// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       block_header_encoder.c

/// \brief      Encodes Block Header for .xz files

//

//  Author:     Lasse Collin

//

///////////////////////////////////////////////////////////////////////////////

#include "common.h"

#include "check.h"

extern LZMA_API(lzma_ret)

lzma_block_header_size(lzma_block *block)

{

  if (block->version > 1)

    return LZMA_OPTIONS_ERROR;

  // Block Header Size + Block Flags + CRC32.

  uint32_t size = 1 + 1 + 4;

  // Compressed Size

  if (block->compressed_size != LZMA_VLI_UNKNOWN) {

    const uint32_t add = lzma_vli_size(block->compressed_size);

    if (add == 0 || block->compressed_size == 0)

      return LZMA_PROG_ERROR;

    size += add;

  }

  // Uncompressed Size

  if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {

    const uint32_t add = lzma_vli_size(block->uncompressed_size);

    if (add == 0)

      return LZMA_PROG_ERROR;

    size += add;

  }

  // List of Filter Flags

  if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)

    return LZMA_PROG_ERROR;

  for (size_t i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {

    // Don't allow too many filters.

    if (i == LZMA_FILTERS_MAX)

      return LZMA_PROG_ERROR;

    uint32_t add;

    return_if_error(lzma_filter_flags_size(&add,

        block->filters + i));

    size += add;

  }

  // Pad to a multiple of four bytes.

  block->header_size = (size + 3) & ~UINT32_C(3);

  // NOTE: We don't verify that the encoded size of the Block stays

  // within limits. This is because it is possible that we are called

  // with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve

  // space for Block Header, and later called again with lower,

  // real values.

  return LZMA_OK;

}

extern LZMA_API(lzma_ret)

lzma_block_header_encode(const lzma_block *block, uint8_t *out)

{

  // Validate everything but filters.

  if (lzma_block_unpadded_size(block) == 0

      || !lzma_vli_is_valid(block->uncompressed_size))

    return LZMA_PROG_ERROR;

  // Indicate the size of the buffer _excluding_ the CRC32 field.

  const size_t out_size = block->header_size - 4;

  // Store the Block Header Size.

  out[0] = out_size / 4;

  // We write Block Flags in pieces.

  out[1] = 0x00;

  size_t out_pos = 2;

  // Compressed Size

  if (block->compressed_size != LZMA_VLI_UNKNOWN) {

    return_if_error(lzma_vli_encode(block->compressed_size, NULL,

        out, &out_pos, out_size));

    out[1] |= 0x40;

  }

  // Uncompressed Size

  if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {

    return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,

        out, &out_pos, out_size));

    out[1] |= 0x80;

  }

  // Filter Flags

  if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)

    return LZMA_PROG_ERROR;

  size_t filter_count = 0;

  do {

    // There can be a maximum of four filters.

    if (filter_count == LZMA_FILTERS_MAX)

      return LZMA_PROG_ERROR;

    return_if_error(lzma_filter_flags_encode(

        block->filters + filter_count,

        out, &out_pos, out_size));

  } while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);

  out[1] |= filter_count - 1;

  // Padding

  memzero(out + out_pos, out_size - out_pos);

  // CRC32

  write32le(out + out_size, lzma_crc32(out, out_size, 0));

  return LZMA_OK;

}