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[]));
48