root/src/liblzma/common/block_header_encoder.c

DEFINITIONS

1. LZMA_API
2. LZMA_API

///////////////////////////////////////////////////////////////////////////////
//
/// \file       block_header_encoder.c
/// \brief      Encodes Block Header for .xz files
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "common.h"
#include "check.h"


extern LZMA_API(lzma_ret)
lzma_block_header_size(lzma_block *block)
{
        if (block->version != 0)
                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
        unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));

        return LZMA_OK;
}