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Diffstat (limited to 'src/libjpeg/jdhuff.h')
| -rw-r--r-- | src/libjpeg/jdhuff.h | 201 |
1 files changed, 0 insertions, 201 deletions
diff --git a/src/libjpeg/jdhuff.h b/src/libjpeg/jdhuff.h deleted file mode 100644 index ae19b6c..0000000 --- a/src/libjpeg/jdhuff.h +++ /dev/null @@ -1,201 +0,0 @@ -/* - * jdhuff.h - * - * Copyright (C) 1991-1997, Thomas G. Lane. - * This file is part of the Independent JPEG Group's software. - * For conditions of distribution and use, see the accompanying README file. - * - * This file contains declarations for Huffman entropy decoding routines - * that are shared between the sequential decoder (jdhuff.c) and the - * progressive decoder (jdphuff.c). No other modules need to see these. - */ - -/* Short forms of external names for systems with brain-damaged linkers. */ - -#ifdef NEED_SHORT_EXTERNAL_NAMES -#define jpeg_make_d_derived_tbl jMkDDerived -#define jpeg_fill_bit_buffer jFilBitBuf -#define jpeg_huff_decode jHufDecode -#endif /* NEED_SHORT_EXTERNAL_NAMES */ - - -/* Derived data constructed for each Huffman table */ - -#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */ - -typedef struct { - /* Basic tables: (element [0] of each array is unused) */ - INT32 maxcode[18]; /* largest code of length k (-1 if none) */ - /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */ - INT32 valoffset[17]; /* huffval[] offset for codes of length k */ - /* valoffset[k] = huffval[] index of 1st symbol of code length k, less - * the smallest code of length k; so given a code of length k, the - * corresponding symbol is huffval[code + valoffset[k]] - */ - - /* Link to public Huffman table (needed only in jpeg_huff_decode) */ - JHUFF_TBL *pub; - - /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of - * the input data stream. If the next Huffman code is no more - * than HUFF_LOOKAHEAD bits long, we can obtain its length and - * the corresponding symbol directly from these tables. - */ - int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */ - UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */ -} d_derived_tbl; - -/* Expand a Huffman table definition into the derived format */ -EXTERN(void) jpeg_make_d_derived_tbl - JPP((j_decompress_ptr cinfo, boolean isDC, int tblno, - d_derived_tbl ** pdtbl)); - - -/* - * Fetching the next N bits from the input stream is a time-critical operation - * for the Huffman decoders. We implement it with a combination of inline - * macros and out-of-line subroutines. Note that N (the number of bits - * demanded at one time) never exceeds 15 for JPEG use. - * - * We read source bytes into get_buffer and dole out bits as needed. - * If get_buffer already contains enough bits, they are fetched in-line - * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough - * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer - * as full as possible (not just to the number of bits needed; this - * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer). - * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension. - * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains - * at least the requested number of bits --- dummy zeroes are inserted if - * necessary. - */ - -typedef INT32 bit_buf_type; /* type of bit-extraction buffer */ -#define BIT_BUF_SIZE 32 /* size of buffer in bits */ - -/* If long is > 32 bits on your machine, and shifting/masking longs is - * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE - * appropriately should be a win. Unfortunately we can't define the size - * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8) - * because not all machines measure sizeof in 8-bit bytes. - */ - -typedef struct { /* Bitreading state saved across MCUs */ - bit_buf_type get_buffer; /* current bit-extraction buffer */ - int bits_left; /* # of unused bits in it */ -} bitread_perm_state; - -typedef struct { /* Bitreading working state within an MCU */ - /* Current data source location */ - /* We need a copy, rather than munging the original, in case of suspension */ - const JOCTET * next_input_byte; /* => next byte to read from source */ - size_t bytes_in_buffer; /* # of bytes remaining in source buffer */ - /* Bit input buffer --- note these values are kept in register variables, - * not in this struct, inside the inner loops. - */ - bit_buf_type get_buffer; /* current bit-extraction buffer */ - int bits_left; /* # of unused bits in it */ - /* Pointer needed by jpeg_fill_bit_buffer. */ - j_decompress_ptr cinfo; /* back link to decompress master record */ -} bitread_working_state; - -/* Macros to declare and load/save bitread local variables. */ -#define BITREAD_STATE_VARS \ - register bit_buf_type get_buffer; \ - register int bits_left; \ - bitread_working_state br_state - -#define BITREAD_LOAD_STATE(cinfop,permstate) \ - br_state.cinfo = cinfop; \ - br_state.next_input_byte = cinfop->src->next_input_byte; \ - br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \ - get_buffer = permstate.get_buffer; \ - bits_left = permstate.bits_left; - -#define BITREAD_SAVE_STATE(cinfop,permstate) \ - cinfop->src->next_input_byte = br_state.next_input_byte; \ - cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \ - permstate.get_buffer = get_buffer; \ - permstate.bits_left = bits_left - -/* - * These macros provide the in-line portion of bit fetching. - * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer - * before using GET_BITS, PEEK_BITS, or DROP_BITS. - * The variables get_buffer and bits_left are assumed to be locals, - * but the state struct might not be (jpeg_huff_decode needs this). - * CHECK_BIT_BUFFER(state,n,action); - * Ensure there are N bits in get_buffer; if suspend, take action. - * val = GET_BITS(n); - * Fetch next N bits. - * val = PEEK_BITS(n); - * Fetch next N bits without removing them from the buffer. - * DROP_BITS(n); - * Discard next N bits. - * The value N should be a simple variable, not an expression, because it - * is evaluated multiple times. - */ - -#define CHECK_BIT_BUFFER(state,nbits,action) \ - { if (bits_left < (nbits)) { \ - if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \ - { action; } \ - get_buffer = (state).get_buffer; bits_left = (state).bits_left; } } - -#define GET_BITS(nbits) \ - (((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1)) - -#define PEEK_BITS(nbits) \ - (((int) (get_buffer >> (bits_left - (nbits)))) & ((1<<(nbits))-1)) - -#define DROP_BITS(nbits) \ - (bits_left -= (nbits)) - -/* Load up the bit buffer to a depth of at least nbits */ -EXTERN(boolean) jpeg_fill_bit_buffer - JPP((bitread_working_state * state, register bit_buf_type get_buffer, - register int bits_left, int nbits)); - - -/* - * Code for extracting next Huffman-coded symbol from input bit stream. - * Again, this is time-critical and we make the main paths be macros. - * - * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits - * without looping. Usually, more than 95% of the Huffman codes will be 8 - * or fewer bits long. The few overlength codes are handled with a loop, - * which need not be inline code. - * - * Notes about the HUFF_DECODE macro: - * 1. Near the end of the data segment, we may fail to get enough bits - * for a lookahead. In that case, we do it the hard way. - * 2. If the lookahead table contains no entry, the next code must be - * more than HUFF_LOOKAHEAD bits long. - * 3. jpeg_huff_decode returns -1 if forced to suspend. - */ - -#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \ -{ register int nb, look; \ - if (bits_left < HUFF_LOOKAHEAD) { \ - if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \ - get_buffer = state.get_buffer; bits_left = state.bits_left; \ - if (bits_left < HUFF_LOOKAHEAD) { \ - nb = 1; goto slowlabel; \ - } \ - } \ - look = PEEK_BITS(HUFF_LOOKAHEAD); \ - if ((nb = htbl->look_nbits[look]) != 0) { \ - DROP_BITS(nb); \ - result = htbl->look_sym[look]; \ - } else { \ - nb = HUFF_LOOKAHEAD+1; \ -slowlabel: \ - if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \ - { failaction; } \ - get_buffer = state.get_buffer; bits_left = state.bits_left; \ - } \ -} - -/* Out-of-line case for Huffman code fetching */ -EXTERN(int) jpeg_huff_decode - JPP((bitread_working_state * state, register bit_buf_type get_buffer, - register int bits_left, d_derived_tbl * htbl, int min_bits)); |