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e1929140 RR |
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[])); |