mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
343 lines
9.6 KiB
343 lines
9.6 KiB
/* SPDX-License-Identifier: GPL-2.0-or-later */ |
|
/* |
|
* decompress_common.h - Code shared by the XPRESS and LZX decompressors |
|
* |
|
* Copyright (C) 2015 Eric Biggers |
|
*/ |
|
|
|
#ifndef _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H |
|
#define _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H |
|
|
|
#include <linux/string.h> |
|
#include <linux/compiler.h> |
|
#include <linux/types.h> |
|
#include <linux/slab.h> |
|
#include <asm/unaligned.h> |
|
|
|
|
|
/* "Force inline" macro (not required, but helpful for performance) */ |
|
#define forceinline __always_inline |
|
|
|
/* Enable whole-word match copying on selected architectures */ |
|
#if defined(__i386__) || defined(__x86_64__) || defined(__ARM_FEATURE_UNALIGNED) |
|
# define FAST_UNALIGNED_ACCESS |
|
#endif |
|
|
|
/* Size of a machine word */ |
|
#define WORDBYTES (sizeof(size_t)) |
|
|
|
static forceinline void |
|
copy_unaligned_word(const void *src, void *dst) |
|
{ |
|
put_unaligned(get_unaligned((const size_t *)src), (size_t *)dst); |
|
} |
|
|
|
|
|
/* Generate a "word" with platform-dependent size whose bytes all contain the |
|
* value 'b'. |
|
*/ |
|
static forceinline size_t repeat_byte(u8 b) |
|
{ |
|
size_t v; |
|
|
|
v = b; |
|
v |= v << 8; |
|
v |= v << 16; |
|
v |= v << ((WORDBYTES == 8) ? 32 : 0); |
|
return v; |
|
} |
|
|
|
/* Structure that encapsulates a block of in-memory data being interpreted as a |
|
* stream of bits, optionally with interwoven literal bytes. Bits are assumed |
|
* to be stored in little endian 16-bit coding units, with the bits ordered high |
|
* to low. |
|
*/ |
|
struct input_bitstream { |
|
|
|
/* Bits that have been read from the input buffer. The bits are |
|
* left-justified; the next bit is always bit 31. |
|
*/ |
|
u32 bitbuf; |
|
|
|
/* Number of bits currently held in @bitbuf. */ |
|
u32 bitsleft; |
|
|
|
/* Pointer to the next byte to be retrieved from the input buffer. */ |
|
const u8 *next; |
|
|
|
/* Pointer to just past the end of the input buffer. */ |
|
const u8 *end; |
|
}; |
|
|
|
/* Initialize a bitstream to read from the specified input buffer. */ |
|
static forceinline void init_input_bitstream(struct input_bitstream *is, |
|
const void *buffer, u32 size) |
|
{ |
|
is->bitbuf = 0; |
|
is->bitsleft = 0; |
|
is->next = buffer; |
|
is->end = is->next + size; |
|
} |
|
|
|
/* Ensure the bit buffer variable for the bitstream contains at least @num_bits |
|
* bits. Following this, bitstream_peek_bits() and/or bitstream_remove_bits() |
|
* may be called on the bitstream to peek or remove up to @num_bits bits. Note |
|
* that @num_bits must be <= 16. |
|
*/ |
|
static forceinline void bitstream_ensure_bits(struct input_bitstream *is, |
|
u32 num_bits) |
|
{ |
|
if (is->bitsleft < num_bits) { |
|
if (is->end - is->next >= 2) { |
|
is->bitbuf |= (u32)get_unaligned_le16(is->next) |
|
<< (16 - is->bitsleft); |
|
is->next += 2; |
|
} |
|
is->bitsleft += 16; |
|
} |
|
} |
|
|
|
/* Return the next @num_bits bits from the bitstream, without removing them. |
|
* There must be at least @num_bits remaining in the buffer variable, from a |
|
* previous call to bitstream_ensure_bits(). |
|
*/ |
|
static forceinline u32 |
|
bitstream_peek_bits(const struct input_bitstream *is, const u32 num_bits) |
|
{ |
|
return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1); |
|
} |
|
|
|
/* Remove @num_bits from the bitstream. There must be at least @num_bits |
|
* remaining in the buffer variable, from a previous call to |
|
* bitstream_ensure_bits(). |
|
*/ |
|
static forceinline void |
|
bitstream_remove_bits(struct input_bitstream *is, u32 num_bits) |
|
{ |
|
is->bitbuf <<= num_bits; |
|
is->bitsleft -= num_bits; |
|
} |
|
|
|
/* Remove and return @num_bits bits from the bitstream. There must be at least |
|
* @num_bits remaining in the buffer variable, from a previous call to |
|
* bitstream_ensure_bits(). |
|
*/ |
|
static forceinline u32 |
|
bitstream_pop_bits(struct input_bitstream *is, u32 num_bits) |
|
{ |
|
u32 bits = bitstream_peek_bits(is, num_bits); |
|
|
|
bitstream_remove_bits(is, num_bits); |
|
return bits; |
|
} |
|
|
|
/* Read and return the next @num_bits bits from the bitstream. */ |
|
static forceinline u32 |
|
bitstream_read_bits(struct input_bitstream *is, u32 num_bits) |
|
{ |
|
bitstream_ensure_bits(is, num_bits); |
|
return bitstream_pop_bits(is, num_bits); |
|
} |
|
|
|
/* Read and return the next literal byte embedded in the bitstream. */ |
|
static forceinline u8 |
|
bitstream_read_byte(struct input_bitstream *is) |
|
{ |
|
if (unlikely(is->end == is->next)) |
|
return 0; |
|
return *is->next++; |
|
} |
|
|
|
/* Read and return the next 16-bit integer embedded in the bitstream. */ |
|
static forceinline u16 |
|
bitstream_read_u16(struct input_bitstream *is) |
|
{ |
|
u16 v; |
|
|
|
if (unlikely(is->end - is->next < 2)) |
|
return 0; |
|
v = get_unaligned_le16(is->next); |
|
is->next += 2; |
|
return v; |
|
} |
|
|
|
/* Read and return the next 32-bit integer embedded in the bitstream. */ |
|
static forceinline u32 |
|
bitstream_read_u32(struct input_bitstream *is) |
|
{ |
|
u32 v; |
|
|
|
if (unlikely(is->end - is->next < 4)) |
|
return 0; |
|
v = get_unaligned_le32(is->next); |
|
is->next += 4; |
|
return v; |
|
} |
|
|
|
/* Read into @dst_buffer an array of literal bytes embedded in the bitstream. |
|
* Return either a pointer to the byte past the last written, or NULL if the |
|
* read overflows the input buffer. |
|
*/ |
|
static forceinline void *bitstream_read_bytes(struct input_bitstream *is, |
|
void *dst_buffer, size_t count) |
|
{ |
|
if ((size_t)(is->end - is->next) < count) |
|
return NULL; |
|
memcpy(dst_buffer, is->next, count); |
|
is->next += count; |
|
return (u8 *)dst_buffer + count; |
|
} |
|
|
|
/* Align the input bitstream on a coding-unit boundary. */ |
|
static forceinline void bitstream_align(struct input_bitstream *is) |
|
{ |
|
is->bitsleft = 0; |
|
is->bitbuf = 0; |
|
} |
|
|
|
extern int make_huffman_decode_table(u16 decode_table[], const u32 num_syms, |
|
const u32 num_bits, const u8 lens[], |
|
const u32 max_codeword_len, |
|
u16 working_space[]); |
|
|
|
|
|
/* Reads and returns the next Huffman-encoded symbol from a bitstream. If the |
|
* input data is exhausted, the Huffman symbol is decoded as if the missing bits |
|
* are all zeroes. |
|
*/ |
|
static forceinline u32 read_huffsym(struct input_bitstream *istream, |
|
const u16 decode_table[], |
|
u32 table_bits, |
|
u32 max_codeword_len) |
|
{ |
|
u32 entry; |
|
u32 key_bits; |
|
|
|
bitstream_ensure_bits(istream, max_codeword_len); |
|
|
|
/* Index the decode table by the next table_bits bits of the input. */ |
|
key_bits = bitstream_peek_bits(istream, table_bits); |
|
entry = decode_table[key_bits]; |
|
if (entry < 0xC000) { |
|
/* Fast case: The decode table directly provided the |
|
* symbol and codeword length. The low 11 bits are the |
|
* symbol, and the high 5 bits are the codeword length. |
|
*/ |
|
bitstream_remove_bits(istream, entry >> 11); |
|
return entry & 0x7FF; |
|
} |
|
/* Slow case: The codeword for the symbol is longer than |
|
* table_bits, so the symbol does not have an entry |
|
* directly in the first (1 << table_bits) entries of the |
|
* decode table. Traverse the appropriate binary tree |
|
* bit-by-bit to decode the symbol. |
|
*/ |
|
bitstream_remove_bits(istream, table_bits); |
|
do { |
|
key_bits = (entry & 0x3FFF) + bitstream_pop_bits(istream, 1); |
|
} while ((entry = decode_table[key_bits]) >= 0xC000); |
|
return entry; |
|
} |
|
|
|
/* |
|
* Copy an LZ77 match at (dst - offset) to dst. |
|
* |
|
* The length and offset must be already validated --- that is, (dst - offset) |
|
* can't underrun the output buffer, and (dst + length) can't overrun the output |
|
* buffer. Also, the length cannot be 0. |
|
* |
|
* @bufend points to the byte past the end of the output buffer. This function |
|
* won't write any data beyond this position. |
|
* |
|
* Returns dst + length. |
|
*/ |
|
static forceinline u8 *lz_copy(u8 *dst, u32 length, u32 offset, const u8 *bufend, |
|
u32 min_length) |
|
{ |
|
const u8 *src = dst - offset; |
|
|
|
/* |
|
* Try to copy one machine 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 (bufend - |
|
* end >= WORDBYTES - 1). |
|
*/ |
|
#ifdef FAST_UNALIGNED_ACCESS |
|
u8 * const end = dst + length; |
|
|
|
if (bufend - end >= (ptrdiff_t)(WORDBYTES - 1)) { |
|
|
|
if (offset >= WORDBYTES) { |
|
/* The source and destination words don't overlap. */ |
|
|
|
/* To improve branch prediction, one iteration of this |
|
* loop is unrolled. Most matches are short and will |
|
* fail the first check. But if that check passes, then |
|
* it becomes increasing likely that the match is long |
|
* and we'll need to continue copying. |
|
*/ |
|
|
|
copy_unaligned_word(src, dst); |
|
src += WORDBYTES; |
|
dst += WORDBYTES; |
|
|
|
if (dst < end) { |
|
do { |
|
copy_unaligned_word(src, dst); |
|
src += WORDBYTES; |
|
dst += WORDBYTES; |
|
} while (dst < end); |
|
} |
|
return end; |
|
} 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. |
|
*/ |
|
size_t v = repeat_byte(*(dst - 1)); |
|
|
|
do { |
|
put_unaligned(v, (size_t *)dst); |
|
src += WORDBYTES; |
|
dst += WORDBYTES; |
|
} while (dst < end); |
|
return end; |
|
} |
|
/* |
|
* 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. |
|
*/ |
|
} |
|
#endif /* FAST_UNALIGNED_ACCESS */ |
|
|
|
/* Fall back to a bytewise copy. */ |
|
|
|
if (min_length >= 2) { |
|
*dst++ = *src++; |
|
length--; |
|
} |
|
if (min_length >= 3) { |
|
*dst++ = *src++; |
|
length--; |
|
} |
|
do { |
|
*dst++ = *src++; |
|
} while (--length); |
|
|
|
return dst; |
|
} |
|
|
|
#endif /* _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H */
|
|
|