public synchronized InputStream getBlockInputStream(Block b, long seekOffset) throws IOException {
File blockFile = getBlockFile(b);
RandomAccessFile blockInFile = new RandomAccessFile(blockFile, "r");
if (seekOffset > 0) {
blockInFile.seek(seekOffset);
}
return new FileInputStream(blockInFile.getFD());
}
private static void truncateBlock(File blockFile, File metaFile, long oldlen, long newlen)
throws IOException {
if (newlen == oldlen) {
return;
}
if (newlen > oldlen) {
throw new IOException(
"Cannout truncate block to from oldlen (=" + oldlen + ") to newlen (=" + newlen + ")");
}
DataChecksum dcs = BlockMetadataHeader.readHeader(metaFile).getChecksum();
int checksumsize = dcs.getChecksumSize();
int bpc = dcs.getBytesPerChecksum();
long n = (newlen - 1) / bpc + 1;
long newmetalen = BlockMetadataHeader.getHeaderSize() + n * checksumsize;
long lastchunkoffset = (n - 1) * bpc;
int lastchunksize = (int) (newlen - lastchunkoffset);
byte[] b = new byte[Math.max(lastchunksize, checksumsize)];
RandomAccessFile blockRAF = new RandomAccessFile(blockFile, "rw");
try {
// truncate blockFile
blockRAF.setLength(newlen);
// read last chunk
blockRAF.seek(lastchunkoffset);
blockRAF.readFully(b, 0, lastchunksize);
} finally {
blockRAF.close();
}
// compute checksum
dcs.update(b, 0, lastchunksize);
dcs.writeValue(b, 0, false);
// update metaFile
RandomAccessFile metaRAF = new RandomAccessFile(metaFile, "rw");
try {
metaRAF.setLength(newmetalen);
metaRAF.seek(newmetalen - checksumsize);
metaRAF.write(b, 0, checksumsize);
} finally {
metaRAF.close();
}
}
/** Returns handles to the block file and its metadata file */
public synchronized BlockInputStreams getTmpInputStreams(Block b, long blkOffset, long ckoff)
throws IOException {
DatanodeBlockInfo info = volumeMap.get(b);
if (info == null) {
throw new IOException("Block " + b + " does not exist in volumeMap.");
}
FSVolume v = info.getVolume();
File blockFile = v.getTmpFile(b);
RandomAccessFile blockInFile = new RandomAccessFile(blockFile, "r");
if (blkOffset > 0) {
blockInFile.seek(blkOffset);
}
File metaFile = getMetaFile(blockFile, b);
RandomAccessFile metaInFile = new RandomAccessFile(metaFile, "r");
if (ckoff > 0) {
metaInFile.seek(ckoff);
}
return new BlockInputStreams(
new FileInputStream(blockInFile.getFD()), new FileInputStream(metaInFile.getFD()));
}