Add GZIP compression support

- Fix a wrong call in PoolByteArray::compress

core/bind/core_bind.cpp

@@ -1780,6 +1780,7 @@ void _File::_bind_methods() {
 	BIND_CONSTANT(COMPRESSION_FASTLZ);
 	BIND_CONSTANT(COMPRESSION_DEFLATE);
 	BIND_CONSTANT(COMPRESSION_ZSTD);
+	BIND_CONSTANT(COMPRESSION_GZIP);
 }
 
 _File::_File() {

core/bind/core_bind.h

@@ -372,7 +372,8 @@ public:
 	enum CompressionMode {
 		COMPRESSION_FASTLZ = Compression::MODE_FASTLZ,
 		COMPRESSION_DEFLATE = Compression::MODE_DEFLATE,
-		COMPRESSION_ZSTD = Compression::MODE_ZSTD
+		COMPRESSION_ZSTD = Compression::MODE_ZSTD,
+		COMPRESSION_GZIP = Compression::MODE_GZIP
 	};
 
 	Error open_encrypted(const String &p_path, int p_mode_flags, const Vector<uint8_t> &p_key);

core/global_config.cpp

@@ -974,6 +974,8 @@ GlobalConfig::GlobalConfig() {
 	custom_prop_info["compression/zstd/compression_level"] = PropertyInfo(Variant::INT, "compression/zstd/compression_level", PROPERTY_HINT_RANGE, "1,22,1");
 	GLOBAL_DEF("compression/zlib/compression_level", Z_DEFAULT_COMPRESSION);
 	custom_prop_info["compression/zlib/compression_level"] = PropertyInfo(Variant::INT, "compression/zlib/compression_level", PROPERTY_HINT_RANGE, "-1,9,1");
+	GLOBAL_DEF("compression/gzip/compression_level", Z_DEFAULT_COMPRESSION);
+	custom_prop_info["compression/gzip/compression_level"] = PropertyInfo(Variant::INT, "compression/gzip/compression_level", PROPERTY_HINT_RANGE, "-1,9,1");
 
 	using_datapack = false;
 }

core/io/compression.cpp

@@ -52,23 +52,22 @@ int Compression::compress(uint8_t *p_dst, const uint8_t *p_src, int p_src_size,
 			}
 
 		} break;
-		case MODE_DEFLATE: {
+		case MODE_DEFLATE:
+		case MODE_GZIP: {
+
+			int window_bits = p_mode == MODE_DEFLATE ? 15 : 15 + 16;
 
 			z_stream strm;
 			strm.zalloc = zipio_alloc;
 			strm.zfree = zipio_free;
 			strm.opaque = Z_NULL;
-			int level = GLOBAL_GET("compression/zlib/compression_level");
-			int err = deflateInit(&strm, level);
+			int level = p_mode == MODE_DEFLATE ? GLOBAL_GET("compression/zlib/compression_level") : GLOBAL_GET("compression/gzip/compression_level");
+			int err = deflateInit2(&strm, level, Z_DEFLATED, window_bits, 8, Z_DEFAULT_STRATEGY);
 			if (err != Z_OK)
 				return -1;
 
 			strm.avail_in = p_src_size;
 			int aout = deflateBound(&strm, p_src_size);
-			/*if (aout>p_src_size) {
-				deflateEnd(&strm);
-				return -1;
-			}*/
 			strm.avail_out = aout;
 			strm.next_in = (Bytef *)p_src;
 			strm.next_out = p_dst;
@@ -100,13 +99,16 @@ int Compression::get_max_compressed_buffer_size(int p_src_size, Mode p_mode) {
 			return ss;
 
 		} break;
-		case MODE_DEFLATE: {
+		case MODE_DEFLATE:
+		case MODE_GZIP: {
+
+			int window_bits = p_mode == MODE_DEFLATE ? 15 : 15 + 16;
 
 			z_stream strm;
 			strm.zalloc = zipio_alloc;
 			strm.zfree = zipio_free;
 			strm.opaque = Z_NULL;
-			int err = deflateInit(&strm, Z_DEFAULT_COMPRESSION);
+			int err = deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, window_bits, 8, Z_DEFAULT_STRATEGY);
 			if (err != Z_OK)
 				return -1;
 			int aout = deflateBound(&strm, p_src_size);
@@ -138,7 +140,10 @@ int Compression::decompress(uint8_t *p_dst, int p_dst_max_size, const uint8_t *p
 			}
 			return ret_size;
 		} break;
-		case MODE_DEFLATE: {
+		case MODE_DEFLATE:
+		case MODE_GZIP: {
+
+			int window_bits = p_mode == MODE_DEFLATE ? 15 : 15 + 16;
 
 			z_stream strm;
 			strm.zalloc = zipio_alloc;
@@ -146,7 +151,7 @@ int Compression::decompress(uint8_t *p_dst, int p_dst_max_size, const uint8_t *p
 			strm.opaque = Z_NULL;
 			strm.avail_in = 0;
 			strm.next_in = Z_NULL;
-			int err = inflateInit(&strm);
+			int err = inflateInit2(&strm, window_bits);
 			ERR_FAIL_COND_V(err != Z_OK, -1);
 
 			strm.avail_in = p_src_size;

core/io/compression.h

@@ -37,7 +37,8 @@ public:
 	enum Mode {
 		MODE_FASTLZ,
 		MODE_DEFLATE,
-		MODE_ZSTD
+		MODE_ZSTD,
+		MODE_GZIP
 	};
 
 	static int compress(uint8_t *p_dst, const uint8_t *p_src, int p_src_size, Mode p_mode = MODE_ZSTD);

core/variant_call.cpp

@@ -516,7 +516,7 @@ struct _VariantCall {
 		PoolByteArray compressed;
 		Compression::Mode mode = (Compression::Mode)(int)(*p_args[0]);
 
-		compressed.resize(Compression::get_max_compressed_buffer_size(ba->size()));
+		compressed.resize(Compression::get_max_compressed_buffer_size(ba->size(), mode));
 		int result = Compression::compress(compressed.write().ptr(), ba->read().ptr(), ba->size(), mode);
 
 		result = result >= 0 ? result : 0;