+++ /dev/null
-/* Copyright 2013 Google Inc. All Rights Reserved.
-
- Distributed under MIT license.
- See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
-*/
-
-/* Bit reading helpers */
-
-#ifndef BROTLI_DEC_BIT_READER_H_
-#define BROTLI_DEC_BIT_READER_H_
-
-#include <stdio.h>
-#include <string.h>
-#include "./port.h"
-#include "./types.h"
-
-#if defined(__cplusplus) || defined(c_plusplus)
-extern "C" {
-#endif
-
-#if (BROTLI_64_BITS)
-#define BROTLI_SHORT_FILL_BIT_WINDOW_READ 4
-typedef uint64_t reg_t;
-#else
-#define BROTLI_SHORT_FILL_BIT_WINDOW_READ 2
-typedef uint32_t reg_t;
-#endif
-
-static const uint32_t kBitMask[33] = { 0x0000,
- 0x00000001, 0x00000003, 0x00000007, 0x0000000F,
- 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,
- 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,
- 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF,
- 0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF,
- 0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF,
- 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF,
- 0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF
-};
-
-static BROTLI_INLINE uint32_t BitMask(uint32_t n) {
- if (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);
- } else {
- return kBitMask[n];
- }
-}
-
-typedef struct {
- reg_t val_; /* pre-fetched bits */
- uint32_t bit_pos_; /* current bit-reading position in val_ */
- const uint8_t* next_in; /* the byte we're reading from */
- size_t avail_in;
-} BrotliBitReader;
-
-typedef struct {
- reg_t val_;
- uint32_t bit_pos_;
- const uint8_t* next_in;
- size_t avail_in;
-} BrotliBitReaderState;
-
-/* Initializes the bitreader fields. */
-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.
- For BROTLI_BUILD_PORTABLE this function also prepares bit reader for aligned
- reading. */
-int BrotliWarmupBitReader(BrotliBitReader* const br);
-
-static BROTLI_INLINE void BrotliBitReaderSaveState(
- BrotliBitReader* const from, BrotliBitReaderState* to) {
- to->val_ = from->val_;
- to->bit_pos_ = from->bit_pos_;
- to->next_in = from->next_in;
- to->avail_in = from->avail_in;
-}
-
-static BROTLI_INLINE void BrotliBitReaderRestoreState(
- BrotliBitReader* const to, BrotliBitReaderState* from) {
- to->val_ = from->val_;
- to->bit_pos_ = from->bit_pos_;
- to->next_in = from->next_in;
- to->avail_in = from->avail_in;
-}
-
-static BROTLI_INLINE uint32_t BrotliGetAvailableBits(
- const BrotliBitReader* br) {
- return (BROTLI_64_BITS ? 64 : 32) - br->bit_pos_;
-}
-
-/* Returns amount of unread bytes the bit reader still has buffered from the
- BrotliInput, including whole bytes in br->val_. */
-static BROTLI_INLINE size_t BrotliGetRemainingBytes(BrotliBitReader* br) {
- return br->avail_in + (BrotliGetAvailableBits(br) >> 3);
-}
-
-/* Checks if there is at least num bytes left in the input ringbuffer (excluding
- the bits remaining in br->val_). */
-static BROTLI_INLINE int BrotliCheckInputAmount(
- BrotliBitReader* const br, size_t num) {
- return br->avail_in >= num;
-}
-
-static BROTLI_INLINE uint16_t BrotliLoad16LE(const uint8_t* in) {
- if (BROTLI_LITTLE_ENDIAN) {
- return *((const uint16_t*)in);
- } else if (BROTLI_BIG_ENDIAN) {
- uint16_t value = *((const uint16_t*)in);
- return (uint16_t)(
- ((value & 0xFFU) << 8) |
- ((value & 0xFF00U) >> 8));
- } else {
- return (uint16_t)(in[0] | (in[1] << 8));
- }
-}
-
-static BROTLI_INLINE uint32_t BrotliLoad32LE(const uint8_t* in) {
- if (BROTLI_LITTLE_ENDIAN) {
- return *((const uint32_t*)in);
- } else if (BROTLI_BIG_ENDIAN) {
- uint32_t value = *((const uint32_t*)in);
- return ((value & 0xFFU) << 24) | ((value & 0xFF00U) << 8) |
- ((value & 0xFF0000U) >> 8) | ((value & 0xFF000000U) >> 24);
- } else {
- uint32_t value = (uint32_t)(*(in++));
- value |= (uint32_t)(*(in++)) << 8;
- value |= (uint32_t)(*(in++)) << 16;
- value |= (uint32_t)(*(in++)) << 24;
- return value;
- }
-}
-
-#if (BROTLI_64_BITS)
-static BROTLI_INLINE uint64_t BrotliLoad64LE(const uint8_t* in) {
- if (BROTLI_LITTLE_ENDIAN) {
- return *((const uint64_t*)in);
- } else if (BROTLI_BIG_ENDIAN) {
- uint64_t value = *((const uint64_t*)in);
- return
- ((value & 0xFFU) << 56) |
- ((value & 0xFF00U) << 40) |
- ((value & 0xFF0000U) << 24) |
- ((value & 0xFF000000U) << 8) |
- ((value & 0xFF00000000U) >> 8) |
- ((value & 0xFF0000000000U) >> 24) |
- ((value & 0xFF000000000000U) >> 40) |
- ((value & 0xFF00000000000000U) >> 56);
- } else {
- uint64_t value = (uint64_t)(*(in++));
- value |= (uint64_t)(*(in++)) << 8;
- value |= (uint64_t)(*(in++)) << 16;
- value |= (uint64_t)(*(in++)) << 24;
- value |= (uint64_t)(*(in++)) << 32;
- value |= (uint64_t)(*(in++)) << 40;
- value |= (uint64_t)(*(in++)) << 48;
- value |= (uint64_t)(*(in++)) << 56;
- return value;
- }
-}
-#endif
-
-/* 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
- 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) {
-#if (BROTLI_64_BITS)
- if (!BROTLI_ALIGNED_READ && IS_CONSTANT(n_bits) && (n_bits <= 8)) {
- if (br->bit_pos_ >= 56) {
- br->val_ >>= 56;
- br->bit_pos_ ^= 56; /* here same as -= 56 because of the if condition */
- br->val_ |= BrotliLoad64LE(br->next_in) << 8;
- br->avail_in -= 7;
- br->next_in += 7;
- }
- } else if (!BROTLI_ALIGNED_READ && IS_CONSTANT(n_bits) && (n_bits <= 16)) {
- if (br->bit_pos_ >= 48) {
- br->val_ >>= 48;
- br->bit_pos_ ^= 48; /* here same as -= 48 because of the if condition */
- br->val_ |= BrotliLoad64LE(br->next_in) << 16;
- br->avail_in -= 6;
- br->next_in += 6;
- }
- } else {
- if (br->bit_pos_ >= 32) {
- br->val_ >>= 32;
- br->bit_pos_ ^= 32; /* here same as -= 32 because of the if condition */
- br->val_ |= ((uint64_t)BrotliLoad32LE(br->next_in)) << 32;
- br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
- br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
- }
- }
-#else
- if (!BROTLI_ALIGNED_READ && IS_CONSTANT(n_bits) && (n_bits <= 8)) {
- if (br->bit_pos_ >= 24) {
- br->val_ >>= 24;
- br->bit_pos_ ^= 24; /* here same as -= 24 because of the if condition */
- br->val_ |= BrotliLoad32LE(br->next_in) << 8;
- br->avail_in -= 3;
- br->next_in += 3;
- }
- } else {
- if (br->bit_pos_ >= 16) {
- br->val_ >>= 16;
- br->bit_pos_ ^= 16; /* here same as -= 16 because of the if condition */
- br->val_ |= ((uint32_t)BrotliLoad16LE(br->next_in)) << 16;
- br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
- br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
- }
- }
-#endif
-}
-
-/* Mosltly like BrotliFillBitWindow, but guarantees only 16 bits and reads no
- more than BROTLI_SHORT_FILL_BIT_WINDOW_READ bytes of input. */
-static BROTLI_INLINE void BrotliFillBitWindow16(BrotliBitReader* const br) {
- BrotliFillBitWindow(br, 17);
-}
-
-/* Pulls one byte of input to accumulator. */
-static BROTLI_INLINE int BrotliPullByte(BrotliBitReader* const br) {
- if (br->avail_in == 0) {
- return 0;
- }
- br->val_ >>= 8;
-#if (BROTLI_64_BITS)
- br->val_ |= ((uint64_t)*br->next_in) << 56;
-#else
- br->val_ |= ((uint32_t)*br->next_in) << 24;
-#endif
- br->bit_pos_ -= 8;
- --br->avail_in;
- ++br->next_in;
- return 1;
-}
-
-/* Returns currently available bits.
- The number of valid bits could be calclulated by BrotliGetAvailableBits. */
-static BROTLI_INLINE reg_t BrotliGetBitsUnmasked(BrotliBitReader* const br) {
- return br->val_ >> br->bit_pos_;
-}
-
-/* Like BrotliGetBits, but does not mask the result.
- The result contains at least 16 valid bits. */
-static BROTLI_INLINE uint32_t BrotliGet16BitsUnmasked(
- BrotliBitReader* const br) {
- BrotliFillBitWindow(br, 16);
- return (uint32_t)BrotliGetBitsUnmasked(br);
-}
-
-/* Returns the specified number of bits from br without advancing bit pos. */
-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. */
-static BROTLI_INLINE int BrotliSafeGetBits(
- BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) {
- while (BrotliGetAvailableBits(br) < n_bits) {
- if (!BrotliPullByte(br)) {
- return 0;
- }
- }
- *val = (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits);
- return 1;
-}
-
-/* Advances the bit pos by n_bits. */
-static BROTLI_INLINE void BrotliDropBits(
- BrotliBitReader* const br, uint32_t n_bits) {
- br->bit_pos_ += n_bits;
-}
-
-static BROTLI_INLINE void BrotliBitReaderUnload(BrotliBitReader* br) {
- uint32_t unused_bytes = BrotliGetAvailableBits(br) >> 3;
- uint32_t unused_bits = unused_bytes << 3;
- br->avail_in += unused_bytes;
- br->next_in -= unused_bytes;
- br->val_ <<= unused_bits;
- br->bit_pos_ += unused_bits;
-}
-
-/* Reads the specified number of bits from br and advances the bit pos.
- 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);
-#ifdef BROTLI_DECODE_DEBUG
- printf("[BrotliReadBits] %d %d %d val: %6x\n",
- (int)br->avail_in, (int)br->bit_pos_, n_bits, (int)*val);
-#endif
- BrotliDropBits(br, n_bits);
-}
-
-/* Reads the specified number of bits from br and advances the bit pos.
- Assumes that there is enough input to perform BrotliFillBitWindow. */
-static BROTLI_INLINE uint32_t BrotliReadBits(
- BrotliBitReader* const br, uint32_t n_bits) {
- if (BROTLI_64_BITS || (n_bits <= 16)) {
- uint32_t val;
- BrotliFillBitWindow(br, n_bits);
- BrotliTakeBits(br, n_bits, &val);
- return val;
- } else {
- uint32_t low_val;
- uint32_t high_val;
- BrotliFillBitWindow(br, 16);
- BrotliTakeBits(br, 16, &low_val);
- BrotliFillBitWindow(br, 8);
- BrotliTakeBits(br, n_bits - 16, &high_val);
- return low_val | (high_val << 16);
- }
-}
-
-/* Tries to read the specified amount of bits. Returns 0, if there is not
- enough input. n_bits MUST be positive. */
-static BROTLI_INLINE int BrotliSafeReadBits(
- BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) {
- while (BrotliGetAvailableBits(br) < n_bits) {
- if (!BrotliPullByte(br)) {
- return 0;
- }
- }
- BrotliTakeBits(br, n_bits, val);
- return 1;
-}
-
-/* Advances the bit reader position to the next byte boundary and verifies
- that any skipped bits are set to zero. */
-static BROTLI_INLINE int BrotliJumpToByteBoundary(BrotliBitReader* br) {
- uint32_t pad_bits_count = BrotliGetAvailableBits(br) & 0x7;
- uint32_t pad_bits = 0;
- if (pad_bits_count != 0) {
- BrotliTakeBits(br, pad_bits_count, &pad_bits);
- }
- return pad_bits == 0;
-}
-
-/* Peeks a byte at specified offset.
- Precondition: bit reader is parked to a byte boundary.
- Returns -1 if operation is not feasible. */
-static BROTLI_INLINE int BrotliPeekByte(BrotliBitReader* br, size_t offset) {
- uint32_t available_bits = BrotliGetAvailableBits(br);
- size_t bytes_left = available_bits >> 3;
- if (available_bits & 7) {
- return -1;
- }
- if (offset < bytes_left) {
- return (BrotliGetBitsUnmasked(br) >> (unsigned)(offset << 3)) & 0xFF;
- }
- offset -= bytes_left;
- if (offset < br->avail_in) {
- return br->next_in[offset];
- }
- return -1;
-}
-
-/* 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
- warmed up again after this. */
-static BROTLI_INLINE void BrotliCopyBytes(uint8_t* dest,
- BrotliBitReader* br, size_t num) {
- while (BrotliGetAvailableBits(br) >= 8 && num > 0) {
- *dest = (uint8_t)BrotliGetBitsUnmasked(br);
- BrotliDropBits(br, 8);
- ++dest;
- --num;
- }
- memcpy(dest, br->next_in, num);
- br->avail_in -= num;
- br->next_in += num;
-}
-
-#if defined(__cplusplus) || defined(c_plusplus)
-} /* extern "C" */
-#endif
-
-#endif /* BROTLI_DEC_BIT_READER_H_ */
projects / io-compress-brotli.git / blobdiff