Документация по криптоалгоритмам / CRYPTO30 / ztrees

#ifndef CRYPTOPP_ZTREES_H
#define CRYPTOPP_ZTREES_H

#include "misc.h"
#include "zbits.h"

NAMESPACE_BEGIN(CryptoPP)

class CodeTree : private BitOutput
{
public:
	CodeTree(int deflate_level, BufferedTransformation &outQ);

	int  ct_tally (int dist, int lc);
	word32  flush_block (byte *buf, word32 stored_len, int eof);

	long block_start;       /* window offset of current block */
	unsigned int strstart; /* window offset of current string */
	const int deflate_level;

	enum {
#ifdef SMALL_MEM
		WSIZE = 0x2000,
#else
#  ifdef MEDIUM_MEM
		WSIZE = 0x4000,
#  else
		WSIZE = 0x8000,
#  endif
#endif
		MIN_MATCH = 3,
		MAX_MATCH = 258,
		MIN_LOOKAHEAD = (MAX_MATCH+MIN_MATCH+1),
		MAX_DIST = (WSIZE-MIN_LOOKAHEAD)
	};

	enum {
		MAX_BITS=15,
		MAX_BL_BITS=7,
		LENGTH_CODES=29,
		LITERALS=256,
		END_BLOCK=256,
		L_CODES=(LITERALS+1+LENGTH_CODES),
		D_CODES=30,
		BL_CODES=19,
		HEAP_SIZE=(2*L_CODES+1)
	};

private:
	enum {
		STORED_BLOCK=0,
		STATIC_TREES=1,
		DYN_TREES   =2
	};

	enum {
#ifdef SMALL_MEM
		LIT_BUFSIZE = 0x2000,
#else
#  ifdef MEDIUM_MEM
		LIT_BUFSIZE = 0x4000,
#  else
		LIT_BUFSIZE = 0x8000,
#  endif
#endif
		DIST_BUFSIZE = LIT_BUFSIZE
	};

	enum {
		REP_3_6     =16,
		REPZ_3_10   =17,
		REPZ_11_138 =18
	};

	static const int extra_lbits[LENGTH_CODES];
	static const int extra_dbits[D_CODES];
	static const int extra_blbits[BL_CODES];
	static const byte bl_order[BL_CODES];

	// Data structure describing a single value and its code string. */
	struct ct_data
	{
		union
		{
			word16  Freq;       /* frequency count */
			word16  Code;       /* bit string */
		};
		union
		{
			word16  Dad;        /* father node in Huffman tree */
			word16  Len;        /* length of bit string */
		};
	};

	SecBlock<ct_data> dyn_ltree, dyn_dtree;

	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 ct_init
	 * below).
	 */

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

	static bool streesBuilt;

	SecBlock<ct_data> bl_tree;
	/* Huffman tree for the bit lengths */

	SecBlock<word16> bl_count;
	/* number of codes at each bit length for an optimal tree */

	struct tree_desc
	{
		tree_desc(ct_data *d, ct_data *s, const int *e, int eb, int el, int ml, int mc)
			: dyn_tree(d), static_tree(s), extra_bits(e), extra_base(eb),
			  elems(el), max_length(ml), max_code(mc) {}
		ct_data *const dyn_tree;      /* the dynamic tree */
		const ct_data *const static_tree;   /* corresponding static tree or NULL */
		const int     *extra_bits;    /* extra bits for each code or NULL */
		const int     extra_base;          /* base index for extra_bits */
		const int     elems;               /* max number of elements in the tree */
		const int     max_length;          /* max bit length for the codes */
		int     max_code;            /* largest code with non zero frequency */
	};

	tree_desc l_desc;
	tree_desc d_desc;
	tree_desc bl_desc;

	SecBlock<int> heap; /* 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.
	 */

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

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

	SecByteBlock dist_code;
	/* 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.
	 */

	SecBlock<int> base_length;
	/* First normalized length for each code (0 = MIN_MATCH) */

	SecBlock<int> base_dist;
	/* First normalized distance for each code (0 = distance of 1) */

	SecByteBlock l_buf;
	SecBlock<word16> d_buf;

	SecByteBlock flag_buf;
	/* 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 */
	byte flags;            /* current flags not yet saved in flag_buf */
	byte 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.
	 */

	word32 opt_len;        /* bit length of current block with optimal trees */
	word32 static_len;     /* bit length of current block with static trees */
	word32 compressed_len; /* total bit length of compressed file */
	word32 input_len;      /* total byte length of input file */
	/* input_len is for debugging only since we can get it by other means. */

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

NAMESPACE_END

#endif