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