Fossil SCM

fossil-scm / compat / zlib / contrib / infback9 / inftree9.h

Source Blame History 61 lines

7ef7284…	drh	1	/* inftree9.h -- header to use inftree9.c
7ef7284…	drh	2	* Copyright (C) 1995-2008 Mark Adler
7ef7284…	drh	3	* For conditions of distribution and use, see copyright notice in zlib.h
7ef7284…	drh	4	*/
7ef7284…	drh	5
7ef7284…	drh	6	/* WARNING: this file should not be used by applications. It is
7ef7284…	drh	7	part of the implementation of the compression library and is
7ef7284…	drh	8	subject to change. Applications should only use zlib.h.
7ef7284…	drh	9	*/
7ef7284…	drh	10
7ef7284…	drh	11	/* Structure for decoding tables. Each entry provides either the
7ef7284…	drh	12	information needed to do the operation requested by the code that
7ef7284…	drh	13	indexed that table entry, or it provides a pointer to another
7ef7284…	drh	14	table that indexes more bits of the code. op indicates whether
7ef7284…	drh	15	the entry is a pointer to another table, a literal, a length or
7ef7284…	drh	16	distance, an end-of-block, or an invalid code. For a table
7ef7284…	drh	17	pointer, the low four bits of op is the number of index bits of
7ef7284…	drh	18	that table. For a length or distance, the low four bits of op
7ef7284…	drh	19	is the number of extra bits to get after the code. bits is
7ef7284…	drh	20	the number of bits in this code or part of the code to drop off
7ef7284…	drh	21	of the bit buffer. val is the actual byte to output in the case
7ef7284…	drh	22	of a literal, the base length or distance, or the offset from
7ef7284…	drh	23	the current table to the next table. Each entry is four bytes. */
7ef7284…	drh	24	typedef struct {
7ef7284…	drh	25	unsigned char op; /* operation, extra bits, table bits */
7ef7284…	drh	26	unsigned char bits; /* bits in this part of the code */
7ef7284…	drh	27	unsigned short val; /* offset in table or code value */
7ef7284…	drh	28	} code;
7ef7284…	drh	29
7ef7284…	drh	30	/* op values as set by inflate_table():
7ef7284…	drh	31	00000000 - literal
7ef7284…	drh	32	0000tttt - table link, tttt != 0 is the number of table index bits
7ef7284…	drh	33	100eeeee - length or distance, eeee is the number of extra bits
7ef7284…	drh	34	01100000 - end of block
7ef7284…	drh	35	01000000 - invalid code
7ef7284…	drh	36	*/
7ef7284…	drh	37
7ef7284…	drh	38	/* Maximum size of the dynamic table. The maximum number of code structures is
7ef7284…	drh	39	1446, which is the sum of 852 for literal/length codes and 594 for distance
7ef7284…	drh	40	codes. These values were found by exhaustive searches using the program
a9e589c…	florian	41	examples/enough.c found in the zlib distribution. The arguments to that
7ef7284…	drh	42	program are the number of symbols, the initial root table size, and the
7ef7284…	drh	43	maximum bit length of a code. "enough 286 9 15" for literal/length codes
64ce68d…	drh	44	returns 852, and "enough 32 6 15" for distance codes returns 594. The
64ce68d…	drh	45	initial root table size (9 or 6) is found in the fifth argument of the
7ef7284…	drh	46	inflate_table() calls in infback9.c. If the root table size is changed,
7ef7284…	drh	47	then these maximum sizes would be need to be recalculated and updated. */
7ef7284…	drh	48	#define ENOUGH_LENS 852
7ef7284…	drh	49	#define ENOUGH_DISTS 594
7ef7284…	drh	50	#define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
7ef7284…	drh	51
7ef7284…	drh	52	/* Type of code to build for inflate_table9() */
7ef7284…	drh	53	typedef enum {
7ef7284…	drh	54	CODES,
7ef7284…	drh	55	LENS,
7ef7284…	drh	56	DISTS
7ef7284…	drh	57	} codetype;
7ef7284…	drh	58
f1f1d6c…	drh	59	extern int inflate_table9(codetype type, unsigned short FAR *lens,
f1f1d6c…	drh	60	unsigned codes, code FAR * FAR *table,
f1f1d6c…	drh	61	unsigned FAR bits, unsigned short FAR work);

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