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(); } }