From 6cf45dac81a7e1c2168d6effdfab7bcc7995c1bb Mon Sep 17 00:00:00 2001 From: Yann Collet Date: Wed, 23 Mar 2016 14:18:37 +0100 Subject: [PATCH] shared const BIT_mask --- lib/bitstream.h | 20 +++++++++----------- lib/zstd_decompress.c | 4 ++-- 2 files changed, 11 insertions(+), 13 deletions(-) diff --git a/lib/bitstream.h b/lib/bitstream.h index f2ed51bc..62d2cb2b 100644 --- a/lib/bitstream.h +++ b/lib/bitstream.h @@ -141,7 +141,7 @@ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits); /*-************************************************************** -* Helper functions +* Internal functions ****************************************************************/ MEM_STATIC unsigned BIT_highbit32 (register U32 val) { @@ -165,6 +165,9 @@ MEM_STATIC unsigned BIT_highbit32 (register U32 val) # endif } +/*===== Local Constants =====*/ +static const unsigned BIT_mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF }; /* up to 26 bits */ + /*-************************************************************** * bitStream encoding @@ -189,8 +192,7 @@ MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* startPtr, size_t ds Does not check for register overflow ! */ MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits) { - static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF }; /* up to 26 bits */ - bitC->bitContainer |= (value & mask[nbBits]) << bitC->bitPos; + bitC->bitContainer |= (value & BIT_mask[nbBits]) << bitC->bitPos; bitC->bitPos += nbBits; } @@ -290,18 +292,14 @@ MEM_STATIC size_t BIT_getUpperBits(size_t bitD, U32 const start) return bitD >> start; } -MEM_STATIC size_t BIT_getNBits(size_t bitD, U32 const nbBits, U32 const start) +MEM_STATIC size_t BIT_getMiddleBits(size_t bitD, U32 const nbBits, U32 const start) { - static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF }; /* up to 26 bits */ - return (bitD >> start) & mask[nbBits]; + return (bitD >> start) & BIT_mask[nbBits]; } -MEM_STATIC size_t BIT_consumeFirstBits(size_t* bitDPtr, U32 const nbBits) +MEM_STATIC size_t BIT_getLowerBits(size_t bitD, U32 const nbBits) { - static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF }; /* up to 26 bits */ - size_t const result = *bitDPtr & mask[nbBits]; - *bitDPtr >>= nbBits; - return result; + return bitD & BIT_mask[nbBits]; } /*! BIT_lookBits() : diff --git a/lib/zstd_decompress.c b/lib/zstd_decompress.c index 3abd6bbc..7749ffd3 100644 --- a/lib/zstd_decompress.c +++ b/lib/zstd_decompress.c @@ -655,8 +655,8 @@ static void ZSTD_decodeSequence(seq_t* seq, seqState_t* seqState, const U32 mls) 0x800000, 0x1000000, 0x2000000, 0x4000000, /*fake*/ 1, 1, 1, 1 }; /* sequence */ - seq->litLength = LL_base[llCode] + BIT_getNBits(allBits, llBits, 0); - seq->matchLength = ML_base[mlCode] + BIT_getNBits(allBits, mlBits, llBits) + mls; + seq->litLength = LL_base[llCode] + BIT_getLowerBits(allBits, llBits); + seq->matchLength = ML_base[mlCode] + mls + BIT_getMiddleBits(allBits, mlBits, llBits); { size_t const offset = ofCode ? OF_base[ofCode] + BIT_getUpperBits(allBits, llBits+mlBits) : llCode ? seq->offset : seqState->prevOffset; if (ofCode | !llCode) seqState->prevOffset = seq->offset; /* cmove */