From 9fa1ad5a91d69158e37ccff1c770f84c972a940a Mon Sep 17 00:00:00 2001 From: Eugene Kliuchnikov Date: Wed, 8 Feb 2017 21:14:01 +0100 Subject: Fix "zero-distance-code", take 2 (#506) --- dec/decode.c | 4 ++-- dec/state.h | 2 ++ 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/dec/decode.c b/dec/decode.c index 1e903c8..2c2006b 100644 --- a/dec/decode.c +++ b/dec/decode.c @@ -1446,6 +1446,7 @@ static BROTLI_INLINE BROTLI_BOOL ReadDistanceInternal( } /* Convert the distance code to the actual distance by possibly */ /* looking up past distances from the s->ringbuffer. */ + s->distance_context = 0; if ((s->distance_code & ~0xf) == 0) { TakeDistanceFromRingBuffer(s); --s->block_length[2]; @@ -1706,6 +1707,7 @@ CommandPostDecodeLiterals: s->state = BROTLI_STATE_COMMAND_POST_DECODE_LITERALS; } if (s->distance_code >= 0) { + s->distance_context = s->distance_code ? 0 : 1; --s->dist_rb_idx; s->distance_code = s->dist_rb[s->dist_rb_idx & 3]; goto postReadDistance; /* We already have the implicit distance */ @@ -1714,8 +1716,6 @@ CommandPostDecodeLiterals: if (BROTLI_PREDICT_FALSE(s->block_length[2] == 0)) { BROTLI_SAFE(DecodeDistanceBlockSwitch(s)); } - /* Reuse distance_context variable. */ - s->distance_context = 0; BROTLI_SAFE(ReadDistance(s, br)); postReadDistance: BROTLI_LOG(("[ProcessCommandsInternal] pos = %d distance = %d\n", diff --git a/dec/state.h b/dec/state.h index de1056d..6a8f093 100644 --- a/dec/state.h +++ b/dec/state.h @@ -140,6 +140,8 @@ struct BrotliDecoderStateStruct { /* This is true if the literal context map histogram type always matches the block type. It is then not needed to keep the context (faster decoding). */ int trivial_literal_context; + /* Distance context is actual after command is decoded and before distance + is computed. After distance computation it is used as a temporary variable. */ int distance_context; int meta_block_remaining_len; uint32_t block_length_index; -- cgit v1.1