Turned compressed savefile wrapper into a generic stream wrapper

svn-id: r34566

3 files changed, 386 insertions, 0 deletions

diff --git a/common/gzip-stream.cpp b/common/gzip-stream.cpp
new file mode 100644
index 0000000000..2756fe1b5c
--- /dev/null
+++ b/common/gzip-stream.cpp
@@ -0,0 +1,327 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * $URL$
+ * $Id$
+ *
+ */
+
+#include "common/gzip-stream.h"
+#include "common/util.h"
+
+#if defined(USE_ZLIB)
+  #include <zlib.h>
+
+  #if ZLIB_VERNUM < 0x1204
+  #error Version 1.2.0.4 or newer of zlib is required for this code
+  #endif
+#endif
+
+
+namespace Common {
+
+
+#if defined(USE_ZLIB)
+
+/**
+ * A simple wrapper class which can be used to wrap around an arbitrary
+ * other SeekableReadStream and will then provide on-the-fly decompression support.
+ * Assumes the compressed data to be in gzip format.
+ */
+class GZipReadStream : public Common::SeekableReadStream {
+protected:
+	enum {
+		BUFSIZE = 16384		// 1 << MAX_WBITS
+	};
+
+	byte	_buf[BUFSIZE];
+
+	Common::SeekableReadStream *_wrapped;
+	z_stream _stream;
+	int _zlibErr;
+	uint32 _pos;
+	uint32 _origSize;
+	bool _eos;
+
+public:
+
+	GZipReadStream(Common::SeekableReadStream *w) : _wrapped(w) {
+		assert(w != 0);
+
+		_stream.zalloc = Z_NULL;
+		_stream.zfree = Z_NULL;
+		_stream.opaque = Z_NULL;
+
+		// Verify file header is correct
+		w->seek(0, SEEK_SET);
+		uint16 header = w->readUint16BE();
+		assert(header == 0x1F8B ||
+		       ((header & 0x0F00) == 0x0800 && header % 31 == 0));
+
+		if (header == 0x1F8B) {
+			// Retrieve the original file size
+			w->seek(-4, SEEK_END);
+			_origSize = w->readUint32LE();
+		} else {
+			// Original size not available in zlib format
+			_origSize = 0;
+		}
+		_pos = 0;
+		w->seek(0, SEEK_SET);
+		_eos = false;
+
+		// Adding 32 to windowBits indicates to zlib that it is supposed to
+		// automatically detect whether gzip or zlib headers are used for
+		// the compressed file. This feature was added in zlib 1.2.0.4,
+		// released 10 August 2003.
+		// Note: This is *crucial* for savegame compatibility, do *not* remove!
+		_zlibErr = inflateInit2(&_stream, MAX_WBITS + 32);
+		if (_zlibErr != Z_OK)
+			return;
+
+		// Setup input buffer
+		_stream.next_in = _buf;
+		_stream.avail_in = 0;
+	}
+
+	~GZipReadStream() {
+		inflateEnd(&_stream);
+		delete _wrapped;
+	}
+
+	bool err() const { return (_zlibErr != Z_OK) && (_zlibErr != Z_STREAM_END); }
+	void clearErr() {
+		// only reset _eos; I/O errors are not recoverable
+		_eos = false;
+	}
+
+	uint32 read(void *dataPtr, uint32 dataSize) {
+		_stream.next_out = (byte *)dataPtr;
+		_stream.avail_out = dataSize;
+
+		// Keep going while we get no error
+		while (_zlibErr == Z_OK && _stream.avail_out) {
+			if (_stream.avail_in == 0 && !_wrapped->eos()) {
+				// If we are out of input data: Read more data, if available.
+				_stream.next_in = _buf;
+				_stream.avail_in = _wrapped->read(_buf, BUFSIZE);
+			}
+			_zlibErr = inflate(&_stream, Z_NO_FLUSH);
+		}
+
+		// Update the position counter
+		_pos += dataSize - _stream.avail_out;
+
+		if (_zlibErr == Z_STREAM_END && _stream.avail_out > 0)
+			_eos = true;
+
+		return dataSize - _stream.avail_out;
+	}
+
+	bool eos() const {
+		return _eos;
+	}
+	int32 pos() const {
+		return _pos;
+	}
+	int32 size() const {
+		return _origSize;
+	}
+	bool seek(int32 offset, int whence = SEEK_SET) {
+		int32 newPos = 0;
+		assert(whence != SEEK_END);	// SEEK_END not supported
+		switch(whence) {
+		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 GZipReadStream detected");
+#endif
+			_pos = 0;
+			_wrapped->seek(0, SEEK_SET);
+			_zlibErr = inflateReset(&_stream);
+			if (_zlibErr != Z_OK)
+				return false;	// FIXME: STREAM REWRITE
+			_stream.next_in = _buf;
+			_stream.avail_in = 0;
+		}
+
+		offset = newPos - _pos;
+
+		// 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.
+		byte tmpBuf[1024];
+		while (!err() && offset > 0) {
+			offset -= read(tmpBuf, MIN((int32)sizeof(tmpBuf), offset));
+		}
+		
+		_eos = false;
+		return true;	// FIXME: STREAM REWRITE
+	}
+};
+
+/**
+ * A simple wrapper class which can be used to wrap around an arbitrary
+ * other WriteStream and will then provide on-the-fly compression support.
+ * The compressed data is written in the gzip format.
+ */
+class GZipWriteStream : public Common::WriteStream {
+protected:
+	enum {
+		BUFSIZE = 16384		// 1 << MAX_WBITS
+	};
+
+	byte	_buf[BUFSIZE];
+	Common::WriteStream *_wrapped;
+	z_stream _stream;
+	int _zlibErr;
+
+	void processData(int flushType) {
+		// This function is called by both write() and finalize().
+		while (_zlibErr == Z_OK && (_stream.avail_in || flushType == Z_FINISH)) {
+			if (_stream.avail_out == 0) {
+				if (_wrapped->write(_buf, BUFSIZE) != BUFSIZE) {
+					_zlibErr = Z_ERRNO;
+					break;
+				}
+				_stream.next_out = _buf;
+				_stream.avail_out = BUFSIZE;
+			}
+			_zlibErr = deflate(&_stream, flushType);
+		}
+	}
+
+public:
+	GZipWriteStream(Common::WriteStream *w) : _wrapped(w) {
+		assert(w != 0);
+		_stream.zalloc = Z_NULL;
+		_stream.zfree = Z_NULL;
+		_stream.opaque = Z_NULL;
+
+		// Adding 16 to windowBits indicates to zlib that it is supposed to
+		// write gzip headers. This feature was added in zlib 1.2.0.4,
+		// released 10 August 2003.
+		// Note: This is *crucial* for savegame compatibility, do *not* remove!
+		_zlibErr = deflateInit2(&_stream,
+		                 Z_DEFAULT_COMPRESSION,
+		                 Z_DEFLATED,
+		                 MAX_WBITS + 16,
+		                 8,
+                         Z_DEFAULT_STRATEGY);
+		assert(_zlibErr == Z_OK);
+
+		_stream.next_out = _buf;
+		_stream.avail_out = BUFSIZE;
+		_stream.avail_in = 0;
+		_stream.next_in = 0;
+	}
+
+	~GZipWriteStream() {
+		finalize();
+		deflateEnd(&_stream);
+		delete _wrapped;
+	}
+
+	bool err() const {
+		// CHECKME: does Z_STREAM_END make sense here?
+		return (_zlibErr != Z_OK && _zlibErr != Z_STREAM_END) || _wrapped->err();
+	}
+
+	void clearErr() {
+		// Note: we don't reset the _zlibErr here, as it is not
+		// clear in general how
+		_wrapped->clearErr();
+	}
+
+	void finalize() {
+		if (_zlibErr != Z_OK)
+			return;
+
+		// Process whatever remaining data there is.
+		processData(Z_FINISH);
+
+		// Since processData only writes out blocks of size BUFSIZE,
+		// we may have to flush some stragglers.
+		uint remainder = BUFSIZE - _stream.avail_out;
+		if (remainder > 0) {
+			if (_wrapped->write(_buf, remainder) != remainder) {
+				_zlibErr = Z_ERRNO;
+			}
+		}
+
+		// Finalize the wrapped savefile, too
+		_wrapped->finalize();
+	}
+
+	uint32 write(const void *dataPtr, uint32 dataSize) {
+		if (err())
+			return 0;
+
+		// Hook in the new data ...
+		// Note: We need to make a const_cast here, as zlib is not aware
+		// of the const keyword.
+		_stream.next_in = const_cast<byte *>((const byte *)dataPtr);
+		_stream.avail_in = dataSize;
+
+		// ... and flush it to disk
+		processData(Z_NO_FLUSH);
+
+		return dataSize - _stream.avail_in;
+	}
+};
+
+#endif	// USE_ZLIB
+
+Common::SeekableReadStream *wrapCompressedReadStream(Common::SeekableReadStream *toBeWrapped) {
+#if defined(USE_ZLIB)
+	if (toBeWrapped) {
+		uint16 header = toBeWrapped->readUint16BE();
+		bool isCompressed = (header == 0x1F8B ||
+				     ((header & 0x0F00) == 0x0800 &&
+				      header % 31 == 0));
+		toBeWrapped->seek(-2, SEEK_CUR);
+		if (isCompressed)
+			return new GZipReadStream(toBeWrapped);
+	}
+#endif
+	return toBeWrapped;
+}
+
+Common::WriteStream *wrapCompressedWriteStream(Common::WriteStream *toBeWrapped) {
+#if defined(USE_ZLIB)
+	if (toBeWrapped)
+		return new GZipWriteStream(toBeWrapped);
+#endif
+	return toBeWrapped;
+}
+
+
+}	// End of namespace Common
diff --git a/common/gzip-stream.h b/common/gzip-stream.h
new file mode 100644
index 0000000000..557f507044
--- /dev/null
+++ b/common/gzip-stream.h
@@ -0,0 +1,58 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * $URL$
+ * $Id$
+ *
+ */
+
+#ifndef COMMON_GZIP_STREAM_H
+#define COMMON_GZIP_STREAM_H
+
+#include "common/stream.h"
+
+namespace Common {
+
+/**
+ * Take an arbitrary SeekableReadStream and wrap it in a custom stream which
+ * provides transparent on-the-fly decompression. Assumes the data it
+ * retrieves from the wrapped stream to be either uncompressed or in gzip
+ * format. In the former case, the original stream is returned unmodified
+ * (and in particular, not wrapped).
+ *
+ * It is safe to call this with a NULL parameter (in this case, NULL is
+ * returned).
+ */
+Common::SeekableReadStream *wrapCompressedReadStream(Common::SeekableReadStream *toBeWrapped);
+
+/**
+ * Take an arbitrary WriteStream and wrap it in a custom stream which provides
+ * transparent on-the-fly compression. The compressed data is written in the
+ * gzip format, unless ZLIB support has been disabled, in which case the given
+ * stream is returned unmodified (and in particular, not wrapped).
+ *
+ * It is safe to call this with a NULL parameter (in this case, NULL is
+ * returned).
+ */
+Common::WriteStream *wrapCompressedWriteStream(Common::WriteStream *toBeWrapped);
+
+}	// End of namespace Common
+
+#endif
diff --git a/common/module.mk b/common/module.mk
index 599ffcf8a6..45a915a613 100644
--- a/common/module.mk
+++ b/common/module.mk
@@ -7,6 +7,7 @@ MODULE_OBJS := \
 	config-manager.o \
 	file.o \
 	fs.o \
+	gzip-stream.o \
 	hashmap.o \
 	memorypool.o \
 	md5.o \