// 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"
typedef struct {
/// Pointer to the dictionary buffer. It can be an allocated buffer
/// internal to liblzma, or it can a be a buffer given by the
/// application when in single-call mode (not implemented yet).
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;
/// Size of the dictionary
size_t size;
/// 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)];
}
/// 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;
// 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 three 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_get(dict, distance);
++dict->pos;
} while (--left > 0);
} else if (distance < dict->pos) {
// The easiest and fastest case
memcpy(dict->buf + dict->pos,
dict->buf + dict->pos - distance - 1,
left);
dict->pos += left;
} else {
// The bigger the dictionary, the more rare this
// case occurs. We need to "wrap" the dict, thus
// we might need two memcpy() to copy all the data.
assert(dict->full == dict->size);
const uint32_t copy_pos
= dict->pos - distance - 1 + dict->size;
uint32_t copy_size = dict->size - copy_pos;
if (copy_size < left) {
memmove(dict->buf + dict->pos, dict->buf + copy_pos,
copy_size);
dict->pos += copy_size;
copy_size = left - copy_size;
memcpy(dict->buf + dict->pos, dict->buf, copy_size);
dict->pos += copy_size;
} else {
memmove(dict->buf + dict->pos, dict->buf + copy_pos,
left);
dict->pos += left;
}
}
// Update how full the dictionary is.
if (dict->full < dict->pos)
dict->full = dict->pos;
return unlikely(*len != 0);
}
/// 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(lzma_dict *dict, uint8_t byte)
{
if (unlikely(dict->pos == dict->limit))
return true;
dict->buf[dict->pos++] = byte;
if (dict->pos > dict->full)
dict->full = dict->pos;
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->pos > dict->full)
dict->full = dict->pos;
return;
}
static inline void
dict_reset(lzma_dict *dict)
{
dict->need_reset = true;
return;
}
#endif
