mirror of
https://git.tukaani.org/xz.git
synced 2024-04-04 12:36:23 +02:00
Moved range decoder initialization (reading the first
five input bytes) from LZMA decoder to range decoder header. Did the same for decoding of direct bits.
This commit is contained in:
Lasse Collin
parent
5db745cd2a
commit
bbfd1f6ab0
2 changed files with 66 additions and 63 deletions
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@ -151,10 +151,6 @@ struct lzma_coder_s {
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/// Length of a repeated match.
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lzma_length_decoder rep_match_len_decoder;
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/// The first five bytes of LZMA compressed data are treated
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/// specially. Once they are read, this stays at zero.
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size_t init_bytes_left;
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};
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@ -166,7 +162,7 @@ struct lzma_coder_s {
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static bool lzma_attribute((pure))
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decode_dummy(const lzma_coder *restrict coder,
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const uint8_t *restrict in, size_t in_pos_local,
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const size_t in_size, uint32_t rc_range, uint32_t rc_code,
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const size_t in_size, lzma_range_decoder rc,
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uint32_t state, uint32_t rep0, const uint32_t now_pos)
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{
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uint32_t rc_bound;
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@ -268,20 +264,11 @@ decode_dummy(const lzma_coder *restrict coder,
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coder->pos_decoders + offset,
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direct_bits);
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} else {
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// Decode direct bits
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assert(pos_slot >= 14);
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assert(direct_bits >= 6);
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direct_bits -= ALIGN_BITS;
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assert(direct_bits >= 2);
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do {
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rc_normalize();
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rc_range >>= 1;
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const uint32_t t
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= (rc_code - rc_range)
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>> 31;
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rc_code -= rc_range & (t - 1);
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} while (--direct_bits > 0);
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rep0 <<= ALIGN_BITS;
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rc_decode_direct_dummy(direct_bits);
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bittree_reverse_decode_dummy(
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coder->pos_align_decoder,
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@ -342,16 +329,9 @@ decode_real(lzma_coder *restrict coder, const uint8_t *restrict in,
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// Initialization //
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////////////////////
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while (coder->init_bytes_left > 0) {
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if (*in_pos == in_size)
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if (!rc_read_init(&coder->rc, in, in_pos, in_size))
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return false;
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coder->rc.code = (coder->rc.code << 8) | in[*in_pos];
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++*in_pos;
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--coder->init_bytes_left;
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}
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///////////////
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// Variables //
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///////////////
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@ -386,7 +366,7 @@ decode_real(lzma_coder *restrict coder, const uint8_t *restrict in,
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while (coder->lz.pos < coder->lz.limit && (in_pos_local < in_limit
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|| (has_safe_buffer && decode_dummy(
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coder, in, in_pos_local, in_size,
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rc_range, rc_code, state, rep0, now_pos)))) {
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rc, state, rep0, now_pos)))) {
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/////////////////////
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// Actual decoding //
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@ -513,20 +493,11 @@ decode_real(lzma_coder *restrict coder, const uint8_t *restrict in,
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coder->pos_decoders + offset,
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direct_bits);
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} else {
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// Decode direct bits
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assert(pos_slot >= 14);
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assert(direct_bits >= 6);
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direct_bits -= ALIGN_BITS;
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assert(direct_bits >= 2);
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do {
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rc_normalize();
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rc_range >>= 1;
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const uint32_t t
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= (rc_code - rc_range)
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>> 31;
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rc_code -= rc_range & (t - 1);
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rep0 = (rep0 << 1) | (1 - t);
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} while (--direct_bits > 0);
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rc_decode_direct(rep0, direct_bits);
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rep0 <<= ALIGN_BITS;
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bittree_reverse_decode(rep0,
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@ -762,7 +733,6 @@ lzma_lzma_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
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next->coder->pos_bits = options->pos_bits;
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next->coder->pos_mask = (1 << next->coder->pos_bits) - 1;
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next->coder->now_pos = 0;
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next->coder->init_bytes_left = 5;
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// Range decoder
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rc_reset(next->coder->rc);
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@ -27,33 +27,47 @@
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typedef struct {
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uint32_t range;
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uint32_t code;
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uint32_t init_bytes_left;
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} lzma_range_decoder;
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static inline bool
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rc_read_init(lzma_range_decoder *rc, const uint8_t *restrict in,
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size_t *restrict in_pos, size_t in_size)
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{
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while (rc->init_bytes_left > 0) {
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if (*in_pos == in_size)
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return false;
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rc->code = (rc->code << 8) | in[*in_pos];
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++*in_pos;
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--rc->init_bytes_left;
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}
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return true;
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}
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/// Makes local copies of range decoder variables.
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#define rc_to_local(rc) \
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uint32_t rc_range = (rc).range; \
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uint32_t rc_code = (rc).code; \
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#define rc_to_local(range_decoder) \
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lzma_range_decoder rc = range_decoder; \
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uint32_t rc_bound
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/// Stores the local copes back to the range decoder structure.
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#define rc_from_local(rc) \
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do {\
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(rc).range = rc_range; \
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(rc).code = rc_code; \
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} while (0)
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#define rc_from_local(range_decoder) \
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range_decoder = rc
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/// Resets the range decoder structure.
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#define rc_reset(rc) \
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#define rc_reset(range_decoder) \
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do { \
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(rc).range = UINT32_MAX; \
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(rc).code = 0; \
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(range_decoder).range = UINT32_MAX; \
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(range_decoder).code = 0; \
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(range_decoder).init_bytes_left = 5; \
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} while (0)
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// All of the macros in this file expect the following variables being defined:
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// - uint32_t rc_range;
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// - uint32_t rc_code;
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// - lzma_range_decoder range_decoder;
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// - uint32_t rc_bound; // Temporary variable
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// - uint8_t *in;
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// - size_t in_pos_local; // Local alias for *in_pos
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@ -66,9 +80,9 @@ do { \
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// Read the next byte of compressed data from buffer_in, if needed.
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#define rc_normalize() \
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do { \
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if (rc_range < TOP_VALUE) { \
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rc_range <<= SHIFT_BITS; \
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rc_code = (rc_code << SHIFT_BITS) | in[in_pos_local++]; \
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if (rc.range < TOP_VALUE) { \
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rc.range <<= SHIFT_BITS; \
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rc.code = (rc.code << SHIFT_BITS) | in[in_pos_local++]; \
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} \
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} while (0)
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@ -88,37 +102,56 @@ do { \
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#define if_bit_0(prob) \
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rc_normalize(); \
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rc_bound = (rc_range >> BIT_MODEL_TOTAL_BITS) * (prob); \
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if (rc_code < rc_bound)
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rc_bound = (rc.range >> BIT_MODEL_TOTAL_BITS) * (prob); \
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if (rc.code < rc_bound)
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#define update_bit_0(prob) \
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do { \
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rc_range = rc_bound; \
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rc.range = rc_bound; \
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prob += (BIT_MODEL_TOTAL - (prob)) >> MOVE_BITS; \
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} while (0)
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#define update_bit_1(prob) \
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do { \
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rc_range -= rc_bound; \
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rc_code -= rc_bound; \
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rc.range -= rc_bound; \
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rc.code -= rc_bound; \
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prob -= (prob) >> MOVE_BITS; \
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} while (0)
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// Dummy versions don't update prob.
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#define rc_decode_direct(dest, count) \
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do { \
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rc_normalize(); \
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rc.range >>= 1; \
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rc_bound = (rc.code - rc.range) >> 31; \
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rc.code -= rc.range & (rc_bound - 1); \
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dest = ((dest) << 1) | (1 - rc_bound);\
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} while (--count > 0)
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// Dummy versions don't update prob or dest.
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#define update_bit_0_dummy() \
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rc_range = rc_bound
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rc.range = rc_bound
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#define update_bit_1_dummy() \
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do { \
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rc_range -= rc_bound; \
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rc_code -= rc_bound; \
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rc.range -= rc_bound; \
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rc.code -= rc_bound; \
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} while (0)
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#define rc_decode_direct_dummy(count) \
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do { \
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rc_normalize(); \
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rc.range >>= 1; \
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rc_bound = (rc.code - rc.range) >> 31; \
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rc.code -= rc.range & (rc_bound - 1); \
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} while (--count > 0)
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///////////////////////
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// Bit tree decoding //
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///////////////////////
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