mirrors/serenity
1
0
Fork 0
mirror of https://github.com/SerenityOS/serenity.git synced 2025-01-23 18:02:05 -05:00
Code Issues Projects Releases Packages Wiki Activity

LibCompress: Move loading XZ blocks into its own function

Browse source
This commit is contained in:
Tim Schumacher 2023-04-05 16:55:25 +02:00 • committed by Brian Gianforcaro
parent e6b1e1bb33
commit e9789e9f36
2 changed files with 126 additions and 119 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

244
Userland/Libraries/LibCompress/Xz.cpp
View file

@ -252,6 +252,130 @@ ErrorOr<bool> XzDecompressor::load_next_stream()
return true;
}
ErrorOr<void> XzDecompressor::load_next_block(u8 encoded_block_header_size)
{
// We already read the encoded Block Header size (one byte) to determine that this is not an Index.
m_current_block_start_offset = m_stream->read_bytes() - 1;
// Ensure that the start of the block is aligned to a multiple of four (in theory, everything in XZ is).
VERIFY(m_current_block_start_offset % 4 == 0);
// 3.1.1. Block Header Size:
// "This field contains the size of the Block Header field,
// including the Block Header Size field itself. Valid values are
// in the range [0x01, 0xFF], which indicate the size of the Block
// Header as multiples of four bytes, minimum size being eight
// bytes:
//
// real_header_size = (encoded_header_size + 1) * 4;"
u64 block_header_size = (encoded_block_header_size + 1) * 4;
// Read the whole header into a buffer to allow calculating the CRC32 later (3.1.7. CRC32).
auto header = TRY(ByteBuffer::create_uninitialized(block_header_size));
header[0] = encoded_block_header_size;
TRY(m_stream->read_until_filled(header.span().slice(1)));
FixedMemoryStream header_stream { header.span().slice(1) };
// 3.1.2. Block Flags:
// "If any reserved bit is set, the decoder MUST indicate an error.
// It is possible that there is a new field present which the
// decoder is not aware of, and can thus parse the Block Header
// incorrectly."
auto flags = TRY(header_stream.read_value<XzBlockFlags>());
if (flags.reserved != 0)
return Error::from_string_literal("XZ block header has reserved non-null block flag bits");
MaybeOwned<Stream> new_block_stream { *m_stream };
// 3.1.3. Compressed Size:
// "This field is present only if the appropriate bit is set in
// the Block Flags field (see Section 3.1.2)."
if (flags.compressed_size_present) {
// "Compressed Size is stored using the encoding described in Section 1.2."
u64 compressed_size = TRY(header_stream.read_value<XzMultibyteInteger>());
// "The Compressed Size field contains the size of the Compressed
// Data field, which MUST be non-zero."
if (compressed_size == 0)
return Error::from_string_literal("XZ block header contains a compressed size of zero");
new_block_stream = TRY(try_make<ConstrainedStream>(move(new_block_stream), compressed_size));
}
// 3.1.4. Uncompressed Size:
// "This field is present only if the appropriate bit is set in
// the Block Flags field (see Section 3.1.2)."
if (flags.uncompressed_size_present) {
// "Uncompressed Size is stored using the encoding described in Section 1.2."
u64 uncompressed_size = TRY(header_stream.read_value<XzMultibyteInteger>());
m_current_block_expected_uncompressed_size = uncompressed_size;
} else {
m_current_block_expected_uncompressed_size.clear();
}
// 3.1.5. List of Filter Flags:
// "The number of Filter Flags fields is stored in the Block Flags
// field (see Section 3.1.2)."
for (size_t i = 0; i < flags.number_of_filters(); i++) {
// "The format of each Filter Flags field is as follows:
// Both Filter ID and Size of Properties are stored using the
// encoding described in Section 1.2."
u64 filter_id = TRY(header_stream.read_value<XzMultibyteInteger>());
u64 size_of_properties = TRY(header_stream.read_value<XzMultibyteInteger>());
// "Size of Properties indicates the size of the Filter Properties field as bytes."
auto filter_properties = TRY(ByteBuffer::create_uninitialized(size_of_properties));
TRY(header_stream.read_until_filled(filter_properties));
// 5.3.1. LZMA2
if (filter_id == 0x21) {
if (size_of_properties < sizeof(XzFilterLzma2Properties))
return Error::from_string_literal("XZ LZMA2 filter has a smaller-than-needed properties size");
auto properties = reinterpret_cast<XzFilterLzma2Properties*>(filter_properties.data());
TRY(properties->validate());
new_block_stream = TRY(Lzma2Decompressor::create_from_raw_stream(move(new_block_stream), properties->dictionary_size()));
continue;
}
return Error::from_string_literal("XZ block header contains unknown filter ID");
}
// 3.1.6. Header Padding:
// "This field contains as many null byte as it is needed to make
// the Block Header have the size specified in Block Header Size."
constexpr size_t size_of_block_header_size = 1;
constexpr size_t size_of_crc32 = 4;
while (MUST(header_stream.tell()) < block_header_size - size_of_block_header_size - size_of_crc32) {
auto padding_byte = TRY(header_stream.read_value<u8>());
// "If any of the bytes are not null bytes, the decoder MUST
// indicate an error."
if (padding_byte != 0)
return Error::from_string_literal("XZ block header padding contains non-null bytes");
}
// 3.1.7. CRC32:
// "The CRC32 is calculated over everything in the Block Header
// field except the CRC32 field itself.
Crypto::Checksum::CRC32 calculated_header_crc32 { header.span().trim(block_header_size - size_of_crc32) };
// It is stored as an unsigned 32-bit little endian integer.
u32 stored_header_crc32 = TRY(header_stream.read_value<LittleEndian<u32>>());
// If the calculated value does not match the stored one, the decoder MUST indicate
// an error."
if (calculated_header_crc32.digest() != stored_header_crc32)
return Error::from_string_literal("Stored XZ block header CRC32 does not match the stored CRC32");
m_current_block_stream = move(new_block_stream);
m_current_block_uncompressed_size = 0;
return {};
}
ErrorOr<void> XzDecompressor::finish_current_block()
{
auto unpadded_size = m_stream->read_bytes() - m_current_block_start_offset;
@ -417,11 +541,6 @@ ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
TRY(finish_current_block());
}
auto start_of_current_block = m_stream->read_bytes();
// Ensure that the start of the block is aligned to a multiple of four (in theory, everything in XZ is).
VERIFY(start_of_current_block % 4 == 0);
// The first byte between Block Header (3.1.1. Block Header Size) and Index (4.1. Index Indicator) overlap.
// Block header sizes have valid values in the range of [0x01, 0xFF], the only valid value for an Index Indicator is therefore 0x00.
auto encoded_block_header_size_or_index_indicator = TRY(m_stream->read_value<u8>());
@ -436,120 +555,7 @@ ErrorOr<Bytes> XzDecompressor::read_some(Bytes bytes)
return bytes.trim(0);
}
m_current_block_start_offset = start_of_current_block;
// 3.1.1. Block Header Size:
// "This field contains the size of the Block Header field,
// including the Block Header Size field itself. Valid values are
// in the range [0x01, 0xFF], which indicate the size of the Block
// Header as multiples of four bytes, minimum size being eight
// bytes:
//
// real_header_size = (encoded_header_size + 1) * 4;"
u64 block_header_size = (encoded_block_header_size_or_index_indicator + 1) * 4;
// Read the whole header into a buffer to allow calculating the CRC32 later (3.1.7. CRC32).
auto header = TRY(ByteBuffer::create_uninitialized(block_header_size));
header[0] = encoded_block_header_size_or_index_indicator;
TRY(m_stream->read_until_filled(header.span().slice(1)));
FixedMemoryStream header_stream { header.span().slice(1) };
// 3.1.2. Block Flags:
// "If any reserved bit is set, the decoder MUST indicate an error.
// It is possible that there is a new field present which the
// decoder is not aware of, and can thus parse the Block Header
// incorrectly."
auto flags = TRY(header_stream.read_value<XzBlockFlags>());
if (flags.reserved != 0)
return Error::from_string_literal("XZ block header has reserved non-null block flag bits");
MaybeOwned<Stream> new_block_stream { *m_stream };
// 3.1.3. Compressed Size:
// "This field is present only if the appropriate bit is set in
// the Block Flags field (see Section 3.1.2)."
if (flags.compressed_size_present) {
// "Compressed Size is stored using the encoding described in Section 1.2."
u64 compressed_size = TRY(header_stream.read_value<XzMultibyteInteger>());
// "The Compressed Size field contains the size of the Compressed
// Data field, which MUST be non-zero."
if (compressed_size == 0)
return Error::from_string_literal("XZ block header contains a compressed size of zero");
new_block_stream = TRY(try_make<ConstrainedStream>(move(new_block_stream), compressed_size));
}
// 3.1.4. Uncompressed Size:
// "This field is present only if the appropriate bit is set in
// the Block Flags field (see Section 3.1.2)."
if (flags.uncompressed_size_present) {
// "Uncompressed Size is stored using the encoding described in Section 1.2."
u64 uncompressed_size = TRY(header_stream.read_value<XzMultibyteInteger>());
m_current_block_expected_uncompressed_size = uncompressed_size;
} else {
m_current_block_expected_uncompressed_size.clear();
}
// 3.1.5. List of Filter Flags:
// "The number of Filter Flags fields is stored in the Block Flags
// field (see Section 3.1.2)."
for (size_t i = 0; i < flags.number_of_filters(); i++) {
// "The format of each Filter Flags field is as follows:
// Both Filter ID and Size of Properties are stored using the
// encoding described in Section 1.2."
u64 filter_id = TRY(header_stream.read_value<XzMultibyteInteger>());
u64 size_of_properties = TRY(header_stream.read_value<XzMultibyteInteger>());
// "Size of Properties indicates the size of the Filter Properties field as bytes."
auto filter_properties = TRY(ByteBuffer::create_uninitialized(size_of_properties));
TRY(header_stream.read_until_filled(filter_properties));
// 5.3.1. LZMA2
if (filter_id == 0x21) {
if (size_of_properties < sizeof(XzFilterLzma2Properties))
return Error::from_string_literal("XZ LZMA2 filter has a smaller-than-needed properties size");
auto properties = reinterpret_cast<XzFilterLzma2Properties*>(filter_properties.data());
TRY(properties->validate());
new_block_stream = TRY(Lzma2Decompressor::create_from_raw_stream(move(new_block_stream), properties->dictionary_size()));
continue;
}
return Error::from_string_literal("XZ block header contains unknown filter ID");
}
// 3.1.6. Header Padding:
// "This field contains as many null byte as it is needed to make
// the Block Header have the size specified in Block Header Size."
constexpr size_t size_of_block_header_size = 1;
constexpr size_t size_of_crc32 = 4;
while (MUST(header_stream.tell()) < block_header_size - size_of_block_header_size - size_of_crc32) {
auto padding_byte = TRY(header_stream.read_value<u8>());
// "If any of the bytes are not null bytes, the decoder MUST
// indicate an error."
if (padding_byte != 0)
return Error::from_string_literal("XZ block header padding contains non-null bytes");
}
// 3.1.7. CRC32:
// "The CRC32 is calculated over everything in the Block Header
// field except the CRC32 field itself.
Crypto::Checksum::CRC32 calculated_header_crc32 { header.span().trim(block_header_size - size_of_crc32) };
// It is stored as an unsigned 32-bit little endian integer.
u32 stored_header_crc32 = TRY(header_stream.read_value<LittleEndian<u32>>());
// If the calculated value does not match the stored one, the decoder MUST indicate
// an error."
if (calculated_header_crc32.digest() != stored_header_crc32)
return Error::from_string_literal("Stored XZ block header CRC32 does not match the stored CRC32");
m_current_block_stream = move(new_block_stream);
m_current_block_uncompressed_size = 0;
TRY(load_next_block(encoded_block_header_size_or_index_indicator));
}
auto result = TRY((*m_current_block_stream)->read_some(bytes));

1
Userland/Libraries/LibCompress/Xz.h
View file

@ -112,6 +112,7 @@ private:
XzDecompressor(NonnullOwnPtr<CountingStream>);
ErrorOr<bool> load_next_stream();
ErrorOr<void> load_next_block(u8 encoded_block_header_size);
ErrorOr<void> finish_current_block();
ErrorOr<void> finish_current_stream();