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1560 lines
48 KiB
C
1560 lines
48 KiB
C
/*
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* jdhuff.c
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*
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* Copyright (C) 1991-1997, Thomas G. Lane.
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* Modified 2006-2019 by Guido Vollbeding.
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* This file is part of the Independent JPEG Group's software.
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* For conditions of distribution and use, see the accompanying README file.
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*
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* This file contains Huffman entropy decoding routines.
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* Both sequential and progressive modes are supported in this single module.
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*
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* Much of the complexity here has to do with supporting input suspension.
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* If the data source module demands suspension, we want to be able to back
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* up to the start of the current MCU. To do this, we copy state variables
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* into local working storage, and update them back to the permanent
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* storage only upon successful completion of an MCU.
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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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/* Derived data constructed for each Huffman table */
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#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
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typedef struct {
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/* Basic tables: (element [0] of each array is unused) */
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INT32 maxcode[18]; /* largest code of length k (-1 if none) */
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/* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
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INT32 valoffset[17]; /* huffval[] offset for codes of length k */
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/* valoffset[k] = huffval[] index of 1st symbol of code length k, less
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* the smallest code of length k; so given a code of length k, the
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* corresponding symbol is huffval[code + valoffset[k]]
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*/
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/* Link to public Huffman table (needed only in jpeg_huff_decode) */
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JHUFF_TBL *pub;
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/* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
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* the input data stream. If the next Huffman code is no more
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* than HUFF_LOOKAHEAD bits long, we can obtain its length and
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* the corresponding symbol directly from these tables.
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*/
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int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
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UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
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} d_derived_tbl;
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/*
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* Fetching the next N bits from the input stream is a time-critical operation
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* for the Huffman decoders. We implement it with a combination of inline
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* macros and out-of-line subroutines. Note that N (the number of bits
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* demanded at one time) never exceeds 15 for JPEG use.
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*
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* We read source bytes into get_buffer and dole out bits as needed.
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* If get_buffer already contains enough bits, they are fetched in-line
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* by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
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* bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
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* as full as possible (not just to the number of bits needed; this
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* prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
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* Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
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* On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
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* at least the requested number of bits --- dummy zeroes are inserted if
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* necessary.
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*/
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typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
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#define BIT_BUF_SIZE 32 /* size of buffer in bits */
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/* If long is > 32 bits on your machine, and shifting/masking longs is
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* reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
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* appropriately should be a win. Unfortunately we can't define the size
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* with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
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* because not all machines measure sizeof in 8-bit bytes.
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*/
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typedef struct { /* Bitreading state saved across MCUs */
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bit_buf_type get_buffer; /* current bit-extraction buffer */
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int bits_left; /* # of unused bits in it */
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} bitread_perm_state;
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typedef struct { /* Bitreading working state within an MCU */
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/* Current data source location */
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/* We need a copy, rather than munging the original, in case of suspension */
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const JOCTET * next_input_byte; /* => next byte to read from source */
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size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
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/* Bit input buffer --- note these values are kept in register variables,
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* not in this struct, inside the inner loops.
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*/
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bit_buf_type get_buffer; /* current bit-extraction buffer */
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int bits_left; /* # of unused bits in it */
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/* Pointer needed by jpeg_fill_bit_buffer. */
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j_decompress_ptr cinfo; /* back link to decompress master record */
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} bitread_working_state;
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/* Macros to declare and load/save bitread local variables. */
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#define BITREAD_STATE_VARS \
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register bit_buf_type get_buffer; \
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register int bits_left; \
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bitread_working_state br_state
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#define BITREAD_LOAD_STATE(cinfop,permstate) \
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br_state.cinfo = cinfop; \
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br_state.next_input_byte = cinfop->src->next_input_byte; \
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br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
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get_buffer = permstate.get_buffer; \
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bits_left = permstate.bits_left;
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#define BITREAD_SAVE_STATE(cinfop,permstate) \
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cinfop->src->next_input_byte = br_state.next_input_byte; \
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cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
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permstate.get_buffer = get_buffer; \
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permstate.bits_left = bits_left
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/*
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* These macros provide the in-line portion of bit fetching.
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* Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
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* before using GET_BITS, PEEK_BITS, or DROP_BITS.
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* The variables get_buffer and bits_left are assumed to be locals,
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* but the state struct might not be (jpeg_huff_decode needs this).
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* CHECK_BIT_BUFFER(state,n,action);
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* Ensure there are N bits in get_buffer; if suspend, take action.
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* val = GET_BITS(n);
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* Fetch next N bits.
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* val = PEEK_BITS(n);
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* Fetch next N bits without removing them from the buffer.
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* DROP_BITS(n);
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* Discard next N bits.
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* The value N should be a simple variable, not an expression, because it
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* is evaluated multiple times.
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*/
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#define CHECK_BIT_BUFFER(state,nbits,action) \
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{ if (bits_left < (nbits)) { \
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if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
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{ action; } \
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get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
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#define GET_BITS(nbits) \
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(((int) (get_buffer >> (bits_left -= (nbits)))) & BIT_MASK(nbits))
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#define PEEK_BITS(nbits) \
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(((int) (get_buffer >> (bits_left - (nbits)))) & BIT_MASK(nbits))
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#define DROP_BITS(nbits) \
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(bits_left -= (nbits))
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/*
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* Code for extracting next Huffman-coded symbol from input bit stream.
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* Again, this is time-critical and we make the main paths be macros.
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*
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* We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
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* without looping. Usually, more than 95% of the Huffman codes will be 8
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* or fewer bits long. The few overlength codes are handled with a loop,
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* which need not be inline code.
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*
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* Notes about the HUFF_DECODE macro:
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* 1. Near the end of the data segment, we may fail to get enough bits
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* for a lookahead. In that case, we do it the hard way.
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* 2. If the lookahead table contains no entry, the next code must be
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* more than HUFF_LOOKAHEAD bits long.
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* 3. jpeg_huff_decode returns -1 if forced to suspend.
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*/
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#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
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{ register int nb, look; \
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if (bits_left < HUFF_LOOKAHEAD) { \
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if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
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get_buffer = state.get_buffer; bits_left = state.bits_left; \
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if (bits_left < HUFF_LOOKAHEAD) { \
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nb = 1; goto slowlabel; \
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} \
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} \
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look = PEEK_BITS(HUFF_LOOKAHEAD); \
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if ((nb = htbl->look_nbits[look]) != 0) { \
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DROP_BITS(nb); \
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result = htbl->look_sym[look]; \
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} else { \
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nb = HUFF_LOOKAHEAD+1; \
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slowlabel: \
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if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
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{ failaction; } \
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get_buffer = state.get_buffer; bits_left = state.bits_left; \
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} \
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}
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/*
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* Expanded entropy decoder object for Huffman decoding.
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*
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* The savable_state subrecord contains fields that change within an MCU,
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* but must not be updated permanently until we complete the MCU.
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*/
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typedef struct {
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unsigned int EOBRUN; /* remaining EOBs in EOBRUN */
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int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
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} savable_state;
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/* This macro is to work around compilers with missing or broken
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* structure assignment. You'll need to fix this code if you have
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* such a compiler and you change MAX_COMPS_IN_SCAN.
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*/
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#ifndef NO_STRUCT_ASSIGN
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#define ASSIGN_STATE(dest,src) ((dest) = (src))
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#else
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#if MAX_COMPS_IN_SCAN == 4
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#define ASSIGN_STATE(dest,src) \
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((dest).EOBRUN = (src).EOBRUN, \
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(dest).last_dc_val[0] = (src).last_dc_val[0], \
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(dest).last_dc_val[1] = (src).last_dc_val[1], \
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(dest).last_dc_val[2] = (src).last_dc_val[2], \
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(dest).last_dc_val[3] = (src).last_dc_val[3])
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#endif
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#endif
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typedef struct {
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struct jpeg_entropy_decoder pub; /* public fields */
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/* These fields are loaded into local variables at start of each MCU.
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* In case of suspension, we exit WITHOUT updating them.
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*/
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bitread_perm_state bitstate; /* Bit buffer at start of MCU */
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savable_state saved; /* Other state at start of MCU */
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/* These fields are NOT loaded into local working state. */
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boolean insufficient_data; /* set TRUE after emitting warning */
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unsigned int restarts_to_go; /* MCUs left in this restart interval */
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/* Following two fields used only in progressive mode */
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/* Pointers to derived tables (these workspaces have image lifespan) */
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d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
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d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */
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/* Following fields used only in sequential mode */
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/* Pointers to derived tables (these workspaces have image lifespan) */
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d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];
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d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];
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/* Precalculated info set up by start_pass for use in decode_mcu: */
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/* Pointers to derived tables to be used for each block within an MCU */
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d_derived_tbl * dc_cur_tbls[D_MAX_BLOCKS_IN_MCU];
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d_derived_tbl * ac_cur_tbls[D_MAX_BLOCKS_IN_MCU];
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/* Whether we care about the DC and AC coefficient values for each block */
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int coef_limit[D_MAX_BLOCKS_IN_MCU];
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} huff_entropy_decoder;
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typedef huff_entropy_decoder * huff_entropy_ptr;
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static const int jpeg_zigzag_order[8][8] = {
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{ 0, 1, 5, 6, 14, 15, 27, 28 },
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{ 2, 4, 7, 13, 16, 26, 29, 42 },
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{ 3, 8, 12, 17, 25, 30, 41, 43 },
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{ 9, 11, 18, 24, 31, 40, 44, 53 },
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{ 10, 19, 23, 32, 39, 45, 52, 54 },
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{ 20, 22, 33, 38, 46, 51, 55, 60 },
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{ 21, 34, 37, 47, 50, 56, 59, 61 },
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{ 35, 36, 48, 49, 57, 58, 62, 63 }
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};
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static const int jpeg_zigzag_order7[7][7] = {
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{ 0, 1, 5, 6, 14, 15, 27 },
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{ 2, 4, 7, 13, 16, 26, 28 },
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{ 3, 8, 12, 17, 25, 29, 38 },
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{ 9, 11, 18, 24, 30, 37, 39 },
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{ 10, 19, 23, 31, 36, 40, 45 },
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{ 20, 22, 32, 35, 41, 44, 46 },
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{ 21, 33, 34, 42, 43, 47, 48 }
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};
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static const int jpeg_zigzag_order6[6][6] = {
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{ 0, 1, 5, 6, 14, 15 },
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{ 2, 4, 7, 13, 16, 25 },
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{ 3, 8, 12, 17, 24, 26 },
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{ 9, 11, 18, 23, 27, 32 },
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{ 10, 19, 22, 28, 31, 33 },
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{ 20, 21, 29, 30, 34, 35 }
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};
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static const int jpeg_zigzag_order5[5][5] = {
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{ 0, 1, 5, 6, 14 },
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{ 2, 4, 7, 13, 15 },
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{ 3, 8, 12, 16, 21 },
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{ 9, 11, 17, 20, 22 },
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{ 10, 18, 19, 23, 24 }
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};
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static const int jpeg_zigzag_order4[4][4] = {
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{ 0, 1, 5, 6 },
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{ 2, 4, 7, 12 },
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{ 3, 8, 11, 13 },
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{ 9, 10, 14, 15 }
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};
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static const int jpeg_zigzag_order3[3][3] = {
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{ 0, 1, 5 },
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{ 2, 4, 6 },
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{ 3, 7, 8 }
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};
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static const int jpeg_zigzag_order2[2][2] = {
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{ 0, 1 },
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{ 2, 3 }
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};
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/*
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* Compute the derived values for a Huffman table.
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* This routine also performs some validation checks on the table.
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*/
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LOCAL(void)
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jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, boolean isDC, int tblno,
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d_derived_tbl ** pdtbl)
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{
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JHUFF_TBL *htbl;
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d_derived_tbl *dtbl;
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int p, i, l, si, numsymbols;
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int lookbits, ctr;
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char huffsize[257];
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unsigned int huffcode[257];
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unsigned int code;
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/* Note that huffsize[] and huffcode[] are filled in code-length order,
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* paralleling the order of the symbols themselves in htbl->huffval[].
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*/
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/* Find the input Huffman table */
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if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
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ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
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htbl =
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isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
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if (htbl == NULL)
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htbl = jpeg_std_huff_table((j_common_ptr) cinfo, isDC, tblno);
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/* Allocate a workspace if we haven't already done so. */
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if (*pdtbl == NULL)
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*pdtbl = (d_derived_tbl *) (*cinfo->mem->alloc_small)
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((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(d_derived_tbl));
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dtbl = *pdtbl;
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dtbl->pub = htbl; /* fill in back link */
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/* Figure C.1: make table of Huffman code length for each symbol */
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p = 0;
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for (l = 1; l <= 16; l++) {
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i = (int) htbl->bits[l];
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if (i < 0 || p + i > 256) /* protect against table overrun */
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ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
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while (i--)
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huffsize[p++] = (char) l;
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}
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huffsize[p] = 0;
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numsymbols = p;
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/* Figure C.2: generate the codes themselves */
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/* We also validate that the counts represent a legal Huffman code tree. */
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code = 0;
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si = huffsize[0];
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p = 0;
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while (huffsize[p]) {
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while (((int) huffsize[p]) == si) {
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huffcode[p++] = code;
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code++;
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}
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/* code is now 1 more than the last code used for codelength si; but
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* it must still fit in si bits, since no code is allowed to be all ones.
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*/
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if (((INT32) code) >= (((INT32) 1) << si))
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ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
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code <<= 1;
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si++;
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}
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/* Figure F.15: generate decoding tables for bit-sequential decoding */
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p = 0;
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for (l = 1; l <= 16; l++) {
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if (htbl->bits[l]) {
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/* valoffset[l] = huffval[] index of 1st symbol of code length l,
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* minus the minimum code of length l
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*/
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dtbl->valoffset[l] = (INT32) p - (INT32) huffcode[p];
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p += htbl->bits[l];
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dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */
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} else {
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dtbl->maxcode[l] = -1; /* -1 if no codes of this length */
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}
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}
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dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */
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/* Compute lookahead tables to speed up decoding.
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* First we set all the table entries to 0, indicating "too long";
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* then we iterate through the Huffman codes that are short enough and
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* fill in all the entries that correspond to bit sequences starting
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* with that code.
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*/
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MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));
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p = 0;
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for (l = 1; l <= HUFF_LOOKAHEAD; l++) {
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for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {
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/* l = current code's length, p = its index in huffcode[] & huffval[]. */
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/* Generate left-justified code followed by all possible bit sequences */
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lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);
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for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {
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dtbl->look_nbits[lookbits] = l;
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dtbl->look_sym[lookbits] = htbl->huffval[p];
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lookbits++;
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}
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}
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}
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/* Validate symbols as being reasonable.
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* For AC tables, we make no check, but accept all byte values 0..255.
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* For DC tables, we require the symbols to be in range 0..15.
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* (Tighter bounds could be applied depending on the data depth and mode,
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* but this is sufficient to ensure safe decoding.)
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*/
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if (isDC) {
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for (i = 0; i < numsymbols; i++) {
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int sym = htbl->huffval[i];
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if (sym < 0 || sym > 15)
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ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
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}
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}
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}
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/*
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* Out-of-line code for bit fetching.
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* Note: current values of get_buffer and bits_left are passed as parameters,
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* but are returned in the corresponding fields of the state struct.
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|
*
|
|
* On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width
|
|
* of get_buffer to be used. (On machines with wider words, an even larger
|
|
* buffer could be used.) However, on some machines 32-bit shifts are
|
|
* quite slow and take time proportional to the number of places shifted.
|
|
* (This is true with most PC compilers, for instance.) In this case it may
|
|
* be a win to set MIN_GET_BITS to the minimum value of 15. This reduces the
|
|
* average shift distance at the cost of more calls to jpeg_fill_bit_buffer.
|
|
*/
|
|
|
|
#ifdef SLOW_SHIFT_32
|
|
#define MIN_GET_BITS 15 /* minimum allowable value */
|
|
#else
|
|
#define MIN_GET_BITS (BIT_BUF_SIZE-7)
|
|
#endif
|
|
|
|
|
|
LOCAL(boolean)
|
|
jpeg_fill_bit_buffer (bitread_working_state * state,
|
|
register bit_buf_type get_buffer, register int bits_left,
|
|
int nbits)
|
|
/* Load up the bit buffer to a depth of at least nbits */
|
|
{
|
|
/* Copy heavily used state fields into locals (hopefully registers) */
|
|
register const JOCTET * next_input_byte = state->next_input_byte;
|
|
register size_t bytes_in_buffer = state->bytes_in_buffer;
|
|
j_decompress_ptr cinfo = state->cinfo;
|
|
|
|
/* Attempt to load at least MIN_GET_BITS bits into get_buffer. */
|
|
/* (It is assumed that no request will be for more than that many bits.) */
|
|
/* We fail to do so only if we hit a marker or are forced to suspend. */
|
|
|
|
if (cinfo->unread_marker == 0) { /* cannot advance past a marker */
|
|
while (bits_left < MIN_GET_BITS) {
|
|
register int c;
|
|
|
|
/* Attempt to read a byte */
|
|
if (bytes_in_buffer == 0) {
|
|
if (! (*cinfo->src->fill_input_buffer) (cinfo))
|
|
return FALSE;
|
|
next_input_byte = cinfo->src->next_input_byte;
|
|
bytes_in_buffer = cinfo->src->bytes_in_buffer;
|
|
}
|
|
bytes_in_buffer--;
|
|
c = GETJOCTET(*next_input_byte++);
|
|
|
|
/* If it's 0xFF, check and discard stuffed zero byte */
|
|
if (c == 0xFF) {
|
|
/* Loop here to discard any padding FF's on terminating marker,
|
|
* so that we can save a valid unread_marker value. NOTE: we will
|
|
* accept multiple FF's followed by a 0 as meaning a single FF data
|
|
* byte. This data pattern is not valid according to the standard.
|
|
*/
|
|
do {
|
|
if (bytes_in_buffer == 0) {
|
|
if (! (*cinfo->src->fill_input_buffer) (cinfo))
|
|
return FALSE;
|
|
next_input_byte = cinfo->src->next_input_byte;
|
|
bytes_in_buffer = cinfo->src->bytes_in_buffer;
|
|
}
|
|
bytes_in_buffer--;
|
|
c = GETJOCTET(*next_input_byte++);
|
|
} while (c == 0xFF);
|
|
|
|
if (c == 0) {
|
|
/* Found FF/00, which represents an FF data byte */
|
|
c = 0xFF;
|
|
} else {
|
|
/* Oops, it's actually a marker indicating end of compressed data.
|
|
* Save the marker code for later use.
|
|
* Fine point: it might appear that we should save the marker into
|
|
* bitread working state, not straight into permanent state. But
|
|
* once we have hit a marker, we cannot need to suspend within the
|
|
* current MCU, because we will read no more bytes from the data
|
|
* source. So it is OK to update permanent state right away.
|
|
*/
|
|
cinfo->unread_marker = c;
|
|
/* See if we need to insert some fake zero bits. */
|
|
goto no_more_bytes;
|
|
}
|
|
}
|
|
|
|
/* OK, load c into get_buffer */
|
|
get_buffer = (get_buffer << 8) | c;
|
|
bits_left += 8;
|
|
} /* end while */
|
|
} else {
|
|
no_more_bytes:
|
|
/* We get here if we've read the marker that terminates the compressed
|
|
* data segment. There should be enough bits in the buffer register
|
|
* to satisfy the request; if so, no problem.
|
|
*/
|
|
if (nbits > bits_left) {
|
|
/* Uh-oh. Report corrupted data to user and stuff zeroes into
|
|
* the data stream, so that we can produce some kind of image.
|
|
* We use a nonvolatile flag to ensure that only one warning message
|
|
* appears per data segment.
|
|
*/
|
|
if (! ((huff_entropy_ptr) cinfo->entropy)->insufficient_data) {
|
|
WARNMS(cinfo, JWRN_HIT_MARKER);
|
|
((huff_entropy_ptr) cinfo->entropy)->insufficient_data = TRUE;
|
|
}
|
|
/* Fill the buffer with zero bits */
|
|
get_buffer <<= MIN_GET_BITS - bits_left;
|
|
bits_left = MIN_GET_BITS;
|
|
}
|
|
}
|
|
|
|
/* Unload the local registers */
|
|
state->next_input_byte = next_input_byte;
|
|
state->bytes_in_buffer = bytes_in_buffer;
|
|
state->get_buffer = get_buffer;
|
|
state->bits_left = bits_left;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* Figure F.12: extend sign bit.
|
|
* On some machines, a shift and sub will be faster than a table lookup.
|
|
*/
|
|
|
|
#ifdef AVOID_TABLES
|
|
|
|
#define BIT_MASK(nbits) ((1<<(nbits))-1)
|
|
#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) - ((1<<(s))-1) : (x))
|
|
|
|
#else
|
|
|
|
#define BIT_MASK(nbits) bmask[nbits]
|
|
#define HUFF_EXTEND(x,s) ((x) <= bmask[(s) - 1] ? (x) - bmask[s] : (x))
|
|
|
|
static const int bmask[16] = /* bmask[n] is mask for n rightmost bits */
|
|
{ 0, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF,
|
|
0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF };
|
|
|
|
#endif /* AVOID_TABLES */
|
|
|
|
|
|
/*
|
|
* Out-of-line code for Huffman code decoding.
|
|
*/
|
|
|
|
LOCAL(int)
|
|
jpeg_huff_decode (bitread_working_state * state,
|
|
register bit_buf_type get_buffer, register int bits_left,
|
|
d_derived_tbl * htbl, int min_bits)
|
|
{
|
|
register int l = min_bits;
|
|
register INT32 code;
|
|
|
|
/* HUFF_DECODE has determined that the code is at least min_bits */
|
|
/* bits long, so fetch that many bits in one swoop. */
|
|
|
|
CHECK_BIT_BUFFER(*state, l, return -1);
|
|
code = GET_BITS(l);
|
|
|
|
/* Collect the rest of the Huffman code one bit at a time. */
|
|
/* This is per Figure F.16 in the JPEG spec. */
|
|
|
|
while (code > htbl->maxcode[l]) {
|
|
code <<= 1;
|
|
CHECK_BIT_BUFFER(*state, 1, return -1);
|
|
code |= GET_BITS(1);
|
|
l++;
|
|
}
|
|
|
|
/* Unload the local registers */
|
|
state->get_buffer = get_buffer;
|
|
state->bits_left = bits_left;
|
|
|
|
/* With garbage input we may reach the sentinel value l = 17. */
|
|
|
|
if (l > 16) {
|
|
WARNMS(state->cinfo, JWRN_HUFF_BAD_CODE);
|
|
return 0; /* fake a zero as the safest result */
|
|
}
|
|
|
|
return htbl->pub->huffval[ (int) (code + htbl->valoffset[l]) ];
|
|
}
|
|
|
|
|
|
/*
|
|
* Finish up at the end of a Huffman-compressed scan.
|
|
*/
|
|
|
|
METHODDEF(void)
|
|
finish_pass_huff (j_decompress_ptr cinfo)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
|
|
/* Throw away any unused bits remaining in bit buffer; */
|
|
/* include any full bytes in next_marker's count of discarded bytes */
|
|
cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;
|
|
entropy->bitstate.bits_left = 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* Check for a restart marker & resynchronize decoder.
|
|
* Returns FALSE if must suspend.
|
|
*/
|
|
|
|
LOCAL(boolean)
|
|
process_restart (j_decompress_ptr cinfo)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
int ci;
|
|
|
|
finish_pass_huff(cinfo);
|
|
|
|
/* Advance past the RSTn marker */
|
|
if (! (*cinfo->marker->read_restart_marker) (cinfo))
|
|
return FALSE;
|
|
|
|
/* Re-initialize DC predictions to 0 */
|
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++)
|
|
entropy->saved.last_dc_val[ci] = 0;
|
|
/* Re-init EOB run count, too */
|
|
entropy->saved.EOBRUN = 0;
|
|
|
|
/* Reset restart counter */
|
|
entropy->restarts_to_go = cinfo->restart_interval;
|
|
|
|
/* Reset out-of-data flag, unless read_restart_marker left us smack up
|
|
* against a marker. In that case we will end up treating the next data
|
|
* segment as empty, and we can avoid producing bogus output pixels by
|
|
* leaving the flag set.
|
|
*/
|
|
if (cinfo->unread_marker == 0)
|
|
entropy->insufficient_data = FALSE;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* Huffman MCU decoding.
|
|
* Each of these routines decodes and returns one MCU's worth of
|
|
* Huffman-compressed coefficients.
|
|
* The coefficients are reordered from zigzag order into natural array order,
|
|
* but are not dequantized.
|
|
*
|
|
* The i'th block of the MCU is stored into the block pointed to by
|
|
* MCU_data[i]. WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
|
|
* (Wholesale zeroing is usually a little faster than retail...)
|
|
*
|
|
* We return FALSE if data source requested suspension. In that case no
|
|
* changes have been made to permanent state. (Exception: some output
|
|
* coefficients may already have been assigned. This is harmless for
|
|
* spectral selection, since we'll just re-assign them on the next call.
|
|
* Successive approximation AC refinement has to be more careful, however.)
|
|
*/
|
|
|
|
/*
|
|
* MCU decoding for DC initial scan (either spectral selection,
|
|
* or first pass of successive approximation).
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
int Al = cinfo->Al;
|
|
register int s, r;
|
|
int blkn, ci;
|
|
JBLOCKROW block;
|
|
BITREAD_STATE_VARS;
|
|
savable_state state;
|
|
d_derived_tbl * tbl;
|
|
jpeg_component_info * compptr;
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* If we've run out of data, just leave the MCU set to zeroes.
|
|
* This way, we return uniform gray for the remainder of the segment.
|
|
*/
|
|
if (! entropy->insufficient_data) {
|
|
|
|
/* Load up working state */
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(state, entropy->saved);
|
|
|
|
/* Outer loop handles each block in the MCU */
|
|
|
|
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
|
|
block = MCU_data[blkn];
|
|
ci = cinfo->MCU_membership[blkn];
|
|
compptr = cinfo->cur_comp_info[ci];
|
|
tbl = entropy->derived_tbls[compptr->dc_tbl_no];
|
|
|
|
/* Decode a single block's worth of coefficients */
|
|
|
|
/* Section F.2.2.1: decode the DC coefficient difference */
|
|
HUFF_DECODE(s, br_state, tbl, return FALSE, label1);
|
|
if (s) {
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
}
|
|
|
|
/* Convert DC difference to actual value, update last_dc_val */
|
|
s += state.last_dc_val[ci];
|
|
state.last_dc_val[ci] = s;
|
|
/* Scale and output the coefficient (assumes jpeg_natural_order[0]=0) */
|
|
(*block)[0] = (JCOEF) (s << Al);
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(entropy->saved, state);
|
|
}
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* MCU decoding for AC initial scan (either spectral selection,
|
|
* or first pass of successive approximation).
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
register int s, k, r;
|
|
unsigned int EOBRUN;
|
|
int Se, Al;
|
|
const int * natural_order;
|
|
JBLOCKROW block;
|
|
BITREAD_STATE_VARS;
|
|
d_derived_tbl * tbl;
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* If we've run out of data, just leave the MCU set to zeroes.
|
|
* This way, we return uniform gray for the remainder of the segment.
|
|
*/
|
|
if (! entropy->insufficient_data) {
|
|
|
|
/* Load up working state.
|
|
* We can avoid loading/saving bitread state if in an EOB run.
|
|
*/
|
|
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
|
|
|
|
/* There is always only one block per MCU */
|
|
|
|
if (EOBRUN) /* if it's a band of zeroes... */
|
|
EOBRUN--; /* ...process it now (we do nothing) */
|
|
else {
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
Se = cinfo->Se;
|
|
Al = cinfo->Al;
|
|
natural_order = cinfo->natural_order;
|
|
block = MCU_data[0];
|
|
tbl = entropy->ac_derived_tbl;
|
|
|
|
for (k = cinfo->Ss; k <= Se; k++) {
|
|
HUFF_DECODE(s, br_state, tbl, return FALSE, label2);
|
|
r = s >> 4;
|
|
s &= 15;
|
|
if (s) {
|
|
k += r;
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
/* Scale and output coefficient in natural (dezigzagged) order */
|
|
(*block)[natural_order[k]] = (JCOEF) (s << Al);
|
|
} else {
|
|
if (r != 15) { /* EOBr, run length is 2^r + appended bits */
|
|
if (r) { /* EOBr, r > 0 */
|
|
EOBRUN = 1 << r;
|
|
CHECK_BIT_BUFFER(br_state, r, return FALSE);
|
|
r = GET_BITS(r);
|
|
EOBRUN += r;
|
|
EOBRUN--; /* this band is processed at this moment */
|
|
}
|
|
break; /* force end-of-band */
|
|
}
|
|
k += 15; /* ZRL: skip 15 zeroes in band */
|
|
}
|
|
}
|
|
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
|
|
}
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* MCU decoding for DC successive approximation refinement scan.
|
|
* Note: we assume such scans can be multi-component,
|
|
* although the spec is not very clear on the point.
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
JCOEF p1;
|
|
int blkn;
|
|
BITREAD_STATE_VARS;
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* Not worth the cycles to check insufficient_data here,
|
|
* since we will not change the data anyway if we read zeroes.
|
|
*/
|
|
|
|
/* Load up working state */
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
|
|
p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
|
|
|
|
/* Outer loop handles each block in the MCU */
|
|
|
|
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
|
|
/* Encoded data is simply the next bit of the two's-complement DC value */
|
|
CHECK_BIT_BUFFER(br_state, 1, return FALSE);
|
|
if (GET_BITS(1))
|
|
MCU_data[blkn][0][0] |= p1;
|
|
/* Note: since we use |=, repeating the assignment later is safe */
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* MCU decoding for AC successive approximation refinement scan.
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
register int s, k, r;
|
|
unsigned int EOBRUN;
|
|
int Se;
|
|
JCOEF p1, m1;
|
|
const int * natural_order;
|
|
JBLOCKROW block;
|
|
JCOEFPTR thiscoef;
|
|
BITREAD_STATE_VARS;
|
|
d_derived_tbl * tbl;
|
|
int num_newnz;
|
|
int newnz_pos[DCTSIZE2];
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* If we've run out of data, don't modify the MCU.
|
|
*/
|
|
if (! entropy->insufficient_data) {
|
|
|
|
Se = cinfo->Se;
|
|
p1 = 1 << cinfo->Al; /* 1 in the bit position being coded */
|
|
m1 = -p1; /* -1 in the bit position being coded */
|
|
natural_order = cinfo->natural_order;
|
|
|
|
/* Load up working state */
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */
|
|
|
|
/* There is always only one block per MCU */
|
|
block = MCU_data[0];
|
|
tbl = entropy->ac_derived_tbl;
|
|
|
|
/* If we are forced to suspend, we must undo the assignments to any newly
|
|
* nonzero coefficients in the block, because otherwise we'd get confused
|
|
* next time about which coefficients were already nonzero.
|
|
* But we need not undo addition of bits to already-nonzero coefficients;
|
|
* instead, we can test the current bit to see if we already did it.
|
|
*/
|
|
num_newnz = 0;
|
|
|
|
/* initialize coefficient loop counter to start of band */
|
|
k = cinfo->Ss;
|
|
|
|
if (EOBRUN == 0) {
|
|
do {
|
|
HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
|
|
r = s >> 4;
|
|
s &= 15;
|
|
if (s) {
|
|
if (s != 1) /* size of new coef should always be 1 */
|
|
WARNMS(cinfo, JWRN_HUFF_BAD_CODE);
|
|
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
|
|
if (GET_BITS(1))
|
|
s = p1; /* newly nonzero coef is positive */
|
|
else
|
|
s = m1; /* newly nonzero coef is negative */
|
|
} else {
|
|
if (r != 15) {
|
|
EOBRUN = 1 << r; /* EOBr, run length is 2^r + appended bits */
|
|
if (r) {
|
|
CHECK_BIT_BUFFER(br_state, r, goto undoit);
|
|
r = GET_BITS(r);
|
|
EOBRUN += r;
|
|
}
|
|
break; /* rest of block is handled by EOB logic */
|
|
}
|
|
/* note s = 0 for processing ZRL */
|
|
}
|
|
/* Advance over already-nonzero coefs and r still-zero coefs,
|
|
* appending correction bits to the nonzeroes. A correction bit is 1
|
|
* if the absolute value of the coefficient must be increased.
|
|
*/
|
|
do {
|
|
thiscoef = *block + natural_order[k];
|
|
if (*thiscoef) {
|
|
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
|
|
if (GET_BITS(1)) {
|
|
if ((*thiscoef & p1) == 0) { /* do nothing if already set it */
|
|
if (*thiscoef >= 0)
|
|
*thiscoef += p1;
|
|
else
|
|
*thiscoef += m1;
|
|
}
|
|
}
|
|
} else {
|
|
if (--r < 0)
|
|
break; /* reached target zero coefficient */
|
|
}
|
|
k++;
|
|
} while (k <= Se);
|
|
if (s) {
|
|
int pos = natural_order[k];
|
|
/* Output newly nonzero coefficient */
|
|
(*block)[pos] = (JCOEF) s;
|
|
/* Remember its position in case we have to suspend */
|
|
newnz_pos[num_newnz++] = pos;
|
|
}
|
|
k++;
|
|
} while (k <= Se);
|
|
}
|
|
|
|
if (EOBRUN) {
|
|
/* Scan any remaining coefficient positions after the end-of-band
|
|
* (the last newly nonzero coefficient, if any). Append a correction
|
|
* bit to each already-nonzero coefficient. A correction bit is 1
|
|
* if the absolute value of the coefficient must be increased.
|
|
*/
|
|
do {
|
|
thiscoef = *block + natural_order[k];
|
|
if (*thiscoef) {
|
|
CHECK_BIT_BUFFER(br_state, 1, goto undoit);
|
|
if (GET_BITS(1)) {
|
|
if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */
|
|
if (*thiscoef >= 0)
|
|
*thiscoef += p1;
|
|
else
|
|
*thiscoef += m1;
|
|
}
|
|
}
|
|
}
|
|
k++;
|
|
} while (k <= Se);
|
|
/* Count one block completed in EOB run */
|
|
EOBRUN--;
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */
|
|
}
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
|
|
undoit:
|
|
/* Re-zero any output coefficients that we made newly nonzero */
|
|
while (num_newnz)
|
|
(*block)[newnz_pos[--num_newnz]] = 0;
|
|
|
|
return FALSE;
|
|
}
|
|
|
|
|
|
/*
|
|
* Decode one MCU's worth of Huffman-compressed coefficients,
|
|
* partial blocks.
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu_sub (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
const int * natural_order;
|
|
int Se, blkn;
|
|
BITREAD_STATE_VARS;
|
|
savable_state state;
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* If we've run out of data, just leave the MCU set to zeroes.
|
|
* This way, we return uniform gray for the remainder of the segment.
|
|
*/
|
|
if (! entropy->insufficient_data) {
|
|
|
|
natural_order = cinfo->natural_order;
|
|
Se = cinfo->lim_Se;
|
|
|
|
/* Load up working state */
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(state, entropy->saved);
|
|
|
|
/* Outer loop handles each block in the MCU */
|
|
|
|
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
|
|
JBLOCKROW block = MCU_data[blkn];
|
|
d_derived_tbl * htbl;
|
|
register int s, k, r;
|
|
int coef_limit, ci;
|
|
|
|
/* Decode a single block's worth of coefficients */
|
|
|
|
/* Section F.2.2.1: decode the DC coefficient difference */
|
|
htbl = entropy->dc_cur_tbls[blkn];
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
|
|
|
|
htbl = entropy->ac_cur_tbls[blkn];
|
|
k = 1;
|
|
coef_limit = entropy->coef_limit[blkn];
|
|
if (coef_limit) {
|
|
/* Convert DC difference to actual value, update last_dc_val */
|
|
if (s) {
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
}
|
|
ci = cinfo->MCU_membership[blkn];
|
|
s += state.last_dc_val[ci];
|
|
state.last_dc_val[ci] = s;
|
|
/* Output the DC coefficient */
|
|
(*block)[0] = (JCOEF) s;
|
|
|
|
/* Section F.2.2.2: decode the AC coefficients */
|
|
/* Since zeroes are skipped, output area must be cleared beforehand */
|
|
for (; k < coef_limit; k++) {
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
|
|
|
|
r = s >> 4;
|
|
s &= 15;
|
|
|
|
if (s) {
|
|
k += r;
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
/* Output coefficient in natural (dezigzagged) order.
|
|
* Note: the extra entries in natural_order[] will save us
|
|
* if k > Se, which could happen if the data is corrupted.
|
|
*/
|
|
(*block)[natural_order[k]] = (JCOEF) s;
|
|
} else {
|
|
if (r != 15)
|
|
goto EndOfBlock;
|
|
k += 15;
|
|
}
|
|
}
|
|
} else {
|
|
if (s) {
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
DROP_BITS(s);
|
|
}
|
|
}
|
|
|
|
/* Section F.2.2.2: decode the AC coefficients */
|
|
/* In this path we just discard the values */
|
|
for (; k <= Se; k++) {
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
|
|
|
|
r = s >> 4;
|
|
s &= 15;
|
|
|
|
if (s) {
|
|
k += r;
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
DROP_BITS(s);
|
|
} else {
|
|
if (r != 15)
|
|
break;
|
|
k += 15;
|
|
}
|
|
}
|
|
|
|
EndOfBlock: ;
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(entropy->saved, state);
|
|
}
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* Decode one MCU's worth of Huffman-compressed coefficients,
|
|
* full-size blocks.
|
|
*/
|
|
|
|
METHODDEF(boolean)
|
|
decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
int blkn;
|
|
BITREAD_STATE_VARS;
|
|
savable_state state;
|
|
|
|
/* Process restart marker if needed; may have to suspend */
|
|
if (cinfo->restart_interval) {
|
|
if (entropy->restarts_to_go == 0)
|
|
if (! process_restart(cinfo))
|
|
return FALSE;
|
|
}
|
|
|
|
/* If we've run out of data, just leave the MCU set to zeroes.
|
|
* This way, we return uniform gray for the remainder of the segment.
|
|
*/
|
|
if (! entropy->insufficient_data) {
|
|
|
|
/* Load up working state */
|
|
BITREAD_LOAD_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(state, entropy->saved);
|
|
|
|
/* Outer loop handles each block in the MCU */
|
|
|
|
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
|
|
JBLOCKROW block = MCU_data[blkn];
|
|
d_derived_tbl * htbl;
|
|
register int s, k, r;
|
|
int coef_limit, ci;
|
|
|
|
/* Decode a single block's worth of coefficients */
|
|
|
|
/* Section F.2.2.1: decode the DC coefficient difference */
|
|
htbl = entropy->dc_cur_tbls[blkn];
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label1);
|
|
|
|
htbl = entropy->ac_cur_tbls[blkn];
|
|
k = 1;
|
|
coef_limit = entropy->coef_limit[blkn];
|
|
if (coef_limit) {
|
|
/* Convert DC difference to actual value, update last_dc_val */
|
|
if (s) {
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
}
|
|
ci = cinfo->MCU_membership[blkn];
|
|
s += state.last_dc_val[ci];
|
|
state.last_dc_val[ci] = s;
|
|
/* Output the DC coefficient */
|
|
(*block)[0] = (JCOEF) s;
|
|
|
|
/* Section F.2.2.2: decode the AC coefficients */
|
|
/* Since zeroes are skipped, output area must be cleared beforehand */
|
|
for (; k < coef_limit; k++) {
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label2);
|
|
|
|
r = s >> 4;
|
|
s &= 15;
|
|
|
|
if (s) {
|
|
k += r;
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
r = GET_BITS(s);
|
|
s = HUFF_EXTEND(r, s);
|
|
/* Output coefficient in natural (dezigzagged) order.
|
|
* Note: the extra entries in jpeg_natural_order[] will save us
|
|
* if k >= DCTSIZE2, which could happen if the data is corrupted.
|
|
*/
|
|
(*block)[jpeg_natural_order[k]] = (JCOEF) s;
|
|
} else {
|
|
if (r != 15)
|
|
goto EndOfBlock;
|
|
k += 15;
|
|
}
|
|
}
|
|
} else {
|
|
if (s) {
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
DROP_BITS(s);
|
|
}
|
|
}
|
|
|
|
/* Section F.2.2.2: decode the AC coefficients */
|
|
/* In this path we just discard the values */
|
|
for (; k < DCTSIZE2; k++) {
|
|
HUFF_DECODE(s, br_state, htbl, return FALSE, label3);
|
|
|
|
r = s >> 4;
|
|
s &= 15;
|
|
|
|
if (s) {
|
|
k += r;
|
|
CHECK_BIT_BUFFER(br_state, s, return FALSE);
|
|
DROP_BITS(s);
|
|
} else {
|
|
if (r != 15)
|
|
break;
|
|
k += 15;
|
|
}
|
|
}
|
|
|
|
EndOfBlock: ;
|
|
}
|
|
|
|
/* Completed MCU, so update state */
|
|
BITREAD_SAVE_STATE(cinfo, entropy->bitstate);
|
|
ASSIGN_STATE(entropy->saved, state);
|
|
}
|
|
|
|
/* Account for restart interval if using restarts */
|
|
if (cinfo->restart_interval)
|
|
entropy->restarts_to_go--;
|
|
|
|
return TRUE;
|
|
}
|
|
|
|
|
|
/*
|
|
* Initialize for a Huffman-compressed scan.
|
|
*/
|
|
|
|
METHODDEF(void)
|
|
start_pass_huff_decoder (j_decompress_ptr cinfo)
|
|
{
|
|
huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;
|
|
int ci, blkn, tbl, i;
|
|
jpeg_component_info * compptr;
|
|
|
|
if (cinfo->progressive_mode) {
|
|
/* Validate progressive scan parameters */
|
|
if (cinfo->Ss == 0) {
|
|
if (cinfo->Se != 0)
|
|
goto bad;
|
|
} else {
|
|
/* need not check Ss/Se < 0 since they came from unsigned bytes */
|
|
if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
|
|
goto bad;
|
|
/* AC scans may have only one component */
|
|
if (cinfo->comps_in_scan != 1)
|
|
goto bad;
|
|
}
|
|
if (cinfo->Ah != 0) {
|
|
/* Successive approximation refinement scan: must have Al = Ah-1. */
|
|
if (cinfo->Ah-1 != cinfo->Al)
|
|
goto bad;
|
|
}
|
|
if (cinfo->Al > 13) { /* need not check for < 0 */
|
|
/* Arguably the maximum Al value should be less than 13 for 8-bit
|
|
* precision, but the spec doesn't say so, and we try to be liberal
|
|
* about what we accept. Note: large Al values could result in
|
|
* out-of-range DC coefficients during early scans, leading to bizarre
|
|
* displays due to overflows in the IDCT math. But we won't crash.
|
|
*/
|
|
bad:
|
|
ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
|
|
cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
|
|
}
|
|
/* Update progression status, and verify that scan order is legal.
|
|
* Note that inter-scan inconsistencies are treated as warnings
|
|
* not fatal errors ... not clear if this is right way to behave.
|
|
*/
|
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
|
|
int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
|
|
int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
|
|
if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
|
|
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
|
|
for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
|
|
int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
|
|
if (cinfo->Ah != expected)
|
|
WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
|
|
coef_bit_ptr[coefi] = cinfo->Al;
|
|
}
|
|
}
|
|
|
|
/* Select MCU decoding routine */
|
|
if (cinfo->Ah == 0) {
|
|
if (cinfo->Ss == 0)
|
|
entropy->pub.decode_mcu = decode_mcu_DC_first;
|
|
else
|
|
entropy->pub.decode_mcu = decode_mcu_AC_first;
|
|
} else {
|
|
if (cinfo->Ss == 0)
|
|
entropy->pub.decode_mcu = decode_mcu_DC_refine;
|
|
else
|
|
entropy->pub.decode_mcu = decode_mcu_AC_refine;
|
|
}
|
|
|
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
|
|
compptr = cinfo->cur_comp_info[ci];
|
|
/* Make sure requested tables are present, and compute derived tables.
|
|
* We may build same derived table more than once, but it's not expensive.
|
|
*/
|
|
if (cinfo->Ss == 0) {
|
|
if (cinfo->Ah == 0) { /* DC refinement needs no table */
|
|
tbl = compptr->dc_tbl_no;
|
|
jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
|
|
& entropy->derived_tbls[tbl]);
|
|
}
|
|
} else {
|
|
tbl = compptr->ac_tbl_no;
|
|
jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
|
|
& entropy->derived_tbls[tbl]);
|
|
/* remember the single active table */
|
|
entropy->ac_derived_tbl = entropy->derived_tbls[tbl];
|
|
}
|
|
/* Initialize DC predictions to 0 */
|
|
entropy->saved.last_dc_val[ci] = 0;
|
|
}
|
|
|
|
/* Initialize private state variables */
|
|
entropy->saved.EOBRUN = 0;
|
|
} else {
|
|
/* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.
|
|
* This ought to be an error condition, but we make it a warning because
|
|
* there are some baseline files out there with all zeroes in these bytes.
|
|
*/
|
|
if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
|
|
((cinfo->is_baseline || cinfo->Se < DCTSIZE2) &&
|
|
cinfo->Se != cinfo->lim_Se))
|
|
WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
|
|
|
|
/* Select MCU decoding routine */
|
|
/* We retain the hard-coded case for full-size blocks.
|
|
* This is not necessary, but it appears that this version is slightly
|
|
* more performant in the given implementation.
|
|
* With an improved implementation we would prefer a single optimized
|
|
* function.
|
|
*/
|
|
if (cinfo->lim_Se != DCTSIZE2-1)
|
|
entropy->pub.decode_mcu = decode_mcu_sub;
|
|
else
|
|
entropy->pub.decode_mcu = decode_mcu;
|
|
|
|
for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
|
|
compptr = cinfo->cur_comp_info[ci];
|
|
/* Compute derived values for Huffman tables */
|
|
/* We may do this more than once for a table, but it's not expensive */
|
|
tbl = compptr->dc_tbl_no;
|
|
jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,
|
|
& entropy->dc_derived_tbls[tbl]);
|
|
if (cinfo->lim_Se) { /* AC needs no table when not present */
|
|
tbl = compptr->ac_tbl_no;
|
|
jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,
|
|
& entropy->ac_derived_tbls[tbl]);
|
|
}
|
|
/* Initialize DC predictions to 0 */
|
|
entropy->saved.last_dc_val[ci] = 0;
|
|
}
|
|
|
|
/* Precalculate decoding info for each block in an MCU of this scan */
|
|
for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
|
|
ci = cinfo->MCU_membership[blkn];
|
|
compptr = cinfo->cur_comp_info[ci];
|
|
/* Precalculate which table to use for each block */
|
|
entropy->dc_cur_tbls[blkn] = entropy->dc_derived_tbls[compptr->dc_tbl_no];
|
|
entropy->ac_cur_tbls[blkn] = /* AC needs no table when not present */
|
|
cinfo->lim_Se ? entropy->ac_derived_tbls[compptr->ac_tbl_no] : NULL;
|
|
/* Decide whether we really care about the coefficient values */
|
|
if (compptr->component_needed) {
|
|
ci = compptr->DCT_v_scaled_size;
|
|
i = compptr->DCT_h_scaled_size;
|
|
switch (cinfo->lim_Se) {
|
|
case (1*1-1):
|
|
entropy->coef_limit[blkn] = 1;
|
|
break;
|
|
case (2*2-1):
|
|
if (ci <= 0 || ci > 2) ci = 2;
|
|
if (i <= 0 || i > 2) i = 2;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order2[ci - 1][i - 1];
|
|
break;
|
|
case (3*3-1):
|
|
if (ci <= 0 || ci > 3) ci = 3;
|
|
if (i <= 0 || i > 3) i = 3;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order3[ci - 1][i - 1];
|
|
break;
|
|
case (4*4-1):
|
|
if (ci <= 0 || ci > 4) ci = 4;
|
|
if (i <= 0 || i > 4) i = 4;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order4[ci - 1][i - 1];
|
|
break;
|
|
case (5*5-1):
|
|
if (ci <= 0 || ci > 5) ci = 5;
|
|
if (i <= 0 || i > 5) i = 5;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order5[ci - 1][i - 1];
|
|
break;
|
|
case (6*6-1):
|
|
if (ci <= 0 || ci > 6) ci = 6;
|
|
if (i <= 0 || i > 6) i = 6;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order6[ci - 1][i - 1];
|
|
break;
|
|
case (7*7-1):
|
|
if (ci <= 0 || ci > 7) ci = 7;
|
|
if (i <= 0 || i > 7) i = 7;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order7[ci - 1][i - 1];
|
|
break;
|
|
default:
|
|
if (ci <= 0 || ci > 8) ci = 8;
|
|
if (i <= 0 || i > 8) i = 8;
|
|
entropy->coef_limit[blkn] = 1 + jpeg_zigzag_order[ci - 1][i - 1];
|
|
}
|
|
} else {
|
|
entropy->coef_limit[blkn] = 0;
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Initialize bitread state variables */
|
|
entropy->bitstate.bits_left = 0;
|
|
entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */
|
|
entropy->insufficient_data = FALSE;
|
|
|
|
/* Initialize restart counter */
|
|
entropy->restarts_to_go = cinfo->restart_interval;
|
|
}
|
|
|
|
|
|
/*
|
|
* Module initialization routine for Huffman entropy decoding.
|
|
*/
|
|
|
|
GLOBAL(void)
|
|
jinit_huff_decoder (j_decompress_ptr cinfo)
|
|
{
|
|
huff_entropy_ptr entropy;
|
|
int i;
|
|
|
|
entropy = (huff_entropy_ptr) (*cinfo->mem->alloc_small)
|
|
((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(huff_entropy_decoder));
|
|
cinfo->entropy = &entropy->pub;
|
|
entropy->pub.start_pass = start_pass_huff_decoder;
|
|
entropy->pub.finish_pass = finish_pass_huff;
|
|
|
|
if (cinfo->progressive_mode) {
|
|
/* Create progression status table */
|
|
int *coef_bit_ptr, ci;
|
|
cinfo->coef_bits = (int (*)[DCTSIZE2]) (*cinfo->mem->alloc_small)
|
|
((j_common_ptr) cinfo, JPOOL_IMAGE,
|
|
cinfo->num_components * DCTSIZE2 * SIZEOF(int));
|
|
coef_bit_ptr = & cinfo->coef_bits[0][0];
|
|
for (ci = 0; ci < cinfo->num_components; ci++)
|
|
for (i = 0; i < DCTSIZE2; i++)
|
|
*coef_bit_ptr++ = -1;
|
|
|
|
/* Mark derived tables unallocated */
|
|
for (i = 0; i < NUM_HUFF_TBLS; i++) {
|
|
entropy->derived_tbls[i] = NULL;
|
|
}
|
|
} else {
|
|
/* Mark derived tables unallocated */
|
|
for (i = 0; i < NUM_HUFF_TBLS; i++) {
|
|
entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
|
|
}
|
|
}
|
|
}
|