- Committed Max' compressed save backseeking support from patch #2050337 "KYRA/SCUMM: Thumbnail support/improvement"

- Extended SCUMM engine to support savegames without thumbnail header. (Increased savegame version to prevent saves to be loaded from older ScummVM versions)
- Fixed KYRA to properly support savegames without thumbnail header.

svn-id: r34054

backends/saves/compressed/compressed-saves.cpp

@@ -62,7 +62,7 @@ public:
 		_stream.zfree = Z_NULL;
 		_stream.opaque = Z_NULL;
 
-		// Verify file header is correct once more
+		// Verify file header is correct
 		w->seek(0, SEEK_SET);
 		uint16 header = w->readUint16BE();
 		assert(header == 0x1F8B ||
@@ -133,28 +133,35 @@ public:
 	}
 	void seek(int32 offset, int whence = SEEK_SET) {
 		int32 newPos = 0;
+		assert(whence != SEEK_END);	// SEEK_END not supported
 		switch(whence) {
-		case SEEK_END:
-			newPos = size() - offset;
-			break;
 		case SEEK_SET:
 			newPos = offset;
 			break;
 		case SEEK_CUR:
 			newPos = _pos + offset;
 		}
+		
+		assert(newPos >= 0);
+
+		if ((uint32)newPos < _pos) {
+			// To search backward, we have to restart the whole decompression
+			// from the start of the file. A rather wasteful operation, best
+			// to avoid it. :/
+#if DEBUG
+			warning("Backward seeking in CompressedInSaveFile detected");
+#endif
+			_pos = 0;
+			_wrapped->seek(0, SEEK_SET);
+			_zlibErr = inflateReset(&_stream);
+			if (_zlibErr != Z_OK)
+				return;
+			_stream.next_in = _buf;
+			_stream.avail_in = 0;
+		}
+
 		offset = newPos - _pos;
 
-		if (offset < 0)
-			error("Backward seeking not supported in compressed savefiles");
-
-		// We could implement backward seeking, but it is tricky to do efficiently.
-		// A simple solution would be to restart the whole decompression from the
-		// start of the file. Or we could decompress the whole file in one go
-		// in the constructor, and wrap it into a MemoryReadStream -- but that
-		// would be rather wasteful. As long as we don't need it, I'd rather not
-		// implement this at all. -- Fingolfin
-
 		// Skip the given amount of data (very inefficient if one tries to skip
 		// huge amounts of data, but usually client code will only skip a few
 		// bytes, so this should be fine.

engines/kyra/saveload.cpp

@@ -113,7 +113,10 @@ KyraEngine_v1::kReadSaveHeaderError KyraEngine_v1::readSaveHeader(Common::Seekab
 		if (loadThumbnail) {
 			header.thumbnail = new Graphics::Surface();
 			assert(header.thumbnail);
-			Graphics::loadThumbnail(*in, *header.thumbnail);
+			if (!Graphics::loadThumbnail(*in, *header.thumbnail)) {
+				delete header.thumbnail;
+				header.thumbnail = 0;
+			}
 		} else {
 			Graphics::skipThumbnailHeader(*in);
 		}

engines/scumm/saveload.cpp

@@ -184,18 +184,8 @@ bool ScummEngine::loadState(int slot, bool compat) {
 	}
 
 	// Since version 52 a thumbnail is saved directly after the header.
-	if (hdr.ver >= VER(52)) {
-		uint32 type = in->readUint32BE();
-		// Check for the THMB header. Also, work around a bug which caused
-		// the chunk type (incorrectly) to be written in LE on LE machines.
-		if (! (type == MKID_BE('THMB') || (hdr.ver < VER(55) && type == MKID_BE('BMHT')))){
-			warning("Can not load thumbnail");
-			delete in;
-			return false;
-		}
-		uint32 size = in->readUint32BE();
-		in->skip(size - 8);
-	}
+	if (hdr.ver >= VER(52))
+		skipThumbnailHeader(in);
 
 	// Since version 56 we save additional information about the creation of
 	// the save game and the save time.

engines/scumm/saveload.h

@@ -50,7 +50,7 @@ namespace Scumm {
  * only saves/loads those which are valid for the version of the savegame
  * which is being loaded/saved currently.
  */
-#define CURRENT_VER 74
+#define CURRENT_VER 75
 
 /**
  * An auxillary macro, used to specify savegame versions. We use this instead

engines/scumm/scumm.h

@@ -636,9 +636,11 @@ public:
 
 protected:
 	Graphics::Surface *loadThumbnail(Common::SeekableReadStream *file);
-	bool loadInfos(Common::SeekableReadStream *file, InfoStuff *stuff);
 	void saveThumbnail(Common::WriteStream *file);
+	void skipThumbnailHeader(Common::SeekableReadStream *file);
+
 	void saveInfos(Common::WriteStream* file);
+	bool loadInfos(Common::SeekableReadStream *file, InfoStuff *stuff);
 
 	int32 _engineStartTime;
 	int32 _pauseStartTime;

engines/scumm/thumbnail.cpp

@@ -33,11 +33,8 @@
 namespace Scumm {
 
 Graphics::Surface *ScummEngine::loadThumbnail(Common::SeekableReadStream *file) {
-	// TODO: Until backwards seeking in compressed save files is not supported
-	// We can not use this.
-
-	//if (!Graphics::checkThumbnailHeader(*file))
-	//	return 0;
+	if (!Graphics::checkThumbnailHeader(*file))
+		return 0;
 
 	Graphics::Surface *thumb = new Graphics::Surface();
 	assert(thumb);
@@ -50,25 +47,13 @@ Graphics::Surface *ScummEngine::loadThumbnail(Common::SeekableReadStream *file)
 }
 
 void ScummEngine::saveThumbnail(Common::OutSaveFile *file) {
-	// Until we support no thumbnails in the SCUMM save formats for NDS
-	// we save a dummy thumbnail.
-	//
-	// TODO: Actually all what has to be done about it, is to update
-	// the code in engines/scumm/saveload.o which skips the saveheader.
-	// Currently impossible because of lacking backward seek support for
-	// compressed save files.
-	// When we change that code to use the new API from graphics/thumbnail.h
-	// it should be all fine to save no header at all for NDS.
-
-	Graphics::Surface thumb;
-
 #if !defined(__DS__)
-	if (!createThumbnailFromScreen(&thumb))
+	Graphics::saveThumbnail(*file);
 #endif
-		thumb.create(kThumbnailWidth, kThumbnailHeight2, sizeof(uint16));
+}
 
-	Graphics::saveThumbnail(*file, thumb);
-	thumb.free();
+void ScummEngine::skipThumbnailHeader(Common::SeekableReadStream *file) {
+	Graphics::skipThumbnailHeader(*file);
 }
 
 } // end of namespace Scumm

graphics/thumbnail.cpp

@@ -91,7 +91,7 @@ bool skipThumbnailHeader(Common::SeekableReadStream &in) {
 	uint32 position = in.pos();
 	ThumbnailHeader header;
 
-	if (!loadHeader(in, header, true)) {
+	if (!loadHeader(in, header, false)) {
 		in.seek(position, SEEK_SET);
 		return false;
 	}