// First, write out the version.
mdOut.writeShort(BlockMetadataHeader.VERSION);
// Create a summer and write out its header.
int bytesPerChecksum = conf.getInt("io.bytes.per.checksum", 512);
DataChecksum sum =
DataChecksum.newDataChecksum(DataChecksum.CHECKSUM_CRC32,
bytesPerChecksum);
sum.writeHeader(mdOut);
// Buffer to read in a chunk of data.
byte[] buf = new byte[bytesPerChecksum];
// Buffer to store the checksum bytes.
byte[] chk = new byte[sum.getChecksumSize()];
// Read data till we reach the end of the input stream.
int bytesSinceFlush = 0;
while (true) {
// Read some bytes.
int bytesRead = dataStream.read(buf, bytesSinceFlush,
bytesPerChecksum-bytesSinceFlush);
if (bytesRead == -1) {
if (bytesSinceFlush > 0) {
boolean reset = true;
sum.writeValue(chk, 0, reset); // This also resets the sum.
// Write the checksum to the stream.
mdOut.write(chk, 0, chk.length);
bytesSinceFlush = 0;
}
break;
}
// Update the checksum.
sum.update(buf, bytesSinceFlush, bytesRead);
bytesSinceFlush += bytesRead;
// Flush the checksum if necessary.
if (bytesSinceFlush == bytesPerChecksum) {
boolean reset = true;
sum.writeValue(chk, 0, reset); // This also resets the sum.
// Write the checksum to the stream.
mdOut.write(chk, 0, chk.length);
bytesSinceFlush = 0;
}
}