diff options
Diffstat (limited to 'c/dec/bit_reader.h')
| -rw-r--r-- | c/dec/bit_reader.h | 33 |
1 files changed, 18 insertions, 15 deletions
diff --git a/c/dec/bit_reader.h b/c/dec/bit_reader.h index 21c59d7..39e4873 100644 --- a/c/dec/bit_reader.h +++ b/c/dec/bit_reader.h @@ -20,7 +20,7 @@ extern "C" { #define BROTLI_SHORT_FILL_BIT_WINDOW_READ (sizeof(brotli_reg_t) >> 1) -static const uint32_t kBitMask[33] = { 0x0000, +static const uint32_t kBitMask[33] = { 0x00000000, 0x00000001, 0x00000003, 0x00000007, 0x0000000F, 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF, 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF, @@ -35,7 +35,7 @@ static BROTLI_INLINE uint32_t BitMask(uint32_t n) { if (BROTLI_IS_CONSTANT(n) || BROTLI_HAS_UBFX) { /* Masking with this expression turns to a single "Unsigned Bit Field Extract" UBFX instruction on ARM. */ - return ~((0xffffffffU) << n); + return ~((0xFFFFFFFFu) << n); } else { return kBitMask[n]; } @@ -58,8 +58,9 @@ typedef struct { /* Initializes the BrotliBitReader fields. */ BROTLI_INTERNAL void BrotliInitBitReader(BrotliBitReader* const br); -/* Ensures that accumulator is not empty. May consume one byte of input. - Returns 0 if data is required but there is no input available. +/* Ensures that accumulator is not empty. + May consume up to sizeof(brotli_reg_t) - 1 bytes of input. + Returns BROTLI_FALSE if data is required but there is no input available. For BROTLI_ALIGNED_READ this function also prepares bit reader for aligned reading. */ BROTLI_INTERNAL BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* const br); @@ -98,9 +99,9 @@ static BROTLI_INLINE BROTLI_BOOL BrotliCheckInputAmount( return TO_BROTLI_BOOL(br->avail_in >= num); } -/* Guarantees that there are at least n_bits + 1 bits in accumulator. +/* Guarantees that there are at least |n_bits| + 1 bits in accumulator. Precondition: accumulator contains at least 1 bit. - n_bits should be in the range [1..24] for regular build. For portable + |n_bits| should be in the range [1..24] for regular build. For portable non-64-bit little-endian build only 16 bits are safe to request. */ static BROTLI_INLINE void BrotliFillBitWindow( BrotliBitReader* const br, uint32_t n_bits) { @@ -158,7 +159,8 @@ static BROTLI_INLINE void BrotliFillBitWindow16(BrotliBitReader* const br) { BrotliFillBitWindow(br, 17); } -/* Pulls one byte of input to accumulator. */ +/* Tries to pull one byte of input to accumulator. + Returns BROTLI_FALSE if there is no input available. */ static BROTLI_INLINE BROTLI_BOOL BrotliPullByte(BrotliBitReader* const br) { if (br->avail_in == 0) { return BROTLI_FALSE; @@ -190,15 +192,16 @@ static BROTLI_INLINE uint32_t BrotliGet16BitsUnmasked( return (uint32_t)BrotliGetBitsUnmasked(br); } -/* Returns the specified number of bits from |br| without advancing bit pos. */ +/* Returns the specified number of bits from |br| without advancing bit + position. */ static BROTLI_INLINE uint32_t BrotliGetBits( BrotliBitReader* const br, uint32_t n_bits) { BrotliFillBitWindow(br, n_bits); return (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits); } -/* Tries to peek the specified amount of bits. Returns 0, if there is not - enough input. */ +/* Tries to peek the specified amount of bits. Returns BROTLI_FALSE, if there + is not enough input. */ static BROTLI_INLINE BROTLI_BOOL BrotliSafeGetBits( BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) { while (BrotliGetAvailableBits(br) < n_bits) { @@ -210,7 +213,7 @@ static BROTLI_INLINE BROTLI_BOOL BrotliSafeGetBits( return BROTLI_TRUE; } -/* Advances the bit pos by n_bits. */ +/* Advances the bit pos by |n_bits|. */ static BROTLI_INLINE void BrotliDropBits( BrotliBitReader* const br, uint32_t n_bits) { br->bit_pos_ += n_bits; @@ -230,7 +233,7 @@ static BROTLI_INLINE void BrotliBitReaderUnload(BrotliBitReader* br) { } /* Reads the specified number of bits from |br| and advances the bit pos. - Precondition: accumulator MUST contain at least n_bits. */ + Precondition: accumulator MUST contain at least |n_bits|. */ static BROTLI_INLINE void BrotliTakeBits( BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) { *val = (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits); @@ -259,8 +262,8 @@ static BROTLI_INLINE uint32_t BrotliReadBits( } } -/* Tries to read the specified amount of bits. Returns 0, if there is not - enough input. n_bits MUST be positive. */ +/* Tries to read the specified amount of bits. Returns BROTLI_FALSE, if there + is not enough input. |n_bits| MUST be positive. */ static BROTLI_INLINE BROTLI_BOOL BrotliSafeReadBits( BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) { while (BrotliGetAvailableBits(br) < n_bits) { @@ -284,7 +287,7 @@ static BROTLI_INLINE BROTLI_BOOL BrotliJumpToByteBoundary(BrotliBitReader* br) { } /* Copies remaining input bytes stored in the bit reader to the output. Value - num may not be larger than BrotliGetRemainingBytes. The bit reader must be + |num| may not be larger than BrotliGetRemainingBytes. The bit reader must be warmed up again after this. */ static BROTLI_INLINE void BrotliCopyBytes(uint8_t* dest, BrotliBitReader* br, size_t num) { |