pgpztrees.c

vc环境下的pgp源码

/*____________________________________________________________________________
	Copyright (C) 1997 Network Associates Inc. and affiliated companies.
	All rights reserved.

	$Id: pgpZTrees.c,v 1.14 1999/03/10 03:00:14 heller Exp $
____________________________________________________________________________*/

/*
 * Copyright (C) 1990-1993 Mark Adler, Richard B. Wales, Jean-loup Gailly,
 * Kai Uwe Rommel and Igor Mandrichenko.
 * Permission is granted to any individual or institution to use, copy,
 * or redistribute this software so long as all of the original files
 * are included, that it is not sold for profit, and that this copyright
 * notice is retained.
 *
 * $Id: pgpZTrees.c,v 1.14 1999/03/10 03:00:14 heller Exp $
 */
 

/*
 *  trees.c by Jean-loup Gailly
 *
 *  This is a new version of im_ctree.c originally written by Richard B. Wales
 *  for the defunct implosion method.
 *
 *  PURPOSE
 *
 *      Encode various sets of source values using variable-length
 *      binary code trees.
 *
 *  DISCUSSION
 *
 *      The PKZIP "deflation" process uses several Huffman trees. The more
 *      common source values are represented by shorter bit sequences.
 *
 *      Each code tree is stored in the ZIP file 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 UNZIP process, as described in the "application note"
 *      (APPNOTE.TXT) distributed as part of PKWARE's PKZIP program.
 *
 *  REFERENCES
 *
 *      Lynch, Thomas J.
 *          Data Compression:  Techniques and Applications, pp. 53-55.
 *          Lifetime Learning Publications, 1985.  ISBN 0-534-03418-7.
 *
 *      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.
 *
 *  INTERFACE
 *
 *      void ct_init (void))
 *          Allocate the match buffer and initialize the various tables.
 *
 *      void ct_tally (unsigned dist, unsigned lc);
 *          Save the match info and tally the frequency counts.
 *
 *      long flush_block (char const *buf, PGPUInt32 stored_len, int eof)
 *          Determine the best encoding for the current block: dynamic trees,
 *          static trees or store, and output the encoded block to the zip
 *          file. Returns the total compressed length for the file so far.
 *
 */

#include "pgpConfig.h"

#include <ctype.h>
#include "pgpZip.h"

/* ===========================================================================
 * Constants
 */

#define MAX_BITS 15
/* All codes must not exceed MAX_BITS bits */

#define MAX_BL_BITS 7
/* Bit length codes must not exceed MAX_BL_BITS bits */

#define LENGTH_CODES 29
/* number of length codes, not counting the special END_BLOCK code */

#define LITERALS  256
/* number of literal bytes 0..255 */

#define END_BLOCK 256
/* end of block literal code */

#define L_CODES (LITERALS+1+LENGTH_CODES)
/* number of Literal or Length codes, including the END_BLOCK code */

#define D_CODES   30
/* number of distance codes */

#define BL_CODES  19
/* number of codes used to transfer the bit lengths */


/* extra bits for each length code */
static int const near extra_lbits[LENGTH_CODES]
   = {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};

/* extra bits for each distance code */
static int const near extra_dbits[D_CODES]
   = {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};

/* extra bits for each bit length code */
static int const near extra_blbits[BL_CODES]
   = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,2,3,7};

static PGPByte const near 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 STORED_BLOCK 0
#define STATIC_TREES 1
#define DYN_TREES    2
/* The three kinds of block type */

#ifndef LIT_BUFSIZE
#  ifdef SMALL_MEM
#    define LIT_BUFSIZE  0x2000
#  else
#    ifdef MEDIUM_MEM
#      define LIT_BUFSIZE  0x4000
#    else
#      define LIT_BUFSIZE  0x8000
#    endif
#  endif
#endif
#define DIST_BUFSIZE  LIT_BUFSIZE
/* Sizes of match buffers for literals/lengths and distances.  There are
 * 4 reasons for limiting LIT_BUFSIZE to < 64K:
 *   - frequencies can be kept in 16 bit counters
 *   - if compression is not successful for the first block, all input data is
 *     still in the window so we can still emit a stored block even when input
 *     comes from standard input.  (This can also be done for all blocks if
 *     LIT_BUFSIZE is not greater than 32K.)
 *   - if compression is not successful for a file smaller than 64K, we can
 *     even emit a stored file instead of a stored block (saving 5 bytes).
 *   - creating new Huffman trees less frequently may not provide fast
 *     adaptation to changes in the input data statistics. (Take for
 *     example a binary file with poorly compressible code followed by
 *     a highly compressible string table.) Smaller buffer sizes give
 *     fast adaptation but have of course the overhead of transmitting trees
 *     more frequently.
 *   - I can't count above 4
 * The current code is general and allows DIST_BUFSIZE < LIT_BUFSIZE (to save
 * memory at the expense of compression). Some optimizations would be possible
 * if we rely on DIST_BUFSIZE == LIT_BUFSIZE.
 */

#define REP_3_6      16
/* repeat previous bit length 3-6 times (2 bits of repeat count) */

#define REPZ_3_10    17
/* repeat a zero length 3-10 times  (3 bits of repeat count) */

#define REPZ_11_138  18
/* repeat a zero length 11-138 times  (7 bits of repeat count) */

/* ===========================================================================
 * Local data
 */

/* Data structure describing a single value and its code string. */
typedef struct ct_data
{
    union {
        PGPUInt16 freq;       /* frequency count */
	PGPUInt16 code;       /* bit string */
    } fc;
    union {
        PGPUInt16 dad;        /* father node in Huffman tree */
        PGPUInt16 len;        /* length of bit string */
    } dl;
} ct_data;

#define Freq fc.freq
#define Code fc.code
#define Dad  dl.dad
#define Len  dl.len

#define HEAP_SIZE (2*L_CODES+1)
/* maximum heap size */

typedef struct tree_desc {
    ct_data near *dyn_tree;    /* the dynamic tree */
    ct_data near *static_tree; /* corresponding static tree or NULL */
    int      const near *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 */
    int                  max_code;    /* largest code with non zero frequency*/
} tree_desc;

/* Tables for initializing context tables.  The local pointers are set up in
 * ct_init.
 */

static const tree_desc near l_desc_init =
{/*dyn_ltree*/0, /*static_ltree*/0, extra_lbits, LITERALS+1, L_CODES,
	MAX_BITS, 0};

static const tree_desc near d_desc_init =
{/*dyn_dtree*/0, /*fstatic_dtree*/0, extra_dbits, 0, D_CODES, MAX_BITS, 0};

static const tree_desc near bl_desc_init =
{/*bl_tree*/0, NULL,   extra_blbits, 0,         BL_CODES, MAX_BL_BITS, 0};

typedef struct ZTreesContext {

	PGPContextRef		cdkContext;

	ct_data near dyn_ltree[HEAP_SIZE];   /* literal and length tree*/
	ct_data near dyn_dtree[2*D_CODES+1]; /* distance tree */

	ct_data near 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 ct_init
	 * below).
	 */

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

	ct_data near bl_tree[2*BL_CODES+1];
	/* Huffman tree for the bit lengths */


	tree_desc near l_desc;
	tree_desc near d_desc;
	tree_desc near bl_desc;

	PGPUInt16 near bl_count[MAX_BITS+1];
	/* number of codes at each bit length for an optimal tree */

	int near heap[2*L_CODES+1]; /*heap used to build the Huffman trees*/
	int heap_len;               /* number of elements in the heap */
	int heap_max;               /* element of largest frequency */
	/* The sons of heap[n] are heap[2*n] and heap[2*n+1]. heap[0] is not used.
	 * The same heap array is used to build all trees.
	 */

	PGPByte near depth[2*L_CODES+1];
	/* Depth of each subtree used as tie breaker for trees of equal frequency*/

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

	PGPByte 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.
	 */

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

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

#ifndef DYN_ALLOC
	  PGPByte far l_buf[LIT_BUFSIZE];  /* buffer for literals/lengths */
	  PGPUInt16 far d_buf[DIST_BUFSIZE]; /* buffer for distances */
#else
	  PGPByte far *l_buf;
	  PGPUInt16 far *d_buf;
#endif

	PGPByte near flag_buf[(LIT_BUFSIZE/8)];
	/* flag_buf is a bit array distinguishing literals from lengths in
	 * l_buf, and thus indicating the presence or absence of a distance.
	 */

	unsigned last_lit;    /* running index in l_buf */
	unsigned last_dist;   /* running index in d_buf */
	unsigned last_flags;  /* running index in flag_buf */
	PGPByte flags;        /* current flags not yet saved in flag_buf */
	PGPByte flag_bit;     /* current bit used in flags */
	/* bits are filled in flags starting at bit 0 (least significant).
	 * Note: these flags are overkill in the current code since we don't
	 * take advantage of DIST_BUFSIZE == LIT_BUFSIZE.
	 */

	/* bit length of current block with optimal trees*/
	PGPUInt32 opt_len;
	/* bit length of current block with static trees */
	PGPUInt32 static_len;

	PGPUInt32 compressed_len; /* total bit length of compressed file */

	PGPUInt32 input_len;      /* total byte length of input file */
	/* input_len is for debugging only since we can get it by other means. */
} ZTreesContext;

#ifdef ZIPDEBUG
extern PGPUInt32 bits_sent;  /* bit length of the compressed data */
extern PGPUInt32 isize;      /* byte length of input file */
#endif

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

static void init_block(ZTreesContext *);
static void pqdownheap(ZTreesContext *, ct_data near *tree, int k);
static void gen_bitlen(ZTreesContext *, tree_desc near *desc);
static void gen_codes(ZTreesContext *, ct_data near *tree, int max_code);
static void build_tree(ZTreesContext *, tree_desc near *desc);
static void scan_tree(ZTreesContext *, ct_data near *tree, int max_code);
static void send_tree(ZTreesContext *, struct ZBitsContext *,
	ct_data near *tree, int max_code);
static int  build_bl_tree(ZTreesContext *);
static void send_all_trees(ZTreesContext *, struct ZBitsContext *,
	int lcodes, int dcodes, int blcodes);
static void compress_block(ZTreesContext *, struct ZBitsContext *,
	ct_data near *ltree, ct_data near *dtree);


#ifndef ZIPDEBUG
#  define send_code(zbctx, c, tree)	send_bits(zbctx, tree[c].Code, tree[c].Len)
   /* Send a code of the given tree. c and tree must not have side effects */

#else /* ZIPDEBUG */
#  define send_code(zbctx, c, tree) \
     { if (verbose > 1) fprintf(stderr,"\ncd %3d ",(c)); \
       send_bits(zbctx, tree[c].Code, tree[c].Len); }
#endif

#define d_code(ctx, dist) \
   ((dist) < 256 ? (ctx)->dist_code[dist] : (ctx)->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.
 */

#define MAX(a,b) (a >= b ? a : b)
/* the arguments must not have side effects */

/* ===========================================================================
 * Reverse k low-order bits in a word.  Not speed-critical.
 */
static unsigned
bit_reverse(unsigned value, int len)
{
	unsigned result = 0;

	do {
		result <<= 1;
		result |= value & 1;
		value >>= 1;
	} while (--len);
	return result;
}

/* ===========================================================================
 * Allocate the match buffer and initialize the various tables.
 */
ZTreesContext *
ct_init(PGPContextRef cdkContext)
{
	ZTreesContext *ctx;
    int n;        /* iterates over tree elements */
    int bits;     /* bit counter */
    int length;   /* length value */
    int code;     /* code value */
    int dist;     /* distance index */

	ctx = (ZTreesContext *) pgpContextMemAlloc (cdkContext,
								sizeof(*ctx), kPGPMemoryMgrFlags_Clear);
	if (IsNull (ctx) )
		return NULL;
	ctx->cdkContext = cdkContext;

	/* Initialize tables */
	pgpCopyMemory (&l_desc_init,  &ctx->l_desc,  sizeof(l_desc_init));
	ctx->l_desc.dyn_tree = ctx->dyn_ltree;
	ctx->l_desc.static_tree = ctx->static_ltree;

	pgpCopyMemory (&d_desc_init,  &ctx->d_desc,  sizeof(d_desc_init));
	ctx->d_desc.dyn_tree = ctx->dyn_dtree;
	ctx->d_desc.static_tree = ctx->static_dtree;

	pgpCopyMemory (&bl_desc_init, &ctx->bl_desc, sizeof(bl_desc_init));
	ctx->bl_desc.dyn_tree = ctx->bl_tree;
	ctx->bl_desc.static_tree = NULL;

    ctx->compressed_len = ctx->input_len = 0L;

#ifdef DYN_ALLOC
    /* Allocate the buffers */

    ctx->d_buf = (PGPUInt16 far *)pgpContextMemAlloc (cdkContext,