///////////////////////////////////////////////////////////////////////////////
//
/// \file delta_encoder.c
/// \brief Delta filter encoder
//
// Copyright (C) 2007, 2008 Lasse Collin
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
///////////////////////////////////////////////////////////////////////////////
#include "delta_encoder.h"
#include "delta_common.h"
/// Copies and encodes the data at the same time. This is used when Delta
/// is the first filter in the chain (and thus the last filter in the
/// encoder's filter stack).
static void
copy_and_encode(lzma_coder *coder,
const uint8_t *restrict in, uint8_t *restrict out, size_t size)
{
const size_t distance = coder->distance;
for (size_t i = 0; i < size; ++i) {
const uint8_t tmp = coder->history[
(distance + coder->pos) & 0xFF];
coder->history[coder->pos-- & 0xFF] = in[i];
out[i] = in[i] - tmp;
}
}
/// Encodes the data in place. This is used when we are the last filter
/// in the chain (and thus non-last filter in the encoder's filter stack).
static void
encode_in_place(lzma_coder *coder, uint8_t *buffer, size_t size)
{
const size_t distance = coder->distance;
for (size_t i = 0; i < size; ++i) {
const uint8_t tmp = coder->history[
(distance + coder->pos) & 0xFF];
coder->history[coder->pos-- & 0xFF] = buffer[i];
buffer[i] -= tmp;
}
}
static lzma_ret
delta_encode(lzma_coder *coder, lzma_allocator *allocator,
const uint8_t *restrict in, size_t *restrict in_pos,
size_t in_size, uint8_t *restrict out,
size_t *restrict out_pos, size_t out_size, lzma_action action)
{
lzma_ret ret;
if (coder->next.code == NULL) {
const size_t in_avail = in_size - *in_pos;
const size_t out_avail = out_size - *out_pos;
const size_t size = MIN(in_avail, out_avail);
copy_and_encode(coder, in + *in_pos, out + *out_pos, size);
*in_pos += size;
*out_pos += size;
ret = action != LZMA_RUN && *in_pos == in_size
? LZMA_STREAM_END : LZMA_OK;
} else {
const size_t out_start = *out_pos;
ret = coder->next.code(coder->next.coder, allocator,
in, in_pos, in_size, out, out_pos, out_size,
action);
encode_in_place(coder, out + out_start, *out_pos - out_start);
}
return ret;
}
extern lzma_ret
lzma_delta_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
const lzma_filter_info *filters)
{
return lzma_delta_coder_init(next, allocator, filters, &delta_encode);
}
extern lzma_ret
lzma_delta_props_encode(const void *options, uint8_t *out)
{
if (options == NULL)
return LZMA_PROG_ERROR;
const lzma_options_delta *opt = options;
// It's possible that newer liblzma versions will support larger
// distance values.
if (opt->type != LZMA_DELTA_TYPE_BYTE
|| opt->distance < LZMA_DELTA_DISTANCE_MIN
|| opt->distance > LZMA_DELTA_DISTANCE_MAX)
return LZMA_OPTIONS_ERROR;
out[0] = opt->distance - LZMA_DELTA_DISTANCE_MIN;
return LZMA_OK;
}
