istream->data_bytes_left = num_data_bytes;
}
-/* Ensures that the bit buffer variable for the bitstream contains @num_bits
- * bits.
+/* Ensures the bit buffer variable for the bitstream contains at least @num_bits
+ * bits. Following this, bitstream_peek_bits() and/or bitstream_remove_bits()
+ * may be called on the bitstream to peek or remove up to @num_bits bits.
*
- * If there are at least @num_bits bits remaining in the bitstream, 0 is
- * returned. Otherwise, -1 is returned. */
-static inline int
+ * If the input data is exhausted, any further bits are assumed to be 0. */
+static inline void
bitstream_ensure_bits(struct input_bitstream *istream, unsigned num_bits)
{
for (int nbits = num_bits; (int)istream->bitsleft < nbits; nbits -= 16) {
u16 nextword;
unsigned shift;
- if (unlikely(istream->data_bytes_left < 2))
- return -1;
-
- wimlib_assert2(istream->bitsleft <= sizeof(istream->bitbuf) * 8 - 16);
+ if (unlikely(istream->data_bytes_left < 2)) {
+ istream->bitsleft = num_bits;
+ return;
+ }
nextword = le16_to_cpu(*(const le16*)istream->data);
shift = sizeof(istream->bitbuf) * 8 - 16 - istream->bitsleft;
istream->data += 2;
istream->bitsleft += 16;
istream->data_bytes_left -= 2;
-
}
- return 0;
}
-/* Returns the next @num_bits bits in the buffer variable, which must contain at
- * least @num_bits bits, for the bitstream. */
+/* Returns the next @num_bits bits from the bitstream, without removing them.
+ * There must be at least @num_bits remaining in the buffer variable, from a
+ * previous call to bitstream_ensure_bits(). */
static inline u32
bitstream_peek_bits(const struct input_bitstream *istream, unsigned num_bits)
{
- wimlib_assert2(istream->bitsleft >= num_bits);
-
if (unlikely(num_bits == 0))
return 0;
-
return istream->bitbuf >> (sizeof(istream->bitbuf) * 8 - num_bits);
}
-/* Removes @num_bits bits from the buffer variable, which must contain at least
- * @num_bits bits, for the bitstream. */
+/* Removes @num_bits from the bitstream. There must be at least @num_bits
+ * remaining in the buffer variable, from a previous call to
+ * bitstream_ensure_bits(). */
static inline void
bitstream_remove_bits(struct input_bitstream *istream, unsigned num_bits)
{
- wimlib_assert2(istream->bitsleft >= num_bits);
-
istream->bitbuf <<= num_bits;
istream->bitsleft -= num_bits;
}
-/* Gets and removes @num_bits bits from the buffer variable, which must contain
- * at least @num_bits bits, for the bitstream. */
+/* Removes and returns @num_bits bits from the bitstream. There must be at
+ * least @num_bits remaining in the buffer variable, from a previous call to
+ * bitstream_ensure_bits(). */
static inline u32
bitstream_pop_bits(struct input_bitstream *istream, unsigned num_bits)
{
return n;
}
-/* Reads @num_bits bits from the input bitstream. On success, returns 0 and
- * returns the requested bits in @n. If there are fewer than @num_bits
- * remaining in the bitstream, -1 is returned. */
-static inline int
-bitstream_read_bits(struct input_bitstream *istream, unsigned num_bits, u32 *n)
+/* Reads and returns the next @num_bits bits from the bitstream.
+ * If the input data is exhausted, the bits are assumed to be 0. */
+static inline u32
+bitstream_read_bits(struct input_bitstream *istream, unsigned num_bits)
{
- if (unlikely(bitstream_ensure_bits(istream, num_bits)))
- return -1;
-
- *n = bitstream_pop_bits(istream, num_bits);
- return 0;
+ bitstream_ensure_bits(istream, num_bits);
+ return bitstream_pop_bits(istream, num_bits);
}
-/* Return the next literal byte embedded in the bitstream, or -1 if the input
- * was exhausted. */
-static inline int
+/* Reads and returns the next literal byte embedded in the bitstream.
+ * If the input data is exhausted, the byte is assumed to be 0. */
+static inline u8
bitstream_read_byte(struct input_bitstream *istream)
{
- if (unlikely(istream->data_bytes_left < 1))
- return -1;
-
+ if (unlikely(istream->data_bytes_left == 0))
+ return 0;
istream->data_bytes_left--;
return *istream->data++;
}
-/* Reads @num_bits bits from the buffer variable for a bistream without checking
- * to see if that many bits are in the buffer or not. */
-static inline u32
-bitstream_read_bits_nocheck(struct input_bitstream *istream, unsigned num_bits)
-{
- u32 n = bitstream_peek_bits(istream, num_bits);
- bitstream_remove_bits(istream, num_bits);
- return n;
-}
-
-extern int
-read_huffsym_near_end_of_input(struct input_bitstream *istream,
- const u16 decode_table[],
- const u8 lens[],
- unsigned num_syms,
- unsigned table_bits,
- unsigned *n);
-
-/* Read a Huffman-encoded symbol from a bitstream. */
-static inline int
+/* Reads and returns the next Huffman-encoded symbol from a bitstream. If the
+ * input data is exhausted, the Huffman symbol is decoded as if the missing bits
+ * are all zeroes. */
+static inline u16
read_huffsym(struct input_bitstream * restrict istream,
const u16 decode_table[restrict],
const u8 lens[restrict],
unsigned num_syms,
unsigned table_bits,
- unsigned *restrict n,
unsigned max_codeword_len)
{
- /* If there are fewer bits remaining in the input than the maximum
- * codeword length, use the slow path that has extra checks. */
- if (unlikely(bitstream_ensure_bits(istream, max_codeword_len))) {
- return read_huffsym_near_end_of_input(istream, decode_table,
- lens, num_syms,
- table_bits, n);
- }
+
+ bitstream_ensure_bits(istream, max_codeword_len);
/* Use the next table_bits of the input as an index into the
* decode_table. */
* end of the decode table. */
bitstream_remove_bits(istream, table_bits);
do {
- key_bits = sym + bitstream_peek_bits(istream, 1);
- bitstream_remove_bits(istream, 1);
+ key_bits = sym + bitstream_pop_bits(istream, 1);
} while ((sym = decode_table[key_bits]) >= num_syms);
}
- *n = sym;
- return 0;
+ return sym;
}
extern int
/*
* Reads a Huffman-encoded symbol using the pre-tree.
*/
-static inline int
+static inline u16
read_huffsym_using_pretree(struct input_bitstream *istream,
const u16 pretree_decode_table[],
- const u8 pretree_lens[], unsigned *n)
+ const u8 pretree_lens[])
{
return read_huffsym(istream, pretree_decode_table, pretree_lens,
- LZX_PRECODE_NUM_SYMBOLS, LZX_PRECODE_TABLEBITS, n,
+ LZX_PRECODE_NUM_SYMBOLS, LZX_PRECODE_TABLEBITS,
LZX_MAX_PRE_CODEWORD_LEN);
}
/* Reads a Huffman-encoded symbol using the main tree. */
-static inline int
+static inline u16
read_huffsym_using_maintree(struct input_bitstream *istream,
const struct lzx_tables *tables,
- unsigned *n,
unsigned num_main_syms)
{
return read_huffsym(istream, tables->maintree_decode_table,
tables->maintree_lens, num_main_syms,
- LZX_MAINCODE_TABLEBITS, n, LZX_MAX_MAIN_CODEWORD_LEN);
+ LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN);
}
/* Reads a Huffman-encoded symbol using the length tree. */
-static inline int
+static inline u16
read_huffsym_using_lentree(struct input_bitstream *istream,
- const struct lzx_tables *tables,
- unsigned *n)
+ const struct lzx_tables *tables)
{
return read_huffsym(istream, tables->lentree_decode_table,
tables->lentree_lens, LZX_LENCODE_NUM_SYMBOLS,
- LZX_LENCODE_TABLEBITS, n, LZX_MAX_LEN_CODEWORD_LEN);
+ LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN);
}
/* Reads a Huffman-encoded symbol using the aligned offset tree. */
-static inline int
+static inline u16
read_huffsym_using_alignedtree(struct input_bitstream *istream,
- const struct lzx_tables *tables,
- unsigned *n)
+ const struct lzx_tables *tables)
{
return read_huffsym(istream, tables->alignedtree_decode_table,
tables->alignedtree_lens,
LZX_ALIGNEDCODE_NUM_SYMBOLS,
- LZX_ALIGNEDCODE_TABLEBITS, n,
+ LZX_ALIGNEDCODE_TABLEBITS,
LZX_MAX_ALIGNED_CODEWORD_LEN);
}
_aligned_attribute(DECODE_TABLE_ALIGNMENT);
u8 pretree_lens[LZX_PRECODE_NUM_SYMBOLS];
unsigned i;
- u32 len;
int ret;
/* Read the code lengths of the pretree codes. There are 20 lengths of
* 4 bits each. */
for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) {
- ret = bitstream_read_bits(istream, LZX_PRECODE_ELEMENT_SIZE,
- &len);
- if (ret)
- return ret;
- pretree_lens[i] = len;
+ pretree_lens[i] = bitstream_read_bits(istream,
+ LZX_PRECODE_ELEMENT_SIZE);
}
/* Make the decoding table for the pretree. */
u32 num_same;
signed char value;
- ret = read_huffsym_using_pretree(istream, pretree_decode_table,
- pretree_lens, &tree_code);
- if (ret)
- return ret;
+ tree_code = read_huffsym_using_pretree(istream,
+ pretree_decode_table,
+ pretree_lens);
switch (tree_code) {
case 17: /* Run of 0's */
- ret = bitstream_read_bits(istream, 4, &num_zeroes);
- if (ret)
- return ret;
+ num_zeroes = bitstream_read_bits(istream, 4);
num_zeroes += 4;
while (num_zeroes--) {
*lens = 0;
}
break;
case 18: /* Longer run of 0's */
- ret = bitstream_read_bits(istream, 5, &num_zeroes);
- if (ret)
- return ret;
+ num_zeroes = bitstream_read_bits(istream, 5);
num_zeroes += 20;
while (num_zeroes--) {
*lens = 0;
}
break;
case 19: /* Run of identical lengths */
- ret = bitstream_read_bits(istream, 1, &num_same);
- if (ret)
- return ret;
+ num_same = bitstream_read_bits(istream, 1);
num_same += 4;
- ret = read_huffsym_using_pretree(istream,
- pretree_decode_table,
- pretree_lens,
- &code);
- if (ret)
- return ret;
+ code = read_huffsym_using_pretree(istream,
+ pretree_decode_table,
+ pretree_lens);
value = (signed char)*lens - (signed char)code;
if (value < 0)
value += 17;
unsigned block_type;
unsigned block_size;
- ret = bitstream_ensure_bits(istream, 4);
- if (ret)
- return ret;
+ bitstream_ensure_bits(istream, 4);
/* The first three bits tell us what kind of block it is, and are one
* of the LZX_BLOCKTYPE_* values. */
- block_type = bitstream_read_bits_nocheck(istream, 3);
+ block_type = bitstream_pop_bits(istream, 3);
/* Read the block size. This mirrors the behavior
* lzx_write_compressed_block() in lzx-compress.c; see that for more
* details. */
- if (bitstream_read_bits_nocheck(istream, 1)) {
+ if (bitstream_pop_bits(istream, 1)) {
block_size = LZX_DEFAULT_BLOCK_SIZE;
} else {
u32 tmp;
block_size = 0;
- ret = bitstream_read_bits(istream, 8, &tmp);
- if (ret)
- return ret;
+ tmp = bitstream_read_bits(istream, 8);
block_size |= tmp;
-
- ret = bitstream_read_bits(istream, 8, &tmp);
- if (ret)
- return ret;
+ tmp = bitstream_read_bits(istream, 8);
block_size <<= 8;
block_size |= tmp;
if (max_window_size >= 65536) {
- ret = bitstream_read_bits(istream, 8, &tmp);
- if (ret)
- return ret;
+ tmp = bitstream_read_bits(istream, 8);
block_size <<= 8;
block_size |= tmp;
}
* then build it. */
for (unsigned i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) {
- u32 len;
-
- ret = bitstream_read_bits(istream,
- LZX_ALIGNEDCODE_ELEMENT_SIZE,
- &len);
- if (ret)
- return ret;
- tables->alignedtree_lens[i] = len;
+ tables->alignedtree_lens[i] =
+ bitstream_read_bits(istream,
+ LZX_ALIGNEDCODE_ELEMENT_SIZE);
}
LZX_DEBUG("Building the aligned tree.");
unsigned position_slot;
unsigned match_len;
unsigned match_offset;
- unsigned additional_len;
unsigned num_extra_bits;
u32 verbatim_bits;
u32 aligned_bits;
unsigned i;
- int ret;
u8 *match_dest;
u8 *match_src;
* the length tree, offset by 9 (LZX_MIN_MATCH_LEN +
* LZX_NUM_PRIMARY_LENS) */
match_len = LZX_MIN_MATCH_LEN + length_header;
- if (length_header == LZX_NUM_PRIMARY_LENS) {
- ret = read_huffsym_using_lentree(istream, tables,
- &additional_len);
- if (ret)
- return ret;
- match_len += additional_len;
- }
-
+ if (length_header == LZX_NUM_PRIMARY_LENS)
+ match_len += read_huffsym_using_lentree(istream, tables);
/* If the position_slot is 0, 1, or 2, the match offset is retrieved
* from the LRU queue. Otherwise, the match offset is not in the LRU
* equal to 3. (Note that in the case with
* num_extra_bits == 3, the assignment to verbatim_bits
* will just set it to 0. ) */
- ret = bitstream_read_bits(istream, num_extra_bits - 3,
- &verbatim_bits);
- if (ret)
- return ret;
-
+ verbatim_bits = bitstream_read_bits(istream,
+ num_extra_bits - 3);
verbatim_bits <<= 3;
-
- ret = read_huffsym_using_alignedtree(istream, tables,
- &aligned_bits);
- if (ret)
- return ret;
+ aligned_bits = read_huffsym_using_alignedtree(istream,
+ tables);
} else {
/* For non-aligned blocks, or for aligned blocks with
* less than 3 extra bits, the extra bits are added
* directly to the match offset, and the correction for
* the alignment is taken to be 0. */
- ret = bitstream_read_bits(istream, num_extra_bits,
- &verbatim_bits);
- if (ret)
- return ret;
-
+ verbatim_bits = bitstream_read_bits(istream, num_extra_bits);
aligned_bits = 0;
}
* currently in use, then copy the source of the match to the current
* position. */
- if (match_len > bytes_remaining) {
+ if (unlikely(match_len > bytes_remaining)) {
LZX_DEBUG("Match of length %u bytes overflows "
"uncompressed block size", match_len);
return -1;
}
- if (match_offset > window_pos) {
+ if (unlikely(match_offset > window_pos)) {
LZX_DEBUG("Match of length %u bytes references "
"data before window (match_offset = %u, "
"window_pos = %u)",
{
unsigned main_element;
unsigned end;
- int ret;
int match_len;
end = window_pos + block_size;
while (window_pos < end) {
- ret = read_huffsym_using_maintree(istream, tables,
- &main_element,
- num_main_syms);
- if (ret)
- return ret;
-
+ main_element = read_huffsym_using_maintree(istream, tables,
+ num_main_syms);
if (main_element < LZX_NUM_CHARS) {
/* literal: 0 to LZX_NUM_CHARS - 1 */
window[window_pos++] = main_element;
tables,
queue,
istream);
- if (match_len < 0)
+ if (unlikely(match_len < 0))
return match_len;
window_pos += match_len;
}
git://wimlib.net / wimlib / commitdiff