| 1 | /*
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| 2 | * jcphuff.c
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| 3 | *
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| 4 | * Copyright (C) 1995-1997, 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 Huffman entropy encoding routines for progressive JPEG.
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| 9 | *
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| 10 | * We do not support output suspension in this module, since the library
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| 11 | * currently does not allow multiple-scan files to be written with output
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| 12 | * suspension.
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| 13 | */
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| 14 |
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| 15 | #define JPEG_INTERNALS
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| 16 | #include "jinclude.h"
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| 17 | #include "jpeglib.h"
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| 18 | #include "jchuff.h" /* Declarations shared with jchuff.c */
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| 19 |
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| 20 | #ifdef C_PROGRESSIVE_SUPPORTED
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| 21 |
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| 22 | /* Expanded entropy encoder object for progressive Huffman encoding. */
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| 23 |
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| 24 | typedef struct {
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| 25 | struct jpeg_entropy_encoder pub; /* public fields */
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| 26 |
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| 27 | /* Mode flag: TRUE for optimization, FALSE for actual data output */
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| 28 | boolean gather_statistics;
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| 29 |
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| 30 | /* Bit-level coding status.
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| 31 | * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
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| 32 | */
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| 33 | JOCTET * next_output_byte; /* => next byte to write in buffer */
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| 34 | size_t free_in_buffer; /* # of byte spaces remaining in buffer */
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| 35 | INT32 put_buffer; /* current bit-accumulation buffer */
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| 36 | int put_bits; /* # of bits now in it */
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| 37 | j_compress_ptr cinfo; /* link to cinfo (needed for dump_buffer) */
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| 38 |
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| 39 | /* Coding status for DC components */
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| 40 | int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
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| 41 |
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| 42 | /* Coding status for AC components */
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| 43 | int ac_tbl_no; /* the table number of the single component */
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| 44 | unsigned int EOBRUN; /* run length of EOBs */
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| 45 | unsigned int BE; /* # of buffered correction bits before MCU */
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| 46 | char * bit_buffer; /* buffer for correction bits (1 per char) */
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| 47 | /* packing correction bits tightly would save some space but cost time... */
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| 48 |
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| 49 | unsigned int restarts_to_go; /* MCUs left in this restart interval */
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| 50 | int next_restart_num; /* next restart number to write (0-7) */
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| 51 |
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| 52 | /* Pointers to derived tables (these workspaces have image lifespan).
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| 53 | * Since any one scan codes only DC or only AC, we only need one set
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| 54 | * of tables, not one for DC and one for AC.
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| 55 | */
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| 56 | c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
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| 57 |
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| 58 | /* Statistics tables for optimization; again, one set is enough */
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| 59 | long * count_ptrs[NUM_HUFF_TBLS];
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| 60 | } phuff_entropy_encoder;
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| 61 |
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| 62 | typedef phuff_entropy_encoder * phuff_entropy_ptr;
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| 63 |
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| 64 | /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
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| 65 | * buffer can hold. Larger sizes may slightly improve compression, but
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| 66 | * 1000 is already well into the realm of overkill.
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| 67 | * The minimum safe size is 64 bits.
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| 68 | */
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| 69 |
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| 70 | #define MAX_CORR_BITS 1000 /* Max # of correction bits I can buffer */
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| 71 |
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| 72 | /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
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| 73 | * We assume that int right shift is unsigned if INT32 right shift is,
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| 74 | * which should be safe.
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| 75 | */
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| 76 |
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| 77 | #ifdef RIGHT_SHIFT_IS_UNSIGNED
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| 78 | #define ISHIFT_TEMPS int ishift_temp;
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| 79 | #define IRIGHT_SHIFT(x,shft) \
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| 80 | ((ishift_temp = (x)) < 0 ? \
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