@Test
public void testPosition() throws IOException {
FileChannel channel = channel(regularFile(10), READ);
assertEquals(0, channel.position());
assertSame(channel, channel.position(100));
assertEquals(100, channel.position());
}
private void insertRecord(int recordPosition, long value) throws IOException {
try {
FileChannel channel = getFileChannel();
long previousPosition = channel.position();
channel.position(RECORD_SIZE * recordPosition);
int trail = (int) (channel.size() - channel.position());
ByteBuffer trailBuffer = null;
if (trail > 0) {
trailBuffer = ByteBuffer.allocate(trail);
channel.read(trailBuffer);
trailBuffer.flip();
}
ByteBuffer buffer = ByteBuffer.allocate(RECORD_SIZE);
buffer.put(Record.IN_USE.byteValue());
buffer.putLong(value);
buffer.flip();
channel.position(RECORD_SIZE * recordPosition);
channel.write(buffer);
if (trail > 0) {
channel.write(trailBuffer);
}
channel.position(previousPosition);
} catch (IOException e) {
throw new RuntimeException(e);
}
}
/**
* @param compressed_size or use null if not known
* @param uncompressed_size or use null if not known
* @return uncompressed ByteArrayOutputStream
* @throws IOException
* @throws DataFormatException
*/
private ByteArrayOutputStream unCompress(Integer compressed_size, Integer uncompressed_size)
throws IOException, DataFormatException {
byte[] uncompressed_data = null;
byte[] input_data = null;
ByteArrayOutputStream ret = new ByteArrayOutputStream();
Inflater decompresser = new Inflater(false);
long first_seek = fileChannel.position();
Boolean uncompressing = true;
while (uncompressing) {
if (decompresser.needsInput()) {
input_data = new byte[(compressed_size != null) ? compressed_size.intValue() : 1024];
fileChannel.read(ByteBuffer.wrap(input_data));
decompresser.setInput(input_data, 0, input_data.length);
}
uncompressed_data =
new byte
[(uncompressed_size != null)
? uncompressed_size.intValue()
: (input_data.length * 4)];
decompresser.inflate(uncompressed_data);
int op = (int) (decompresser.getBytesWritten() - (long) ret.size());
if (op > 0) ret.write(uncompressed_data, 0, op);
if (decompresser.finished()) uncompressing = false;
}
fileChannel.position(
(first_seek + decompresser.getBytesRead())); // move file pointer to start of next stream
decompresser.end();
return ret;
}
public static void copyFile(File srcFile, File destFile) throws Exception {
int bufferSize = 2048;
FileInputStream in = new FileInputStream(srcFile);
FileOutputStream out = new FileOutputStream(destFile);
FileChannel inChannel = in.getChannel();
FileChannel outChannel = out.getChannel();
ByteBuffer buffer = null;
int length = -1;
try {
while (true) {
if (inChannel.position() == inChannel.size()) {
// finish copying
break;
} else if (inChannel.size() - inChannel.position() < length) {
// copy last chunk of data
length = (int) (inChannel.size() - inChannel.position());
} else {
length = bufferSize;
}
buffer = ByteBuffer.allocateDirect(length);
inChannel.read(buffer);
buffer.flip();
outChannel.write(buffer);
outChannel.force(false);
}
} finally {
_close(inChannel);
_close(in);
_close(outChannel);
_close(out);
}
}
public void writeRequest(final OutputStream out) throws IOException {
int readCount = 0;
Iterator<OnDatatransferProgressListener> it = null;
try {
mChannel.position(mOffset);
long size = mFile.length();
if (size == 0) size = -1;
long maxCount = Math.min(mOffset + mChunkSize, mChannel.size());
while (mChannel.position() < maxCount) {
readCount = mChannel.read(mBuffer);
out.write(mBuffer.array(), 0, readCount);
mBuffer.clear();
if (mTransferred < maxCount) { // condition to avoid accumulate progress for repeated chunks
mTransferred += readCount;
}
synchronized (mDataTransferListeners) {
it = mDataTransferListeners.iterator();
while (it.hasNext()) {
it.next().onTransferProgress(readCount, mTransferred, size, mFile.getName());
}
}
}
} catch (IOException io) {
Log.e(TAG, io.getMessage());
throw new RuntimeException(
"Ugly solution to workaround the default policy of retries when the server falls while uploading ; temporal fix; really",
io);
}
}
private void upgradeRatings(BinaryFormat newFormat) throws IOException {
Preconditions.checkArgument(
newFormat.getRatingSize() > format.getRatingSize(), "new format is not wider than old");
logger.info("upgrading {} ratings from {} to {}", index, format, newFormat);
ByteBuffer oldBuffer = ByteBuffer.allocateDirect(format.getRatingSize());
ByteBuffer newBuffer = ByteBuffer.allocateDirect(newFormat.getRatingSize());
MutableRating scratch = new MutableRating();
long oldPos = BinaryHeader.HEADER_SIZE + index * format.getRatingSize();
Preconditions.checkState(channel.position() == oldPos, "channel is at the wrong position");
long newPos = BinaryHeader.HEADER_SIZE + index * newFormat.getRatingSize();
channel.position(newPos);
// loop backwards, coping each rating to later in the file
for (int i = index - 1; i >= 0; i--) {
oldPos -= format.getRatingSize();
newPos -= newFormat.getRatingSize();
// read the old rating
BinaryUtils.readBuffer(channel, oldBuffer, oldPos);
oldBuffer.flip();
format.readRating(oldBuffer, scratch);
oldBuffer.clear();
// write the new rating
newFormat.renderRating(scratch, newBuffer);
newBuffer.flip();
BinaryUtils.writeBuffer(channel, newBuffer, newPos);
newBuffer.clear();
}
assert oldPos == BinaryHeader.HEADER_SIZE;
assert newPos == BinaryHeader.HEADER_SIZE;
format = newFormat;
ratingBuffer = ByteBuffer.allocateDirect(newFormat.getRatingSize());
}
public boolean copyFromChannel(FileChannel channel, TableStats stats) throws IOException {
if (channel.position() < channel.size()) {
clear();
buffer.clear();
channel.read(buffer);
memorySize = buffer.position();
while (position < memorySize) {
long recordPtr = address + position;
if (remain() < SizeOf.SIZE_OF_INT) {
channel.position(channel.position() - remain());
memorySize = (int) (memorySize - remain());
return true;
}
int recordSize = UNSAFE.getInt(recordPtr);
if (remain() < recordSize) {
channel.position(channel.position() - remain());
memorySize = (int) (memorySize - remain());
return true;
}
position += recordSize;
rowNum++;
}
return true;
} else {
return false;
}
}
/**
* Sets the version for the given neostore file in {@code storeDir}.
*
* @param storeDir the store dir to locate the neostore file in.
* @param version the version to set.
* @return the previous version before writing.
*/
public static long setVersion(String storeDir, long version) {
RandomAccessFile file = null;
try {
file = new RandomAccessFile(new File(storeDir, NeoStore.DEFAULT_NAME), "rw");
FileChannel channel = file.getChannel();
channel.position(RECORD_SIZE * 2 + 1 /*inUse*/);
ByteBuffer buffer = ByteBuffer.allocate(8);
channel.read(buffer);
buffer.flip();
long previous = buffer.getLong();
channel.position(RECORD_SIZE * 2 + 1 /*inUse*/);
buffer.clear();
buffer.putLong(version).flip();
channel.write(buffer);
return previous;
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
if (file != null) file.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
@Test
public void testAppend() throws IOException {
RegularFile file = regularFile(0);
FileChannel channel = channel(file, WRITE, APPEND);
assertEquals(0, channel.position());
ByteBuffer buf = buffer("1234567890");
ByteBuffer buf2 = buffer("1234567890");
assertEquals(10, channel.write(buf));
assertEquals(10, channel.position());
buf.flip();
channel.position(0);
assertEquals(20, channel.write(new ByteBuffer[] {buf, buf2}));
assertEquals(30, channel.position());
buf.flip();
buf2.flip();
channel.position(0);
assertEquals(20, channel.write(new ByteBuffer[] {buf, buf2}, 0, 2));
assertEquals(50, channel.position());
buf.flip();
channel.position(0);
assertEquals(10, channel.write(buf, 5));
assertEquals(60, channel.position());
buf.flip();
channel.position(0);
assertEquals(10, channel.transferFrom(new ByteBufferChannel(buf), 0, 10));
assertEquals(70, channel.position());
}
/**
* Closes this store. This will cause all buffers and channels to be closed. Requesting an
* operation from after this method has been invoked is illegal and an exception will be thrown.
*
* <p>This method will start by invoking the {@link #closeStorage} method giving the implementing
* store way to do anything that it needs to do before the fileChannel is closed.
*/
public void close() {
if (fileChannel == null) {
return;
}
closeStorage();
if (windowPool != null) {
windowPool.close();
windowPool = null;
}
if ((isReadOnly() && !isBackupSlave()) || idGenerator == null || !storeOk) {
releaseFileLockAndCloseFileChannel();
return;
}
long highId = idGenerator.getHighId();
int recordSize = -1;
if (this instanceof AbstractDynamicStore) {
recordSize = ((AbstractDynamicStore) this).getBlockSize();
} else if (this instanceof AbstractStore) {
recordSize = ((AbstractStore) this).getRecordSize();
}
idGenerator.close();
boolean success = false;
IOException storedIoe = null;
// hack for WINBLOWS
if (!readOnly || backupSlave) {
for (int i = 0; i < 10; i++) {
try {
fileChannel.position(highId * recordSize);
ByteBuffer buffer = ByteBuffer.wrap(UTF8.encode(getTypeAndVersionDescriptor()));
fileChannel.write(buffer);
stringLogger.debug(
"Closing "
+ storageFileName
+ ", truncating at "
+ fileChannel.position()
+ " vs file size "
+ fileChannel.size());
fileChannel.truncate(fileChannel.position());
fileChannel.force(false);
releaseFileLockAndCloseFileChannel();
success = true;
break;
} catch (IOException e) {
storedIoe = e;
System.gc();
}
}
} else {
releaseFileLockAndCloseFileChannel();
success = true;
}
if (!success) {
throw new UnderlyingStorageException(
"Unable to close store " + getStorageFileName(), storedIoe);
}
}
private void storeSerializedRecord(File file, byte[] serialized) throws IOException {
RandomAccessFile recordFile = new RandomAccessFile(file, "rw");
FileChannel out = recordFile.getChannel();
out.position(0);
writeInteger(CURRENT_VERSION_MARKER, out);
writeBlob(serialized, out);
out.truncate(out.position());
recordFile.close();
}
/**
* Invalidate buffer before a position change has occurred (e.g. seek), flushing writes if
* required, and correcting file position if reading
*
* @throws IOException
*/
private void invalidateBuffer() throws IOException, BadDescriptorException {
if (!reading) flushWrite();
int posOverrun = buffer.remaining(); // how far ahead we are when reading
buffer.clear();
if (reading) {
buffer.flip();
// if the read buffer is ahead, back up
FileChannel fileChannel = (FileChannel) descriptor.getChannel();
if (posOverrun != 0) fileChannel.position(fileChannel.position() - posOverrun);
}
}
private void resetForWrite() throws IOException {
if (descriptor.isSeekable()) {
FileChannel fileChannel = (FileChannel) descriptor.getChannel();
if (buffer.hasRemaining()) { // we have read ahead, and need to back up
fileChannel.position(fileChannel.position() - buffer.remaining());
}
}
// FIXME: Clearing read buffer here...is this appropriate?
buffer.clear();
reading = false;
}
/**
* Append a message and return its id (position in the file plus the firstMessageId of the file).
* Returns -1 if this file is too full for the message.
*/
public long append(
long timestamp, String routingKey, ReadableByteChannel payload, int payloadSize)
throws IOException {
int n = routingKey.length();
if (n > 255)
throw new IllegalArgumentException("Routing key length " + n + " > 255 characters");
byte[] routingKeyBytes = routingKey.getBytes(UTF8);
synchronized (channel) {
if (length + MESSAGE_HEADER_SIZE + routingKeyBytes.length + payloadSize > maxFileSize)
return -1;
header.clear();
channel.position(length);
header.put(TYPE_MESSAGE);
header.putLong(timestamp);
header.putShort((short) routingKeyBytes.length);
header.putInt(payloadSize);
header.put(routingKeyBytes);
header.flip();
int id = length - FILE_HEADER_SIZE;
channel.write(header);
long sz = channel.transferFrom(payload, channel.position(), payloadSize);
if (sz != payloadSize) {
throw new IOException(
"Only read " + sz + " bytes from payload channel instead of " + payloadSize);
}
length =
(int) channel.position()
+ payloadSize; // update after write so a partial write won't corrupt file
// see if we need to start a new histogram bucket
if (bucketIndex < 0
|| ((id - bucketMessageId >= bytesPerBucket) && bucketIndex < MAX_BUCKETS - 1)) {
if (bucketIndex >= 0) {
putBucketDataInFileHeader();
++bucketIndex;
} else {
bucketIndex = 0;
}
bucketMessageId = id;
bucketTimestamp = timestamp;
bucketCount = 1;
} else {
++bucketCount;
}
mostRecentTimestamp = timestamp;
return firstMessageId + id;
}
}
/**
* Load enough bytes from channel to buffer. After the loading process, the caller can make sure
* the amount in buffer is of size 'amount' if we haven't reached the end of channel.
*
* @param amount The amount of bytes in buffer after returning, no larger than bufferSize
* @param reload Whether to reload or append
*/
private void fillBuffer(long amount, boolean reload) {
try {
if (amount > bufferSize) {
amount = bufferSize;
}
// Read all remaining bytes if the requested amount reach the end
// of channel.
if (channelSize - channel.position() < amount) {
amount = channelSize - channel.position();
}
if (in == null) {
switch (bufferType) {
case HEAP:
in = ByteBuffer.allocate(bufferSize, false);
break;
case DIRECT:
in = ByteBuffer.allocate(bufferSize, true);
break;
case AUTO:
in = ByteBuffer.allocate(bufferSize);
break;
default:
in = ByteBuffer.allocate(bufferSize);
}
channel.read(in.buf());
in.flip();
useLoadBuf = true;
}
if (!useLoadBuf) {
return;
}
if (reload || in.remaining() < amount) {
if (!reload) {
in.compact();
} else {
in.clear();
}
channel.read(in.buf());
in.flip();
}
} catch (Exception e) {
log.error("Error fillBuffer", e);
}
}
public int read() throws IOException {
if (channel.position() >= channel.size()) {
return -1;
}
FileUtils.readFully(channel, ByteBuffer.wrap(buffer));
return buffer[0] & 0xff;
}
public long getContentLength() {
try {
return Math.min(mChunkSize, mChannel.size() - mChannel.position());
} catch (IOException e) {
return mChunkSize;
}
}
/**
* Moves the reader to the specified byte offset in the file. Mind that:
*
* <ul>
* <li>it's your responsibility to ensure the offset corresponds to the actual beginning of a
* shape struct
* <li>once you call this, reading with hasNext/next on sparse shapefiles will be broken (we
* don't know anymore at which shape we are)
* </ul>
*
* @param offset
* @throws IOException
* @throws UnsupportedOperationException
*/
public void goTo(int offset) throws IOException, UnsupportedOperationException {
disableShxUsage();
if (randomAccessEnabled) {
if (this.useMemoryMappedBuffer) {
buffer.position(offset);
} else {
/*
* Check to see if requested offset is already loaded; ensure
* that record header is in the buffer
*/
if (this.currentOffset <= offset && this.currentOffset + buffer.limit() >= offset + 8) {
buffer.position(this.toBufferOffset(offset));
} else {
FileChannel fc = (FileChannel) this.channel;
fc.position(offset);
this.currentOffset = offset;
buffer.position(0);
buffer.limit(buffer.capacity());
fill(buffer, fc);
buffer.position(0);
}
}
int oldRecordOffset = record.end;
record.end = offset;
try {
hasNext(false); // don't check for next logical record equality
} catch (IOException ioe) {
record.end = oldRecordOffset;
throw ioe;
}
} else {
throw new UnsupportedOperationException("Random Access not enabled");
}
}
@Override
public void close() throws IOException, InterruptedException {
try {
m_outstandingWriteTasksLock.lock();
try {
while (m_outstandingWriteTasks.get() > 0) {
m_noMoreOutstandingWriteTasksCondition.await();
}
} finally {
m_outstandingWriteTasksLock.unlock();
}
m_syncTask.cancel(false);
m_channel.force(false);
} finally {
m_bytesAllowedBeforeSync.release(m_bytesWrittenSinceLastSync.getAndSet(0));
}
m_channel.position(8);
ByteBuffer completed = ByteBuffer.allocate(1);
if (m_writeFailed) {
completed.put((byte) 0).flip();
} else {
completed.put((byte) 1).flip();
}
m_channel.write(completed);
m_channel.force(false);
m_channel.close();
if (m_onCloseHandler != null) {
m_onCloseHandler.run();
}
}
private ByteList bufferedRead(int number) throws IOException, BadDescriptorException {
checkReadable();
ensureRead();
int resultSize = 0;
// 128K seems to be the minimum at which the stat+seek is faster than reallocation
final int BULK_THRESHOLD = 128 * 1024;
if (number >= BULK_THRESHOLD
&& descriptor.isSeekable()
&& descriptor.getChannel() instanceof FileChannel) {
//
// If it is a file channel, then we can pre-allocate the output buffer
// to the total size of buffered + remaining bytes in file
//
FileChannel fileChannel = (FileChannel) descriptor.getChannel();
resultSize =
(int)
Math.min(
fileChannel.size() - fileChannel.position() + bufferedInputBytesRemaining(),
number);
} else {
//
// Cannot discern the total read length - allocate at least enough for the buffered data
//
resultSize = Math.min(bufferedInputBytesRemaining(), number);
}
ByteList result = new ByteList(resultSize);
bufferedRead(result, number);
return result;
}
@Override
public synchronized void reset() throws IOException {
if (mark == -1) {
throw new IOException("not marked");
}
myFileChannel.position(mark);
}
public int write(ByteBuffer src) throws IOException {
if (filePointer >= length && filePointer > maxLength) {
// may need to extend and create files
long oldFilePointer = filePointer;
long x = length - (length % maxLength) + maxLength;
for (; x < filePointer; x += maxLength) {
if (x > length) {
// expand the file size
position(x - 1);
write(ByteBuffer.wrap(new byte[1]));
}
filePointer = oldFilePointer;
}
}
long offset = filePointer % maxLength;
int len = src.remaining();
FileChannel channel = getFileChannel();
channel.position(offset);
int l = (int) Math.min(len, maxLength - offset);
if (l == len) {
l = channel.write(src);
} else {
int oldLimit = src.limit();
src.limit(src.position() + l);
l = channel.write(src);
src.limit(oldLimit);
}
filePointer += l;
length = Math.max(length, filePointer);
return l;
}
// Read up to 'len' bytes of Value. Value should already be persisted to
// disk. A racing delete can trigger a failure where we get a null return,
// but no crash (although one could argue that a racing load&delete is a bug
// no matter what).
@Override
public byte[] load(Value v) {
long skip = 0;
Key k = v._key;
// Convert an arraylet chunk into a long-offset from the base file.
if (k._kb[0] == Key.ARRAYLET_CHUNK) {
skip = ValueArray.getChunkOffset(k); // The offset
k = ValueArray.getArrayKey(k); // From the base file key
}
if (k._kb[0] == Key.DVEC) {
skip = water.fvec.NFSFileVec.chunkOffset(k); // The offset
}
try {
FileInputStream s = null;
try {
s = new FileInputStream(getFileForKey(k));
FileChannel fc = s.getChannel();
fc.position(skip);
AutoBuffer ab = new AutoBuffer(fc, true, Value.NFS);
byte[] b = ab.getA1(v._max);
ab.close();
assert v.isPersisted();
return b;
} finally {
if (s != null) s.close();
}
} catch (IOException e) { // Broken disk / short-file???
H2O.ignore(e);
return null;
}
}
// from https://gist.github.com/889747
// TODO use Jakarta Commons IO..! This implementation needs to be improved.
private static void copyFile(File sourceFile, File destFile) throws IOException {
if (!destFile.exists()) {
destFile.createNewFile();
}
FileInputStream fIn = null;
FileOutputStream fOut = null;
FileChannel source = null;
FileChannel destination = null;
try {
fIn = new FileInputStream(sourceFile);
source = fIn.getChannel();
fOut = new FileOutputStream(destFile);
destination = fOut.getChannel();
long transfered = 0;
long bytes = source.size();
while (transfered < bytes) {
transfered += destination.transferFrom(source, 0, source.size());
destination.position(transfered);
}
} finally {
if (source != null) {
source.close();
} else if (fIn != null) {
fIn.close();
}
if (destination != null) {
destination.close();
} else if (fOut != null) {
fOut.close();
}
}
}
/**
* @param startByte
* @param endByte
* @return
* @throws Exception
* @return true if all the bytes between in the file between startByte and endByte are null, false
* otherwise
*/
private boolean isFilePortionNull(int startByte, int endByte) throws IOException {
logger.config("Checking file portion:" + Hex.asHex(startByte) + ":" + Hex.asHex(endByte));
FileInputStream fis = null;
FileChannel fc = null;
try {
fis = new FileInputStream(file);
fc = fis.getChannel();
fc.position(startByte);
ByteBuffer bb = ByteBuffer.allocateDirect(endByte - startByte);
fc.read(bb);
while (bb.hasRemaining()) {
if (bb.get() != 0) {
return false;
}
}
} finally {
if (fc != null) {
fc.close();
}
if (fis != null) {
fis.close();
}
}
return true;
}
public void test_getChannel() {
// Test for method FileChannel FileInputStream.getChannel()
FileChannel channel;
byte[] buffer = new byte[100];
byte[] stringBytes;
final int offset = 5;
boolean equal = true;
try {
FileInputStream fis = new FileInputStream(fileName);
channel = fis.getChannel();
assertNotNull(channel);
assertTrue("Channel is closed.", channel.isOpen());
// Check that the channel is associated with the input stream.
channel.position(offset);
fis.read(buffer, 0, 10);
stringBytes = fileString.getBytes();
for (int i = 0; i < 10; i++) {
equal &= (buffer[i] == stringBytes[i + offset]);
}
assertTrue("Channel is not associated with this stream.", equal);
fis.close();
assertFalse("Channel has not been closed.", channel.isOpen());
} catch (FileNotFoundException e) {
fail("Could not find : " + fileName);
} catch (IOException e) {
fail("Exception during test : " + e.getMessage());
}
}
/**
* write properties to disk
*
* @return success True if successfully written
* @throws IOException
*/
private void write() throws IOException {
if (channel != null) {
channel.position(0);
}
om.writeValue(fos, properties);
fos.flush();
}
/**
* Picks a block with samplingRate probability Used in the first phase of up-front partitioning.
*
* @param filename
* @param samplingRate
*/
public void scanWithBlockSampling(String filename, double samplingRate, OutputStream out) {
initScan(blockSampleSize);
FileChannel ch = IOUtils.openFileChannel(filename);
try {
for (long position = 0; ; position += blockSampleSize) {
while (sampleSucceed(samplingRate) == false) {
position += blockSampleSize;
}
ch.position(position);
if ((nRead = ch.read(bb)) == -1) {
break;
}
byteArrayIdx = previous = 0;
if (position != 0) {
// skip the first tuple if not starting of file.
while (byteArrayIdx < nRead && byteArray[byteArrayIdx] != newLine) {
byteArrayIdx++;
}
previous = ++byteArrayIdx;
}
processByteBuffer(null, out);
bb.clear();
out.flush(); // It only helps get an exact profiling?
}
} catch (IOException e) {
e.printStackTrace();
}
IOUtils.closeFileChannel(ch);
firstPass = false;
}
private static long getRecord(String storeDir, long recordPosition) {
RandomAccessFile file = null;
try {
file = new RandomAccessFile(new File(storeDir), "rw");
FileChannel channel = file.getChannel();
/*
* We have to check size, because the store version
* field was introduced with 1.5, so if there is a non-clean
* shutdown we may have a buffer underflow.
*/
if (recordPosition > 3 && channel.size() < RECORD_SIZE * 5) {
return -1;
}
channel.position(RECORD_SIZE * recordPosition + 1 /*inUse*/);
ByteBuffer buffer = ByteBuffer.allocate(8);
channel.read(buffer);
buffer.flip();
long previous = buffer.getLong();
return previous;
} catch (IOException e) {
throw new RuntimeException(e);
} finally {
try {
if (file != null) file.close();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
public int read(byte[] b, int off, int len) throws IOException {
if (channel.position() + len < channel.size()) {
FileUtils.readFully(channel, ByteBuffer.wrap(b, off, len));
return len;
}
return super.read(b, off, len);
}