gzip support for miniz

ext/tmxlite/src/TileLayer.cpp

@@ -29,10 +29,14 @@ source distribution.
 #include "tmxlite/FreeFuncs.hpp"
 #include "tmxlite/TileLayer.hpp"
 #include "tmxlite/detail/Log.hpp"
+#ifndef USE_ZLIB
+# include "tmxlite/detail/gzip.hpp"
+#endif
 
 #include <pugixml.hpp>
 #include <zstd.h>
 #include <sstream>
+#include <span>
 
 using namespace tmx;
 
@@ -140,8 +144,18 @@ void TileLayer::parseBase64(const pugi::xml_node& node)
             break;
         case CompressionType::GZip:
 #ifndef USE_ZLIB
-            Logger::log("Library must be built with USE_ZLIB for GZip compression", Logger::Type::Error);
-            return {};
+            {
+                byteData.resize(expectedSize);
+                const auto source = std::span(reinterpret_cast<const uint8_t*>(dataString.data()), dataString.size());
+
+                GZipReader reader;
+                if (!reader.OpenMemory(source) || !reader.Read(byteData) || !reader.Check())
+                {
+                    LOG("Failed to decompress layer data, node skipped.", Logger::Type::Error);
+                    return {};
+                }
+            }
+            break;
 #endif
             //[[fallthrough]];
         case CompressionType::Zlib:

ext/tmxlite/src/detail/gzip.cpp

@@ -0,0 +1,125 @@
+// gzip.cpp - portable memory miniz based gzip reader
+// SPDX-License-Identifier: Zlib
+// SPDX-FileCopyrightText: (c) 2024 a dinosaur
+
+#include "tmxlite/detail/gzip.hpp"
+#include <string_view>
+
+
+GZipReader::GZipReader() noexcept :
+	mSourceLen(0), mBytesRead(0),
+	mModificationTime(0), mCrc(0), mInputSize(0), mComputedCrc(0),
+	crc16(0), mFlags(0), mXflags(0), mOsId(0)
+{
+	tinfl_init(&mState);
+	mComputedCrc = static_cast<uint32_t>(mz_crc32(0, nullptr, 0));
+}
+
+bool GZipReader::OpenMemory(const std::span<const uint8_t> source) noexcept
+{
+	if (source.size() < 20)
+		return false;
+
+	auto it = std::cbegin(source), end = std::cend(source);
+
+	constexpr uint8_t magic[2] = { 0x1F, 0x8B };
+	if (*it++ != magic[0] || *it++ != magic[1])
+		return false;
+
+	constexpr uint8_t CM_DEFLATE = 8;
+	uint8_t compression = *it++;
+	if (compression != CM_DEFLATE)
+		return false;
+
+	mFlags = *it++;
+	mModificationTime = *it++;
+	mModificationTime |= *it++ << 8;
+	mModificationTime |= *it++ << 16;
+	mModificationTime |= *it++ << 24;
+	mXflags = *it++;
+	mOsId = *it++;
+
+	if (mFlags & FEXTRA)
+	{
+		// Skip "extra" field
+		if (it + 2 >= end)
+			return false;
+		uint16_t extraLen = *it++;
+		extraLen = *it++ << 8;
+		if (it + extraLen >= end)
+			return false;
+		it += extraLen;
+	}
+	if (mFlags & FNAME)
+	{
+		// Skip null-terminated name string
+		do
+		{
+			if (++it == end)
+				return false;
+		} while (*it != '\0');
+		if (++it == end)
+			return false;
+	}
+	if (mFlags & FCOMMENT)
+	{
+		// Skip null-terminated comment string
+		do
+		{
+			if (++it == end)
+				return false;
+		} while (*it != '\0');
+		if (++it == end)
+			return false;
+	}
+	if (mFlags & FHCRC)
+	{
+		if (it + 2 >= end)
+			return false;
+		crc16 = *it++;
+		crc16 |= *it++;
+	}
+
+	mIt = it;
+	mSourceLen = end - it - 8;
+
+	it += mSourceLen;
+	mCrc = *it++;
+	mCrc |= *it++ << 8;
+	mCrc |= *it++ << 16;
+	mCrc |= *it++ << 24;
+	mInputSize = *it++;
+	mInputSize |= *it++ << 8;
+	mInputSize |= *it++ << 16;
+	mInputSize |= *it++ << 24;
+
+	return true;
+}
+
+bool GZipReader::Read(std::span<uint8_t> out) noexcept
+{
+	size_t outLen = out.size();
+	auto res = tinfl_decompress(&mState,
+		static_cast<const mz_uint8*>(&*mIt), &mSourceLen,
+		static_cast<mz_uint8*>(out.data()), static_cast<mz_uint8*>(out.data()), &outLen,
+		TINFL_FLAG_USING_NON_WRAPPING_OUTPUT_BUF);
+	if (res != TINFL_STATUS_DONE)
+		return false;
+
+	mIt += outLen;
+	mBytesRead += outLen;
+	mComputedCrc = static_cast<uint32_t>(mz_crc32(static_cast<mz_ulong>(mComputedCrc), out.data(), outLen));
+
+	return true;
+}
+
+bool GZipReader::Check() const noexcept
+{
+	if (mComputedCrc != mCrc)
+		return false;
+
+	if (static_cast<uint32_t>(mBytesRead & UINT32_MAX) != mInputSize)
+		return false;
+
+	return true;
+}