public static long checksumMappedFile(Path filename) throws IOException {
try (FileChannel channel = FileChannel.open(filename)) {
CRC32 crc = new CRC32();
int length = (int) channel.size();
MappedByteBuffer buffer = channel.map(FileChannel.MapMode.READ_ONLY, 0, length);
for (int p = 0; p < length; p++) {
int c = buffer.get(p);
crc.update(c);
}
return crc.getValue();
}
}
