// 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;

}