1  ///////////////////////////////////////////////////////////////////////////////
       2  //
       3  /// \file       block_header_encoder.c
       4  /// \brief      Encodes Block Header for .xz files
       5  //
       6  //  Author:     Lasse Collin
       7  //
       8  //  This file has been put into the public domain.
       9  //  You can do whatever you want with this file.
      10  //
      11  ///////////////////////////////////////////////////////////////////////////////
      12  
      13  #include "common.h"
      14  #include "check.h"
      15  
      16  
      17  extern LZMA_API(lzma_ret)
      18  lzma_block_header_size(lzma_block *block)
      19  {
      20  	if (block->version > 1)
      21  		return LZMA_OPTIONS_ERROR;
      22  
      23  	// Block Header Size + Block Flags + CRC32.
      24  	uint32_t size = 1 + 1 + 4;
      25  
      26  	// Compressed Size
      27  	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
      28  		const uint32_t add = lzma_vli_size(block->compressed_size);
      29  		if (add == 0 || block->compressed_size == 0)
      30  			return LZMA_PROG_ERROR;
      31  
      32  		size += add;
      33  	}
      34  
      35  	// Uncompressed Size
      36  	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
      37  		const uint32_t add = lzma_vli_size(block->uncompressed_size);
      38  		if (add == 0)
      39  			return LZMA_PROG_ERROR;
      40  
      41  		size += add;
      42  	}
      43  
      44  	// List of Filter Flags
      45  	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
      46  		return LZMA_PROG_ERROR;
      47  
      48  	for (size_t i = 0; block->filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
      49  		// Don't allow too many filters.
      50  		if (i == LZMA_FILTERS_MAX)
      51  			return LZMA_PROG_ERROR;
      52  
      53  		uint32_t add;
      54  		return_if_error(lzma_filter_flags_size(&add,
      55  				block->filters + i));
      56  
      57  		size += add;
      58  	}
      59  
      60  	// Pad to a multiple of four bytes.
      61  	block->header_size = (size + 3) & ~UINT32_C(3);
      62  
      63  	// NOTE: We don't verify that the encoded size of the Block stays
      64  	// within limits. This is because it is possible that we are called
      65  	// with exaggerated Compressed Size (e.g. LZMA_VLI_MAX) to reserve
      66  	// space for Block Header, and later called again with lower,
      67  	// real values.
      68  
      69  	return LZMA_OK;
      70  }
      71  
      72  
      73  extern LZMA_API(lzma_ret)
      74  lzma_block_header_encode(const lzma_block *block, uint8_t *out)
      75  {
      76  	// Validate everything but filters.
      77  	if (lzma_block_unpadded_size(block) == 0
      78  			|| !lzma_vli_is_valid(block->uncompressed_size))
      79  		return LZMA_PROG_ERROR;
      80  
      81  	// Indicate the size of the buffer _excluding_ the CRC32 field.
      82  	const size_t out_size = block->header_size - 4;
      83  
      84  	// Store the Block Header Size.
      85  	out[0] = out_size / 4;
      86  
      87  	// We write Block Flags in pieces.
      88  	out[1] = 0x00;
      89  	size_t out_pos = 2;
      90  
      91  	// Compressed Size
      92  	if (block->compressed_size != LZMA_VLI_UNKNOWN) {
      93  		return_if_error(lzma_vli_encode(block->compressed_size, NULL,
      94  				out, &out_pos, out_size));
      95  
      96  		out[1] |= 0x40;
      97  	}
      98  
      99  	// Uncompressed Size
     100  	if (block->uncompressed_size != LZMA_VLI_UNKNOWN) {
     101  		return_if_error(lzma_vli_encode(block->uncompressed_size, NULL,
     102  				out, &out_pos, out_size));
     103  
     104  		out[1] |= 0x80;
     105  	}
     106  
     107  	// Filter Flags
     108  	if (block->filters == NULL || block->filters[0].id == LZMA_VLI_UNKNOWN)
     109  		return LZMA_PROG_ERROR;
     110  
     111  	size_t filter_count = 0;
     112  	do {
     113  		// There can be a maximum of four filters.
     114  		if (filter_count == LZMA_FILTERS_MAX)
     115  			return LZMA_PROG_ERROR;
     116  
     117  		return_if_error(lzma_filter_flags_encode(
     118  				block->filters + filter_count,
     119  				out, &out_pos, out_size));
     120  
     121  	} while (block->filters[++filter_count].id != LZMA_VLI_UNKNOWN);
     122  
     123  	out[1] |= filter_count - 1;
     124  
     125  	// Padding
     126  	memzero(out + out_pos, out_size - out_pos);
     127  
     128  	// CRC32
     129  	write32le(out + out_size, lzma_crc32(out, out_size, 0));
     130  
     131  	return LZMA_OK;
     132  }