COMMON: Implement ConcatReadStream

common/concatstream.cpp

@@ -0,0 +1,140 @@
+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "common/concatstream.h"
+
+namespace Common {
+
+ConcatReadStream::ConcatReadStream(ParentStreamArray parentStreams) : _parentStreams(parentStreams), _totalSize(0), _linearPos(0), _volume(0), _volumePos(0), _err(false), _eos(false) {
+	_sizes.resize(parentStreams.size());
+	_startOffsets.resize(parentStreams.size());
+	for (uint i = 0; i < parentStreams.size(); i++) {
+		_sizes[i] = parentStreams[i]->size();
+		_totalSize += _sizes[i];
+	}
+	_startOffsets[0] = 0;
+	for (uint i = 1; i < parentStreams.size(); i++)
+		_startOffsets[i] = _startOffsets[i - 1] + _sizes[i - 1];
+}
+
+bool ConcatReadStream::seek(int64 offset, int whence) {
+	int64 target = 0;
+	switch (whence) {
+	case SEEK_SET:
+		target = offset;
+		break;
+	case SEEK_CUR:
+		target = _linearPos + offset;
+		break;
+	case SEEK_END:
+		target = _totalSize + offset;
+		break;
+	default:
+		return false;
+	}
+
+	if (target < 0 || target > _totalSize) {
+		return false;
+	}
+
+	_linearPos = target;
+	_eos = false;
+	_err = false;
+
+	// Special case: seek'ing to the EOF.
+	if (target == _totalSize) {
+		if (_parentStreams.empty()) {
+			_volume = 0;
+			_volumePos = 0;
+			return true;
+		}
+		_volume = _parentStreams.size() - 1;
+		_volumePos = _sizes[_parentStreams.size() - 1];
+		return true;
+	}
+
+	// Find volume
+	for (unsigned vol = 0; vol < _parentStreams.size(); vol++) {
+		if (_startOffsets[vol] <= _linearPos &&
+		    _linearPos < _startOffsets[vol] + _sizes[vol]) {
+			_volume = vol;
+			_volumePos = _linearPos - _startOffsets[vol];
+			return true;
+		}
+	}
+
+	// Should never be reached.
+	_err = true;
+	return false;
+}
+
+bool ConcatReadStream::seekToVolume(int volume, int64 offset) {
+	if (volume < 0 || (uint) volume >= _parentStreams.size()
+	    || offset < 0 || offset >= _sizes[volume]) {
+		_err = true;
+		return false;
+	}
+
+	_err = false;
+	_eos = false;
+	_volume = volume;
+	_volumePos = offset;
+	_linearPos = _startOffsets[volume] + offset;
+	return true;
+}
+
+uint32 ConcatReadStream::read(void *dataPtr, uint32 dataSize) {
+	uint32 rem = dataSize;
+	uint32 alreadyRead = 0;
+	byte *curPtr = (byte*) dataPtr;
+	while (rem > 0) {
+		int64 avail = _startOffsets[_volume] + _sizes[_volume];
+		while (avail == 0) {
+			if (_volume + 1 >= _startOffsets.size()) {
+				_eos = true;
+				return alreadyRead;
+			}
+			_volume++;
+			_volumePos = 0;
+			avail = _startOffsets[_volume] + _sizes[_volume];
+		}
+
+		uint32 toRead = MIN((int64) rem, avail);
+		_parentStreams[_volume]->seek(_volumePos); // Also clears error and EOS.
+		uint32 actuallyRead = _parentStreams[_volume]->read(curPtr, toRead);
+		alreadyRead += actuallyRead;
+		rem -= actuallyRead;
+		curPtr += actuallyRead;
+		_volumePos += actuallyRead;
+		_linearPos += actuallyRead;
+		if (_volumePos == _sizes[_volume] && _volume + 1 < _startOffsets.size()) {
+			_volume++;
+			_volumePos = 0;			
+		}
+		if (_parentStreams[_volume]->err()) {
+			_err = true;
+			return alreadyRead;
+		}
+	}
+
+	return alreadyRead;
+}
+} // End of namespace Common

common/concatstream.h

@@ -0,0 +1,67 @@
+/* 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef COMMON_CONCATSTREAM_H
+#define COMMON_CONCATSTREAM_H
+
+#include "common/array.h"
+#include "common/ptr.h"
+#include "common/stream.h"
+
+namespace Common {
+/*
+ * ConcatReadStream provides access to a virtually concatenated stream.
+ *
+ * Manipulating the parent stream directly /will/ mess up a concatstream.
+ *
+ * Assumptions:
+ * - number of streams is small so iterating through array sized by N is cheap
+ * - size of streams doesn't change
+ */
+class ConcatReadStream : public SeekableReadStream {
+private:
+	typedef Common::Array<Common::SharedPtr<Common::SeekableReadStream>> ParentStreamArray;
+	ParentStreamArray _parentStreams;
+	Common::Array<int64> _sizes;
+	Common::Array<int64> _startOffsets;
+
+	uint32 _totalSize, _linearPos;
+	uint32 _volume, _volumePos;
+	bool _err, _eos;
+public:
+	ConcatReadStream(ParentStreamArray parentStreams);
+
+	int64 pos() const override { return _linearPos; }
+	int64 size() const override { return _totalSize; }
+	bool eos() const override { return _eos; }
+	bool err() const override { return _err; }
+	void clearErr() override {
+		_err = false;
+		_eos = false;
+	}
+	bool seek(int64 offset, int whence = SEEK_SET) override;
+	uint32 read(void *dataPtr, uint32 dataSize) override;
+	bool seekToVolume(int volume, int64 offset);
+};
+
+}
+
+#endif // COMMON_CONCATSTREAM_H

common/module.mk

@@ -5,6 +5,7 @@ MODULE_OBJS := \
 	archive.o \
 	base-str.o \
 	clickteam.o \
+	concatstream.o \
 	config-manager.o \
 	coroutines.o \
 	dcl.o \