1 /*
2  * jchuff.h
3  *
4  * This file was part of the Independent JPEG Group's software:
5  * Copyright (C) 1991-1997, Thomas G. Lane.
6  * It was modified by The libjpeg-turbo Project to include only code relevant
7  * to libjpeg-turbo.
8  * For conditions of distribution and use, see the accompanying README.ijg
9  * file.
10  *
11  * This file contains declarations for Huffman entropy encoding routines
12  * that are shared between the sequential encoder (jchuff.c) and the
13  * progressive encoder (jcphuff.c).  No other modules need to see these.
14  */
15 
16 /* The legal range of a DCT coefficient is
17  *  -1024 .. +1023  for 8-bit data;
18  * -16384 .. +16383 for 12-bit data.
19  * Hence the magnitude should always fit in 10 or 14 bits respectively.
20  */
21 
22 #if BITS_IN_JSAMPLE == 8
23 #define MAX_COEF_BITS  10
24 #else
25 #define MAX_COEF_BITS  14
26 #endif
27 
28 /* Derived data constructed for each Huffman table */
29 
30 typedef struct {
31   unsigned int ehufco[256];     /* code for each symbol */
32   char ehufsi[256];             /* length of code for each symbol */
33   /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
34 } c_derived_tbl;
35 
36 /* Expand a Huffman table definition into the derived format */
37 EXTERN(void) jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC,
38                                      int tblno, c_derived_tbl **pdtbl);
39 
40 /* Generate an optimal table definition given the specified counts */
41 EXTERN(void) jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl,
42                                     long freq[]);
43