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35c26a06fc
Since it's used both by CGzip and PNGLoader, it seems most appropriate to keep this in LibCore.
123 lines
3.6 KiB
C++
123 lines
3.6 KiB
C++
#include "CGzip.h"
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#include <AK/ByteBuffer.h>
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#include <AK/Optional.h>
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#include <LibCore/puff.h>
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#include <LibCore/puff.c>
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#include <limits.h>
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#include <stddef.h>
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bool CGzip::is_compressed(const ByteBuffer& data)
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{
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return data.size() > 2 && data[0] == 0x1F && data[1] == 0x8b;
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}
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// skips the gzip header
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// see: https://tools.ietf.org/html/rfc1952#page-5
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static Optional<ByteBuffer> get_gzip_payload(const ByteBuffer& data)
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{
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int current = 0;
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auto read_byte = [&]() {
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if (current >= data.size()) {
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ASSERT_NOT_REACHED();
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return (u8)0;
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}
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// dbg() << "read_byte: " << String::format("%x", data[current]);
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return data[current++];
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};
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dbg() << "get_gzip_payload: Skipping over gzip header.";
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// Magic Header
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if (read_byte() != 0x1F || read_byte() != 0x8B) {
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dbg() << "get_gzip_payload: Wrong magic number.";
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return Optional<ByteBuffer>();
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}
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// Compression method
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auto method = read_byte();
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if (method != 8) {
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dbg() << "get_gzip_payload: Wrong compression method = " << method;
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return Optional<ByteBuffer>();
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}
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u8 flags = read_byte();
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// Timestamp, Extra flags, OS
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current += 6;
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// FEXTRA
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if (flags & 4) {
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u16 length = read_byte() & read_byte() << 8;
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dbg() << "get_gzip_payload: Header has FEXTRA flag set. Length = " << length;
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current += length;
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}
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// FNAME
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if (flags & 8) {
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dbg() << "get_gzip_payload: Header has FNAME flag set.";
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while (read_byte() != '\0')
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;
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}
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// FCOMMENT
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if (flags & 16) {
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dbg() << "get_gzip_payload: Header has FCOMMENT flag set.";
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while (read_byte() != '\0')
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;
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}
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// FHCRC
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if (flags & 2) {
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dbg() << "get_gzip_payload: Header has FHCRC flag set.";
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current += 2;
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}
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auto new_size = data.size() - current;
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dbg() << "get_gzip_payload: Returning slice from " << current << " with size " << new_size;
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return data.slice(current, new_size);
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}
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Optional<ByteBuffer> CGzip::decompress(const ByteBuffer& data)
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{
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ASSERT(is_compressed(data));
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dbg() << "Gzip::decompress: Decompressing gzip compressed data. Size = " << data.size();
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auto optional_payload = get_gzip_payload(data);
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if (!optional_payload.has_value()) {
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return Optional<ByteBuffer>();
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}
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auto source = optional_payload.value();
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unsigned long source_len = source.size();
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auto destination = ByteBuffer::create_uninitialized(1024);
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while (true) {
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unsigned long destination_len = destination.size();
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// FIXME: dbg() cannot take ulong?
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// dbg() << "Gzip::decompress: Calling puff()\n"
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// << " destination_data = " << destination.data() << "\n"
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// << " destination_len = " << (int)destination_len << "\n"
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// << " source_data = " << source.data() << "\n"
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// << " source_len = " << (int)source_len;
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auto puff_ret = puff(
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destination.data(), &destination_len,
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source.data(), &source_len);
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if (puff_ret == 0) {
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dbg() << "Gzip::decompress: Decompression success.";
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break;
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}
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if (puff_ret == 1) {
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// FIXME: Find a better way of decompressing without needing to try over and over again.
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dbg() << "Gzip::decompress: Output buffer exhausted. Growing.";
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destination.grow(destination.size() * 2);
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} else {
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dbg() << "Gzip::decompress: Error. puff() returned: " << puff_ret;
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ASSERT_NOT_REACHED();
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}
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}
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return destination;
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}
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