1 /*

2 * jchuff.h

3 *

4 * Copyright (C) 1991-1997, Thomas G. Lane.

5 * This file is part of the Independent JPEG Group's software.

6 * For conditions of distribution and use, see the accompanying README file.

7 *

8 * This file contains declarations for Huffman entropy encoding routines

9 * that are shared between the sequential encoder (jchuff.c) and the

10 * progressive encoder (jcphuff.c). No other modules need to see these.

11 */

12

13 /* The legal range of a DCT coefficient is

14 * -1024 .. +1023 for 8-bit data;

15 * -16384 .. +16383 for 12-bit data.

16 * Hence the magnitude should always fit in 10 or 14 bits respectively.

17 */

18

19 #if BITS_IN_JSAMPLE == 8

20 #define MAX_COEF_BITS 10

21 #else

22 #define MAX_COEF_BITS 14

23 #endif

24

25 /* Derived data constructed for each Huffman table */

26

27 typedef struct {

28 unsigned int ehufco[256]; /* code for each symbol */

29 char ehufsi[256]; /* length of code for each symbol */

30 /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */

31 } c_derived_tbl;

32

33 /* Short forms of external names for systems with brain-damaged linkers. */

34

35 #ifdef NEED_SHORT_EXTERNAL_NAMES

36 #define jpeg_make_c_derived_tbl jMkCDerived

37 #define jpeg_gen_optimal_table jGenOptTbl

38 #endif /* NEED_SHORT_EXTERNAL_NAMES */

39

40 /* Expand a Huffman table definition into the derived format */

41 EXTERN(void) jpeg_make_c_derived_tbl

42 JPP((j_compress_ptr cinfo, boolean isDC, int tblno,

43 c_derived_tbl ** pdtbl));

44

45 /* Generate an optimal table definition given the specified counts */

46 EXTERN(void) jpeg_gen_optimal_table

47 JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]));