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SDK for Microsoft Azure Storage Clients
/**
* Copyright Microsoft Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.microsoft.azure.storage.blob;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import com.microsoft.azure.storage.AccessCondition;
import com.microsoft.azure.storage.Constants;
import com.microsoft.azure.storage.DoesServiceRequest;
import com.microsoft.azure.storage.OperationContext;
import com.microsoft.azure.storage.StorageErrorCode;
import com.microsoft.azure.storage.StorageErrorCodeStrings;
import com.microsoft.azure.storage.StorageException;
import com.microsoft.azure.storage.core.Base64;
import com.microsoft.azure.storage.core.SR;
import com.microsoft.azure.storage.core.Utility;
/**
* Provides an input stream to read a given blob resource.
*/
public final class BlobInputStream extends InputStream {
/**
* Holds the reference to the blob this stream is associated with.
*/
private final CloudBlob parentBlobRef;
/**
* Holds the reference to the MD5 digest for the blob.
*/
private MessageDigest md5Digest;
/**
* A flag to determine if the stream is faulted, if so the last error will be thrown on next operation.
*/
private volatile boolean streamFaulted;
/**
* Holds the last exception this stream encountered.
*/
private IOException lastError;
/**
* Holds the OperationContext for the current stream.
*/
private final OperationContext opContext;
/**
* Holds the options for the current stream
*/
private final BlobRequestOptions options;
/**
* Holds the stream length.
*/
private long streamLength = -1;
/**
* Holds the stream read size for both block and page blobs.
*/
private final int readSize;
/**
* A flag indicating if the Blob MD5 should be validated.
*/
private boolean validateBlobMd5;
/**
* Holds the Blob MD5.
*/
private final String retrievedContentMD5Value;
/**
* Holds the reference to the current buffered data.
*/
private ByteArrayInputStream currentBuffer;
/**
* Holds an absolute byte position for the mark feature.
*/
private long markedPosition;
/**
* Holds the mark delta for which the mark position is expired.
*/
private int markExpiry;
/**
* Holds an absolute byte position of the current read position.
*/
private long currentAbsoluteReadPosition;
/**
* Holds the absolute byte position of the start of the current buffer.
*/
private long bufferStartOffset;
/**
* Holds the length of the current buffer in bytes.
*/
private int bufferSize;
/**
* Holds the {@link AccessCondition} object that represents the access conditions for the blob.
*/
private AccessCondition accessCondition = null;
/**
* Initializes a new instance of the BlobInputStream class.
*
* @param parentBlob
* A {@link CloudBlob} object which represents the blob that this stream is associated with.
* @param accessCondition
* An {@link AccessCondition} object which represents the access conditions for the blob.
* @param options
* A {@link BlobRequestOptions} object which represents that specifies any additional options for the
* request.
* @param opContext
* An {@link OperationContext} object which is used to track the execution of the operation.
*
* @throws StorageException
* An exception representing any error which occurred during the operation.
*/
@DoesServiceRequest
protected BlobInputStream(final CloudBlob parentBlob, final AccessCondition accessCondition,
final BlobRequestOptions options, final OperationContext opContext) throws StorageException {
this.parentBlobRef = parentBlob;
this.parentBlobRef.assertCorrectBlobType();
this.options = new BlobRequestOptions(options);
this.opContext = opContext;
this.streamFaulted = false;
this.currentAbsoluteReadPosition = 0;
this.readSize = parentBlob.getStreamMinimumReadSizeInBytes();
if (options.getUseTransactionalContentMD5() && this.readSize > 4 * Constants.MB) {
throw new IllegalArgumentException(SR.INVALID_RANGE_CONTENT_MD5_HEADER);
}
parentBlob.downloadAttributes(accessCondition, this.options, this.opContext);
this.retrievedContentMD5Value = parentBlob.getProperties().getContentMD5();
// Will validate it if it was returned
this.validateBlobMd5 = !options.getDisableContentMD5Validation()
&& !Utility.isNullOrEmpty(this.retrievedContentMD5Value);
// Validates the first option, and sets future requests to use if match
// request option.
// If there is an existing conditional validate it, as we intend to
// replace if for future requests.
String previousLeaseId = null;
if (accessCondition != null) {
previousLeaseId = accessCondition.getLeaseID();
if (!accessCondition.verifyConditional(this.parentBlobRef.getProperties().getEtag(), this.parentBlobRef
.getProperties().getLastModified())) {
throw new StorageException(StorageErrorCode.CONDITION_FAILED.toString(),
SR.INVALID_CONDITIONAL_HEADERS, HttpURLConnection.HTTP_PRECON_FAILED, null, null);
}
}
this.accessCondition = AccessCondition.generateIfMatchCondition(this.parentBlobRef.getProperties().getEtag());
this.accessCondition.setLeaseID(previousLeaseId);
this.streamLength = parentBlob.getProperties().getLength();
if (this.validateBlobMd5) {
try {
this.md5Digest = MessageDigest.getInstance("MD5");
}
catch (final NoSuchAlgorithmException e) {
// This wont happen, throw fatal.
throw Utility.generateNewUnexpectedStorageException(e);
}
}
this.reposition(0);
}
/**
* Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without
* blocking by the next invocation of a method for this input stream. The next invocation might be the same thread
* or another thread. A single read or skip of this many bytes will not block, but may read or skip fewer bytes.
*
* @return An int which represents an estimate of the number of bytes that can be read (or skipped
* over)
* from this input stream without blocking, or 0 when it reaches the end of the input stream.
*
* @throws IOException
* If an I/O error occurs.
*/
@Override
public synchronized int available() throws IOException {
return this.bufferSize - (int) (this.currentAbsoluteReadPosition - this.bufferStartOffset);
}
/**
* Helper function to check if the stream is faulted, if it is it surfaces the exception.
*
* @throws IOException
* If an I/O error occurs. In particular, an IOException may be thrown if the output stream has been
* closed.
*/
private synchronized void checkStreamState() throws IOException {
if (this.streamFaulted) {
throw this.lastError;
}
}
/**
* Closes this input stream and releases any system resources associated with the stream.
*
* @throws IOException
* If an I/O error occurs.
*/
@Override
public synchronized void close() throws IOException {
this.currentBuffer = null;
this.streamFaulted = true;
this.lastError = new IOException(SR.STREAM_CLOSED);
}
/**
* Dispatches a read operation of N bytes. When using sparspe page blobs the page ranges are evaluated and zero
* bytes may be generated on the client side for some ranges that do not exist.
*
* @param readLength
* An int which represents the number of bytes to read.
*
* @throws IOException
* If an I/O error occurs.
*/
@DoesServiceRequest
private synchronized void dispatchRead(final int readLength) throws IOException {
try {
final byte[] byteBuffer = new byte[readLength];
this.parentBlobRef.downloadRangeInternal(this.currentAbsoluteReadPosition, (long) readLength, byteBuffer,
0, this.accessCondition, this.options, this.opContext);
this.currentBuffer = new ByteArrayInputStream(byteBuffer);
this.bufferSize = readLength;
this.bufferStartOffset = this.currentAbsoluteReadPosition;
}
catch (final StorageException e) {
this.streamFaulted = true;
this.lastError = Utility.initIOException(e);
throw this.lastError;
}
}
/**
* Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at
* the last marked position so that subsequent reads re-read the same bytes.
*
* @param readlimit
* An int which represents the maximum limit of bytes that can be read before the mark
* position becomes invalid.
*/
@Override
public synchronized void mark(final int readlimit) {
this.markedPosition = this.currentAbsoluteReadPosition;
this.markExpiry = readlimit;
}
/**
* Tests if this input stream supports the mark and reset methods. Whether or not mark and reset are supported is an
* invariant property of a particular input stream instance. The markSupported method of {@link InputStream} returns
* false.
*
* @return True if this stream instance supports the mark and reset methods; False
* otherwise.
*/
@Override
public boolean markSupported() {
return true;
}
/**
* Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If
* no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks
* until input data is available, the end of the stream is detected, or an exception is thrown.
*
* @return An int which represents the total number of bytes read into the buffer, or -1 if
* there is no more data because the end of the stream has been reached.
*
* @throws IOException
* If an I/O error occurs.
*/
@Override
@DoesServiceRequest
public int read() throws IOException {
final byte[] tBuff = new byte[1];
final int numberOfBytesRead = this.read(tBuff, 0, 1);
if (numberOfBytesRead > 0) {
return tBuff[0] & 0xFF;
}
else if (numberOfBytesRead == 0) {
throw new IOException(SR.UNEXPECTED_STREAM_READ_ERROR);
}
else {
return -1;
}
}
/**
* Reads some number of bytes from the input stream and stores them into the buffer array b. The number
* of bytes
* actually read is returned as an integer. This method blocks until input data is available, end of file is
* detected, or an exception is thrown. If the length of b is zero, then no bytes are read and 0 is
* returned;
* otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at the
* end of the file, the value -1 is returned; otherwise, at least one byte is read and stored into b.
*
* The first byte read is stored into element b[0], the next one into b[1], and so on. The
* number of bytes read is,
* at most, equal to the length of b. Let k be the number of bytes actually read; these
* bytes will be stored in
* elements b[0] through b[k-1], leaving elements b[k] through
* b[b.length-1] unaffected.
*
* The read(b) method for class {@link InputStream} has the same effect as:
*
* read(b, 0, b.length)
*
* @param b
* A byte array which represents the buffer into which the data is read.
*
* @throws IOException
* If the first byte cannot be read for any reason other than the end of the file, if the input stream
* has been closed, or if some other I/O error occurs.
* @throws NullPointerException
* If the byte array b is null.
*/
@Override
@DoesServiceRequest
public int read(final byte[] b) throws IOException {
return this.read(b, 0, b.length);
}
/**
* Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to
* read as many as len bytes, but a smaller number may be read. The number of bytes actually read is
* returned as an integer. This
* method blocks until input data is available, end of file is detected, or an exception is thrown.
*
* If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at
* least one
* byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least
* one byte is read and stored into b.
*
* The first byte read is stored into element b[off], the next one into b[off+1], and so
* on. The number of bytes
* read is, at most, equal to len. Let k be the number of bytes actually read; these bytes
* will be stored in
* elements b[off] through b[off+k-1], leaving elements b[off+k] through
* b[off+len-1] unaffected.
*
* In every case, elements b[0] through b[off] and elements b[off+len]
* through b[b.length-1] are unaffected.
*
* The read(b, off, len) method for class {@link InputStream} simply calls the method
* read() repeatedly. If the first such
* call results in an IOException, that exception is returned from the call to the
* read(b, off, len) method. If any
* subsequent call to read() results in a IOException, the exception is caught and treated
* as if it were end of
* file; the bytes read up to that point are stored into b and the number of bytes read before the
* exception
* occurred is returned. The default implementation of this method blocks until the requested amount of input data
* len has been read, end of file is detected, or an exception is thrown. Subclasses are encouraged to
* provide a
* more efficient implementation of this method.
*
* @param b
* A byte array which represents the buffer into which the data is read.
* @param off
* An int which represents the start offset in the byte array at which the data
* is written.
* @param len
* An int which represents the maximum number of bytes to read.
*
* @return An int which represents the total number of bytes read into the buffer, or -1 if
* there is no more data because the end of the stream has been reached.
*
* @throws IOException
* If the first byte cannot be read for any reason other than end of file, or if the input stream has
* been closed, or if some other I/O error occurs.
* @throws NullPointerException
* If the byte array b is null.
* @throws IndexOutOfBoundsException
* If off is negative, len is negative, or len is greater than
* b.length - off.
*/
@Override
@DoesServiceRequest
public int read(final byte[] b, final int off, final int len) throws IOException {
if (off < 0 || len < 0 || len > b.length - off) {
throw new IndexOutOfBoundsException();
}
return this.readInternal(b, off, len);
}
/**
* Performs internal read to the given byte buffer.
*
* @param b
* A byte array which represents the buffer into which the data is read.
* @param off
* An int which represents the start offset in the byte array b at
* which the data is written.
* @param len
* An int which represents the maximum number of bytes to read.
*
* @return An int which represents the total number of bytes read into the buffer, or -1 if
* there is no more data because the end of the stream has been reached.
*
* @throws IOException
* If the first byte cannot be read for any reason other than end of file, or if the input stream has
* been closed, or if some other I/O error occurs.
*/
@DoesServiceRequest
private synchronized int readInternal(final byte[] b, final int off, int len) throws IOException {
this.checkStreamState();
// if buffer is empty do next get operation
if ((this.currentBuffer == null || this.currentBuffer.available() == 0)
&& this.currentAbsoluteReadPosition < this.streamLength) {
this.dispatchRead((int) Math.min(this.readSize, this.streamLength - this.currentAbsoluteReadPosition));
}
len = Math.min(len, this.readSize);
// do read from buffer
final int numberOfBytesRead = this.currentBuffer.read(b, off, len);
if (numberOfBytesRead > 0) {
this.currentAbsoluteReadPosition += numberOfBytesRead;
if (this.validateBlobMd5) {
this.md5Digest.update(b, off, numberOfBytesRead);
if (this.currentAbsoluteReadPosition == this.streamLength) {
// Reached end of stream, validate md5.
final String calculatedMd5 = Base64.encode(this.md5Digest.digest());
if (!calculatedMd5.equals(this.retrievedContentMD5Value)) {
this.lastError = Utility
.initIOException(new StorageException(
StorageErrorCodeStrings.INVALID_MD5,
String.format(
"Blob data corrupted (integrity check failed), Expected value is %s, retrieved %s",
this.retrievedContentMD5Value, calculatedMd5),
Constants.HeaderConstants.HTTP_UNUSED_306, null, null));
this.streamFaulted = true;
throw this.lastError;
}
}
}
}
// update markers
if (this.markExpiry > 0 && this.markedPosition + this.markExpiry < this.currentAbsoluteReadPosition) {
this.markedPosition = 0;
this.markExpiry = 0;
}
return numberOfBytesRead;
}
/**
* Repositions the stream to the given absolute byte offset.
*
* @param absolutePosition
* A long which represents the absolute byte offset withitn the stream reposition.
*/
private synchronized void reposition(final long absolutePosition) {
this.currentAbsoluteReadPosition = absolutePosition;
this.currentBuffer = new ByteArrayInputStream(new byte[0]);
}
/**
* Repositions this stream to the position at the time the mark method was last called on this input stream. Note
* repositioning the blob read stream will disable blob MD5 checking.
*
* @throws IOException
* If this stream has not been marked or if the mark has been invalidated.
*/
@Override
public synchronized void reset() throws IOException {
if (this.markedPosition + this.markExpiry < this.currentAbsoluteReadPosition) {
throw new IOException(SR.MARK_EXPIRED);
}
this.validateBlobMd5 = false;
this.md5Digest = null;
this.reposition(this.markedPosition);
}
/**
* Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons,
* end up skipping over some smaller number of bytes, possibly 0. This may result from any of a number of
* conditions; reaching end of file before n bytes have been skipped is only one possibility. The actual number of
* bytes skipped is returned. If n is negative, no bytes are skipped.
*
* Note repositioning the blob read stream will disable blob MD5 checking.
*
* @param n
* A long which represents the number of bytes to skip.
*/
@Override
public synchronized long skip(final long n) throws IOException {
if (n == 0) {
return 0;
}
if (n < 0 || this.currentAbsoluteReadPosition + n > this.streamLength) {
throw new IndexOutOfBoundsException();
}
this.validateBlobMd5 = false;
this.md5Digest = null;
this.reposition(this.currentAbsoluteReadPosition + n);
return n;
}
}