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();
}
}
/** Test exceptions specified by map method */
private static void testExceptions() throws Exception {
// check exceptions when channel opened for read access
try (FileChannel fc = FileChannel.open(blah.toPath(), READ)) {
testExceptions(fc);
checkException(fc, MapMode.READ_WRITE, 0L, fc.size(), NonWritableChannelException.class);
checkException(
fc,
MapMode.READ_WRITE,
-1L,
fc.size(),
NonWritableChannelException.class,
IllegalArgumentException.class);
checkException(
fc,
MapMode.READ_WRITE,
0L,
-1L,
NonWritableChannelException.class,
IllegalArgumentException.class);
checkException(fc, MapMode.PRIVATE, 0L, fc.size(), NonWritableChannelException.class);
checkException(
fc,
MapMode.PRIVATE,
-1L,
fc.size(),
NonWritableChannelException.class,
IllegalArgumentException.class);
checkException(
fc,
MapMode.PRIVATE,
0L,
-1L,
NonWritableChannelException.class,
IllegalArgumentException.class);
}
// check exceptions when channel opened for write access
try (FileChannel fc = FileChannel.open(blah.toPath(), WRITE)) {
testExceptions(fc);
checkException(fc, MapMode.READ_ONLY, 0L, fc.size(), NonReadableChannelException.class);
checkException(
fc,
MapMode.READ_ONLY,
-1L,
fc.size(),
NonReadableChannelException.class,
IllegalArgumentException.class);
/*
* implementation/spec mismatch, these tests disabled for now
*/
// checkException(fc, MapMode.READ_WRITE, 0L, fc.size(),
// NonWritableChannelException.class);
// checkException(fc, MapMode.PRIVATE, 0L, fc.size(),
// NonWritableChannelException.class);
}
// check exceptions when channel opened for read and write access
try (FileChannel fc = FileChannel.open(blah.toPath(), READ, WRITE)) {
testExceptions(fc);
}
}