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1 /*
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2 * jchuff.h
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3 *
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4 * Copyright (C) 1991-1997, Thomas G. Lane.
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5 * This file is part of the Independent JPEG Group's software.
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6 * For conditions of distribution and use, see the accompanying README file.
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7 *
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8 * This file contains declarations for Huffman entropy encoding routines
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9 * that are shared between the sequential encoder (jchuff.c) and the
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10 * progressive encoder (jcphuff.c). No other modules need to see these.
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11 */
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12
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13 /* The legal range of a DCT coefficient is
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14 * -1024 .. +1023 for 8-bit data;
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15 * -16384 .. +16383 for 12-bit data.
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16 * Hence the magnitude should always fit in 10 or 14 bits respectively.
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17 */
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18
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19 #if BITS_IN_JSAMPLE == 8
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20 #define MAX_COEF_BITS 10
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21 #else
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22 #define MAX_COEF_BITS 14
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23 #endif
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24
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25 /* Derived data constructed for each Huffman table */
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26
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27 typedef struct {
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28 unsigned int ehufco[256]; /* code for each symbol */
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29 char ehufsi[256]; /* length of code for each symbol */
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30 /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
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31 } c_derived_tbl;
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32
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33 /* Short forms of external names for systems with brain-damaged linkers. */
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34
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35 #ifdef NEED_SHORT_EXTERNAL_NAMES
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36 #define jpeg_make_c_derived_tbl jMkCDerived
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37 #define jpeg_gen_optimal_table jGenOptTbl
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38 #endif /* NEED_SHORT_EXTERNAL_NAMES */
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39
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40 /* Expand a Huffman table definition into the derived format */
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41 EXTERN(void) jpeg_make_c_derived_tbl
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42 JPP((j_compress_ptr cinfo, boolean isDC, int tblno,
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43 c_derived_tbl ** pdtbl));
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44
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45 /* Generate an optimal table definition given the specified counts */
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46 EXTERN(void) jpeg_gen_optimal_table
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47 JPP((j_compress_ptr cinfo, JHUFF_TBL * htbl, long freq[]));
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