LibCore: Add a gzip implementation

Libraries/LibCore/CGzip.cpp

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

Libraries/LibCore/CGzip.h

@@ -0,0 +1,9 @@
+#include <AK/ByteBuffer.h>
+#include <AK/Optional.h>
+#include <AK/String.h>
+
+class Gzip {
+public:
+ static bool is_compressed(const ByteBuffer& data);
+ static Optional<ByteBuffer> decompress(const ByteBuffer& data);
+};

Libraries/LibCore/Makefile

@@ -23,7 +23,8 @@ OBJS = \
  CEvent.o \
  CProcessStatisticsReader.o \
  CDirIterator.o \
- CUserInfo.o
+ CUserInfo.o \
+ CGzip.o
 
 LIBRARY = libcore.a
 DEFINES += -DUSERLAND