1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/media/libjpeg/jdhuff.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,235 @@
1.4 +/*
1.5 + * jdhuff.h
1.6 + *
1.7 + * This file was part of the Independent JPEG Group's software:
1.8 + * Copyright (C) 1991-1997, Thomas G. Lane.
1.9 + * Modifications:
1.10 + * Copyright (C) 2010-2011, D. R. Commander.
1.11 + * For conditions of distribution and use, see the accompanying README file.
1.12 + *
1.13 + * This file contains declarations for Huffman entropy decoding routines
1.14 + * that are shared between the sequential decoder (jdhuff.c) and the
1.15 + * progressive decoder (jdphuff.c). No other modules need to see these.
1.16 + */
1.17 +
1.18 +/* Short forms of external names for systems with brain-damaged linkers. */
1.19 +
1.20 +#ifdef NEED_SHORT_EXTERNAL_NAMES
1.21 +#define jpeg_make_d_derived_tbl jMkDDerived
1.22 +#define jpeg_fill_bit_buffer jFilBitBuf
1.23 +#define jpeg_huff_decode jHufDecode
1.24 +#endif /* NEED_SHORT_EXTERNAL_NAMES */
1.25 +
1.26 +
1.27 +/* Derived data constructed for each Huffman table */
1.28 +
1.29 +#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
1.30 +
1.31 +typedef struct {
1.32 + /* Basic tables: (element [0] of each array is unused) */
1.33 + INT32 maxcode[18]; /* largest code of length k (-1 if none) */
1.34 + /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
1.35 + INT32 valoffset[18]; /* huffval[] offset for codes of length k */
1.36 + /* valoffset[k] = huffval[] index of 1st symbol of code length k, less
1.37 + * the smallest code of length k; so given a code of length k, the
1.38 + * corresponding symbol is huffval[code + valoffset[k]]
1.39 + */
1.40 +
1.41 + /* Link to public Huffman table (needed only in jpeg_huff_decode) */
1.42 + JHUFF_TBL *pub;
1.43 +
1.44 + /* Lookahead table: indexed by the next HUFF_LOOKAHEAD bits of
1.45 + * the input data stream. If the next Huffman code is no more
1.46 + * than HUFF_LOOKAHEAD bits long, we can obtain its length and
1.47 + * the corresponding symbol directly from this tables.
1.48 + *
1.49 + * The lower 8 bits of each table entry contain the number of
1.50 + * bits in the corresponding Huffman code, or HUFF_LOOKAHEAD + 1
1.51 + * if too long. The next 8 bits of each entry contain the
1.52 + * symbol.
1.53 + */
1.54 + int lookup[1<<HUFF_LOOKAHEAD];
1.55 +} d_derived_tbl;
1.56 +
1.57 +/* Expand a Huffman table definition into the derived format */
1.58 +EXTERN(void) jpeg_make_d_derived_tbl
1.59 + JPP((j_decompress_ptr cinfo, boolean isDC, int tblno,
1.60 + d_derived_tbl ** pdtbl));
1.61 +
1.62 +
1.63 +/*
1.64 + * Fetching the next N bits from the input stream is a time-critical operation
1.65 + * for the Huffman decoders. We implement it with a combination of inline
1.66 + * macros and out-of-line subroutines. Note that N (the number of bits
1.67 + * demanded at one time) never exceeds 15 for JPEG use.
1.68 + *
1.69 + * We read source bytes into get_buffer and dole out bits as needed.
1.70 + * If get_buffer already contains enough bits, they are fetched in-line
1.71 + * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
1.72 + * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
1.73 + * as full as possible (not just to the number of bits needed; this
1.74 + * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
1.75 + * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
1.76 + * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
1.77 + * at least the requested number of bits --- dummy zeroes are inserted if
1.78 + * necessary.
1.79 + */
1.80 +
1.81 +#if __WORDSIZE == 64 || defined(_WIN64)
1.82 +
1.83 +typedef size_t bit_buf_type; /* type of bit-extraction buffer */
1.84 +#define BIT_BUF_SIZE 64 /* size of buffer in bits */
1.85 +
1.86 +#else
1.87 +
1.88 +typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
1.89 +#define BIT_BUF_SIZE 32 /* size of buffer in bits */
1.90 +
1.91 +#endif
1.92 +
1.93 +/* If long is > 32 bits on your machine, and shifting/masking longs is
1.94 + * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
1.95 + * appropriately should be a win. Unfortunately we can't define the size
1.96 + * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
1.97 + * because not all machines measure sizeof in 8-bit bytes.
1.98 + */
1.99 +
1.100 +typedef struct { /* Bitreading state saved across MCUs */
1.101 + bit_buf_type get_buffer; /* current bit-extraction buffer */
1.102 + int bits_left; /* # of unused bits in it */
1.103 +} bitread_perm_state;
1.104 +
1.105 +typedef struct { /* Bitreading working state within an MCU */
1.106 + /* Current data source location */
1.107 + /* We need a copy, rather than munging the original, in case of suspension */
1.108 + const JOCTET * next_input_byte; /* => next byte to read from source */
1.109 + size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
1.110 + /* Bit input buffer --- note these values are kept in register variables,
1.111 + * not in this struct, inside the inner loops.
1.112 + */
1.113 + bit_buf_type get_buffer; /* current bit-extraction buffer */
1.114 + int bits_left; /* # of unused bits in it */
1.115 + /* Pointer needed by jpeg_fill_bit_buffer. */
1.116 + j_decompress_ptr cinfo; /* back link to decompress master record */
1.117 +} bitread_working_state;
1.118 +
1.119 +/* Macros to declare and load/save bitread local variables. */
1.120 +#define BITREAD_STATE_VARS \
1.121 + register bit_buf_type get_buffer; \
1.122 + register int bits_left; \
1.123 + bitread_working_state br_state
1.124 +
1.125 +#define BITREAD_LOAD_STATE(cinfop,permstate) \
1.126 + br_state.cinfo = cinfop; \
1.127 + br_state.next_input_byte = cinfop->src->next_input_byte; \
1.128 + br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
1.129 + get_buffer = permstate.get_buffer; \
1.130 + bits_left = permstate.bits_left;
1.131 +
1.132 +#define BITREAD_SAVE_STATE(cinfop,permstate) \
1.133 + cinfop->src->next_input_byte = br_state.next_input_byte; \
1.134 + cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
1.135 + permstate.get_buffer = get_buffer; \
1.136 + permstate.bits_left = bits_left
1.137 +
1.138 +/*
1.139 + * These macros provide the in-line portion of bit fetching.
1.140 + * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
1.141 + * before using GET_BITS, PEEK_BITS, or DROP_BITS.
1.142 + * The variables get_buffer and bits_left are assumed to be locals,
1.143 + * but the state struct might not be (jpeg_huff_decode needs this).
1.144 + * CHECK_BIT_BUFFER(state,n,action);
1.145 + * Ensure there are N bits in get_buffer; if suspend, take action.
1.146 + * val = GET_BITS(n);
1.147 + * Fetch next N bits.
1.148 + * val = PEEK_BITS(n);
1.149 + * Fetch next N bits without removing them from the buffer.
1.150 + * DROP_BITS(n);
1.151 + * Discard next N bits.
1.152 + * The value N should be a simple variable, not an expression, because it
1.153 + * is evaluated multiple times.
1.154 + */
1.155 +
1.156 +#define CHECK_BIT_BUFFER(state,nbits,action) \
1.157 + { if (bits_left < (nbits)) { \
1.158 + if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
1.159 + { action; } \
1.160 + get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
1.161 +
1.162 +#define GET_BITS(nbits) \
1.163 + (((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1))
1.164 +
1.165 +#define PEEK_BITS(nbits) \
1.166 + (((int) (get_buffer >> (bits_left - (nbits)))) & ((1<<(nbits))-1))
1.167 +
1.168 +#define DROP_BITS(nbits) \
1.169 + (bits_left -= (nbits))
1.170 +
1.171 +/* Load up the bit buffer to a depth of at least nbits */
1.172 +EXTERN(boolean) jpeg_fill_bit_buffer
1.173 + JPP((bitread_working_state * state, register bit_buf_type get_buffer,
1.174 + register int bits_left, int nbits));
1.175 +
1.176 +
1.177 +/*
1.178 + * Code for extracting next Huffman-coded symbol from input bit stream.
1.179 + * Again, this is time-critical and we make the main paths be macros.
1.180 + *
1.181 + * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
1.182 + * without looping. Usually, more than 95% of the Huffman codes will be 8
1.183 + * or fewer bits long. The few overlength codes are handled with a loop,
1.184 + * which need not be inline code.
1.185 + *
1.186 + * Notes about the HUFF_DECODE macro:
1.187 + * 1. Near the end of the data segment, we may fail to get enough bits
1.188 + * for a lookahead. In that case, we do it the hard way.
1.189 + * 2. If the lookahead table contains no entry, the next code must be
1.190 + * more than HUFF_LOOKAHEAD bits long.
1.191 + * 3. jpeg_huff_decode returns -1 if forced to suspend.
1.192 + */
1.193 +
1.194 +#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
1.195 +{ register int nb, look; \
1.196 + if (bits_left < HUFF_LOOKAHEAD) { \
1.197 + if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
1.198 + get_buffer = state.get_buffer; bits_left = state.bits_left; \
1.199 + if (bits_left < HUFF_LOOKAHEAD) { \
1.200 + nb = 1; goto slowlabel; \
1.201 + } \
1.202 + } \
1.203 + look = PEEK_BITS(HUFF_LOOKAHEAD); \
1.204 + if ((nb = (htbl->lookup[look] >> HUFF_LOOKAHEAD)) <= HUFF_LOOKAHEAD) { \
1.205 + DROP_BITS(nb); \
1.206 + result = htbl->lookup[look] & ((1 << HUFF_LOOKAHEAD) - 1); \
1.207 + } else { \
1.208 +slowlabel: \
1.209 + if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
1.210 + { failaction; } \
1.211 + get_buffer = state.get_buffer; bits_left = state.bits_left; \
1.212 + } \
1.213 +}
1.214 +
1.215 +#define HUFF_DECODE_FAST(s,nb,htbl) \
1.216 + FILL_BIT_BUFFER_FAST; \
1.217 + s = PEEK_BITS(HUFF_LOOKAHEAD); \
1.218 + s = htbl->lookup[s]; \
1.219 + nb = s >> HUFF_LOOKAHEAD; \
1.220 + /* Pre-execute the common case of nb <= HUFF_LOOKAHEAD */ \
1.221 + DROP_BITS(nb); \
1.222 + s = s & ((1 << HUFF_LOOKAHEAD) - 1); \
1.223 + if (nb > HUFF_LOOKAHEAD) { \
1.224 + /* Equivalent of jpeg_huff_decode() */ \
1.225 + /* Don't use GET_BITS() here because we don't want to modify bits_left */ \
1.226 + s = (get_buffer >> bits_left) & ((1 << (nb)) - 1); \
1.227 + while (s > htbl->maxcode[nb]) { \
1.228 + s <<= 1; \
1.229 + s |= GET_BITS(1); \
1.230 + nb++; \
1.231 + } \
1.232 + s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) & 0xFF ]; \
1.233 + }
1.234 +
1.235 +/* Out-of-line case for Huffman code fetching */
1.236 +EXTERN(int) jpeg_huff_decode
1.237 + JPP((bitread_working_state * state, register bit_buf_type get_buffer,
1.238 + register int bits_left, d_derived_tbl * htbl, int min_bits));
