// SPDX-License-Identifier: 0BSD
///////////////////////////////////////////////////////////////////////////////
//
/// \file lz_decoder.h
/// \brief LZ out window
///
// Authors: Igor Pavlov
// Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////
#ifndef LZMA_LZ_DECODER_H
#define LZMA_LZ_DECODER_H
#include "common.h"
/// Maximum length of a match rounded up to a nice power of 2 which is
/// a good size for aligned memcpy(). The allocated dictionary buffer will
/// be 2 * LZ_DICT_REPEAT_MAX bytes larger than the actual dictionary size:
///
/// (1) Every time the decoder reaches the end of the dictionary buffer,
/// the last LZ_DICT_REPEAT_MAX bytes will be copied to the beginning.
/// This way dict_repeat() will only need to copy from one place,
/// never from both the end and beginning of the buffer.
///
/// (2) The other LZ_DICT_REPEAT_MAX bytes is kept as a buffer between
/// the oldest byte still in the dictionary and the current write
/// position. This way dict_repeat(dict, dict->size - 1, &len)
/// won't need memmove() as the copying cannot overlap.
///
/// Note that memcpy() still cannot be used if distance < len.
///
/// LZMA's longest match length is 273 so pick a multiple of 16 above that.
#define LZ_DICT_REPEAT_MAX 288
typedef struct {
/// Pointer to the dictionary buffer.
uint8_t *buf;
/// Write position in dictionary. The next byte will be written to
/// buf[pos].
size_t pos;
/// Indicates how full the dictionary is. This is used by
/// dict_is_distance_valid() to detect corrupt files that would
/// read beyond the beginning of the dictionary.
size_t full;
/// Write limit
size_t limit;
/// Allocated size of buf. This is 2 * LZ_DICT_REPEAT_MAX bytes
/// larger than the actual dictionary size. This is enforced by
/// how the value for "full" is set; it can be at most
/// "size - 2 * LZ_DICT_REPEAT_MAX".
size_t size;
/// True once the dictionary has become full and the writing position
/// has been wrapped in decode_buffer() in lz_decoder.c.
bool has_wrapped;
/// True when dictionary should be reset before decoding more data.
bool need_reset;
} lzma_dict;
typedef struct {
size_t dict_size;
const uint8_t *preset_dict;
size_t preset_dict_size;
} lzma_lz_options;
typedef struct {
/// Data specific to the LZ-based decoder
void *coder;
/// Function to decode from in[] to *dict
lzma_ret (*code)(void *coder,
lzma_dict *restrict dict, const uint8_t *restrict in,
size_t *restrict in_pos, size_t in_size);
void (*reset)(void *coder, const void *options);
/// Set the uncompressed size. If uncompressed_size == LZMA_VLI_UNKNOWN
/// then allow_eopm will always be true.
void (*set_uncompressed)(void *coder, lzma_vli uncompressed_size,
bool allow_eopm);
/// Free allocated resources
void (*end)(void *coder, const lzma_allocator *allocator);
} lzma_lz_decoder;
#define LZMA_LZ_DECODER_INIT \
(lzma_lz_decoder){ \
.coder = NULL, \
.code = NULL, \
.reset = NULL, \
.set_uncompressed = NULL, \
.end = NULL, \
}
extern lzma_ret lzma_lz_decoder_init(lzma_next_coder *next,
const lzma_allocator *allocator,
const lzma_filter_info *filters,
lzma_ret (*lz_init)(lzma_lz_decoder *lz,
const lzma_allocator *allocator,
lzma_vli id, const void *options,
lzma_lz_options *lz_options));
extern uint64_t lzma_lz_decoder_memusage(size_t dictionary_size);
//////////////////////
// Inline functions //
//////////////////////
/// Get a byte from the history buffer.
static inline uint8_t
dict_get(const lzma_dict *const dict, const uint32_t distance)
{
return dict->buf[dict->pos - distance - 1
+ (distance < dict->pos
? 0 : dict->size - LZ_DICT_REPEAT_MAX)];
}
/// Optimized version of dict_get(dict, 0)
static inline uint8_t
dict_get0(const lzma_dict *const dict)
{
return dict->buf[dict->pos - 1];
}
/// Test if dictionary is empty.
static inline bool
dict_is_empty(const lzma_dict *const dict)
{
return dict->full == 0;
}
/// Validate the match distance
static inline bool
dict_is_distance_valid(const lzma_dict *const dict, const size_t distance)
{
return dict->full > distance;
}
/// Repeat *len bytes at distance.
static inline bool
dict_repeat(lzma_dict *dict, uint32_t distance, uint32_t *len)
{
// Don't write past the end of the dictionary.
const size_t dict_avail = dict->limit - dict->pos;
uint32_t left = my_min(dict_avail, *len);
*len -= left;
size_t back = dict->pos - distance - 1;
if (distance >= dict->pos)
back += dict->size - LZ_DICT_REPEAT_MAX;
// Repeat a block of data from the history. Because memcpy() is faster
// than copying byte by byte in a loop, the copying process gets split
// into two cases.
if (distance < left) {
// Source and target areas overlap, thus we can't use
// memcpy() nor even memmove() safely.
do {
dict->buf[dict->pos++] = dict->buf[back++];
} while (--left > 0);
} else {
memcpy(dict->buf + dict->pos, dict->buf + back, left);
dict->pos += left;
}
// Update how full the dictionary is.
if (!dict->has_wrapped)
dict->full = dict->pos - 2 * LZ_DICT_REPEAT_MAX;
return *len != 0;
}
static inline void
dict_put(lzma_dict *dict, uint8_t byte)
{
dict->buf[dict->pos++] = byte;
if (!dict->has_wrapped)
dict->full = dict->pos - 2 * LZ_DICT_REPEAT_MAX;
}
/// Puts one byte into the dictionary. Returns true if the dictionary was
/// already full and the byte couldn't be added.
static inline bool
dict_put_safe(lzma_dict *dict, uint8_t byte)
{
if (unlikely(dict->pos == dict->limit))
return true;
dict_put(dict, byte);
return false;
}
/// Copies arbitrary amount of data into the dictionary.
static inline void
dict_write(lzma_dict *restrict dict, const uint8_t *restrict in,
size_t *restrict in_pos, size_t in_size,
size_t *restrict left)
{
// NOTE: If we are being given more data than the size of the
// dictionary, it could be possible to optimize the LZ decoder
// so that not everything needs to go through the dictionary.
// This shouldn't be very common thing in practice though, and
// the slowdown of one extra memcpy() isn't bad compared to how
// much time it would have taken if the data were compressed.
if (in_size - *in_pos > *left)
in_size = *in_pos + *left;
*left -= lzma_bufcpy(in, in_pos, in_size,
dict->buf, &dict->pos, dict->limit);
if (!dict->has_wrapped)
dict->full = dict->pos - 2 * LZ_DICT_REPEAT_MAX;
return;
}
static inline void
dict_reset(lzma_dict *dict)
{
dict->need_reset = true;
return;
}
#endif
