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Don't check cur_ix_masked against ring_buffer_mask.

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`cur_ix_masked` isn't changing from iteration to iteration, and `max_length` ensures we never find a match long enough to walk off the ring buffer.

PiperOrigin-RevId: 624701948
This commit is contained in:
Evgenii Kliuchnikov 2024-04-14 06:35:19 -07:00 committed by Copybara-Service
parent 709c4672d4
commit c1c76e993f
4 changed files with 13 additions and 11 deletions
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6
c/enc/hash.h
View File

@ -557,7 +557,6 @@ static BROTLI_INLINE void FindCompoundDictionaryMatch(
offset = distance_offset - distance;
limit = source_size - offset;
limit = limit > max_length ? max_length : limit;
BROTLI_DCHECK(cur_ix_masked + limit <= ring_buffer_mask);
len = FindMatchLengthWithLimit(&source[offset], &data[cur_ix_masked],
limit);
if (len >= 2) {
@ -592,7 +591,7 @@ static BROTLI_INLINE void FindCompoundDictionaryMatch(
limit = source_size - offset;
limit = (limit > max_length) ? max_length : limit;
if (distance > max_distance) continue;
if (best_len >= limit ||
if (cur_ix_masked + best_len > ring_buffer_mask || best_len >= limit ||
/* compare 4 bytes ending at best_len + 1 */
BrotliUnalignedRead32(&data[cur_ix_masked + best_len - 3]) !=
BrotliUnalignedRead32(&source[offset + best_len - 3])) {
@ -671,7 +670,8 @@ static BROTLI_INLINE size_t FindAllCompoundDictionaryMatches(
limit = source_size - offset;
limit = (limit > max_length) ? max_length : limit;
if (distance > max_distance) continue;
if (best_len >= limit ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
best_len >= limit ||
data[cur_ix_masked + best_len] != source[offset + best_len]) {
continue;
}

4
c/enc/hash_forgetful_chain_inc.h
View File

@ -208,7 +208,6 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
score_t best_score = out->score;
size_t best_len = out->len;
size_t i;
BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
const size_t key = FN(HashBytes)(&data[cur_ix_masked]);
const uint8_t tiny_hash = (uint8_t)(key);
out->len = 0;
@ -261,7 +260,8 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
prev_ix = (cur_ix - backward) & ring_buffer_mask;
slot = banks[bank].slots[last].next;
delta = banks[bank].slots[last].delta;
if (prev_ix + best_len > ring_buffer_mask ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
prev_ix + best_len > ring_buffer_mask ||
/* compare 4 bytes ending at best_len + 1 */
BrotliUnalignedRead32(&data[cur_ix_masked + best_len - 3]) !=
BrotliUnalignedRead32(&data[prev_ix + best_len - 3])) {

7
c/enc/hash_longest_match64_inc.h
View File

@ -170,7 +170,6 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
score_t best_score = out->score;
size_t best_len = out->len;
size_t i;
BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
out->len = 0;
out->len_code_delta = 0;
/* Try last distance first. */
@ -185,7 +184,8 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
}
prev_ix &= ring_buffer_mask;
if (prev_ix + best_len > ring_buffer_mask ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
prev_ix + best_len > ring_buffer_mask ||
data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {
continue;
}
@ -233,7 +233,8 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
break;
}
prev_ix &= ring_buffer_mask;
if (prev_ix + best_len > ring_buffer_mask ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
prev_ix + best_len > ring_buffer_mask ||
/* compare 4 bytes ending at best_len + 1 */
BrotliUnalignedRead32(&data[cur_ix_masked + best_len - 3]) !=
BrotliUnalignedRead32(&data[prev_ix + best_len - 3])) {

7
c/enc/hash_longest_match_inc.h
View File

@ -169,7 +169,6 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
score_t best_score = out->score;
size_t best_len = out->len;
size_t i;
BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
out->len = 0;
out->len_code_delta = 0;
/* Try last distance first. */
@ -184,7 +183,8 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
}
prev_ix &= ring_buffer_mask;
if (prev_ix + best_len > ring_buffer_mask ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
prev_ix + best_len > ring_buffer_mask ||
data[cur_ix_masked + best_len] != data[prev_ix + best_len]) {
continue;
}
@ -228,7 +228,8 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
break;
}
prev_ix &= ring_buffer_mask;
if (prev_ix + best_len > ring_buffer_mask ||
if (cur_ix_masked + best_len > ring_buffer_mask ||
prev_ix + best_len > ring_buffer_mask ||
/* compare 4 bytes ending at best_len + 1 */
BrotliUnalignedRead32(&data[cur_ix_masked + best_len - 3]) !=
BrotliUnalignedRead32(&data[prev_ix + best_len - 3])) {