michael@0: /*
michael@0:  * jchuff.h
michael@0:  *
michael@0:  * Copyright (C) 1991-1997, Thomas G. Lane.
michael@0:  * This file is part of the Independent JPEG Group's software.
michael@0:  * For conditions of distribution and use, see the accompanying README file.
michael@0:  *
michael@0:  * This file contains declarations for Huffman entropy encoding routines
michael@0:  * that are shared between the sequential encoder (jchuff.c) and the
michael@0:  * progressive encoder (jcphuff.c).  No other modules need to see these.
michael@0:  */
michael@0: 
michael@0: /* The legal range of a DCT coefficient is
michael@0:  *  -1024 .. +1023  for 8-bit data;
michael@0:  * -16384 .. +16383 for 12-bit data.
michael@0:  * Hence the magnitude should always fit in 10 or 14 bits respectively.
michael@0:  */
michael@0: 
michael@0: #if BITS_IN_JSAMPLE == 8
michael@0: #define MAX_COEF_BITS 10
michael@0: #else
michael@0: #define MAX_COEF_BITS 14
michael@0: #endif
michael@0: 
michael@0: /* Derived data constructed for each Huffman table */
michael@0: 
michael@0: typedef struct {
michael@0:   unsigned int ehufco[256];	/* code for each symbol */
michael@0:   char ehufsi[256];		/* length of code for each symbol */
michael@0:   /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
michael@0: } c_derived_tbl;
michael@0: 
michael@0: /* Short forms of external names for systems with brain-damaged linkers. */
michael@0: 
michael@0: #ifdef NEED_SHORT_EXTERNAL_NAMES
michael@0: #define jpeg_make_c_derived_tbl	jMkCDerived
michael@0: #define jpeg_gen_optimal_table	jGenOptTbl
michael@0: #endif /* NEED_SHORT_EXTERNAL_NAMES */
michael@0: 
michael@0: /* Expand a Huffman table definition into the derived format */
michael@0: EXTERN(void) jpeg_make_c_derived_tbl
michael@0: 	JPP((j_compress_ptr cinfo, boolean isDC, int tblno,
michael@0: 	     c_derived_tbl ** pdtbl));
michael@0: 
michael@0: /* Generate an optimal table definition given the specified counts */
michael@0: EXTERN(void) jpeg_gen_optimal_table
michael@0: 	JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]));