~ubuntu-branches/ubuntu/precise/pristine-tar/precise-proposed : revision 9

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/* trees.c -- output deflated data using Huffman coding

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This program is free software; you can redistribute it and/or modify

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it under the terms of the GNU General Public License as published by

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the Free Software Foundation; either version 2, or (at your option)

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any later version.

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This program is distributed in the hope that it will be useful,

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but WITHOUT ANY WARRANTY; without even the implied warranty of

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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

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GNU General Public License for more details.

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You should have received a copy of the GNU General Public License

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along with this program; if not, write to the Free Software Foundation,

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Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */

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/*

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* PURPOSE

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*

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* Encode various sets of source values using variable-length

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* binary code trees.

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*

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* DISCUSSION

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*

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* The PKZIP "deflation" process uses several Huffman trees. The more

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* common source values are represented by shorter bit sequences.

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*

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* Each code tree is stored in the ZIP file in a compressed form

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* which is itself a Huffman encoding of the lengths of

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* all the code strings (in ascending order by source values).

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* The actual code strings are reconstructed from the lengths in

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* the UNZIP process, as described in the "application note"

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* (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.

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*

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* REFERENCES

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*

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* Lynch, Thomas J.

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* Data Compression: Techniques and Applications, pp. 53-55.

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* Lifetime Learning Publications, 1985. ISBN 0-534-03418-7.

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*

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* Storer, James A.

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* Data Compression: Methods and Theory, pp. 49-50.

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* Computer Science Press, 1988. ISBN 0-7167-8156-5.

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*

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* Sedgewick, R.

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* Algorithms, p290.

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* Addison-Wesley, 1983. ISBN 0-201-06672-6.

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*

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* INTERFACE

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*

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* void ct_init (void)

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* Allocate the match buffer and initialize the various tables

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*

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* void ct_tally (int pack_level, int dist, int lc);

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* Save the match info and tally the frequency counts.

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*

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* void flush_block (char *buf, ulg stored_len, int pad, int eof)

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* Determine the best encoding for the current block: dynamic trees,

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* static trees or store, and output the encoded block to the zip

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* file. If pad is set, pads the block to the next byte.

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* */

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#include <ctype.h>

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#include "gzip.h"

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/* ===========================================================================

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* Constants

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*/

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#define MAX_BITS 15

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/* All codes must not exceed MAX_BITS bits */

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#define MAX_BL_BITS 7

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/* Bit length codes must not exceed MAX_BL_BITS bits */

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#define LENGTH_CODES 29

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/* number of length codes, not counting the special END_BLOCK code */

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#define LITERALS 256

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/* number of literal bytes 0..255 */

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#define END_BLOCK 256

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/* end of block literal code */

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#define L_CODES (LITERALS+1+LENGTH_CODES)

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/* number of Literal or Length codes, including the END_BLOCK code */

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#define D_CODES 30

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/* number of distance codes */

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#define BL_CODES 19

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/* number of codes used to transfer the bit lengths */

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static int extra_lbits[LENGTH_CODES] /* extra bits for each length code */

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= {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};

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static int extra_dbits[D_CODES] /* extra bits for each distance code */

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= {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};

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static int extra_blbits[BL_CODES]/* extra bits for each bit length code */

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= {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};

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#define STORED_BLOCK 0

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#define STATIC_TREES 1

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#define DYN_TREES 2

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/* The three kinds of block type */

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#define LIT_BUFSIZE 0x8000

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/* Sizes of match buffers for literals/lengths and distances. There are

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* 4 reasons for limiting LIT_BUFSIZE to 64K:

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* - frequencies can be kept in 16 bit counters

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* - if compression is not successful for the first block, all input data is

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* still in the window so we can still emit a stored block even when input

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* comes from standard input. (This can also be done for all blocks if

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* LIT_BUFSIZE is not greater than 32K.)

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* - if compression is not successful for a file smaller than 64K, we can

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* even emit a stored file instead of a stored block (saving 5 bytes).

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* - creating new Huffman trees less frequently may not provide fast

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* adaptation to changes in the input data statistics. (Take for

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* example a binary file with poorly compressible code followed by

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* a highly compressible string table.) Smaller buffer sizes give

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* fast adaptation but have of course the overhead of transmitting trees

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* more frequently.

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* - I can't count above 4

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* The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save

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* memory at the expense of compression). Some optimizations would be possible

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* if we rely on DIST_BUFSIZE == LIT_BUFSIZE.

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*/

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#define REP_3_6 16

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/* repeat previous bit length 3-6 times (2 bits of repeat count) */

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#define REPZ_3_10 17

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/* repeat a zero length 3-10 times (3 bits of repeat count) */

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#define REPZ_11_138 18

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/* repeat a zero length 11-138 times (7 bits of repeat count) */

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/* ===========================================================================

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* Local data

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*/

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/* Data structure describing a single value and its code string. */

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typedef struct ct_data {

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union {

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ush freq; /* frequency count */

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ush code; /* bit string */

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} fc;

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union {

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ush dad; /* father node in Huffman tree */

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ush len; /* length of bit string */

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} dl;

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} ct_data;

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#define Freq fc.freq

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#define Code fc.code

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#define Dad dl.dad

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#define Len dl.len

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#define HEAP_SIZE (2*L_CODES+1)

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/* maximum heap size */

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static ct_data dyn_ltree[HEAP_SIZE]; /* literal and length tree */

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static ct_data dyn_dtree[2*D_CODES+1]; /* distance tree */

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static ct_data static_ltree[L_CODES+2];

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/* The static literal tree. Since the bit lengths are imposed, there is no

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* need for the L_CODES extra codes used during heap construction. However

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* The codes 286 and 287 are needed to build a canonical tree (see ct_init

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* below).

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*/

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static ct_data static_dtree[D_CODES];

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/* The static distance tree. (Actually a trivial tree since all codes use

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* 5 bits.)

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*/

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static ct_data bl_tree[2*BL_CODES+1];

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/* Huffman tree for the bit lengths */

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typedef struct tree_desc {

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ct_data *dyn_tree; /* the dynamic tree */

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ct_data *static_tree; /* corresponding static tree or NULL */

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int *extra_bits; /* extra bits for each code or NULL */

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int extra_base; /* base index for extra_bits */

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int elems; /* max number of elements in the tree */

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int max_length; /* max bit length for the codes */

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int max_code; /* largest code with non zero frequency */

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} tree_desc;

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static tree_desc l_desc =

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{dyn_ltree, static_ltree, extra_lbits, LITERALS+1, L_CODES, MAX_BITS, 0};

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static tree_desc d_desc =

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{dyn_dtree, static_dtree, extra_dbits, 0, D_CODES, MAX_BITS, 0};

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static tree_desc bl_desc =

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{bl_tree, (ct_data *)0, extra_blbits, 0, BL_CODES, MAX_BL_BITS, 0};

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static ush bl_count[MAX_BITS+1];

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/* number of codes at each bit length for an optimal tree */

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static uch bl_order[BL_CODES]

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= {16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15};

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/* The lengths of the bit length codes are sent in order of decreasing

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* probability, to avoid transmitting the lengths for unused bit length codes.

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*/

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static int heap[2*L_CODES+1]; /* heap used to build the Huffman trees */

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static int heap_len; /* number of elements in the heap */

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static int heap_max; /* element of largest frequency */

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/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.

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* The same heap array is used to build all trees.

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*/

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static uch depth[2*L_CODES+1];

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/* Depth of each subtree used as tie breaker for trees of equal frequency */

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static uch length_code[MAX_MATCH-MIN_MATCH+1];

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/* length code for each normalized match length (0 == MIN_MATCH) */

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static uch dist_code[512];

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/* distance codes. The first 256 values correspond to the distances

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* 3 .. 258, the last 256 values correspond to the top 8 bits of

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* the 15 bit distances.

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*/

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static int base_length[LENGTH_CODES];

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/* First normalized length for each code (0 = MIN_MATCH) */

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static int base_dist[D_CODES];

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/* First normalized distance for each code (0 = distance of 1) */

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static uch l_buf[INBUFSIZ]; /* buffer for literals or lengths */

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static ush d_buf[DIST_BUFSIZE]; /* buffer for distances */

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static uch flag_buf[(LIT_BUFSIZE/8)];

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/* flag_buf is a bit array distinguishing literals from lengths in

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* l_buf, thus indicating the presence or absence of a distance.

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*/

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static unsigned last_lit; /* running index in l_buf */

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static unsigned last_dist; /* running index in d_buf */

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static unsigned last_flags; /* running index in flag_buf */

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static uch flags; /* current flags not yet saved in flag_buf */

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static uch flag_bit; /* current bit used in flags */

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/* bits are filled in flags starting at bit 0 (least significant).

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* Note: these flags are overkill in the current code since we don't

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* take advantage of DIST_BUFSIZE == LIT_BUFSIZE.

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*/

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static ulg opt_len; /* bit length of current block with optimal trees */

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static ulg static_len; /* bit length of current block with static trees */

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static off_t compressed_len; /* total bit length of compressed file */

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extern long block_start; /* window offset of current block */

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extern unsigned strstart; /* window offset of current string */

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/* ===========================================================================

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* Local (static) routines in this file.

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*/

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static void init_block(void);

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static void pqdownheap(ct_data *tree, int k);

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static void gen_bitlen(tree_desc *desc);

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static void gen_codes(ct_data *tree, int max_code);

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static void build_tree(tree_desc *desc);

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static void scan_tree(ct_data *tree, int max_code);

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static void send_tree(ct_data *tree, int max_code);

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static int build_bl_tree(void);

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static void send_all_trees(int lcodes, int dcodes, int blcodes);

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static void compress_block(ct_data *ltree, ct_data *dtree);

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#define send_code(c, tree) send_bits(tree[c].Code, tree[c].Len)

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/* Send a code of the given tree. c and tree must not have side effects */

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#define d_code(dist) \

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((dist) < 256 ? dist_code[dist] : dist_code[256+((dist)>>7)])

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/* Mapping from a distance to a distance code. dist is the distance - 1 and

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* must not have side effects. dist_code[256] and dist_code[257] are never

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* used.

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*/

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#define MAX(a,b) (a >= b ? a : b)

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/* the arguments must not have side effects */

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/* ===========================================================================

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* Allocate the match buffer and initialize the various tables

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*/

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void ct_init(void)

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{

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int n; /* iterates over tree elements */

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int bits; /* bit counter */

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int length; /* length value */

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int code; /* code value */

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int dist; /* distance index */

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compressed_len = 0L;

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if (static_dtree[0].Len != 0) return; /* ct_init already called */

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/* Initialize the mapping length (0..255) -> length code (0..28) */

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length = 0;

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for (code = 0; code < LENGTH_CODES-1; code++) {

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base_length[code] = length;

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for (n = 0; n < (1<<extra_lbits[code]); n++) {

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length_code[length++] = (uch)code;

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}

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}

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Assert (length == 256, "ct_init: length != 256");

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/* Note that the length 255 (match length 258) can be represented

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* in two different ways: code 284 + 5 bits or code 285, so we

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* overwrite length_code[255] to use the best encoding:

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*/

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length_code[length-1] = (uch)code;

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/* Initialize the mapping dist (0..32K) -> dist code (0..29) */

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dist = 0;

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for (code = 0 ; code < 16; code++) {

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base_dist[code] = dist;

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for (n = 0; n < (1<<extra_dbits[code]); n++) {

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dist_code[dist++] = (uch)code;

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}

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}

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Assert (dist == 256, "ct_init: dist != 256");

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dist >>= 7; /* from now on, all distances are divided by 128 */

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for ( ; code < D_CODES; code++) {

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base_dist[code] = dist << 7;

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for (n = 0; n < (1<<(extra_dbits[code]-7)); n++) {

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dist_code[256 + dist++] = (uch)code;

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}

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}

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Assert (dist == 256, "ct_init: 256+dist != 512");

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/* Construct the codes of the static literal tree */

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for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;

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n = 0;

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while (n <= 143) static_ltree[n++].Len = 8, bl_count[8]++;

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while (n <= 255) static_ltree[n++].Len = 9, bl_count[9]++;

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while (n <= 279) static_ltree[n++].Len = 7, bl_count[7]++;

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while (n <= 287) static_ltree[n++].Len = 8, bl_count[8]++;

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/* Codes 286 and 287 do not exist, but we must include them in the

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* tree construction to get a canonical Huffman tree (longest code

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* all ones)

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*/

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gen_codes((ct_data *)static_ltree, L_CODES+1);

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/* The static distance tree is trivial: */

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for (n = 0; n < D_CODES; n++) {

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static_dtree[n].Len = 5;

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static_dtree[n].Code = bi_reverse(n, 5);

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}

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/* Initialize the first block of the first file: */

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init_block();

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}

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/* ===========================================================================

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* Initialize a new block.

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*/

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static void init_block(void)

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{

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int n; /* iterates over tree elements */

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/* Initialize the trees. */

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for (n = 0; n < L_CODES; n++) dyn_ltree[n].Freq = 0;

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for (n = 0; n < D_CODES; n++) dyn_dtree[n].Freq = 0;

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for (n = 0; n < BL_CODES; n++) bl_tree[n].Freq = 0;

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dyn_ltree[END_BLOCK].Freq = 1;

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opt_len = static_len = 0L;

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last_lit = last_dist = last_flags = 0;

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flags = 0; flag_bit = 1;

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}

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#define SMALLEST 1

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/* Index within the heap array of least frequent node in the Huffman tree */

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/* ===========================================================================

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* Remove the smallest element from the heap and recreate the heap with

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* one less element. Updates heap and heap_len.

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*/

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#define pqremove(tree, top) \

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{\

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top = heap[SMALLEST]; \

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heap[SMALLEST] = heap[heap_len--]; \

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pqdownheap(tree, SMALLEST); \

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}

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/* ===========================================================================

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* Compares to subtrees, using the tree depth as tie breaker when

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* the subtrees have equal frequency. This minimizes the worst case length.

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*/

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#define smaller(tree, n, m) \

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(tree[n].Freq < tree[m].Freq || \

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(tree[n].Freq == tree[m].Freq && depth[n] <= depth[m]))

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/* ===========================================================================

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* Restore the heap property by moving down the tree starting at node k,

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* exchanging a node with the smallest of its two sons if necessary, stopping

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* when the heap property is re-established (each father smaller than its

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* two sons).

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*/

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static void pqdownheap(ct_data *tree, /* the tree to restore */

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int k) /* node to move down */

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{

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int v = heap[k];

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int j = k << 1; /* left son of k */

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while (j <= heap_len) {

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/* Set j to the smallest of the two sons: */

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if (j < heap_len && smaller(tree, heap[j+1], heap[j])) j++;

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/* Exit if v is smaller than both sons */

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if (smaller(tree, v, heap[j])) break;

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/* Exchange v with the smallest son */

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heap[k] = heap[j]; k = j;

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/* And continue down the tree, setting j to the left son of k */

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j <<= 1;

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}

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heap[k] = v;

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}

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/* ===========================================================================

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* Compute the optimal bit lengths for a tree and update the total bit length

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* for the current block.

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* IN assertion: the fields freq and dad are set, heap[heap_max] and

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* above are the tree nodes sorted by increasing frequency.

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* OUT assertions: the field len is set to the optimal bit length, the

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* array bl_count contains the frequencies for each bit length.

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* The length opt_len is updated; static_len is also updated if stree is

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* not null.

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*/

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static void gen_bitlen(tree_desc *desc)

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{

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ct_data *tree = desc->dyn_tree;

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int *extra = desc->extra_bits;

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int base = desc->extra_base;

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int max_code = desc->max_code;

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int max_length = desc->max_length;

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ct_data *stree = desc->static_tree;

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int h; /* heap index */

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int n, m; /* iterate over the tree elements */

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int bits; /* bit length */

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int xbits; /* extra bits */

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ush f; /* frequency */

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int overflow = 0; /* number of elements with bit length too large */

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for (bits = 0; bits <= MAX_BITS; bits++) bl_count[bits] = 0;

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/* In a first pass, compute the optimal bit lengths (which may

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* overflow in the case of the bit length tree).

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*/

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tree[heap[heap_max]].Len = 0; /* root of the heap */

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for (h = heap_max+1; h < HEAP_SIZE; h++) {

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n = heap[h];

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bits = tree[tree[n].Dad].Len + 1;

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if (bits > max_length) bits = max_length, overflow++;

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tree[n].Len = (ush)bits;

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/* We overwrite tree[n].Dad which is no longer needed */

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if (n > max_code) continue; /* not a leaf node */

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bl_count[bits]++;

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xbits = 0;

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if (n >= base) xbits = extra[n-base];

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f = tree[n].Freq;

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opt_len += (ulg)f * (bits + xbits);

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if (stree) static_len += (ulg)f * (stree[n].Len + xbits);

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}

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if (overflow == 0) return;

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Trace((stderr,"\nbit length overflow\n"));

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/* This happens for example on obj2 and pic of the Calgary corpus */

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/* Find the first bit length which could increase: */

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do {

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bits = max_length-1;

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while (bl_count[bits] == 0) bits--;

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bl_count[bits]--; /* move one leaf down the tree */

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bl_count[bits+1] += 2; /* move one overflow item as its brother */

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bl_count[max_length]--;

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/* The brother of the overflow item also moves one step up,

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* but this does not affect bl_count[max_length]

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*/

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overflow -= 2;

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} while (overflow > 0);

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/* Now recompute all bit lengths, scanning in increasing frequency.

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* h is still equal to HEAP_SIZE. (It is simpler to reconstruct all

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* lengths instead of fixing only the wrong ones. This idea is taken

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* from 'ar' written by Haruhiko Okumura.)

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*/

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for (bits = max_length; bits != 0; bits--) {

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n = bl_count[bits];

507

while (n != 0) {

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m = heap[--h];

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if (m > max_code) continue;

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if (tree[m].Len != (unsigned) bits) {

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Trace((stderr,"code %d bits %d->%d\n", m, tree[m].Len, bits));

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opt_len += ((long)bits-(long)tree[m].Len)*(long)tree[m].Freq;

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tree[m].Len = (ush)bits;

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}

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n--;

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}

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}

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}

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/* ===========================================================================

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* Generate the codes for a given tree and bit counts (which need not be

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* optimal).

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* IN assertion: the array bl_count contains the bit length statistics for

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* the given tree and the field len is set for all tree elements.

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* OUT assertion: the field code is set for all tree elements of non

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* zero code length.

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*/

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static void gen_codes (ct_data *tree, /* the tree to decorate */

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int max_code) /* largest code with non zero frequency */

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{

531

ush next_code[MAX_BITS+1]; /* next code value for each bit length */

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ush code = 0; /* running code value */

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int bits; /* bit index */

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int n; /* code index */

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/* The distribution counts are first used to generate the code values

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* without bit reversal.

538

*/

539

for (bits = 1; bits <= MAX_BITS; bits++) {

540

next_code[bits] = code = (code + bl_count[bits-1]) << 1;

541

}

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/* Check that the bit counts in bl_count are consistent. The last code

543

* must be all ones.

544

*/

545

Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,

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"inconsistent bit counts");

547

Tracev((stderr,"\ngen_codes: max_code %d ", max_code));

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for (n = 0; n <= max_code; n++) {

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int len = tree[n].Len;

551

if (len == 0) continue;

552

/* Now reverse the bits */

553

tree[n].Code = bi_reverse(next_code[len]++, len);

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Tracec(tree != static_ltree, (stderr,"\nn %3d %c l %2d c %4x (%x) ",

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n, (isgraph(n) ? n : ' '), len, tree[n].Code, next_code[len]-1));

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}

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}

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/* ===========================================================================

561

* Construct one Huffman tree and assigns the code bit strings and lengths.

562

* Update the total bit length for the current block.

563

* IN assertion: the field freq is set for all tree elements.

564

* OUT assertions: the fields len and code are set to the optimal bit length

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* and corresponding code. The length opt_len is updated; static_len is

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* also updated if stree is not null. The field max_code is set.

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*/

568

static void build_tree(tree_desc *desc)

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{

570

ct_data *tree = desc->dyn_tree;

571

ct_data *stree = desc->static_tree;

572

int elems = desc->elems;

573

int n, m; /* iterate over heap elements */

574

int max_code = -1; /* largest code with non zero frequency */

575

int node = elems; /* next internal node of the tree */

576

577

/* Construct the initial heap, with least frequent element in

578

* heap[SMALLEST]. The sons of heap[n] are heap[2*n] and heap[2*n+1].

579

* heap[0] is not used.

580

*/

581

heap_len = 0, heap_max = HEAP_SIZE;

582

583

for (n = 0; n < elems; n++) {

584

if (tree[n].Freq != 0) {

585

heap[++heap_len] = max_code = n;

586

depth[n] = 0;

587

} else {

588

tree[n].Len = 0;

589

}

590

}

591

592

/* The pkzip format requires that at least one distance code exists,

593

* and that at least one bit should be sent even if there is only one

594

* possible code. So to avoid special checks later on we force at least

595

* two codes of non zero frequency.

596

*/

597

while (heap_len < 2) {

598

int new = heap[++heap_len] = (max_code < 2 ? ++max_code : 0);

599

tree[new].Freq = 1;

600

depth[new] = 0;

601

opt_len--; if (stree) static_len -= stree[new].Len;

602

/* new is 0 or 1 so it does not have extra bits */

603

}

604

desc->max_code = max_code;

605

606

/* The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,

607

* establish sub-heaps of increasing lengths:

608

*/

609

for (n = heap_len/2; n >= 1; n--) pqdownheap(tree, n);

610

611

/* Construct the Huffman tree by repeatedly combining the least two

612

* frequent nodes.

613

*/

614

do {

615

pqremove(tree, n); /* n = node of least frequency */

616

m = heap[SMALLEST]; /* m = node of next least frequency */

617

618

heap[--heap_max] = n; /* keep the nodes sorted by frequency */

619

heap[--heap_max] = m;

620

621

/* Create a new node father of n and m */

622

tree[node].Freq = tree[n].Freq + tree[m].Freq;

623

depth[node] = (uch) (MAX(depth[n], depth[m]) + 1);

624

tree[n].Dad = tree[m].Dad = (ush)node;

625

#ifdef DUMP_BL_TREE

626

if (tree == bl_tree) {

627

fprintf(stderr,"\nnode %d(%d), sons %d(%d) %d(%d)",

628

node, tree[node].Freq, n, tree[n].Freq, m, tree[m].Freq);

629

}

630

#endif

631

/* and insert the new node in the heap */

632

heap[SMALLEST] = node++;

633

pqdownheap(tree, SMALLEST);

634

635

} while (heap_len >= 2);

636

637

heap[--heap_max] = heap[SMALLEST];

638

639

/* At this point, the fields freq and dad are set. We can now

640

* generate the bit lengths.

641

*/

642

gen_bitlen((tree_desc *)desc);

643

644

/* The field len is now set, we can generate the bit codes */

645

gen_codes ((ct_data *)tree, max_code);

646

}

647

648

/* ===========================================================================

649

* Scan a literal or distance tree to determine the frequencies of the codes

650

* in the bit length tree. Updates opt_len to take into account the repeat

651

* counts. (The contribution of the bit length codes will be added later

652

* during the construction of bl_tree.)

653

*/

654

static void scan_tree (ct_data *tree, /* the tree to be scanned */

655

int max_code) /* and its largest code of non zero frequency */

656

{

657

int n; /* iterates over all tree elements */

658

int prevlen = -1; /* last emitted length */

659

int curlen; /* length of current code */

660

int nextlen = tree[0].Len; /* length of next code */

661

int count = 0; /* repeat count of the current code */

662

int max_count = 7; /* max repeat count */

663

int min_count = 4; /* min repeat count */

664

665

if (nextlen == 0) max_count = 138, min_count = 3;

666

tree[max_code+1].Len = (ush)0xffff; /* guard */

667

668

for (n = 0; n <= max_code; n++) {

669

curlen = nextlen; nextlen = tree[n+1].Len;

670

if (++count < max_count && curlen == nextlen) {

671

continue;

672

} else if (count < min_count) {

673

bl_tree[curlen].Freq += count;

674

} else if (curlen != 0) {

675

if (curlen != prevlen) bl_tree[curlen].Freq++;

676

bl_tree[REP_3_6].Freq++;

677

} else if (count <= 10) {

678

bl_tree[REPZ_3_10].Freq++;

679

} else {

680

bl_tree[REPZ_11_138].Freq++;

681

}

682

count = 0; prevlen = curlen;

683

if (nextlen == 0) {

684

max_count = 138, min_count = 3;

685

} else if (curlen == nextlen) {

686

max_count = 6, min_count = 3;

687

} else {

688

max_count = 7, min_count = 4;

689

}

690

}

691

}

692

693

/* ===========================================================================

694

* Send a literal or distance tree in compressed form, using the codes in

695

* bl_tree.

696

*/

697

static void send_tree (ct_data *tree, /* the tree to be scanned */

698

int max_code) /* and its largest code of non zero frequency */

699

{

700

int n; /* iterates over all tree elements */

701

int prevlen = -1; /* last emitted length */

702

int curlen; /* length of current code */

703

int nextlen = tree[0].Len; /* length of next code */

704

int count = 0; /* repeat count of the current code */

705

int max_count = 7; /* max repeat count */

706

int min_count = 4; /* min repeat count */

707

708

/* tree[max_code+1].Len = -1; */ /* guard already set */

709

if (nextlen == 0) max_count = 138, min_count = 3;

710

711

for (n = 0; n <= max_code; n++) {

712

curlen = nextlen; nextlen = tree[n+1].Len;

713

if (++count < max_count && curlen == nextlen) {

714

continue;

715

} else if (count < min_count) {

716

do { send_code(curlen, bl_tree); } while (--count != 0);

717

718

} else if (curlen != 0) {

719

if (curlen != prevlen) {

720

send_code(curlen, bl_tree); count--;

721

}

722

Assert(count >= 3 && count <= 6, " 3_6?");

723

send_code(REP_3_6, bl_tree); send_bits(count-3, 2);

724

725

} else if (count <= 10) {

726

send_code(REPZ_3_10, bl_tree); send_bits(count-3, 3);

727

728

} else {

729

send_code(REPZ_11_138, bl_tree); send_bits(count-11, 7);

730

}

731

count = 0; prevlen = curlen;

732

if (nextlen == 0) {

733

max_count = 138, min_count = 3;

734

} else if (curlen == nextlen) {

735

max_count = 6, min_count = 3;

736

} else {

737

max_count = 7, min_count = 4;

738

}

739

}

740

}

741

742

/* ===========================================================================

743

* Construct the Huffman tree for the bit lengths and return the index in

744

* bl_order of the last bit length code to send.

745

*/

746

static int build_bl_tree(void)

747

{

748

int max_blindex; /* index of last bit length code of non zero freq */

749

750

/* Determine the bit length frequencies for literal and distance trees */

751

scan_tree((ct_data *)dyn_ltree, l_desc.max_code);

752

scan_tree((ct_data *)dyn_dtree, d_desc.max_code);

753

754

/* Build the bit length tree: */

755

build_tree((tree_desc *)(&bl_desc));

756

/* opt_len now includes the length of the tree representations, except

757

* the lengths of the bit lengths codes and the 5+5+4 bits for the counts.

758

*/

759

760

/* Determine the number of bit length codes to send. The pkzip format

761

* requires that at least 4 bit length codes be sent. (appnote.txt says

762

* 3 but the actual value used is 4.)

763

*/

764

for (max_blindex = BL_CODES-1; max_blindex >= 3; max_blindex--) {

765

if (bl_tree[bl_order[max_blindex]].Len != 0) break;

766

}

767

/* Update opt_len to include the bit length tree and counts */

768

opt_len += 3*(max_blindex+1) + 5+5+4;

769

Tracev((stderr, "\ndyn trees: dyn %lu, stat %lu", opt_len, static_len));

770

771

return max_blindex;

772

}

773

774

/* ===========================================================================

775

* Send the header for a block using dynamic Huffman trees: the counts, the

776

* lengths of the bit length codes, the literal tree and the distance tree.

777

* IN assertion: lcodes >= 257, dcodes >= 1, blcodes >= 4.

778

*/

779

static void send_all_trees(int lcodes, int dcodes, int blcodes)

780

{

781

int rank; /* index in bl_order */

782

783

Assert (lcodes >= 257 && dcodes >= 1 && blcodes >= 4, "not enough codes");

784

Assert (lcodes <= L_CODES && dcodes <= D_CODES && blcodes <= BL_CODES,

785

"too many codes");

786

Tracev((stderr, "\nbl counts: "));

787

send_bits(lcodes-257, 5); /* not +255 as stated in appnote.txt */

788

send_bits(dcodes-1, 5);

789

send_bits(blcodes-4, 4); /* not -3 as stated in appnote.txt */

790

for (rank = 0; rank < blcodes; rank++) {

791

Tracev((stderr, "\nbl code %2d ", bl_order[rank]));

792

send_bits(bl_tree[bl_order[rank]].Len, 3);

793

}

794

795

send_tree((ct_data *)dyn_ltree, lcodes-1); /* send the literal tree */

796

797

send_tree((ct_data *)dyn_dtree, dcodes-1); /* send the distance tree */

798

}

799

800

/* ===========================================================================

801

* Determine the best encoding for the current block: dynamic trees, static

802

* trees or store, and output the encoded block to the zip file. This function

803

* returns the total compressed length for the file so far.

804

*/

805

void flush_block(char *buf, /* input block, or NULL if too old */

806

ulg stored_len, /* length of input block */

807

int pad, /* pad output to byte boundary */

808

int eof) /* true if this is the last block for a file */

809

{

810

ulg opt_lenb, static_lenb; /* opt_len and static_len in bytes */

811

int max_blindex; /* index of last bit length code of non zero freq */

812

813

flag_buf[last_flags] = flags; /* Save the flags for the last 8 items */

814

815

/* Construct the literal and distance trees */

816

build_tree((tree_desc *)(&l_desc));

817

Tracev((stderr, "\nlit data: dyn %lu, stat %lu", opt_len, static_len));

818

819

build_tree((tree_desc *)(&d_desc));

820

Tracev((stderr, "\ndist data: dyn %lu, stat %lu", opt_len, static_len));

821

/* At this point, opt_len and static_len are the total bit lengths of

822

* the compressed block data, excluding the tree representations.

823

*/

824

825

/* Build the bit length tree for the above two trees, and get the index

826

* in bl_order of the last bit length code to send.

827

*/

828

max_blindex = build_bl_tree();

829

830

/* Determine the best encoding. Compute first the block length in bytes */

831

opt_lenb = (opt_len+3+7)>>3;

832

static_lenb = (static_len+3+7)>>3;

833

834

Trace((stderr, "\nopt %lu(%lu) stat %lu(%lu) stored %lu lit %u dist %u ",

835

opt_lenb, opt_len, static_lenb, static_len, stored_len,

836

last_lit, last_dist));

837

838

if (static_lenb <= opt_lenb) opt_lenb = static_lenb;

839

840

if (stored_len+4 <= opt_lenb && buf != (char*)0) {

841

/* 4: two words for the lengths */

842

/* The test buf != NULL is only necessary if LIT_BUFSIZE > WSIZE.

843

* Otherwise we can't have processed more than WSIZE input bytes since

844

* the last block flush, because compression would have been

845

* successful. If LIT_BUFSIZE <= WSIZE, it is never too late to

846

* transform a block into a stored block.

847

*/

848

send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */

849

compressed_len = (compressed_len + 3 + 7) & ~7L;

850

compressed_len += (stored_len + 4) << 3;

851

852

copy_block(buf, (unsigned)stored_len, 1); /* with header */

853

854

} else if (static_lenb == opt_lenb) {

855

send_bits((STATIC_TREES<<1)+eof, 3);

856

compress_block((ct_data *)static_ltree, (ct_data *)static_dtree);

857

compressed_len += 3 + static_len;

858

} else {

859

send_bits((DYN_TREES<<1)+eof, 3);

860

send_all_trees(l_desc.max_code+1, d_desc.max_code+1, max_blindex+1);

861

compress_block((ct_data *)dyn_ltree, (ct_data *)dyn_dtree);

862

compressed_len += 3 + opt_len;

863

}

864

Assert (compressed_len == bits_sent, "bad compressed size");

865

init_block();

866

867

if (eof) {

868

/* Assert (input_len == bytes_in, "bad input size"); */

869

bi_windup();

870

compressed_len += 7; /* align on byte boundary */

871

} else if (pad && (compressed_len % 8) != 0) {

872

send_bits((STORED_BLOCK<<1)+eof, 3); /* send block type */

873

compressed_len = (compressed_len + 3 + 7) & ~7L;

874

copy_block(buf, 0, 1); /* with header */

875

}

876

}

877

878

/* ===========================================================================

879

* Save the match info and tally the frequency counts. Return true if

880

* the current block must be flushed.

881

*/

882

int ct_tally (int pack_level, /* Compression level, 1 to 9 */

883

int dist, /* distance of matched string */

884

int lc) /* match length-MIN_MATCH or unmatched char (if dist==0) */

885

{

886

l_buf[last_lit++] = (uch)lc;

887

if (dist == 0) {

888

/* lc is the unmatched char */

889

dyn_ltree[lc].Freq++;

890

} else {

891

/* Here, lc is the match length - MIN_MATCH */

892

dist--; /* dist = match distance - 1 */

893

Assert((ush)dist < (ush)MAX_DIST &&

894

(ush)lc <= (ush)(MAX_MATCH-MIN_MATCH) &&

895

(ush)d_code(dist) < (ush)D_CODES, "ct_tally: bad match");

896

897

dyn_ltree[length_code[lc]+LITERALS+1].Freq++;

898

dyn_dtree[d_code(dist)].Freq++;

899

900

d_buf[last_dist++] = (ush)dist;

901

flags |= flag_bit;

902

}

903

flag_bit <<= 1;

904

905

/* Output the flags if they fill a byte: */

906

if ((last_lit & 7) == 0) {

907

flag_buf[last_flags++] = flags;

908

flags = 0, flag_bit = 1;

909

}

910

/* Try to guess if it is profitable to stop the current block here */

911

if (pack_level > 2 && (last_lit & 0xfff) == 0) {

912

/* Compute an upper bound for the compressed length */

913

ulg out_length = (ulg)last_lit*8L;

914

ulg in_length = (ulg)strstart-block_start;

915

int dcode;

916

for (dcode = 0; dcode < D_CODES; dcode++) {

917

out_length += (ulg)dyn_dtree[dcode].Freq*(5L+extra_dbits[dcode]);

918

}

919

out_length >>= 3;

920

Trace((stderr,"\nlast_lit %u, last_dist %u, in %ld, out ~%ld(%ld%%) ",

921

last_lit, last_dist, in_length, out_length,

922

100L - out_length*100L/in_length));

923

if (last_dist < last_lit/2 && out_length < in_length/2) return 1;

924

}

925

return (last_lit == LIT_BUFSIZE-1 || last_dist == DIST_BUFSIZE);

926

/* We avoid equality with LIT_BUFSIZE because of wraparound at 64K

927

* on 16 bit machines and because stored blocks are restricted to

928

* 64K-1 bytes.

929

*/

930

}

931

932

/* ===========================================================================

933

* Send the block data compressed using the given Huffman trees

934

*/

935

static void compress_block(ct_data *ltree, /* literal tree */

936

ct_data *dtree) /* distance tree */

937

{

938

unsigned dist; /* distance of matched string */

939

int lc; /* match length or unmatched char (if dist == 0) */

940

unsigned lx = 0; /* running index in l_buf */

941

unsigned dx = 0; /* running index in d_buf */

942

unsigned fx = 0; /* running index in flag_buf */

943

uch flag = 0; /* current flags */

944

unsigned code; /* the code to send */

945

int extra; /* number of extra bits to send */

946

947

if (last_lit != 0) do {

948

if ((lx & 7) == 0) flag = flag_buf[fx++];

949

lc = l_buf[lx++];

950

if ((flag & 1) == 0) {

951

send_code(lc, ltree); /* send a literal byte */

952

Tracecv(isgraph(lc), (stderr," '%c' ", lc));

953

} else {

954

/* Here, lc is the match length - MIN_MATCH */

955

code = length_code[lc];

956

send_code(code+LITERALS+1, ltree); /* send the length code */

957

extra = extra_lbits[code];

958

if (extra != 0) {

959

lc -= base_length[code];

960

send_bits(lc, extra); /* send the extra length bits */

961

}

962

dist = d_buf[dx++];

963

/* Here, dist is the match distance - 1 */

964

code = d_code(dist);

965

Assert (code < D_CODES, "bad d_code");

966

967

send_code(code, dtree); /* send the distance code */

968

extra = extra_dbits[code];

969

if (extra != 0) {

970

dist -= base_dist[code];

971

send_bits(dist, extra); /* send the extra distance bits */

972

}

973

} /* literal or match pair ? */

974

flag >>= 1;

975

} while (lx < last_lit);

976

977

send_code(END_BLOCK, ltree);

978

}