src/liblzma/common/stream_buffer_encoder.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       stream_buffer_encoder.c
   6 /// \brief      Single-call .xz Stream encoder
   7 //
   8 //  Author:     Lasse Collin
   9 //
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 #include "common.h"
  13 #include "index.h"
  14
  15
  16 /// Maximum size of Index that has exactly one Record.
  17 /// Index Indicator + Number of Records + Record + CRC32 rounded up to
  18 /// the next multiple of four.
  19 #define INDEX_BOUND ((1 + 1 + 2 * LZMA_VLI_BYTES_MAX + 4 + 3) & ~3)
  20
  21 /// Stream Header, Stream Footer, and Index
  22 #define HEADERS_BOUND (2 * LZMA_STREAM_HEADER_SIZE + INDEX_BOUND)
  23
  24
  25 extern LZMA_API(size_t)
  26 lzma_stream_buffer_bound(size_t uncompressed_size)
  27 {
  28         // Get the maximum possible size of a Block.
  29         const size_t block_bound = lzma_block_buffer_bound(uncompressed_size);
  30         if (block_bound == 0)
  31                 return 0;
  32
  33         // Catch the possible integer overflow and also prevent the size of
  34         // the Stream exceeding LZMA_VLI_MAX (theoretically possible on
  35         // 64-bit systems).
  36         if (my_min(SIZE_MAX, LZMA_VLI_MAX) - block_bound < HEADERS_BOUND)
  37                 return 0;
  38
  39         return block_bound + HEADERS_BOUND;
  40 }
  41
  42
  43 extern LZMA_API(lzma_ret)
  44 lzma_stream_buffer_encode(lzma_filter *filters, lzma_check check,
  45                 const lzma_allocator *allocator,
  46                 const uint8_t *in, size_t in_size,
  47                 uint8_t *out, size_t *out_pos_ptr, size_t out_size)
  48 {
  49         // Sanity checks
  50         if (filters == NULL || (unsigned int)(check) > LZMA_CHECK_ID_MAX
  51                         || (in == NULL && in_size != 0) || out == NULL
  52                         || out_pos_ptr == NULL || *out_pos_ptr > out_size)
  53                 return LZMA_PROG_ERROR;
  54
  55         if (!lzma_check_is_supported(check))
  56                 return LZMA_UNSUPPORTED_CHECK;
  57
  58         // Note for the paranoids: Index encoder prevents the Stream from
  59         // getting too big and still being accepted with LZMA_OK, and Block
  60         // encoder catches if the input is too big. So we don't need to
  61         // separately check if the buffers are too big.
  62
  63         // Use a local copy. We update *out_pos_ptr only if everything
  64         // succeeds.
  65         size_t out_pos = *out_pos_ptr;
  66
  67         // Check that there's enough space for both Stream Header and
  68         // Stream Footer.
  69         if (out_size - out_pos <= 2 * LZMA_STREAM_HEADER_SIZE)
  70                 return LZMA_BUF_ERROR;
  71
  72         // Reserve space for Stream Footer so we don't need to check for
  73         // available space again before encoding Stream Footer.
  74         out_size -= LZMA_STREAM_HEADER_SIZE;
  75
  76         // Encode the Stream Header.
  77         lzma_stream_flags stream_flags = {
  78                 .version = 0,
  79                 .check = check,
  80         };
  81
  82         if (lzma_stream_header_encode(&stream_flags, out + out_pos)
  83                         != LZMA_OK)
  84                 return LZMA_PROG_ERROR;
  85
  86         out_pos += LZMA_STREAM_HEADER_SIZE;
  87
  88         // Encode a Block but only if there is at least one byte of input.
  89         lzma_block block = {
  90                 .version = 0,
  91                 .check = check,
  92                 .filters = filters,
  93         };
  94
  95         if (in_size > 0)
  96                 return_if_error(lzma_block_buffer_encode(&block, allocator,
  97                                 in, in_size, out, &out_pos, out_size));
  98
  99         // Index
 100         {
 101                 // Create an Index. It will have one Record if there was
 102                 // at least one byte of input to encode. Otherwise the
 103                 // Index will be empty.
 104                 lzma_index *i = lzma_index_init(allocator);
 105                 if (i == NULL)
 106                         return LZMA_MEM_ERROR;
 107
 108                 lzma_ret ret = LZMA_OK;
 109
 110                 if (in_size > 0)
 111                         ret = lzma_index_append(i, allocator,
 112                                         lzma_block_unpadded_size(&block),
 113                                         block.uncompressed_size);
 114
 115                 // If adding the Record was successful, encode the Index
 116                 // and get its size which will be stored into Stream Footer.
 117                 if (ret == LZMA_OK) {
 118                         ret = lzma_index_buffer_encode(
 119                                         i, out, &out_pos, out_size);
 120
 121                         stream_flags.backward_size = lzma_index_size(i);
 122                 }
 123
 124                 lzma_index_end(i, allocator);
 125
 126                 if (ret != LZMA_OK)
 127                         return ret;
 128         }
 129
 130         // Stream Footer. We have already reserved space for this.
 131         if (lzma_stream_footer_encode(&stream_flags, out + out_pos)
 132                         != LZMA_OK)
 133                 return LZMA_PROG_ERROR;
 134
 135         out_pos += LZMA_STREAM_HEADER_SIZE;
 136
 137         // Everything went fine, make the new output position available
 138         // to the application.
 139         *out_pos_ptr = out_pos;
 140         return LZMA_OK;
 141 }