source: vbox/trunk/src/libs/liblzma-5.8.1/delta/delta_decoder.c

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       delta_decoder.c
/// \brief      Delta filter decoder
//
//  Author:     Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include "delta_decoder.h"
#include "delta_private.h"


static void
decode_buffer(lzma_delta_coder *coder, uint8_t *buffer, size_t size)
{
        const size_t distance = coder->distance;

        for (size_t i = 0; i < size; ++i) {
                buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
                coder->history[coder->pos-- & 0xFF] = buffer[i];
        }
}


// For an unknown reason NVIDIA HPC Compiler needs this pragma
// to produce working code.
#ifdef __NVCOMPILER
#       pragma routine novector
#endif
static lzma_ret
delta_decode(void *coder_ptr, const 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_delta_coder *coder = coder_ptr;

        assert(coder->next.code != NULL);

        const size_t out_start = *out_pos;

        const lzma_ret ret = coder->next.code(coder->next.coder, allocator,
                        in, in_pos, in_size, out, out_pos, out_size,
                        action);

        // out might be NULL. In that case size == 0. Null pointer + 0 is
        // undefined behavior so skip the call in that case as it would
        // do nothing anyway.
        const size_t size = *out_pos - out_start;
        if (size > 0)
                decode_buffer(coder, out + out_start, size);

        return ret;
}


extern lzma_ret
lzma_delta_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                const lzma_filter_info *filters)
{
        next->code = &delta_decode;
        return lzma_delta_coder_init(next, allocator, filters);
}


extern lzma_ret
lzma_delta_props_decode(void **options, const lzma_allocator *allocator,
                const uint8_t *props, size_t props_size)
{
        if (props_size != 1)
                return LZMA_OPTIONS_ERROR;

        lzma_options_delta *opt
                        = lzma_alloc(sizeof(lzma_options_delta), allocator);
        if (opt == NULL)
                return LZMA_MEM_ERROR;

        opt->type = LZMA_DELTA_TYPE_BYTE;
        opt->dist = props[0] + 1U;

        *options = opt;

        return LZMA_OK;
}