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/*
* Copyright (c) 2020-2022, the SerenityOS developers.
* Copyright (c) 2021, Idan Horowitz <idan.horowitz@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibCompress/Gzip.h>
#include <AK/DeprecatedString.h>
#include <AK/MemoryStream.h>
#include <LibCore/DateTime.h>
#include <LibCore/MemoryStream.h>
namespace Compress {
bool GzipDecompressor::is_likely_compressed(ReadonlyBytes bytes)
{
return bytes.size() >= 2 && bytes[0] == gzip_magic_1 && bytes[1] == gzip_magic_2;
}
bool BlockHeader::valid_magic_number() const
{
return identification_1 == gzip_magic_1 && identification_2 == gzip_magic_2;
}
bool BlockHeader::supported_by_implementation() const
{
if (compression_method != 0x08) {
// RFC 1952 does not define any compression methods other than deflate.
return false;
}
if (flags > Flags::MAX) {
// RFC 1952 does not define any more flags.
return false;
}
return true;
}
GzipDecompressor::GzipDecompressor(NonnullOwnPtr<Core::Stream::Stream> stream)
: m_input_stream(move(stream))
{
}
GzipDecompressor::~GzipDecompressor()
{
m_current_member.clear();
}
ErrorOr<Bytes> GzipDecompressor::read(Bytes bytes)
{
size_t total_read = 0;
while (total_read < bytes.size()) {
if (is_eof())
break;
auto slice = bytes.slice(total_read);
if (m_current_member.has_value()) {
auto current_slice = TRY(current_member().m_stream.read(slice));
current_member().m_checksum.update(current_slice);
current_member().m_nread += current_slice.size();
if (current_slice.size() < slice.size()) {
LittleEndian<u32> crc32, input_size;
TRY(m_input_stream->read(crc32.bytes()));
TRY(m_input_stream->read(input_size.bytes()));
if (crc32 != current_member().m_checksum.digest())
return Error::from_string_literal("Stored CRC32 does not match the calculated CRC32 of the current member");
if (input_size != current_member().m_nread)
return Error::from_string_literal("Input size does not match the number of read bytes");
m_current_member.clear();
total_read += current_slice.size();
continue;
}
total_read += current_slice.size();
continue;
} else {
auto current_partial_header_slice = Bytes { m_partial_header, sizeof(BlockHeader) }.slice(m_partial_header_offset);
auto current_partial_header_data = TRY(m_input_stream->read(current_partial_header_slice));
m_partial_header_offset += current_partial_header_data.size();
if (is_eof())
break;
if (m_partial_header_offset < sizeof(BlockHeader)) {
break; // partial header read
}
m_partial_header_offset = 0;
BlockHeader header = *(reinterpret_cast<BlockHeader*>(m_partial_header));
if (!header.valid_magic_number())
return Error::from_string_literal("Header does not have a valid magic number");
if (!header.supported_by_implementation())
return Error::from_string_literal("Header is not supported by implementation");
if (header.flags & Flags::FEXTRA) {
LittleEndian<u16> subfield_id, length;
TRY(m_input_stream->read(subfield_id.bytes()));
TRY(m_input_stream->read(length.bytes()));
TRY(m_input_stream->discard(length));
}
auto discard_string = [&]() -> ErrorOr<void> {
char next_char;
do {
TRY(m_input_stream->read({ &next_char, sizeof(next_char) }));
} while (next_char);
return {};
};
if (header.flags & Flags::FNAME)
TRY(discard_string());
if (header.flags & Flags::FCOMMENT)
TRY(discard_string());
if (header.flags & Flags::FHCRC) {
LittleEndian<u16> crc16;
TRY(m_input_stream->read(crc16.bytes()));
// FIXME: we should probably verify this instead of just assuming it matches
}
m_current_member.emplace(header, *m_input_stream);
continue;
}
}
return bytes.slice(0, total_read);
}
Optional<DeprecatedString> GzipDecompressor::describe_header(ReadonlyBytes bytes)
{
if (bytes.size() < sizeof(BlockHeader))
return {};
auto& header = *(reinterpret_cast<BlockHeader const*>(bytes.data()));
if (!header.valid_magic_number() || !header.supported_by_implementation())
return {};
LittleEndian<u32> original_size = *reinterpret_cast<u32 const*>(bytes.offset(bytes.size() - sizeof(u32)));
return DeprecatedString::formatted("last modified: {}, original size {}", Core::DateTime::from_timestamp(header.modification_time).to_deprecated_string(), (u32)original_size);
}
ErrorOr<ByteBuffer> GzipDecompressor::decompress_all(ReadonlyBytes bytes)
{
auto memory_stream = TRY(Core::Stream::FixedMemoryStream::construct(bytes));
auto gzip_stream = make<GzipDecompressor>(move(memory_stream));
DuplexMemoryStream output_stream;
auto buffer = TRY(ByteBuffer::create_uninitialized(4096));
while (!gzip_stream->is_eof()) {
auto const data = TRY(gzip_stream->read(buffer));
output_stream.write_or_error(data);
}
return output_stream.copy_into_contiguous_buffer();
}
bool GzipDecompressor::is_eof() const { return m_input_stream->is_eof(); }
ErrorOr<size_t> GzipDecompressor::write(ReadonlyBytes)
{
VERIFY_NOT_REACHED();
}
GzipCompressor::GzipCompressor(OutputStream& stream)
: m_output_stream(stream)
{
}
size_t GzipCompressor::write(ReadonlyBytes bytes)
{
BlockHeader header;
header.identification_1 = 0x1f;
header.identification_2 = 0x8b;
header.compression_method = 0x08;
header.flags = 0;
header.modification_time = 0;
header.extra_flags = 3; // DEFLATE sets 2 for maximum compression and 4 for minimum compression
header.operating_system = 3; // unix
m_output_stream << Bytes { &header, sizeof(header) };
DeflateCompressor compressed_stream { m_output_stream };
VERIFY(compressed_stream.write_or_error(bytes));
compressed_stream.final_flush();
Crypto::Checksum::CRC32 crc32;
crc32.update(bytes);
LittleEndian<u32> digest = crc32.digest();
LittleEndian<u32> size = bytes.size();
m_output_stream << digest << size;
return bytes.size();
}
bool GzipCompressor::write_or_error(ReadonlyBytes bytes)
{
if (write(bytes) < bytes.size()) {
set_fatal_error();
return false;
}
return true;
}
Optional<ByteBuffer> GzipCompressor::compress_all(ReadonlyBytes bytes)
{
DuplexMemoryStream output_stream;
GzipCompressor gzip_stream { output_stream };
gzip_stream.write_or_error(bytes);
if (gzip_stream.handle_any_error())
return {};
return output_stream.copy_into_contiguous_buffer();
}
}
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