553 lines
20 KiB
C
553 lines
20 KiB
C
/*
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* decompress_common.h
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*
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* Header for decompression code shared by multiple compression formats.
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*
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* Copyright 2022 Eric Biggers
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef _DECOMPRESS_COMMON_H
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#define _DECOMPRESS_COMMON_H
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#include <errno.h>
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#include <string.h>
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#include "common_defs.h"
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/******************************************************************************/
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/* Input bitstream for XPRESS and LZX */
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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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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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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 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
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init_input_bitstream(struct input_bitstream *is, 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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/* Note: for performance reasons, the following methods don't return error codes
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* to the caller if the input buffer is overrun. Instead, they just assume that
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* all overrun data is zeroes. This has no effect on well-formed compressed
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* data. The only disadvantage is that bad compressed data may go undetected,
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* but even this is irrelevant if higher level code checksums the uncompressed
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* data anyway. */
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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. */
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static forceinline void
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bitstream_ensure_bits(struct input_bitstream *is, const unsigned num_bits)
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{
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/* This currently works for at most 17 bits. */
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if (is->bitsleft >= num_bits)
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return;
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if (unlikely(is->end - is->next < 2))
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goto overflow;
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is->bitbuf |= (u32)get_unaligned_le16(is->next) << (16 - is->bitsleft);
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is->next += 2;
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is->bitsleft += 16;
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if (unlikely(num_bits == 17 && is->bitsleft == 16)) {
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if (unlikely(is->end - is->next < 2))
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goto overflow;
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is->bitbuf |= (u32)get_unaligned_le16(is->next);
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is->next += 2;
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is->bitsleft = 32;
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}
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return;
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overflow:
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is->bitsleft = 32;
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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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static forceinline u32
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bitstream_peek_bits(const struct input_bitstream *is, const unsigned 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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static forceinline void
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bitstream_remove_bits(struct input_bitstream *is, unsigned 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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static forceinline u32
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bitstream_pop_bits(struct input_bitstream *is, unsigned 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, unsigned 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 0 if there were enough bytes remaining in the input, otherwise -1. */
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static forceinline int
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bitstream_read_bytes(struct input_bitstream *is, void *dst_buffer, size_t count)
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{
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if (unlikely(is->end - is->next < count))
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return -1;
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memcpy(dst_buffer, is->next, count);
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is->next += count;
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return 0;
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}
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/* Align the input bitstream on a coding-unit boundary. */
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static forceinline void
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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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/******************************************************************************/
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/* Huffman decoding */
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/*----------------------------------------------------------------------------*/
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/*
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* Required alignment for the Huffman decode tables. We require this alignment
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* so that we can fill the entries with vector or word instructions and not have
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* to deal with misaligned buffers.
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*/
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#define DECODE_TABLE_ALIGNMENT 16
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/*
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* Each decode table entry is 16 bits divided into two fields: 'symbol' (high 12
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* bits) and 'length' (low 4 bits). The precise meaning of these fields depends
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* on the type of entry:
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*
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* Root table entries which are *not* subtable pointers:
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* symbol: symbol to decode
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* length: codeword length in bits
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*
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* Root table entries which are subtable pointers:
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* symbol: index of start of subtable
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* length: number of bits with which the subtable is indexed
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*
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* Subtable entries:
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* symbol: symbol to decode
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* length: codeword length in bits, minus the number of bits with which the
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* root table is indexed
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*/
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#define DECODE_TABLE_SYMBOL_SHIFT 4
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#define DECODE_TABLE_MAX_SYMBOL ((1 << (16 - DECODE_TABLE_SYMBOL_SHIFT)) - 1)
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#define DECODE_TABLE_MAX_LENGTH ((1 << DECODE_TABLE_SYMBOL_SHIFT) - 1)
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#define DECODE_TABLE_LENGTH_MASK DECODE_TABLE_MAX_LENGTH
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#define MAKE_DECODE_TABLE_ENTRY(symbol, length) \
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(((symbol) << DECODE_TABLE_SYMBOL_SHIFT) | (length))
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/*
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* Read and return the next Huffman-encoded symbol from the given bitstream
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* using the given decode table.
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*
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* If the input data is exhausted, then the Huffman symbol will be decoded as if
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* the missing bits were all zeroes.
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*
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* XXX: This is mostly duplicated in lzms_decode_huffman_symbol() in
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* lzms_decompress.c; keep them in sync!
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*/
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static forceinline unsigned
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read_huffsym(struct input_bitstream *is, const u16 decode_table[],
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unsigned table_bits, unsigned max_codeword_len)
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{
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unsigned entry;
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unsigned symbol;
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unsigned length;
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/* Preload the bitbuffer with 'max_codeword_len' bits so that we're
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* guaranteed to be able to fully decode a codeword. */
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bitstream_ensure_bits(is, max_codeword_len);
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/* Index the root table by the next 'table_bits' bits of input. */
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entry = decode_table[bitstream_peek_bits(is, table_bits)];
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/* Extract the "symbol" and "length" from the entry. */
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symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
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length = entry & DECODE_TABLE_LENGTH_MASK;
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/* If the root table is indexed by the full 'max_codeword_len' bits,
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* then there cannot be any subtables, and this will be known at compile
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* time. Otherwise, we must check whether the decoded symbol is really
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* a subtable pointer. If so, we must discard the bits with which the
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* root table was indexed, then index the subtable by the next 'length'
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* bits of input to get the real entry. */
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if (max_codeword_len > table_bits &&
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entry >= (1U << (table_bits + DECODE_TABLE_SYMBOL_SHIFT)))
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{
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/* Subtable required */
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bitstream_remove_bits(is, table_bits);
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entry = decode_table[symbol + bitstream_peek_bits(is, length)];
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symbol = entry >> DECODE_TABLE_SYMBOL_SHIFT;
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length = entry & DECODE_TABLE_LENGTH_MASK;
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}
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/* Discard the bits (or the remaining bits, if a subtable was required)
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* of the codeword. */
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bitstream_remove_bits(is, length);
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/* Return the decoded symbol. */
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return symbol;
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}
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/*
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* The DECODE_TABLE_ENOUGH() macro evaluates to the maximum number of decode
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* table entries, including all subtable entries, that may be required for
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* decoding a given Huffman code. This depends on three parameters:
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*
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* num_syms: the maximum number of symbols in the code
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* table_bits: the number of bits with which the root table will be indexed
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* max_codeword_len: the maximum allowed codeword length in the code
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*
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* Given these parameters, the utility program 'enough' from zlib, when passed
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* the three arguments 'num_syms', 'table_bits', and 'max_codeword_len', will
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* compute the maximum number of entries required. This has already been done
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* for the combinations we need and incorporated into the macro below so that
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* the mapping can be done at compilation time. If an unknown combination is
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* used, then a compilation error will result. To fix this, use 'enough' to
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* find the missing value and add it below. If that still doesn't fix the
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* compilation error, then most likely a constraint would be violated by the
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* requested parameters, so they cannot be used, at least without other changes
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* to the decode table --- see DECODE_TABLE_SIZE().
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*/
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#define DECODE_TABLE_ENOUGH(num_syms, table_bits, max_codeword_len) ( \
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((num_syms) == 8 && (table_bits) == 7 && (max_codeword_len) == 15) ? 128 : \
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((num_syms) == 8 && (table_bits) == 5 && (max_codeword_len) == 7) ? 36 : \
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((num_syms) == 8 && (table_bits) == 6 && (max_codeword_len) == 7) ? 66 : \
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((num_syms) == 8 && (table_bits) == 7 && (max_codeword_len) == 7) ? 128 : \
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((num_syms) == 20 && (table_bits) == 5 && (max_codeword_len) == 15) ? 1062 : \
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((num_syms) == 20 && (table_bits) == 6 && (max_codeword_len) == 15) ? 582 : \
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((num_syms) == 20 && (table_bits) == 7 && (max_codeword_len) == 15) ? 390 : \
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((num_syms) == 54 && (table_bits) == 9 && (max_codeword_len) == 15) ? 618 : \
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((num_syms) == 54 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1098 : \
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((num_syms) == 249 && (table_bits) == 9 && (max_codeword_len) == 16) ? 878 : \
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((num_syms) == 249 && (table_bits) == 10 && (max_codeword_len) == 16) ? 1326 : \
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((num_syms) == 249 && (table_bits) == 11 && (max_codeword_len) == 16) ? 2318 : \
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((num_syms) == 256 && (table_bits) == 9 && (max_codeword_len) == 15) ? 822 : \
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((num_syms) == 256 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1302 : \
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((num_syms) == 256 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2310 : \
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((num_syms) == 512 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1558 : \
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((num_syms) == 512 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2566 : \
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((num_syms) == 512 && (table_bits) == 12 && (max_codeword_len) == 15) ? 4606 : \
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((num_syms) == 656 && (table_bits) == 10 && (max_codeword_len) == 16) ? 1734 : \
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((num_syms) == 656 && (table_bits) == 11 && (max_codeword_len) == 16) ? 2726 : \
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((num_syms) == 656 && (table_bits) == 12 && (max_codeword_len) == 16) ? 4758 : \
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((num_syms) == 799 && (table_bits) == 9 && (max_codeword_len) == 15) ? 1366 : \
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((num_syms) == 799 && (table_bits) == 10 && (max_codeword_len) == 15) ? 1846 : \
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((num_syms) == 799 && (table_bits) == 11 && (max_codeword_len) == 15) ? 2854 : \
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-1)
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/* Wrapper around DECODE_TABLE_ENOUGH() that does additional compile-time
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* validation. */
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#define DECODE_TABLE_SIZE(num_syms, table_bits, max_codeword_len) ( \
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\
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/* All values must be positive. */ \
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STATIC_ASSERT_ZERO((num_syms) > 0) + \
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STATIC_ASSERT_ZERO((table_bits) > 0) + \
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STATIC_ASSERT_ZERO((max_codeword_len) > 0) + \
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\
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/* There cannot be more symbols than possible codewords. */ \
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STATIC_ASSERT_ZERO((num_syms) <= 1U << (max_codeword_len)) + \
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\
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/* There is no reason for the root table to be indexed with
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* more bits than the maximum codeword length. */ \
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STATIC_ASSERT_ZERO((table_bits) <= (max_codeword_len)) + \
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\
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/* The maximum symbol value must fit in the 'symbol' field. */ \
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STATIC_ASSERT_ZERO((num_syms) - 1 <= DECODE_TABLE_MAX_SYMBOL) + \
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\
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/* The maximum codeword length in the root table must fit in
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* the 'length' field. */ \
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STATIC_ASSERT_ZERO((table_bits) <= DECODE_TABLE_MAX_LENGTH) + \
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\
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/* The maximum codeword length in a subtable must fit in the
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* 'length' field. */ \
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STATIC_ASSERT_ZERO((max_codeword_len) - (table_bits) <= \
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DECODE_TABLE_MAX_LENGTH) + \
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\
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/* The minimum subtable index must be greater than the maximum
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* symbol value. If this were not the case, then there would
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* be no way to tell whether a given root table entry is a
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* "subtable pointer" or not. (An alternate solution would be
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* to reserve a flag bit specifically for this purpose.) */ \
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STATIC_ASSERT_ZERO((1U << table_bits) > (num_syms) - 1) + \
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\
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/* The needed 'enough' value must have been defined. */ \
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STATIC_ASSERT_ZERO(DECODE_TABLE_ENOUGH( \
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(num_syms), (table_bits), \
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(max_codeword_len)) > 0) + \
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\
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/* The maximum subtable index must fit in the 'symbol' field. */\
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STATIC_ASSERT_ZERO(DECODE_TABLE_ENOUGH( \
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(num_syms), (table_bits), \
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(max_codeword_len)) - 1 <= \
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DECODE_TABLE_MAX_SYMBOL) + \
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\
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/* Finally, make the macro evaluate to the needed maximum
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* number of decode table entries. */ \
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DECODE_TABLE_ENOUGH((num_syms), (table_bits), \
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(max_codeword_len)) \
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)
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/*
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* Declare the decode table for a Huffman code, given several compile-time
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* constants that describe the code. See DECODE_TABLE_ENOUGH() for details.
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*
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* Decode tables must be aligned to a DECODE_TABLE_ALIGNMENT-byte boundary.
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* This implies that if a decode table is nested inside a dynamically allocated
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* structure, then the outer structure must be allocated on a
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* DECODE_TABLE_ALIGNMENT-byte aligned boundary as well.
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*/
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#define DECODE_TABLE(name, num_syms, table_bits, max_codeword_len) \
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u16 name[DECODE_TABLE_SIZE((num_syms), (table_bits), \
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(max_codeword_len))] \
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_aligned_attribute(DECODE_TABLE_ALIGNMENT)
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/*
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* Declare the temporary "working_space" array needed for building the decode
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* table for a Huffman code.
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*/
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#define DECODE_TABLE_WORKING_SPACE(name, num_syms, max_codeword_len) \
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u16 name[2 * ((max_codeword_len) + 1) + (num_syms)];
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extern int
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make_huffman_decode_table(u16 decode_table[], unsigned num_syms,
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unsigned table_bits, const u8 lens[],
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unsigned max_codeword_len, u16 working_space[]);
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/******************************************************************************/
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/* LZ match copying */
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/*----------------------------------------------------------------------------*/
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static forceinline void
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copy_word_unaligned(const void *src, void *dst)
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{
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store_word_unaligned(load_word_unaligned(src), dst);
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}
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static forceinline machine_word_t
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repeat_u16(u16 b)
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{
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machine_word_t v = b;
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STATIC_ASSERT(WORDBITS == 32 || WORDBITS == 64);
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v |= v << 16;
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v |= v << ((WORDBITS == 64) ? 32 : 0);
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return v;
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}
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static forceinline machine_word_t
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repeat_byte(u8 b)
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{
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return repeat_u16(((u16)b << 8) | b);
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}
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/*
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* Copy an LZ77 match of 'length' bytes from the match source at 'out_next -
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* offset' to the match destination at 'out_next'. The source and destination
|
|
* may overlap.
|
|
*
|
|
* This handles validating the length and offset. It is validated that the
|
|
* beginning of the match source is '>= out_begin' and that end of the match
|
|
* destination is '<= out_end'. The return value is 0 if the match was valid
|
|
* (and was copied), otherwise -1.
|
|
*
|
|
* 'min_length' is a hint which specifies the minimum possible match length.
|
|
* This should be a compile-time constant.
|
|
*/
|
|
static forceinline int
|
|
lz_copy(u32 length, u32 offset, u8 *out_begin, u8 *out_next, u8 *out_end,
|
|
u32 min_length)
|
|
{
|
|
const u8 *src;
|
|
u8 *end;
|
|
|
|
/* Validate the offset. */
|
|
if (unlikely(offset > out_next - out_begin))
|
|
return -1;
|
|
|
|
/*
|
|
* Fast path: copy a match which is no longer than a few words, is not
|
|
* overlapped such that copying a word at a time would produce incorrect
|
|
* results, and is not too close to the end of the buffer. Note that
|
|
* this might copy more than the length of the match, but that's okay in
|
|
* this scenario.
|
|
*/
|
|
src = out_next - offset;
|
|
if (UNALIGNED_ACCESS_IS_FAST && length <= 3 * WORDBYTES &&
|
|
offset >= WORDBYTES && out_end - out_next >= 3 * WORDBYTES)
|
|
{
|
|
copy_word_unaligned(src + WORDBYTES*0, out_next + WORDBYTES*0);
|
|
copy_word_unaligned(src + WORDBYTES*1, out_next + WORDBYTES*1);
|
|
copy_word_unaligned(src + WORDBYTES*2, out_next + WORDBYTES*2);
|
|
return 0;
|
|
}
|
|
|
|
/* Validate the length. This isn't needed in the fast path above, due
|
|
* to the additional conditions tested, but we do need it here. */
|
|
if (unlikely(length > out_end - out_next))
|
|
return -1;
|
|
end = out_next + length;
|
|
|
|
/*
|
|
* Try to copy one word at a time. On i386 and x86_64 this is faster
|
|
* than copying one byte at a time, unless the data is near-random and
|
|
* all the matches have very short lengths. Note that since this
|
|
* requires unaligned memory accesses, it won't necessarily be faster on
|
|
* every architecture.
|
|
*
|
|
* Also note that we might copy more than the length of the match. For
|
|
* example, if a word is 8 bytes and the match is of length 5, then
|
|
* we'll simply copy 8 bytes. This is okay as long as we don't write
|
|
* beyond the end of the output buffer, hence the check for (out_end -
|
|
* end >= WORDBYTES - 1).
|
|
*/
|
|
if (UNALIGNED_ACCESS_IS_FAST && likely(out_end - end >= WORDBYTES - 1))
|
|
{
|
|
if (offset >= WORDBYTES) {
|
|
/* The source and destination words don't overlap. */
|
|
do {
|
|
copy_word_unaligned(src, out_next);
|
|
src += WORDBYTES;
|
|
out_next += WORDBYTES;
|
|
} while (out_next < end);
|
|
return 0;
|
|
} else if (offset == 1) {
|
|
/* Offset 1 matches are equivalent to run-length
|
|
* encoding of the previous byte. This case is common
|
|
* if the data contains many repeated bytes. */
|
|
machine_word_t v = repeat_byte(*(out_next - 1));
|
|
do {
|
|
store_word_unaligned(v, out_next);
|
|
src += WORDBYTES;
|
|
out_next += WORDBYTES;
|
|
} while (out_next < end);
|
|
return 0;
|
|
}
|
|
/*
|
|
* We don't bother with special cases for other 'offset <
|
|
* WORDBYTES', which are usually rarer than 'offset == 1'.
|
|
* Extra checks will just slow things down. Actually, it's
|
|
* possible to handle all the 'offset < WORDBYTES' cases using
|
|
* the same code, but it still becomes more complicated doesn't
|
|
* seem any faster overall; it definitely slows down the more
|
|
* common 'offset == 1' case.
|
|
*/
|
|
}
|
|
|
|
/* Fall back to a bytewise copy. */
|
|
if (min_length >= 2)
|
|
*out_next++ = *src++;
|
|
if (min_length >= 3)
|
|
*out_next++ = *src++;
|
|
if (min_length >= 4)
|
|
*out_next++ = *src++;
|
|
do {
|
|
*out_next++ = *src++;
|
|
} while (out_next != end);
|
|
return 0;
|
|
}
|
|
|
|
#endif /* _DECOMPRESS_COMMON_H */
|