BlobInputStream Class

Package:

com.microsoft.azure.storage.blob

• java.lang.Object
• • InputStream
  • • com.microsoft.azure.storage.blob.BlobInputStream

public class BlobInputStream

Provides an input stream to read a given blob resource.

Constructor Summary

Constructor	Description
BlobInputStream(final CloudBlob parentBlob, final AccessCondition accessCondition, final BlobRequestOptions options, final OperationContext opContext)	Initializes a new instance of the BlobInputStream class.
BlobInputStream(long blobRangeOffset, Long blobRangeLength, final CloudBlob parentBlob, final AccessCondition accessCondition, final BlobRequestOptions options, final OperationContext opContext)	Initializes a new instance of the BlobInputStream class. Note that ifblobRangeOffset  </code> is not<code>0  </code> or<code>blobRangeLength  </code> is not<code>null  </code> , there will be no content MD5 verification.</p>

Method Summary

Modifier and Type	Method and Description
synchronized int	available() 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.
synchronized void	close() Closes this input stream and releases any system resources associated with the stream.
synchronized void	mark(final int readlimit) 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.
boolean	markSupported() 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 InputStream returns false.
int	read() 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.
int	read(final byte[] b) Reads some number of bytes from the input stream and stores them into the buffer array . 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 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 . The first byte read is stored into element , the next one into , and so on. The number of bytes read is, at most, equal to the length of . Let be the number of bytes actually read; these bytes will be stored in elements through , leaving elements through unaffected. The method for class InputStream has the same effect as:
int	read(final byte[] b, final int off, final int len) Reads up to bytes of data from the input stream into an array of bytes. An attempt is made to read as many as 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 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 . The first byte read is stored into element , the next one into , and so on. The number of bytes read is, at most, equal to . Let be the number of bytes actually read; these bytes will be stored in elements through , leaving elements through unaffected. In every case, elements through and elements through are unaffected. The method for class InputStream simply calls the method repeatedly. If the first such call results in an , that exception is returned from the call to the method. If any subsequent call to results in a , the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into 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 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.
synchronized void	reset() 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.
synchronized long	skip(final long n) 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.

Constructor Details

BlobInputStream

protected BlobInputStream(final CloudBlob parentBlob, final AccessCondition accessCondition, final BlobRequestOptions options, final OperationContext opContext)

Initializes a new instance of the BlobInputStream class.

Parameters:

parentBlob - A CloudBlob object which represents the blob that this stream is associated with.

accessCondition - An AccessCondition object which represents the access conditions for the blob.

options - A BlobRequestOptions object which represents that specifies any additional options for the request.

opContext - An OperationContext object which is used to track the execution of the operation.

Throws:

StorageException - An exception representing any error which occurred during the operation.

BlobInputStream

protected BlobInputStream(long blobRangeOffset, Long blobRangeLength, final CloudBlob parentBlob, final AccessCondition accessCondition, final BlobRequestOptions options, final OperationContext opContext)

Initializes a new instance of the BlobInputStream class. Note that ifblobRangeOffset 

</code> is not<code>0 

</code> or<code>blobRangeLength 

</code> is not<code>null 

</code> , there will be no content MD5 verification.</p>

Parameters:

blobRangeOffset - The offset of blob data to begin stream.

blobRangeLength - How much data the stream should return after blobRangeOffset.

parentBlob - A CloudBlob object which represents the blob that this stream is associated with.

accessCondition - An AccessCondition object which represents the access conditions for the blob.

options - A BlobRequestOptions object which represents that specifies any additional options for the request.

opContext - An OperationContext object which is used to track the execution of the operation.

Throws:

StorageException - An exception representing any error which occurred during the operation.

Method Details

available

public synchronized int available()

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.

Returns:

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.

close

public synchronized void close()

Closes this input stream and releases any system resources associated with the stream.

Throws:

IOException - If an I/O error occurs.

mark

public synchronized void mark(final int readlimit)

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.

Parameters:

readlimit - An int which represents the maximum limit of bytes that can be read before the mark position becomes invalid.

markSupported

public boolean markSupported()

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 InputStream returns false.

Returns:

True if this stream instance supports the mark and reset methods; False otherwise.

read

public int read()

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.

Returns:

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.

read

public int read(final byte[] b)

Reads some number of bytes from the input stream and stores them into the buffer array . 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 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 .

The first byte read is stored into element , the next one into , and so on. The number of bytes read is, at most, equal to the length of . Let be the number of bytes actually read; these bytes will be stored in elements through , leaving elements through unaffected.

The method for class InputStream has the same effect as:

Parameters:

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.

NullPointerException - If the byte array b is null.

read

public int read(final byte[] b, final int off, final int len)

Reads up to bytes of data from the input stream into an array of bytes. An attempt is made to read as many as 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 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 .

The first byte read is stored into element , the next one into , and so on. The number of bytes read is, at most, equal to . Let be the number of bytes actually read; these bytes will be stored in elements through , leaving elements through unaffected.

In every case, elements through and elements through are unaffected.

The method for class InputStream simply calls the method repeatedly. If the first such call results in an , that exception is returned from the call to the method. If any subsequent call to results in a , the exception is caught and treated as if it were end of file; the bytes read up to that point are stored into 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 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.

Parameters:

b - A byte array which represents the buffer into which the data is read.

off - An int which represents the start offset in the byte array at which the data is written.

len - An int which represents the maximum number of bytes to read.

Returns:

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.

NullPointerException - If the byte array b is null.

IndexOutOfBoundsException - If off is negative, len is negative, or len is greater than b.length - off.

reset

public synchronized void reset()

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.

skip

public synchronized long skip(final long n)

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.

Parameters:

n - A long which represents the number of bytes to skip.