freq; s->depth[node] = (uch) (max(s->depth[n], s->depth[m]) + 1); tree[n].Dad = tree[m].Dad = (ush)node; #ifdef DUMP_BL_TREE if (tree == s->bl_tree) { fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)", node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq); } #endif /* and insert the new node in the heap */ s->heap[SMALLEST] = node++; pqdownheap(s, tree, SMALLEST); } while (s->heap_len >= 2); s->heap[--(s->heap_max)] = s->heap[SMALLEST]; /* At this point, the fields freq and dad are set. We can now * generate the bit lengths. */ gen_bitlen(s, (tree_desc *)desc); /* The field len is now set, we can generate the bit codes */ gen_codes ((ct_data *)tree, max_code, s->bl_count); }

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andrew mortonandrew morton10.20%125.00%
Total501100.00%4100.00%

/* =========================================================================== * Scan a literal or distance tree to determine the frequencies of the codes * in the bit length tree. */
static void scan_tree( deflate_state *s, ct_data *tree, /* the tree to be scanned */ int max_code /* and its largest code of non zero frequency */ ) { int n; /* iterates over all tree elements */ int prevlen = -1; /* last emitted length */ int curlen; /* length of current code */ int nextlen = tree[0].Len; /* length of next code */ int count = 0; /* repeat count of the current code */ int max_count = 7; /* max repeat count */ int min_count = 4; /* min repeat count */ if (nextlen == 0) max_count = 138, min_count = 3; tree[max_code+1].Len = (ush)0xffff; /* guard */ for (n = 0; n <= max_code; n++) { curlen = nextlen; nextlen = tree[n+1].Len; if (++count < max_count && curlen == nextlen) { continue; } else if (count < min_count) { s->bl_tree[curlen].Freq += count; } else if (curlen != 0) { if (curlen != prevlen) s->bl_tree[curlen].Freq++; s->bl_tree[REP_3_6].Freq++; } else if (count <= 10) { s->bl_tree[REPZ_3_10].Freq++; } else { s->bl_tree[REPZ_11_138].Freq++; } count = 0; prevlen = curlen; if (nextlen == 0) { max_count = 138, min_count = 3; } else if (curlen == nextlen) { max_count = 6, min_count = 3; } else { max_count = 7, min_count = 4; } } }

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Total275100.00%3100.00%

/* =========================================================================== * Send a literal or distance tree in compressed form, using the codes in * bl_tree. */
static void send_tree( deflate_state *s, ct_data *tree, /* the tree to be scanned */ int max_code /* and its largest code of non zero frequency */ ) { int n; /* iterates over all tree elements */ int prevlen = -1; /* last emitted length */ int curlen; /* length of current code */ int nextlen = tree[0].Len; /* length of next code */ int count = 0; /* repeat count of the current code */ int max_count = 7; /* max repeat count */ int min_count = 4; /* min repeat count */ /* tree[max_code+1].Len = -1; */ /* guard already set */ if (nextlen == 0) max_count = 138, min_count = 3; for (n = 0; n <= max_code; n++) { curlen = nextlen; nextlen = tree[n+1].Len; if (++count < max_count && curlen == nextlen) { continue; } else if (count < min_count) { do { send_code(s, curlen, s->bl_tree); } while (--count != 0); } else if (curlen != 0) { if (curlen != prevlen) { send_code(s, curlen, s->bl_tree); count--; } Assert(count >= 3 && count <= 6, " 3_6?"); send_code(s, REP_3_6, s->bl_tree); send_bits(s, count-3, 2); } else if (count <= 10) { send_code(s, REPZ_3_10, s->bl_tree); send_bits(s, count-3, 3); } else { send_code(s, REPZ_11_138, s->bl_tree); send_bits(s, count-11, 7); } count = 0; prevlen = curlen; if (nextlen == 0) { max_count = 138, min_count = 3; } else if (curlen == nextlen) { max_count = 6, min_count = 3; } else { max_count = 7, min_count = 4; } } }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds32498.78%133.33%
steven colesteven cole30.91%133.33%
joern engeljoern engel10.30%133.33%
Total328100.00%3100.00%

/* =========================================================================== * Construct the Huffman tree for the bit lengths and return the index in * bl_order of the last bit length code to send. */
static int build_bl_tree( deflate_state *s ) { int max_blindex; /* index of last bit length code of non zero freq */ /* Determine the bit length frequencies for literal and distance trees */ scan_tree(s, (ct_data *)s->dyn_ltree, s->l_desc.max_code); scan_tree(s, (ct_data *)s->dyn_dtree, s->d_desc.max_code); /* Build the bit length tree: */ build_tree(s, (tree_desc *)(&(s->bl_desc))); /* opt_len now includes the length of the tree representations, except * the lengths of the bit lengths codes and the 5+5+4 bits for the counts. */ /* Determine the number of bit length codes to send. The pkzip format * requires that at least 4 bit length codes be sent. (appnote.txt says * 3 but the actual value used is 4.) */ for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) { if (s->bl_tree[bl_order[max_blindex]].Len != 0) break; } /* Update opt_len to include the bit length tree and counts */ s->opt_len += 3*(max_blindex+1) + 5+5+4; Tracev((stderr, "\ndyn trees: dyn %ld, stat %ld", s->opt_len, s->static_len)); return max_blindex; }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds14598.64%133.33%
joern engeljoern engel10.68%133.33%
steven colesteven cole10.68%133.33%
Total147100.00%3100.00%

/* =========================================================================== * Send the header for a block using dynamic Huffman trees: the counts, the * lengths of the bit length codes, the literal tree and the distance tree. * IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4. */
static void send_all_trees( deflate_state *s, int lcodes, /* number of codes for each tree */ int dcodes, /* number of codes for each tree */ int blcodes /* number of codes for each tree */ ) { int rank; /* index in bl_order */ Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes"); Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES, "too many codes"); Tracev((stderr, "\nbl counts: ")); send_bits(s, lcodes-257, 5); /* not +255 as stated in appnote.txt */ send_bits(s, dcodes-1, 5); send_bits(s, blcodes-4, 4); /* not -3 as stated in appnote.txt */ for (rank = 0; rank < blcodes; rank++) { Tracev((stderr, "\nbl code %2d ", bl_order[rank])); send_bits(s, s->bl_tree[bl_order[rank]].Len, 3); } Tracev((stderr, "\nbl tree: sent %ld", s->bits_sent)); send_tree(s, (ct_data *)s->dyn_ltree, lcodes-1); /* literal tree */ Tracev((stderr, "\nlit tree: sent %ld", s->bits_sent)); send_tree(s, (ct_data *)s->dyn_dtree, dcodes-1); /* distance tree */ Tracev((stderr, "\ndist tree: sent %ld", s->bits_sent)); }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds21996.48%133.33%
steven colesteven cole73.08%133.33%
joern engeljoern engel10.44%133.33%
Total227100.00%3100.00%

/* =========================================================================== * Send a stored block */
void zlib_tr_stored_block( deflate_state *s, char *buf, /* input block */ ulg stored_len, /* length of input block */ int eof /* true if this is the last block for a file */ ) { send_bits(s, (STORED_BLOCK<<1)+eof, 3); /* send block type */ s->compressed_len = (s->compressed_len + 3 + 7) & (ulg)~7L; s->compressed_len += (stored_len + 4) << 3; copy_block(s, buf, (unsigned)stored_len, 1); /* with header */ }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds8094.12%133.33%
steven colesteven cole44.71%133.33%
joern engeljoern engel11.18%133.33%
Total85100.00%3100.00%

/* Send just the `stored block' type code without any length bytes or data. */
void zlib_tr_stored_type_only( deflate_state *s ) { send_bits(s, (STORED_BLOCK << 1), 3); bi_windup(s); s->compressed_len = (s->compressed_len + 3) & ~7L; }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds4197.62%150.00%
steven colesteven cole12.38%150.00%
Total42100.00%2100.00%

/* =========================================================================== * Send one empty static block to give enough lookahead for inflate. * This takes 10 bits, of which 7 may remain in the bit buffer. * The current inflate code requires 9 bits of lookahead. If the * last two codes for the previous block (real code plus EOB) were coded * on 5 bits or less, inflate may have only 5+3 bits of lookahead to decode * the last real code. In this case we send two empty static blocks instead * of one. (There are no problems if the previous block is stored or fixed.) * To simplify the code, we assume the worst case of last real code encoded * on one bit only. */
void zlib_tr_align( deflate_state *s ) { send_bits(s, STATIC_TREES<<1, 3); send_code(s, END_BLOCK, static_ltree); s->compressed_len += 10L; /* 3 for block type, 7 for EOB */ bi_flush(s); /* Of the 10 bits for the empty block, we have already sent * (10 - bi_valid) bits. The lookahead for the last real code (before * the EOB of the previous block) was thus at least one plus the length * of the EOB plus what we have just sent of the empty static block. */ if (1 + s->last_eob_len + 10 - s->bi_valid < 9) { send_bits(s, STATIC_TREES<<1, 3); send_code(s, END_BLOCK, static_ltree); s->compressed_len += 10L; bi_flush(s); } s->last_eob_len = 7; }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds9698.97%150.00%
steven colesteven cole11.03%150.00%
Total97100.00%2100.00%

/* =========================================================================== * Determine the best encoding for the current block: dynamic trees, static * trees or store, and output the encoded block to the zip file. This function * returns the total compressed length for the file so far. */
ulg zlib_tr_flush_block( deflate_state *s, char *buf, /* input block, or NULL if too old */ ulg stored_len, /* length of input block */ int eof /* true if this is the last block for a file */ ) { ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */ int max_blindex = 0; /* index of last bit length code of non zero freq */ /* Build the Huffman trees unless a stored block is forced */ if (s->level > 0) { /* Check if the file is ascii or binary */ if (s->data_type == Z_UNKNOWN) set_data_type(s); /* Construct the literal and distance trees */ build_tree(s, (tree_desc *)(&(s->l_desc))); Tracev((stderr, "\nlit data: dyn %ld, stat %ld", s->opt_len, s->static_len)); build_tree(s, (tree_desc *)(&(s->d_desc))); Tracev((stderr, "\ndist data: dyn %ld, stat %ld", s->opt_len, s->static_len)); /* At this point, opt_len and static_len are the total bit lengths of * the compressed block data, excluding the tree representations. */ /* Build the bit length tree for the above two trees, and get the index * in bl_order of the last bit length code to send. */ max_blindex = build_bl_tree(s); /* Determine the best encoding. Compute first the block length in bytes*/ opt_lenb = (s->opt_len+3+7)>>3; static_lenb = (s->static_len+3+7)>>3; Tracev((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u ", opt_lenb, s->opt_len, static_lenb, s->static_len, stored_len, s->last_lit)); if (static_lenb <= opt_lenb) opt_lenb = static_lenb; } else { Assert(buf != (char*)0, "lost buf"); opt_lenb = static_lenb = stored_len + 5; /* force a stored block */ } /* If compression failed and this is the first and last block, * and if the .zip file can be seeked (to rewrite the local header), * the whole file is transformed into a stored file: */ #ifdef STORED_FILE_OK # ifdef FORCE_STORED_FILE if (eof && s->compressed_len == 0L) { /* force stored file */ # else if (stored_len <= opt_lenb && eof && s->compressed_len==0L && seekable()) { # endif /* Since LIT_BUFSIZE <= 2*WSIZE, the input data must be there: */ if (buf == (char*)0) error ("block vanished"); copy_block(s, buf, (unsigned)stored_len, 0); /* without header */ s->compressed_len = stored_len << 3; s->method = STORED; } else #endif /* STORED_FILE_OK */ #ifdef FORCE_STORED if (buf != (char*)0) { /* force stored block */ #else if (stored_len+4 <= opt_lenb && buf != (char*)0) { /* 4: two words for the lengths */ #endif /* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE. * Otherwise we can't have processed more than WSIZE input bytes since * the last block flush, because compression would have been * successful. If LIT_BUFSIZE <= WSIZE, it is never too late to * transform a block into a stored block. */ zlib_tr_stored_block(s, buf, stored_len, eof); #ifdef FORCE_STATIC } else if (static_lenb >= 0) { /* force static trees */ #else } else if (static_lenb == opt_lenb) { #endif send_bits(s, (STATIC_TREES<<1)+eof, 3); compress_block(s, (ct_data *)static_ltree, (ct_data *)static_dtree); s->compressed_len += 3 + s->static_len; } else { send_bits(s, (DYN_TREES<<1)+eof, 3); send_all_trees(s, s->l_desc.max_code+1, s->d_desc.max_code+1, max_blindex+1); compress_block(s, (ct_data *)s->dyn_ltree, (ct_data *)s->dyn_dtree); s->compressed_len += 3 + s->opt_len; } Assert (s->compressed_len == s->bits_sent, "bad compressed size"); init_block(s); if (eof) { bi_windup(s); s->compressed_len += 7; /* align on byte boundary */ } Tracev((stderr,"\ncomprlen %lu(%lu) ", s->compressed_len>>3, s->compressed_len-7*eof)); return s->compressed_len >> 3; } /* =========================================================================== * Save the match info and tally the frequency counts. Return true if * the current block must be flushed. */ int zlib_tr_tally( deflate_state *s, unsigned dist, /* distance of matched string */ unsigned lc /* match length-MIN_MATCH or unmatched char (if dist==0) */ ) { s->d_buf[s->last_lit] = (ush)dist; s->l_buf[s->last_lit++] = (uch)lc; if (dist == 0) { /* lc is the unmatched char */ s->dyn_ltree[lc].Freq++; } else { s->matches++; /* Here, lc is the match length - MIN_MATCH */ dist--; /* dist = match distance - 1 */ Assert((ush)dist < (ush)MAX_DIST(s) && (ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) && (ush)d_code(dist) < (ush)D_CODES, "zlib_tr_tally: bad match"); s->dyn_ltree[length_code[lc]+LITERALS+1].Freq++; s->dyn_dtree[d_code(dist)].Freq++; } /* Try to guess if it is profitable to stop the current block here */ if ((s->last_lit & 0xfff) == 0 && s->level > 2) { /* Compute an upper bound for the compressed length */ ulg out_length = (ulg)s->last_lit*8L; ulg in_length = (ulg)((long)s->strstart - s->block_start); int dcode; for (dcode = 0; dcode < D_CODES; dcode++) { out_length += (ulg)s->dyn_dtree[dcode].Freq * (5L+extra_dbits[dcode]); } out_length >>= 3; Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ", s->last_lit, in_length, out_length, 100L - out_length*100L/in_length)); if (s->matches < s->last_lit/2 && out_length < in_length/2) return 1; } return (s->last_lit == s->lit_bufsize-1); /* We avoid equality with lit_bufsize because of wraparound at 64K * on 16 bit machines and because stored blocks are restricted to * 64K-1 bytes. */ } /* =========================================================================== * Send the block data compressed using the given Huffman trees */ static void compress_block( deflate_state *s, ct_data *ltree, /* literal tree */ ct_data *dtree /* distance tree */ ) { unsigned dist; /* distance of matched string */ int lc; /* match length or unmatched char (if dist == 0) */ unsigned lx = 0; /* running index in l_buf */ unsigned code; /* the code to send */ int extra; /* number of extra bits to send */ if (s->last_lit != 0) do { dist = s->d_buf[lx]; lc = s->l_buf[lx++]; if (dist == 0) { send_code(s, lc, ltree); /* send a literal byte */ Tracecv(isgraph(lc), (stderr," '%c' ", lc)); } else { /* Here, lc is the match length - MIN_MATCH */ code = length_code[lc]; send_code(s, code+LITERALS+1, ltree); /* send the length code */ extra = extra_lbits[code]; if (extra != 0) { lc -= base_length[code]; send_bits(s, lc, extra); /* send the extra length bits */ } dist--; /* dist is now the match distance - 1 */ code = d_code(dist); Assert (code < D_CODES, "bad d_code"); send_code(s, code, dtree); /* send the distance code */ extra = extra_dbits[code]; if (extra != 0) { dist -= base_dist[code]; send_bits(s, dist, extra); /* send the extra distance bits */ } } /* literal or match pair ? */ /* Check that the overlay between pending_buf and d_buf+l_buf is ok: */ Assert(s->pending < s->lit_bufsize + 2*lx, "pendingBuf overflow"); } while (lx < s->last_lit); send_code(s, END_BLOCK, ltree); s->last_eob_len = ltree[END_BLOCK].Len; } /* =========================================================================== * Set the data type to ASCII or BINARY, using a crude approximation: * binary if more than 20% of the bytes are <= 6 or >= 128, ascii otherwise. * IN assertion: the fields freq of dyn_ltree are set and the total of all * frequencies does not exceed 64K (to fit in an int on 16 bit machines). */ static void set_data_type( deflate_state *s ) { int n = 0; unsigned ascii_freq = 0; unsigned bin_freq = 0; while (n < 7) bin_freq += s->dyn_ltree[n++].Freq; while (n < 128) ascii_freq += s->dyn_ltree[n++].Freq; while (n < LITERALS) bin_freq += s->dyn_ltree[n++].Freq; s->data_type = (Byte)(bin_freq > (ascii_freq >> 2) ? Z_BINARY : Z_ASCII); } /* =========================================================================== * Copy a stored block, storing first the length and its * one's complement if requested. */ static void copy_block( deflate_state *s, char *buf, /* the input data */ unsigned len, /* its length */ int header /* true if block header must be written */ ) { bi_windup(s); /* align on byte boundary */ s->last_eob_len = 8; /* enough lookahead for inflate */ if (header) { put_short(s, (ush)len); put_short(s, (ush)~len); #ifdef DEBUG_ZLIB s->bits_sent += 2*16; #endif } #ifdef DEBUG_ZLIB s->bits_sent += (ulg)len<<3; #endif /* bundle up the put_byte(s, *buf++) calls */ memcpy(&s->pending_buf[s->pending], buf, len); s->pending += len; }

Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds136298.48%125.00%
steven colesteven cole151.08%125.00%
joern engeljoern engel60.43%250.00%
Total1383100.00%4100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
linus torvaldslinus torvalds529395.99%112.50%
joern engeljoern engel1442.61%337.50%
steven colesteven cole530.96%225.00%
yalin wangyalin wang230.42%112.50%
andrew mortonandrew morton10.02%112.50%
Total5514100.00%8100.00%
Directory: lib/zlib_deflate