compressZlib: don't use a SharedBuffer but a raw u8 * pointer

Remove usage of the SharedBuffer in zlib compression which has two problems:
* We copied the whole memory block to compress it (not good with mapblocks)
* We copied sometimes strings to SharedBuffer to SharedBuffer (2nd time)

Use this method in MapNode::serializeBulk + optimize serialization but merging 3 identical loops in a single loop

src/mapnode.cpp

@@ -658,7 +658,7 @@ void MapNode::serializeBulk(std::ostream &os, int version,
 		const MapNode *nodes, u32 nodecount,
 		u8 content_width, u8 params_width, bool compressed)
 {
-	if(!ser_ver_supported(version))
+	if (!ser_ver_supported(version))
 		throw VersionMismatchException("ERROR: MapNode format not supported");
 
 	sanity_check(content_width == 2);
@@ -666,38 +666,33 @@ void MapNode::serializeBulk(std::ostream &os, int version,
 
 	// Can't do this anymore; we have 16-bit dynamically allocated node IDs
 	// in memory; conversion just won't work in this direction.
-	if(version < 24)
+	if (version < 24)
 		throw SerializationError("MapNode::serializeBulk: serialization to "
 				"version < 24 not possible");
 
-	SharedBuffer<u8> databuf(nodecount * (content_width + params_width));
+	size_t databuf_size = nodecount * (content_width + params_width);
+	u8 *databuf = new u8[databuf_size];
+
+	u32 start1 = content_width * nodecount;
+	u32 start2 = (content_width + 1) * nodecount;
 
 	// Serialize content
-	for(u32 i=0; i<nodecount; i++)
-		writeU16(&databuf[i*2], nodes[i].param0);
-
-	// Serialize param1
-	u32 start1 = content_width * nodecount;
-	for(u32 i=0; i<nodecount; i++)
+	for (u32 i = 0; i < nodecount; i++) {
+		writeU16(&databuf[i * 2], nodes[i].param0);
 		writeU8(&databuf[start1 + i], nodes[i].param1);
-
-	// Serialize param2
-	u32 start2 = (content_width + 1) * nodecount;
-	for(u32 i=0; i<nodecount; i++)
 		writeU8(&databuf[start2 + i], nodes[i].param2);
+	}
 
 	/*
 		Compress data to output stream
 	*/
 
-	if(compressed)
-	{
-		compressZlib(databuf, os);
-	}
+	if (compressed)
+		compressZlib(databuf, databuf_size, os);
 	else
-	{
-		os.write((const char*) &databuf[0], databuf.getSize());
-	}
+		os.write((const char*) &databuf[0], databuf_size);
+
+	delete [] databuf;
 }
 
 // Deserialize bulk node data

src/serialization.cpp

@@ -53,7 +53,7 @@ void zerr(int ret)
     }
 }
 
-void compressZlib(SharedBuffer<u8> data, std::ostream &os, int level)
+void compressZlib(const u8 *data, size_t data_size, std::ostream &os, int level)
 {
 	z_stream z;
 	const s32 bufsize = 16384;
@@ -71,7 +71,7 @@ void compressZlib(SharedBuffer<u8> data, std::ostream &os, int level)
 
 	// Point zlib to our input buffer
 	z.next_in = (Bytef*)&data[0];
-	z.avail_in = data.getSize();
+	z.avail_in = data_size;
 	// And get all output
 	for(;;)
 	{
@@ -98,8 +98,7 @@ void compressZlib(SharedBuffer<u8> data, std::ostream &os, int level)
 
 void compressZlib(const std::string &data, std::ostream &os, int level)
 {
-	SharedBuffer<u8> databuf((u8*)data.c_str(), data.size());
-	compressZlib(databuf, os, level);
+	compressZlib((u8*)data.c_str(), data.size(), os, level);
 }
 
 void decompressZlib(std::istream &is, std::ostream &os)
@@ -186,11 +185,11 @@ void decompressZlib(std::istream &is, std::ostream &os)
 	inflateEnd(&z);
 }
 
-void compress(SharedBuffer<u8> data, std::ostream &os, u8 version)
+void compress(const SharedBuffer<u8> &data, std::ostream &os, u8 version)
 {
 	if(version >= 11)
 	{
-		compressZlib(data, os);
+		compressZlib(*data ,data.getSize(), os);
 		return;
 	}
 

src/serialization.h

@@ -86,12 +86,12 @@ inline bool ser_ver_supported(s32 v) {
 	Misc. serialization functions
 */
 
-void compressZlib(SharedBuffer<u8> data, std::ostream &os, int level = -1);
+void compressZlib(const u8 *data, size_t data_size, std::ostream &os, int level = -1);
 void compressZlib(const std::string &data, std::ostream &os, int level = -1);
 void decompressZlib(std::istream &is, std::ostream &os);
 
 // These choose between zlib and a self-made one according to version
-void compress(SharedBuffer<u8> data, std::ostream &os, u8 version);
+void compress(const SharedBuffer<u8> &data, std::ostream &os, u8 version);
 //void compress(const std::string &data, std::ostream &os, u8 version);
 void decompress(std::istream &is, std::ostream &os, u8 version);