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0e0f34b8e4
Note that this slightly changes how lzma_block_header_decode() has been documented. Earlier it said that the .version is set to the lowest required value, but now it says that the .version field is kept unchanged if possible. In practice this doesn't affect any old code, because before this commit the only possible .version was 0.
132 lines
3.3 KiB
C
132 lines
3.3 KiB
C
///////////////////////////////////////////////////////////////////////////////
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//
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/// \file block_header_encoder.c
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/// \brief Encodes Block Header for .xz files
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//
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// Author: Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "common.h"
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#include "check.h"
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extern LZMA_API(lzma_ret)
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lzma_block_header_size(lzma_block *block)
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{
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if (block->version > 1)
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return LZMA_OPTIONS_ERROR;
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// Block Header Size + Block Flags + CRC32.
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uint32_t size = 1 + 1 + 4;
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// Compressed Size
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if (block->compressed_size != LZMA_VLI_UNKNOWN) {
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const uint32_t add = lzma_vli_size(block->compressed_size);
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if (add == 0 || block->compressed_size == 0)
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return LZMA_PROG_ERROR;
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size += add;
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}
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// Uncompressed Size
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if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
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const uint32_t add = lzma_vli_size(block->uncompressed_size);
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if (add == 0)
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return LZMA_PROG_ERROR;
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size += add;
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}
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// List of Filter Flags
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if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
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return LZMA_PROG_ERROR;
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for (size_t i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
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// Don't allow too many filters.
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if (i == LZMA_FILTERS_MAX)
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return LZMA_PROG_ERROR;
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uint32_t add;
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return_if_error(lzma_filter_flags_size(&add,
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block->filters + i));
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size += add;
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}
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// Pad to a multiple of four bytes.
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block->header_size = (size + 3) & ~UINT32_C(3);
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// NOTE: We don't verify that the encoded size of the Block stays
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// within limits. This is because it is possible that we are called
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// with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve
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// space for Block Header, and later called again with lower,
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// real values.
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return LZMA_OK;
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}
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extern LZMA_API(lzma_ret)
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lzma_block_header_encode(const lzma_block *block, uint8_t *out)
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{
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// Validate everything but filters.
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if (lzma_block_unpadded_size(block) == 0
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|| !lzma_vli_is_valid(block->uncompressed_size))
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return LZMA_PROG_ERROR;
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// Indicate the size of the buffer _excluding_ the CRC32 field.
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const size_t out_size = block->header_size - 4;
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// Store the Block Header Size.
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out[0] = out_size / 4;
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// We write Block Flags in pieces.
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out[1] = 0x00;
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size_t out_pos = 2;
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// Compressed Size
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if (block->compressed_size != LZMA_VLI_UNKNOWN) {
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return_if_error(lzma_vli_encode(block->compressed_size, NULL,
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out, &out_pos, out_size));
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out[1] |= 0x40;
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}
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// Uncompressed Size
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if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
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return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,
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out, &out_pos, out_size));
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out[1] |= 0x80;
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}
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// Filter Flags
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if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
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return LZMA_PROG_ERROR;
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size_t filter_count = 0;
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do {
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// There can be a maximum of four filters.
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if (filter_count == LZMA_FILTERS_MAX)
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return LZMA_PROG_ERROR;
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return_if_error(lzma_filter_flags_encode(
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block->filters + filter_count,
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out, &out_pos, out_size));
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} while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);
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out[1] |= filter_count - 1;
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// Padding
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memzero(out + out_pos, out_size - out_pos);
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// CRC32
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unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0));
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return LZMA_OK;
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}
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