/*
* gets an (uncompressed) stream representing the chunk data returns null if
* the chunk is not found or an error occurs
*/
public synchronized DataInputStream getChunkDataInputStream(int x, int z) {
if (outOfBounds(x, z)) {
debugln("READ", x, z, "out of bounds");
return null;
}
try {
int offset = getOffset(x, z);
if (offset == 0) {
// debugln("READ", x, z, "miss");
return null;
}
int sectorNumber = offset >> 8;
int numSectors = offset & 0xFF;
if (sectorNumber + numSectors > sectorFree.size()) {
debugln("READ", x, z, "invalid sector");
return null;
}
file.seek(sectorNumber * SECTOR_BYTES);
int length = file.readInt();
if (length > SECTOR_BYTES * numSectors) {
debugln("READ", x, z, "invalid length: " + length + " > 4096 * " + numSectors);
return null;
}
byte version = file.readByte();
if (version == VERSION_GZIP) {
byte[] data = new byte[length - 1];
file.read(data);
DataInputStream ret =
new DataInputStream(
new BufferedInputStream(new GZIPInputStream(new ByteArrayInputStream(data))));
// debug("READ", x, z, " = found");
return ret;
} else if (version == VERSION_DEFLATE) {
byte[] data = new byte[length - 1];
file.read(data);
DataInputStream ret =
new DataInputStream(
new BufferedInputStream(new InflaterInputStream(new ByteArrayInputStream(data))));
// debug("READ", x, z, " = found");
return ret;
}
debugln("READ", x, z, "unknown version " + version);
return null;
} catch (IOException e) {
debugln("READ", x, z, "exception");
return null;
}
}
public static long checksumRandomAccessFile(Path filename) throws IOException {
try (RandomAccessFile file = new RandomAccessFile(filename.toFile(), "r")) {
long length = file.length();
CRC32 crc = new CRC32();
for (long p = 0; p < length; p++) {
file.seek(p);
int c = file.readByte();
crc.update(c);
}
return crc.getValue();
}
}