1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/libs/libjpeg/jdhuff.h	Thu Sep 08 06:28:38 2011 +0300
     1.3 @@ -0,0 +1,201 @@
     1.4 +/*
     1.5 + * jdhuff.h
     1.6 + *
     1.7 + * Copyright (C) 1991-1997, Thomas G. Lane.
     1.8 + * This file is part of the Independent JPEG Group's software.
     1.9 + * For conditions of distribution and use, see the accompanying README file.
    1.10 + *
    1.11 + * This file contains declarations for Huffman entropy decoding routines
    1.12 + * that are shared between the sequential decoder (jdhuff.c) and the
    1.13 + * progressive decoder (jdphuff.c).  No other modules need to see these.
    1.14 + */
    1.15 +
    1.16 +/* Short forms of external names for systems with brain-damaged linkers. */
    1.17 +
    1.18 +#ifdef NEED_SHORT_EXTERNAL_NAMES
    1.19 +#define jpeg_make_d_derived_tbl	jMkDDerived
    1.20 +#define jpeg_fill_bit_buffer	jFilBitBuf
    1.21 +#define jpeg_huff_decode	jHufDecode
    1.22 +#endif /* NEED_SHORT_EXTERNAL_NAMES */
    1.23 +
    1.24 +
    1.25 +/* Derived data constructed for each Huffman table */
    1.26 +
    1.27 +#define HUFF_LOOKAHEAD	8	/* # of bits of lookahead */
    1.28 +
    1.29 +typedef struct {
    1.30 +  /* Basic tables: (element [0] of each array is unused) */
    1.31 +  INT32 maxcode[18];		/* largest code of length k (-1 if none) */
    1.32 +  /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
    1.33 +  INT32 valoffset[17];		/* huffval[] offset for codes of length k */
    1.34 +  /* valoffset[k] = huffval[] index of 1st symbol of code length k, less
    1.35 +   * the smallest code of length k; so given a code of length k, the
    1.36 +   * corresponding symbol is huffval[code + valoffset[k]]
    1.37 +   */
    1.38 +
    1.39 +  /* Link to public Huffman table (needed only in jpeg_huff_decode) */
    1.40 +  JHUFF_TBL *pub;
    1.41 +
    1.42 +  /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
    1.43 +   * the input data stream.  If the next Huffman code is no more
    1.44 +   * than HUFF_LOOKAHEAD bits long, we can obtain its length and
    1.45 +   * the corresponding symbol directly from these tables.
    1.46 +   */
    1.47 +  int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
    1.48 +  UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
    1.49 +} d_derived_tbl;
    1.50 +
    1.51 +/* Expand a Huffman table definition into the derived format */
    1.52 +EXTERN(void) jpeg_make_d_derived_tbl
    1.53 +	JPP((j_decompress_ptr cinfo, boolean isDC, int tblno,
    1.54 +	     d_derived_tbl ** pdtbl));
    1.55 +
    1.56 +
    1.57 +/*
    1.58 + * Fetching the next N bits from the input stream is a time-critical operation
    1.59 + * for the Huffman decoders.  We implement it with a combination of inline
    1.60 + * macros and out-of-line subroutines.  Note that N (the number of bits
    1.61 + * demanded at one time) never exceeds 15 for JPEG use.
    1.62 + *
    1.63 + * We read source bytes into get_buffer and dole out bits as needed.
    1.64 + * If get_buffer already contains enough bits, they are fetched in-line
    1.65 + * by the macros CHECK_BIT_BUFFER and GET_BITS.  When there aren't enough
    1.66 + * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
    1.67 + * as full as possible (not just to the number of bits needed; this
    1.68 + * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
    1.69 + * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
    1.70 + * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
    1.71 + * at least the requested number of bits --- dummy zeroes are inserted if
    1.72 + * necessary.
    1.73 + */
    1.74 +
    1.75 +typedef INT32 bit_buf_type;	/* type of bit-extraction buffer */
    1.76 +#define BIT_BUF_SIZE  32	/* size of buffer in bits */
    1.77 +
    1.78 +/* If long is > 32 bits on your machine, and shifting/masking longs is
    1.79 + * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
    1.80 + * appropriately should be a win.  Unfortunately we can't define the size
    1.81 + * with something like  #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
    1.82 + * because not all machines measure sizeof in 8-bit bytes.
    1.83 + */
    1.84 +
    1.85 +typedef struct {		/* Bitreading state saved across MCUs */
    1.86 +  bit_buf_type get_buffer;	/* current bit-extraction buffer */
    1.87 +  int bits_left;		/* # of unused bits in it */
    1.88 +} bitread_perm_state;
    1.89 +
    1.90 +typedef struct {		/* Bitreading working state within an MCU */
    1.91 +  /* Current data source location */
    1.92 +  /* We need a copy, rather than munging the original, in case of suspension */
    1.93 +  const JOCTET * next_input_byte; /* => next byte to read from source */
    1.94 +  size_t bytes_in_buffer;	/* # of bytes remaining in source buffer */
    1.95 +  /* Bit input buffer --- note these values are kept in register variables,
    1.96 +   * not in this struct, inside the inner loops.
    1.97 +   */
    1.98 +  bit_buf_type get_buffer;	/* current bit-extraction buffer */
    1.99 +  int bits_left;		/* # of unused bits in it */
   1.100 +  /* Pointer needed by jpeg_fill_bit_buffer. */
   1.101 +  j_decompress_ptr cinfo;	/* back link to decompress master record */
   1.102 +} bitread_working_state;
   1.103 +
   1.104 +/* Macros to declare and load/save bitread local variables. */
   1.105 +#define BITREAD_STATE_VARS  \
   1.106 +	register bit_buf_type get_buffer;  \
   1.107 +	register int bits_left;  \
   1.108 +	bitread_working_state br_state
   1.109 +
   1.110 +#define BITREAD_LOAD_STATE(cinfop,permstate)  \
   1.111 +	br_state.cinfo = cinfop; \
   1.112 +	br_state.next_input_byte = cinfop->src->next_input_byte; \
   1.113 +	br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
   1.114 +	get_buffer = permstate.get_buffer; \
   1.115 +	bits_left = permstate.bits_left;
   1.116 +
   1.117 +#define BITREAD_SAVE_STATE(cinfop,permstate)  \
   1.118 +	cinfop->src->next_input_byte = br_state.next_input_byte; \
   1.119 +	cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
   1.120 +	permstate.get_buffer = get_buffer; \
   1.121 +	permstate.bits_left = bits_left
   1.122 +
   1.123 +/*
   1.124 + * These macros provide the in-line portion of bit fetching.
   1.125 + * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
   1.126 + * before using GET_BITS, PEEK_BITS, or DROP_BITS.
   1.127 + * The variables get_buffer and bits_left are assumed to be locals,
   1.128 + * but the state struct might not be (jpeg_huff_decode needs this).
   1.129 + *	CHECK_BIT_BUFFER(state,n,action);
   1.130 + *		Ensure there are N bits in get_buffer; if suspend, take action.
   1.131 + *      val = GET_BITS(n);
   1.132 + *		Fetch next N bits.
   1.133 + *      val = PEEK_BITS(n);
   1.134 + *		Fetch next N bits without removing them from the buffer.
   1.135 + *	DROP_BITS(n);
   1.136 + *		Discard next N bits.
   1.137 + * The value N should be a simple variable, not an expression, because it
   1.138 + * is evaluated multiple times.
   1.139 + */
   1.140 +
   1.141 +#define CHECK_BIT_BUFFER(state,nbits,action) \
   1.142 +	{ if (bits_left < (nbits)) {  \
   1.143 +	    if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits))  \
   1.144 +	      { action; }  \
   1.145 +	    get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
   1.146 +
   1.147 +#define GET_BITS(nbits) \
   1.148 +	(((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1))
   1.149 +
   1.150 +#define PEEK_BITS(nbits) \
   1.151 +	(((int) (get_buffer >> (bits_left -  (nbits)))) & ((1<<(nbits))-1))
   1.152 +
   1.153 +#define DROP_BITS(nbits) \
   1.154 +	(bits_left -= (nbits))
   1.155 +
   1.156 +/* Load up the bit buffer to a depth of at least nbits */
   1.157 +EXTERN(boolean) jpeg_fill_bit_buffer
   1.158 +	JPP((bitread_working_state * state, register bit_buf_type get_buffer,
   1.159 +	     register int bits_left, int nbits));
   1.160 +
   1.161 +
   1.162 +/*
   1.163 + * Code for extracting next Huffman-coded symbol from input bit stream.
   1.164 + * Again, this is time-critical and we make the main paths be macros.
   1.165 + *
   1.166 + * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
   1.167 + * without looping.  Usually, more than 95% of the Huffman codes will be 8
   1.168 + * or fewer bits long.  The few overlength codes are handled with a loop,
   1.169 + * which need not be inline code.
   1.170 + *
   1.171 + * Notes about the HUFF_DECODE macro:
   1.172 + * 1. Near the end of the data segment, we may fail to get enough bits
   1.173 + *    for a lookahead.  In that case, we do it the hard way.
   1.174 + * 2. If the lookahead table contains no entry, the next code must be
   1.175 + *    more than HUFF_LOOKAHEAD bits long.
   1.176 + * 3. jpeg_huff_decode returns -1 if forced to suspend.
   1.177 + */
   1.178 +
   1.179 +#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
   1.180 +{ register int nb, look; \
   1.181 +  if (bits_left < HUFF_LOOKAHEAD) { \
   1.182 +    if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
   1.183 +    get_buffer = state.get_buffer; bits_left = state.bits_left; \
   1.184 +    if (bits_left < HUFF_LOOKAHEAD) { \
   1.185 +      nb = 1; goto slowlabel; \
   1.186 +    } \
   1.187 +  } \
   1.188 +  look = PEEK_BITS(HUFF_LOOKAHEAD); \
   1.189 +  if ((nb = htbl->look_nbits[look]) != 0) { \
   1.190 +    DROP_BITS(nb); \
   1.191 +    result = htbl->look_sym[look]; \
   1.192 +  } else { \
   1.193 +    nb = HUFF_LOOKAHEAD+1; \
   1.194 +slowlabel: \
   1.195 +    if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
   1.196 +	{ failaction; } \
   1.197 +    get_buffer = state.get_buffer; bits_left = state.bits_left; \
   1.198 +  } \
   1.199 +}
   1.200 +
   1.201 +/* Out-of-line case for Huffman code fetching */
   1.202 +EXTERN(int) jpeg_huff_decode
   1.203 +	JPP((bitread_working_state * state, register bit_buf_type get_buffer,
   1.204 +	     register int bits_left, d_derived_tbl * htbl, int min_bits));