integrate lzma

[zpackage] / lzma / common / block_header_decoder.c

diff --git a/lzma/common/block_header_decoder.c b/lzma/common/block_header_decoder.c
new file mode 100644 (file)
index 0000000..1dd982f
--- /dev/null
+++ b/lzma/common/block_header_decoder.c
@@ -0,0 +1,124 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file       block_header_decoder.c
+/// \brief      Decodes Block Header from .xz files
+//
+//  Author:     Lasse Collin
+//
+//  This file has been put into the public domain.
+//  You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "common.h"
+#include "check.h"
+
+
+static void
+free_properties(lzma_block *block, const lzma_allocator *allocator)
+{
+       // Free allocated filter options. The last array member is not
+       // touched after the initialization in the beginning of
+       // lzma_block_header_decode(), so we don't need to touch that here.
+       for (size_t i = 0; i < LZMA_FILTERS_MAX; ++i) {
+               lzma_free(block->filters[i].options, allocator);
+               block->filters[i].id = LZMA_VLI_UNKNOWN;
+               block->filters[i].options = NULL;
+       }
+
+       return;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_block_header_decode(lzma_block *block,
+               const lzma_allocator *allocator, const uint8_t *in)
+{
+       // NOTE: We consider the header to be corrupt not only when the
+       // CRC32 doesn't match, but also when variable-length integers
+       // are invalid or over 63 bits, or if the header is too small
+       // to contain the claimed information.
+
+       // Initialize the filter options array. This way the caller can
+       // safely free() the options even if an error occurs in this function.
+       for (size_t i = 0; i <= LZMA_FILTERS_MAX; ++i) {
+               block->filters[i].id = LZMA_VLI_UNKNOWN;
+               block->filters[i].options = NULL;
+       }
+
+       // Versions 0 and 1 are supported. If a newer version was specified,
+       // we need to downgrade it.
+       if (block->version > 1)
+               block->version = 1;
+
+       // This isn't a Block Header option, but since the decompressor will
+       // read it if version >= 1, it's better to initialize it here than
+       // to expect the caller to do it since in almost all cases this
+       // should be false.
+       block->ignore_check = false;
+
+       // Validate Block Header Size and Check type. The caller must have
+       // already set these, so it is a programming error if this test fails.
+       if (lzma_block_header_size_decode(in[0]) != block->header_size
+                       || (unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
+               return LZMA_PROG_ERROR;
+
+       // Exclude the CRC32 field.
+       const size_t in_size = block->header_size - 4;
+
+       // Verify CRC32
+       if (lzma_crc32(in, in_size, 0) != unaligned_read32le(in + in_size))
+               return LZMA_DATA_ERROR;
+
+       // Check for unsupported flags.
+       if (in[1] & 0x3C)
+               return LZMA_OPTIONS_ERROR;
+
+       // Start after the Block Header Size and Block Flags fields.
+       size_t in_pos = 2;
+
+       // Compressed Size
+       if (in[1] & 0x40) {
+               return_if_error(lzma_vli_decode(&block->compressed_size,
+                               NULL, in, &in_pos, in_size));
+
+               // Validate Compressed Size. This checks that it isn't zero
+               // and that the total size of the Block is a valid VLI.
+               if (lzma_block_unpadded_size(block) == 0)
+                       return LZMA_DATA_ERROR;
+       } else {
+               block->compressed_size = LZMA_VLI_UNKNOWN;
+       }
+
+       // Uncompressed Size
+       if (in[1] & 0x80)
+               return_if_error(lzma_vli_decode(&block->uncompressed_size,
+                               NULL, in, &in_pos, in_size));
+       else
+               block->uncompressed_size = LZMA_VLI_UNKNOWN;
+
+       // Filter Flags
+       const size_t filter_count = (in[1] & 3) + 1;
+       for (size_t i = 0; i < filter_count; ++i) {
+               const lzma_ret ret = lzma_filter_flags_decode(
+                               &block->filters[i], allocator,
+                               in, &in_pos, in_size);
+               if (ret != LZMA_OK) {
+                       free_properties(block, allocator);
+                       return ret;
+               }
+       }
+
+       // Padding
+       while (in_pos < in_size) {
+               if (in[in_pos++] != 0x00) {
+                       free_properties(block, allocator);
+
+                       // Possibly some new field present so use
+                       // LZMA_OPTIONS_ERROR instead of LZMA_DATA_ERROR.
+                       return LZMA_OPTIONS_ERROR;
+               }
+       }
+
+       return LZMA_OK;
+}