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 unaligned_write32le(out + out_size, lzma_crc32(out, out_size, 0)); 130 131 return LZMA_OK; 132 } 133