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b6ba81034b
size_t needs header. Add missing header guards so that compiler will only include these ones. Signed-off-by: Kari Argillander <kari.argillander@gmail.com> Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
344 lines
9.6 KiB
C
344 lines
9.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* decompress_common.h - Code shared by the XPRESS and LZX decompressors
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*
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* Copyright (C) 2015 Eric Biggers
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*/
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#ifndef _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H
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#define _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H
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#include <linux/string.h>
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#include <linux/compiler.h>
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <asm/unaligned.h>
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/* "Force inline" macro (not required, but helpful for performance) */
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#define forceinline __always_inline
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/* Enable whole-word match copying on selected architectures */
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#if defined(__i386__) || defined(__x86_64__) || defined(__ARM_FEATURE_UNALIGNED)
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# define FAST_UNALIGNED_ACCESS
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#endif
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/* Size of a machine word */
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#define WORDBYTES (sizeof(size_t))
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static forceinline void
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copy_unaligned_word(const void *src, void *dst)
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{
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put_unaligned(get_unaligned((const size_t *)src), (size_t *)dst);
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}
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/* Generate a "word" with platform-dependent size whose bytes all contain the
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* value 'b'.
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*/
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static forceinline size_t repeat_byte(u8 b)
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{
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size_t v;
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v = b;
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v |= v << 8;
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v |= v << 16;
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v |= v << ((WORDBYTES == 8) ? 32 : 0);
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return v;
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}
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/* Structure that encapsulates a block of in-memory data being interpreted as a
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* stream of bits, optionally with interwoven literal bytes. Bits are assumed
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* to be stored in little endian 16-bit coding units, with the bits ordered high
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* to low.
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*/
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struct input_bitstream {
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/* Bits that have been read from the input buffer. The bits are
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* left-justified; the next bit is always bit 31.
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*/
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u32 bitbuf;
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/* Number of bits currently held in @bitbuf. */
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u32 bitsleft;
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/* Pointer to the next byte to be retrieved from the input buffer. */
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const u8 *next;
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/* Pointer to just past the end of the input buffer. */
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const u8 *end;
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};
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/* Initialize a bitstream to read from the specified input buffer. */
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static forceinline void init_input_bitstream(struct input_bitstream *is,
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const void *buffer, u32 size)
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{
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is->bitbuf = 0;
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is->bitsleft = 0;
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is->next = buffer;
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is->end = is->next + size;
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}
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/* Ensure the bit buffer variable for the bitstream contains at least @num_bits
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* bits. Following this, bitstream_peek_bits() and/or bitstream_remove_bits()
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* may be called on the bitstream to peek or remove up to @num_bits bits. Note
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* that @num_bits must be <= 16.
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*/
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static forceinline void bitstream_ensure_bits(struct input_bitstream *is,
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u32 num_bits)
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{
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if (is->bitsleft < num_bits) {
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if (is->end - is->next >= 2) {
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is->bitbuf |= (u32)get_unaligned_le16(is->next)
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<< (16 - is->bitsleft);
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is->next += 2;
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}
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is->bitsleft += 16;
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}
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}
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/* Return the next @num_bits bits from the bitstream, without removing them.
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* There must be at least @num_bits remaining in the buffer variable, from a
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* previous call to bitstream_ensure_bits().
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*/
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static forceinline u32
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bitstream_peek_bits(const struct input_bitstream *is, const u32 num_bits)
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{
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return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1);
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}
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/* Remove @num_bits from the bitstream. There must be at least @num_bits
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* remaining in the buffer variable, from a previous call to
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* bitstream_ensure_bits().
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*/
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static forceinline void
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bitstream_remove_bits(struct input_bitstream *is, u32 num_bits)
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{
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is->bitbuf <<= num_bits;
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is->bitsleft -= num_bits;
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}
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/* Remove and return @num_bits bits from the bitstream. There must be at least
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* @num_bits remaining in the buffer variable, from a previous call to
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* bitstream_ensure_bits().
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*/
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static forceinline u32
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bitstream_pop_bits(struct input_bitstream *is, u32 num_bits)
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{
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u32 bits = bitstream_peek_bits(is, num_bits);
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bitstream_remove_bits(is, num_bits);
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return bits;
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}
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/* Read and return the next @num_bits bits from the bitstream. */
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static forceinline u32
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bitstream_read_bits(struct input_bitstream *is, u32 num_bits)
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{
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bitstream_ensure_bits(is, num_bits);
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return bitstream_pop_bits(is, num_bits);
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}
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/* Read and return the next literal byte embedded in the bitstream. */
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static forceinline u8
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bitstream_read_byte(struct input_bitstream *is)
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{
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if (unlikely(is->end == is->next))
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return 0;
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return *is->next++;
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}
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/* Read and return the next 16-bit integer embedded in the bitstream. */
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static forceinline u16
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bitstream_read_u16(struct input_bitstream *is)
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{
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u16 v;
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if (unlikely(is->end - is->next < 2))
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return 0;
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v = get_unaligned_le16(is->next);
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is->next += 2;
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return v;
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}
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/* Read and return the next 32-bit integer embedded in the bitstream. */
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static forceinline u32
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bitstream_read_u32(struct input_bitstream *is)
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{
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u32 v;
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if (unlikely(is->end - is->next < 4))
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return 0;
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v = get_unaligned_le32(is->next);
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is->next += 4;
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return v;
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}
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/* Read into @dst_buffer an array of literal bytes embedded in the bitstream.
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* Return either a pointer to the byte past the last written, or NULL if the
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* read overflows the input buffer.
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*/
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static forceinline void *bitstream_read_bytes(struct input_bitstream *is,
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void *dst_buffer, size_t count)
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{
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if ((size_t)(is->end - is->next) < count)
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return NULL;
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memcpy(dst_buffer, is->next, count);
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is->next += count;
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return (u8 *)dst_buffer + count;
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}
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/* Align the input bitstream on a coding-unit boundary. */
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static forceinline void bitstream_align(struct input_bitstream *is)
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{
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is->bitsleft = 0;
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is->bitbuf = 0;
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}
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extern int make_huffman_decode_table(u16 decode_table[], const u32 num_syms,
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const u32 num_bits, const u8 lens[],
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const u32 max_codeword_len,
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u16 working_space[]);
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/* Reads and returns the next Huffman-encoded symbol from a bitstream. If the
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* input data is exhausted, the Huffman symbol is decoded as if the missing bits
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* are all zeroes.
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*/
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static forceinline u32 read_huffsym(struct input_bitstream *istream,
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const u16 decode_table[],
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u32 table_bits,
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u32 max_codeword_len)
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{
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u32 entry;
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u32 key_bits;
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bitstream_ensure_bits(istream, max_codeword_len);
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/* Index the decode table by the next table_bits bits of the input. */
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key_bits = bitstream_peek_bits(istream, table_bits);
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entry = decode_table[key_bits];
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if (entry < 0xC000) {
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/* Fast case: The decode table directly provided the
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* symbol and codeword length. The low 11 bits are the
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* symbol, and the high 5 bits are the codeword length.
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*/
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bitstream_remove_bits(istream, entry >> 11);
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return entry & 0x7FF;
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}
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/* Slow case: The codeword for the symbol is longer than
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* table_bits, so the symbol does not have an entry
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* directly in the first (1 << table_bits) entries of the
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* decode table. Traverse the appropriate binary tree
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* bit-by-bit to decode the symbol.
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*/
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bitstream_remove_bits(istream, table_bits);
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do {
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key_bits = (entry & 0x3FFF) + bitstream_pop_bits(istream, 1);
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} while ((entry = decode_table[key_bits]) >= 0xC000);
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return entry;
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}
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/*
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* Copy an LZ77 match at (dst - offset) to dst.
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*
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* The length and offset must be already validated --- that is, (dst - offset)
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* can't underrun the output buffer, and (dst + length) can't overrun the output
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* buffer. Also, the length cannot be 0.
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*
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* @bufend points to the byte past the end of the output buffer. This function
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* won't write any data beyond this position.
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*
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* Returns dst + length.
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*/
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static forceinline u8 *lz_copy(u8 *dst, u32 length, u32 offset, const u8 *bufend,
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u32 min_length)
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{
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const u8 *src = dst - offset;
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/*
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* Try to copy one machine word at a time. On i386 and x86_64 this is
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* faster than copying one byte at a time, unless the data is
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* near-random and all the matches have very short lengths. Note that
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* since this requires unaligned memory accesses, it won't necessarily
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* be faster on every architecture.
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*
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* Also note that we might copy more than the length of the match. For
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* example, if a word is 8 bytes and the match is of length 5, then
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* we'll simply copy 8 bytes. This is okay as long as we don't write
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* beyond the end of the output buffer, hence the check for (bufend -
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* end >= WORDBYTES - 1).
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*/
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#ifdef FAST_UNALIGNED_ACCESS
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u8 * const end = dst + length;
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if (bufend - end >= (ptrdiff_t)(WORDBYTES - 1)) {
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if (offset >= WORDBYTES) {
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/* The source and destination words don't overlap. */
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/* To improve branch prediction, one iteration of this
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* loop is unrolled. Most matches are short and will
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* fail the first check. But if that check passes, then
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* it becomes increasing likely that the match is long
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* and we'll need to continue copying.
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*/
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copy_unaligned_word(src, dst);
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src += WORDBYTES;
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dst += WORDBYTES;
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if (dst < end) {
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do {
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copy_unaligned_word(src, dst);
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src += WORDBYTES;
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dst += WORDBYTES;
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} while (dst < end);
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}
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return end;
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} else if (offset == 1) {
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/* Offset 1 matches are equivalent to run-length
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* encoding of the previous byte. This case is common
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* if the data contains many repeated bytes.
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*/
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size_t v = repeat_byte(*(dst - 1));
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do {
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put_unaligned(v, (size_t *)dst);
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src += WORDBYTES;
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dst += WORDBYTES;
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} while (dst < end);
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return end;
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}
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/*
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* We don't bother with special cases for other 'offset <
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* WORDBYTES', which are usually rarer than 'offset == 1'. Extra
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* checks will just slow things down. Actually, it's possible
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* to handle all the 'offset < WORDBYTES' cases using the same
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* code, but it still becomes more complicated doesn't seem any
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* faster overall; it definitely slows down the more common
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* 'offset == 1' case.
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*/
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}
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#endif /* FAST_UNALIGNED_ACCESS */
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/* Fall back to a bytewise copy. */
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if (min_length >= 2) {
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*dst++ = *src++;
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length--;
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}
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if (min_length >= 3) {
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*dst++ = *src++;
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length--;
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}
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do {
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*dst++ = *src++;
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} while (--length);
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return dst;
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}
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#endif /* _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H */
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