~tom-gall/libjpeg-turbo/upstream-1.2 : contents of jdhuff.h at revision 58

~tom-gall/libjpeg-turbo/upstream-1.2 : (revision 58)

/*
 * jdhuff.h
 *
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * Copyright (C) 2010-2011, D. R. Commander.
 * 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[18];		/* 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 table: 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 this tables.
   *
   * The lower 8 bits of each table entry contain the number of
   * bits in the corresponding Huffman code, or HUFF_LOOKAHEAD + 1
   * if too long.  The next 8 bits of each entry contain the
   * symbol.
   */
  int lookup[1<<HUFF_LOOKAHEAD];
} 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.
 */

#if __WORDSIZE == 64 || defined(_WIN64)

typedef size_t bit_buf_type;	/* type of bit-extraction buffer */
#define BIT_BUF_SIZE  64		/* size of buffer in bits */

#else

typedef INT32 bit_buf_type;	/* type of bit-extraction buffer */
#define BIT_BUF_SIZE  32		/* size of buffer in bits */

#endif

/* 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->lookup[look] >> HUFF_LOOKAHEAD)) <= HUFF_LOOKAHEAD) { \
    DROP_BITS(nb); \
    result = htbl->lookup[look] & ((1 << HUFF_LOOKAHEAD) - 1); \
  } else { \
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; \
  } \
}

#define HUFF_DECODE_FAST(s,nb,htbl) \
  FILL_BIT_BUFFER_FAST; \
  s = PEEK_BITS(HUFF_LOOKAHEAD); \
  s = htbl->lookup[s]; \
  nb = s >> HUFF_LOOKAHEAD; \
  /* Pre-execute the common case of nb <= HUFF_LOOKAHEAD */ \
  DROP_BITS(nb); \
  s = s & ((1 << HUFF_LOOKAHEAD) - 1); \
  if (nb > HUFF_LOOKAHEAD) { \
    /* Equivalent of jpeg_huff_decode() */ \
    /* Don't use GET_BITS() here because we don't want to modify bits_left */ \
    s = (get_buffer >> bits_left) & ((1 << (nb)) - 1); \
    while (s > htbl->maxcode[nb]) { \
      s <<= 1; \
      s |= GET_BITS(1); \
      nb++; \
    } \
    s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) & 0xFF ]; \
  }

/* 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));

1 by Tom Gall initial import based on mandeeps git tree and my packaging	1	/*
	2	* jdhuff.h
	3	*
	4	* Copyright (C) 1991-1997, Thomas G. Lane.
6 by Tom Gall merge in 1.1.90 from upstream	5	* Copyright (C) 2010-2011, D. R. Commander.
1 by Tom Gall initial import based on mandeeps git tree and my packaging	6	* This file is part of the Independent JPEG Group's software.
	7	* For conditions of distribution and use, see the accompanying README file.
	8	*
	9	* This file contains declarations for Huffman entropy decoding routines
	10	* that are shared between the sequential decoder (jdhuff.c) and the
	11	* progressive decoder (jdphuff.c). No other modules need to see these.
	12	*/
	13
	14	/* Short forms of external names for systems with brain-damaged linkers. */
	15
	16	#ifdef NEED_SHORT_EXTERNAL_NAMES
	17	#define jpeg_make_d_derived_tbl jMkDDerived
	18	#define jpeg_fill_bit_buffer jFilBitBuf
	19	#define jpeg_huff_decode jHufDecode
	20	#endif /* NEED_SHORT_EXTERNAL_NAMES */
	21
	22
	23	/* Derived data constructed for each Huffman table */
	24
	25	#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
	26
	27	typedef struct {
	28	/* Basic tables: (element [0] of each array is unused) */
	29	INT32 maxcode[18]; /* largest code of length k (-1 if none) */
	30	/* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
	31	INT32 valoffset[18]; /* huffval[] offset for codes of length k */
	32	/* valoffset[k] = huffval[] index of 1st symbol of code length k, less
	33	* the smallest code of length k; so given a code of length k, the
	34	* corresponding symbol is huffval[code + valoffset[k]]
	35	*/
	36
	37	/* Link to public Huffman table (needed only in jpeg_huff_decode) */
	38	JHUFF_TBL *pub;
	39
	40	/* Lookahead table: indexed by the next HUFF_LOOKAHEAD bits of
	41	* the input data stream. If the next Huffman code is no more
	42	* than HUFF_LOOKAHEAD bits long, we can obtain its length and
	43	* the corresponding symbol directly from this tables.
	44	*
	45	* The lower 8 bits of each table entry contain the number of
	46	* bits in the corresponding Huffman code, or HUFF_LOOKAHEAD + 1
	47	* if too long. The next 8 bits of each entry contain the
	48	* symbol.
	49	*/
	50	int lookup[1<<HUFF_LOOKAHEAD];
	51	} d_derived_tbl;
	52
	53	/* Expand a Huffman table definition into the derived format */
	54	EXTERN(void) jpeg_make_d_derived_tbl
	55	JPP((j_decompress_ptr cinfo, boolean isDC, int tblno,
	56	d_derived_tbl ** pdtbl));
	57
	58
	59	/*
	60	* Fetching the next N bits from the input stream is a time-critical operation
	61	* for the Huffman decoders. We implement it with a combination of inline
	62	* macros and out-of-line subroutines. Note that N (the number of bits
	63	* demanded at one time) never exceeds 15 for JPEG use.
	64	*
	65	* We read source bytes into get_buffer and dole out bits as needed.
	66	* If get_buffer already contains enough bits, they are fetched in-line
	67	* by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
	68	* bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
	69	* as full as possible (not just to the number of bits needed; this
70	* prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
71	* Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
72	* On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
73	* at least the requested number of bits --- dummy zeroes are inserted if
74	* necessary.
75	*/
76
77	#if __WORDSIZE == 64 \|\| defined(_WIN64)
78
79	typedef size_t bit_buf_type; /* type of bit-extraction buffer */
80	#define BIT_BUF_SIZE 64 /* size of buffer in bits */
81
82	#else
83
84	typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
85	#define BIT_BUF_SIZE 32 /* size of buffer in bits */
86
87	#endif
88
89	/* If long is > 32 bits on your machine, and shifting/masking longs is
90	* reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
91	* appropriately should be a win. Unfortunately we can't define the size
92	* with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
93	* because not all machines measure sizeof in 8-bit bytes.
94	*/
95
96	typedef struct { /* Bitreading state saved across MCUs */
97	bit_buf_type get_buffer; /* current bit-extraction buffer */
98	int bits_left; /* # of unused bits in it */
99	} bitread_perm_state;
100
101	typedef struct { /* Bitreading working state within an MCU */
102	/* Current data source location */
103	/* We need a copy, rather than munging the original, in case of suspension */
104	const JOCTET * next_input_byte; /* => next byte to read from source */
105	size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
106	/* Bit input buffer --- note these values are kept in register variables,
107	* not in this struct, inside the inner loops.
108	*/
109	bit_buf_type get_buffer; /* current bit-extraction buffer */
110	int bits_left; /* # of unused bits in it */
111	/* Pointer needed by jpeg_fill_bit_buffer. */
112	j_decompress_ptr cinfo; /* back link to decompress master record */
113	} bitread_working_state;
114
115	/* Macros to declare and load/save bitread local variables. */
116	#define BITREAD_STATE_VARS \
117	register bit_buf_type get_buffer; \
118	register int bits_left; \
119	bitread_working_state br_state
120
121	#define BITREAD_LOAD_STATE(cinfop,permstate) \
122	br_state.cinfo = cinfop; \
123	br_state.next_input_byte = cinfop->src->next_input_byte; \
124	br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
125	get_buffer = permstate.get_buffer; \
126	bits_left = permstate.bits_left;
127
128	#define BITREAD_SAVE_STATE(cinfop,permstate) \
129	cinfop->src->next_input_byte = br_state.next_input_byte; \
130	cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
131	permstate.get_buffer = get_buffer; \
132	permstate.bits_left = bits_left
133
134	/*
135	* These macros provide the in-line portion of bit fetching.
136	* Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
137	* before using GET_BITS, PEEK_BITS, or DROP_BITS.
138	* The variables get_buffer and bits_left are assumed to be locals,
139	* but the state struct might not be (jpeg_huff_decode needs this).
140	* CHECK_BIT_BUFFER(state,n,action);
141	* Ensure there are N bits in get_buffer; if suspend, take action.
142	* val = GET_BITS(n);
143	* Fetch next N bits.
144	* val = PEEK_BITS(n);
145	* Fetch next N bits without removing them from the buffer.
146	* DROP_BITS(n);
147	* Discard next N bits.
148	* The value N should be a simple variable, not an expression, because it
149	* is evaluated multiple times.
150	*/
151
152	#define CHECK_BIT_BUFFER(state,nbits,action) \
153	{ if (bits_left < (nbits)) { \
154	if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
155	{ action; } \
156	get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
157
158	#define GET_BITS(nbits) \
159	(((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1))
160
161	#define PEEK_BITS(nbits) \
162	(((int) (get_buffer >> (bits_left - (nbits)))) & ((1<<(nbits))-1))
163
164	#define DROP_BITS(nbits) \
165	(bits_left -= (nbits))
166
167	/* Load up the bit buffer to a depth of at least nbits */
168	EXTERN(boolean) jpeg_fill_bit_buffer
169	JPP((bitread_working_state * state, register bit_buf_type get_buffer,
170	register int bits_left, int nbits));
171
172
173	/*
174	* Code for extracting next Huffman-coded symbol from input bit stream.
175	* Again, this is time-critical and we make the main paths be macros.
176	*
177	* We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
178	* without looping. Usually, more than 95% of the Huffman codes will be 8
179	* or fewer bits long. The few overlength codes are handled with a loop,
180	* which need not be inline code.
181	*
182	* Notes about the HUFF_DECODE macro:
183	* 1. Near the end of the data segment, we may fail to get enough bits
184	* for a lookahead. In that case, we do it the hard way.
185	* 2. If the lookahead table contains no entry, the next code must be
186	* more than HUFF_LOOKAHEAD bits long.
187	* 3. jpeg_huff_decode returns -1 if forced to suspend.
188	*/
189
190	#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
191	{ register int nb, look; \
192	if (bits_left < HUFF_LOOKAHEAD) { \
193	if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
194	get_buffer = state.get_buffer; bits_left = state.bits_left; \
195	if (bits_left < HUFF_LOOKAHEAD) { \
196	nb = 1; goto slowlabel; \
197	} \
198	} \
199	look = PEEK_BITS(HUFF_LOOKAHEAD); \
200	if ((nb = (htbl->lookup[look] >> HUFF_LOOKAHEAD)) <= HUFF_LOOKAHEAD) { \
201	DROP_BITS(nb); \
202	result = htbl->lookup[look] & ((1 << HUFF_LOOKAHEAD) - 1); \
203	} else { \
204	slowlabel: \
205	if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
206	{ failaction; } \
207	get_buffer = state.get_buffer; bits_left = state.bits_left; \
208	} \
209	}
210
6 by Tom Gall merge in 1.1.90 from upstream	211	#define HUFF_DECODE_FAST(s,nb,htbl) \
	212	FILL_BIT_BUFFER_FAST; \
	213	s = PEEK_BITS(HUFF_LOOKAHEAD); \
	214	s = htbl->lookup[s]; \
	215	nb = s >> HUFF_LOOKAHEAD; \
	216	/* Pre-execute the common case of nb <= HUFF_LOOKAHEAD */ \
	217	DROP_BITS(nb); \
	218	s = s & ((1 << HUFF_LOOKAHEAD) - 1); \
	219	if (nb > HUFF_LOOKAHEAD) { \
	220	/* Equivalent of jpeg_huff_decode() */ \
	221	/* Don't use GET_BITS() here because we don't want to modify bits_left */ \
	222	s = (get_buffer >> bits_left) & ((1 << (nb)) - 1); \
	223	while (s > htbl->maxcode[nb]) { \
	224	s <<= 1; \
	225	s \|= GET_BITS(1); \
	226	nb++; \
	227	} \
	228	s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) & 0xFF ]; \
	229	}
	230
1 by Tom Gall initial import based on mandeeps git tree and my packaging	231	/* Out-of-line case for Huffman code fetching */
	232	EXTERN(int) jpeg_huff_decode
	233	JPP((bitread_working_state * state, register bit_buf_type get_buffer,
	234	register int bits_left, d_derived_tbl * htbl, int min_bits));