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[]));