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