inftrees.h 2.9 KB

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  1. /* inftrees.h -- header to use inftrees.c
  2. * Copyright (C) 1995-2005, 2010 Mark Adler
  3. * For conditions of distribution and use, see copyright notice in zlib.h
  4. */
  5. /* WARNING: this file should *not* be used by applications. It is
  6. part of the implementation of the compression library and is
  7. subject to change. Applications should only use zlib.h.
  8. */
  9. /* Structure for decoding tables. Each entry provides either the
  10. information needed to do the operation requested by the code that
  11. indexed that table entry, or it provides a pointer to another
  12. table that indexes more bits of the code. op indicates whether
  13. the entry is a pointer to another table, a literal, a length or
  14. distance, an end-of-block, or an invalid code. For a table
  15. pointer, the low four bits of op is the number of index bits of
  16. that table. For a length or distance, the low four bits of op
  17. is the number of extra bits to get after the code. bits is
  18. the number of bits in this code or part of the code to drop off
  19. of the bit buffer. val is the actual byte to output in the case
  20. of a literal, the base length or distance, or the offset from
  21. the current table to the next table. Each entry is four bytes. */
  22. typedef struct {
  23. unsigned char op; /* operation, extra bits, table bits */
  24. unsigned char bits; /* bits in this part of the code */
  25. unsigned short val; /* offset in table or code value */
  26. } code;
  27. /* op values as set by inflate_table():
  28. 00000000 - literal
  29. 0000tttt - table link, tttt != 0 is the number of table index bits
  30. 0001eeee - length or distance, eeee is the number of extra bits
  31. 01100000 - end of block
  32. 01000000 - invalid code
  33. */
  34. /* Maximum size of the dynamic table. The maximum number of code structures is
  35. 1444, which is the sum of 852 for literal/length codes and 592 for distance
  36. codes. These values were found by exhaustive searches using the program
  37. examples/enough.c found in the zlib distribtution. The arguments to that
  38. program are the number of symbols, the initial root table size, and the
  39. maximum bit length of a code. "enough 286 9 15" for literal/length codes
  40. returns returns 852, and "enough 30 6 15" for distance codes returns 592.
  41. The initial root table size (9 or 6) is found in the fifth argument of the
  42. inflate_table() calls in inflate.c and infback.c. If the root table size is
  43. changed, then these maximum sizes would be need to be recalculated and
  44. updated. */
  45. #define ENOUGH_LENS 852
  46. #define ENOUGH_DISTS 592
  47. #define ENOUGH (ENOUGH_LENS+ENOUGH_DISTS)
  48. /* Type of code to build for inflate_table() */
  49. typedef enum {
  50. CODES,
  51. LENS,
  52. DISTS
  53. } codetype;
  54. int ZLIB_INTERNAL inflate_table OF((codetype type, unsigned short FAR *lens,
  55. unsigned codes, code FAR * FAR *table,
  56. unsigned FAR *bits, unsigned short FAR *work));