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Diffstat (limited to 'src/main/java/de/waldheinz/fs/util/RamDisk.java')
| -rw-r--r-- | src/main/java/de/waldheinz/fs/util/RamDisk.java | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/src/main/java/de/waldheinz/fs/util/RamDisk.java b/src/main/java/de/waldheinz/fs/util/RamDisk.java new file mode 100644 index 0000000..51a1be1 --- /dev/null +++ b/src/main/java/de/waldheinz/fs/util/RamDisk.java @@ -0,0 +1,199 @@ +/* + * Copyright (C) 2009,2010 Matthias Treydte <mt@waldheinz.de> + * + * This library is free software; you can redistribute it and/or modify it + * under the terms of the GNU Lesser General Public License as published + * by the Free Software Foundation; either version 2.1 of the License, or + * (at your option) any later version. + * + * This library 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 Lesser General Public + * License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with this library; If not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +package de.waldheinz.fs.util; + +import de.waldheinz.fs.*; +import java.io.ByteArrayOutputStream; +import java.io.IOException; +import java.io.InputStream; +import java.nio.ByteBuffer; +import java.util.zip.GZIPInputStream; + +/** + * A {@link BlockDevice} that lives entirely in heap memory. This is basically + * a RAM disk. A {@code RamDisk} is always writable. + * + * @author Matthias Treydte <waldheinz at gmail.com> + */ +public final class RamDisk implements BlockDevice { + + /** + * The default sector size for {@code RamDisk}s. + */ + public final static int DEFAULT_SECTOR_SIZE = 512; + + private final int sectorSize; + private final ByteBuffer data; + private final int size; + private boolean closed; + + /** + * Reads a GZIP compressed disk image from the specified input stream and + * returns a {@code RamDisk} holding the decompressed image. + * + * @param in the stream to read the disk image from + * @return the decompressed {@code RamDisk} + * @throws IOException on read or decompression error + */ + public static RamDisk readGzipped(InputStream in) throws IOException { + final GZIPInputStream zis = new GZIPInputStream(in); + ByteArrayOutputStream bos = new ByteArrayOutputStream(); + + final byte[] buffer = new byte[4096]; + + int read = zis.read(buffer); + int total = 0; + + while (read >= 0) { + total += read; + bos.write(buffer, 0, read); + read = zis.read(buffer); + } + + if (total < DEFAULT_SECTOR_SIZE) throw new IOException( + "read only " + total + " bytes"); //NOI18N + + final ByteBuffer bb = ByteBuffer.wrap(bos.toByteArray(), 0, total); + return new RamDisk(bb, DEFAULT_SECTOR_SIZE); + } + + private RamDisk(ByteBuffer buffer, int sectorSize) { + this.size = buffer.limit(); + this.sectorSize = sectorSize; + this.data = buffer; + this.closed = false; + } + + /** + * Creates a new instance of {@code RamDisk} of this specified + * size and using the {@link #DEFAULT_SECTOR_SIZE}. + * + * @param size the size of the new block device + */ + public RamDisk(int size) { + this(size, DEFAULT_SECTOR_SIZE); + } + + /** + * Creates a new instance of {@code RamDisk} of this specified + * size and sector size + * + * @param size the size of the new block device + * @param sectorSize the sector size of the new block device + */ + public RamDisk(int size, int sectorSize) { + if (sectorSize < 1) throw new IllegalArgumentException( + "invalid sector size"); //NOI18N + + this.sectorSize = sectorSize; + this.size = size; + this.data = ByteBuffer.allocate(size); + } + + @Override + public long getSize() { + checkClosed(); + return this.size; + } + + @Override + public void read(long devOffset, ByteBuffer dest) throws IOException { + checkClosed(); + + if (devOffset > getSize()){ + final StringBuilder sb = new StringBuilder(); + sb.append("read at ").append(devOffset); + sb.append(" is off size (").append(getSize()).append(")"); + + throw new IllegalArgumentException(sb.toString()); + } + + data.limit((int) (devOffset + dest.remaining())); + data.position((int) devOffset); + + dest.put(data); + } + + @Override + public void write(long devOffset, ByteBuffer src) throws IOException { + checkClosed(); + + if (devOffset + src.remaining() > getSize()) throw new + IllegalArgumentException( + "offset=" + devOffset + + ", length=" + src.remaining() + + ", size=" + getSize()); + + data.limit((int) (devOffset + src.remaining())); + data.position((int) devOffset); + + + data.put(src); + } + + /** + * Returns a slice of the {@code ByteBuffer} that is used by this + * {@code RamDisk} as it's backing store. The returned buffer will be + * live (reflecting any changes made through the + * {@link #write(long, java.nio.ByteBuffer) method}, but read-only. + * + * @return a buffer holding the contents of this {@code RamDisk} + */ + public ByteBuffer getBuffer() { + return this.data.asReadOnlyBuffer(); + } + + @Override + public void flush() throws IOException { + checkClosed(); + } + + @Override + public int getSectorSize() { + checkClosed(); + return this.sectorSize; + } + + @Override + public void close() throws IOException { + this.closed = true; + } + + @Override + public boolean isClosed() { + return this.closed; + } + + private void checkClosed() { + if (closed) throw new IllegalStateException("device already closed"); + } + + /** + * Returns always {@code false}, as a {@code RamDisk} is always writable. + * + * @return always {@code false} + */ + @Override + public boolean isReadOnly() { + checkClosed(); + + return false; + } + +} |