mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-24 16:27:42 +01:00
310 lines
10 KiB
C
310 lines
10 KiB
C
/* Copyright 2013 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Bit reading helpers */
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#ifndef BROTLI_DEC_BIT_READER_H_
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#define BROTLI_DEC_BIT_READER_H_
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//#include <string.h> /* memcpy */
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#include "../common/platform.h"
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#include <brotli/types.h>
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#define BROTLI_SHORT_FILL_BIT_WINDOW_READ (sizeof(brotli_reg_t) >> 1)
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static const uint32_t kBitMask[33] = { 0x00000000,
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0x00000001, 0x00000003, 0x00000007, 0x0000000F,
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0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF,
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0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF,
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0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF,
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0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF,
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0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF,
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0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF,
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0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF
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};
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static BROTLI_INLINE uint32_t BitMask(uint32_t n) {
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if (BROTLI_IS_CONSTANT(n) || BROTLI_HAS_UBFX) {
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/* Masking with this expression turns to a single
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"Unsigned Bit Field Extract" UBFX instruction on ARM. */
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return ~((0xFFFFFFFFu) << n);
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} else {
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return kBitMask[n];
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}
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}
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typedef struct {
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brotli_reg_t val_; /* pre-fetched bits */
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uint32_t bit_pos_; /* current bit-reading position in val_ */
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const uint8_t* next_in; /* the byte we're reading from */
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size_t avail_in;
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} BrotliBitReader;
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typedef struct {
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brotli_reg_t val_;
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uint32_t bit_pos_;
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const uint8_t* next_in;
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size_t avail_in;
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} BrotliBitReaderState;
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/* Initializes the BrotliBitReader fields. */
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BROTLI_INTERNAL void BrotliInitBitReader(BrotliBitReader* const br);
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/* Ensures that accumulator is not empty.
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May consume up to sizeof(brotli_reg_t) - 1 bytes of input.
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Returns BROTLI_FALSE if data is required but there is no input available.
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For BROTLI_ALIGNED_READ this function also prepares bit reader for aligned
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reading. */
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BROTLI_INTERNAL BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* const br);
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static BROTLI_INLINE void BrotliBitReaderSaveState(
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BrotliBitReader* const from, BrotliBitReaderState* to) {
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to->val_ = from->val_;
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to->bit_pos_ = from->bit_pos_;
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to->next_in = from->next_in;
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to->avail_in = from->avail_in;
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}
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static BROTLI_INLINE void BrotliBitReaderRestoreState(
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BrotliBitReader* const to, BrotliBitReaderState* from) {
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to->val_ = from->val_;
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to->bit_pos_ = from->bit_pos_;
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to->next_in = from->next_in;
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to->avail_in = from->avail_in;
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}
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static BROTLI_INLINE uint32_t BrotliGetAvailableBits(
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const BrotliBitReader* br) {
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return (BROTLI_64_BITS ? 64 : 32) - br->bit_pos_;
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}
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/* Returns amount of unread bytes the bit reader still has buffered from the
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BrotliInput, including whole bytes in br->val_. */
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static BROTLI_INLINE size_t BrotliGetRemainingBytes(BrotliBitReader* br) {
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return br->avail_in + (BrotliGetAvailableBits(br) >> 3);
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}
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/* Checks if there is at least |num| bytes left in the input ring-buffer
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(excluding the bits remaining in br->val_). */
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static BROTLI_INLINE BROTLI_BOOL BrotliCheckInputAmount(
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BrotliBitReader* const br, size_t num) {
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return TO_BROTLI_BOOL(br->avail_in >= num);
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}
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/* Guarantees that there are at least |n_bits| + 1 bits in accumulator.
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Precondition: accumulator contains at least 1 bit.
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|n_bits| should be in the range [1..24] for regular build. For portable
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non-64-bit little-endian build only 16 bits are safe to request. */
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static BROTLI_INLINE void BrotliFillBitWindow(
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BrotliBitReader* const br, uint32_t n_bits) {
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#if (BROTLI_64_BITS)
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if (!BROTLI_ALIGNED_READ && BROTLI_IS_CONSTANT(n_bits) && (n_bits <= 8)) {
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if (br->bit_pos_ >= 56) {
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br->val_ >>= 56;
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br->bit_pos_ ^= 56; /* here same as -= 56 because of the if condition */
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br->val_ |= BROTLI_UNALIGNED_LOAD64LE(br->next_in) << 8;
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br->avail_in -= 7;
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br->next_in += 7;
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}
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} else if (
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!BROTLI_ALIGNED_READ && BROTLI_IS_CONSTANT(n_bits) && (n_bits <= 16)) {
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if (br->bit_pos_ >= 48) {
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br->val_ >>= 48;
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br->bit_pos_ ^= 48; /* here same as -= 48 because of the if condition */
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br->val_ |= BROTLI_UNALIGNED_LOAD64LE(br->next_in) << 16;
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br->avail_in -= 6;
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br->next_in += 6;
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}
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} else {
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if (br->bit_pos_ >= 32) {
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br->val_ >>= 32;
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br->bit_pos_ ^= 32; /* here same as -= 32 because of the if condition */
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br->val_ |= ((uint64_t)BROTLI_UNALIGNED_LOAD32LE(br->next_in)) << 32;
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br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
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br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
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}
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}
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#else
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if (!BROTLI_ALIGNED_READ && BROTLI_IS_CONSTANT(n_bits) && (n_bits <= 8)) {
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if (br->bit_pos_ >= 24) {
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br->val_ >>= 24;
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br->bit_pos_ ^= 24; /* here same as -= 24 because of the if condition */
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br->val_ |= BROTLI_UNALIGNED_LOAD32LE(br->next_in) << 8;
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br->avail_in -= 3;
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br->next_in += 3;
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}
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} else {
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if (br->bit_pos_ >= 16) {
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br->val_ >>= 16;
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br->bit_pos_ ^= 16; /* here same as -= 16 because of the if condition */
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br->val_ |= ((uint32_t)BROTLI_UNALIGNED_LOAD16LE(br->next_in)) << 16;
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br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
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br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
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}
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}
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#endif
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}
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/* Mostly like BrotliFillBitWindow, but guarantees only 16 bits and reads no
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more than BROTLI_SHORT_FILL_BIT_WINDOW_READ bytes of input. */
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static BROTLI_INLINE void BrotliFillBitWindow16(BrotliBitReader* const br) {
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BrotliFillBitWindow(br, 17);
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}
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/* Tries to pull one byte of input to accumulator.
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Returns BROTLI_FALSE if there is no input available. */
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static BROTLI_INLINE BROTLI_BOOL BrotliPullByte(BrotliBitReader* const br) {
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if (br->avail_in == 0) {
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return BROTLI_FALSE;
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}
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br->val_ >>= 8;
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#if (BROTLI_64_BITS)
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br->val_ |= ((uint64_t)*br->next_in) << 56;
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#else
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br->val_ |= ((uint32_t)*br->next_in) << 24;
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#endif
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br->bit_pos_ -= 8;
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--br->avail_in;
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++br->next_in;
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return BROTLI_TRUE;
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}
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/* Returns currently available bits.
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The number of valid bits could be calculated by BrotliGetAvailableBits. */
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static BROTLI_INLINE brotli_reg_t BrotliGetBitsUnmasked(
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BrotliBitReader* const br) {
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return br->val_ >> br->bit_pos_;
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}
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/* Like BrotliGetBits, but does not mask the result.
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The result contains at least 16 valid bits. */
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static BROTLI_INLINE uint32_t BrotliGet16BitsUnmasked(
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BrotliBitReader* const br) {
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BrotliFillBitWindow(br, 16);
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return (uint32_t)BrotliGetBitsUnmasked(br);
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}
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/* Returns the specified number of bits from |br| without advancing bit
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position. */
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static BROTLI_INLINE uint32_t BrotliGetBits(
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BrotliBitReader* const br, uint32_t n_bits) {
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BrotliFillBitWindow(br, n_bits);
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return (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits);
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}
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/* Tries to peek the specified amount of bits. Returns BROTLI_FALSE, if there
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is not enough input. */
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static BROTLI_INLINE BROTLI_BOOL BrotliSafeGetBits(
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BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) {
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while (BrotliGetAvailableBits(br) < n_bits) {
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if (!BrotliPullByte(br)) {
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return BROTLI_FALSE;
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}
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}
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*val = (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits);
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return BROTLI_TRUE;
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}
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/* Advances the bit pos by |n_bits|. */
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static BROTLI_INLINE void BrotliDropBits(
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BrotliBitReader* const br, uint32_t n_bits) {
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br->bit_pos_ += n_bits;
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}
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static BROTLI_INLINE void BrotliBitReaderUnload(BrotliBitReader* br) {
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uint32_t unused_bytes = BrotliGetAvailableBits(br) >> 3;
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uint32_t unused_bits = unused_bytes << 3;
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br->avail_in += unused_bytes;
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br->next_in -= unused_bytes;
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if (unused_bits == sizeof(br->val_) << 3) {
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br->val_ = 0;
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} else {
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br->val_ <<= unused_bits;
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}
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br->bit_pos_ += unused_bits;
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}
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/* Reads the specified number of bits from |br| and advances the bit pos.
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Precondition: accumulator MUST contain at least |n_bits|. */
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static BROTLI_INLINE void BrotliTakeBits(
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BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) {
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*val = (uint32_t)BrotliGetBitsUnmasked(br) & BitMask(n_bits);
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BROTLI_LOG(("[BrotliReadBits] %d %d %d val: %6x\n",
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(int)br->avail_in, (int)br->bit_pos_, (int)n_bits, (int)*val));
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BrotliDropBits(br, n_bits);
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}
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/* Reads the specified number of bits from |br| and advances the bit pos.
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Assumes that there is enough input to perform BrotliFillBitWindow. */
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static BROTLI_INLINE uint32_t BrotliReadBits(
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BrotliBitReader* const br, uint32_t n_bits) {
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if (BROTLI_64_BITS || (n_bits <= 16)) {
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uint32_t val;
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BrotliFillBitWindow(br, n_bits);
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BrotliTakeBits(br, n_bits, &val);
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return val;
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} else {
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uint32_t low_val;
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uint32_t high_val;
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BrotliFillBitWindow(br, 16);
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BrotliTakeBits(br, 16, &low_val);
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BrotliFillBitWindow(br, 8);
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BrotliTakeBits(br, n_bits - 16, &high_val);
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return low_val | (high_val << 16);
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}
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}
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/* Tries to read the specified amount of bits. Returns BROTLI_FALSE, if there
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is not enough input. |n_bits| MUST be positive. */
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static BROTLI_INLINE BROTLI_BOOL BrotliSafeReadBits(
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BrotliBitReader* const br, uint32_t n_bits, uint32_t* val) {
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while (BrotliGetAvailableBits(br) < n_bits) {
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if (!BrotliPullByte(br)) {
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return BROTLI_FALSE;
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}
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}
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BrotliTakeBits(br, n_bits, val);
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return BROTLI_TRUE;
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}
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/* Advances the bit reader position to the next byte boundary and verifies
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that any skipped bits are set to zero. */
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static BROTLI_INLINE BROTLI_BOOL BrotliJumpToByteBoundary(BrotliBitReader* br) {
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uint32_t pad_bits_count = BrotliGetAvailableBits(br) & 0x7;
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uint32_t pad_bits = 0;
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if (pad_bits_count != 0) {
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BrotliTakeBits(br, pad_bits_count, &pad_bits);
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}
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return TO_BROTLI_BOOL(pad_bits == 0);
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}
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/* Copies remaining input bytes stored in the bit reader to the output. Value
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|num| may not be larger than BrotliGetRemainingBytes. The bit reader must be
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warmed up again after this. */
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static BROTLI_INLINE void BrotliCopyBytes(uint8_t* dest,
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BrotliBitReader* br, size_t num) {
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while (BrotliGetAvailableBits(br) >= 8 && num > 0) {
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*dest = (uint8_t)BrotliGetBitsUnmasked(br);
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BrotliDropBits(br, 8);
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++dest;
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--num;
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}
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memcpy(dest, br->next_in, num);
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br->avail_in -= num;
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br->next_in += num;
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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} /* extern "C" */
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#endif
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#endif /* BROTLI_DEC_BIT_READER_H_ */
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