org.apache.poi.poifs.filesystem
Class DocumentInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by org.apache.poi.poifs.filesystem.DocumentInputStream
All Implemented Interfaces:
java.io.Closeable

public class DocumentInputStream
extends java.io.InputStream

This class provides methods to read a DocumentEntry managed by a Filesystem instance.

Author:
Marc Johnson (mjohnson at apache dot org)

Constructor Summary
DocumentInputStream(DocumentEntry document)
          Create an InputStream from the specified DocumentEntry
DocumentInputStream(POIFSDocument document)
          Create an InputStream from the specified Document
 
Method Summary
 int available()
          Returns the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream.
 void close()
          Closes this input stream and releases any system resources associated with the stream.
 void mark(int ignoredReadlimit)
          Marks the current position in this input stream.
 boolean markSupported()
          Tests if this input stream supports the mark and reset methods.
 int read()
          Reads the next byte of data from the input stream.
 int read(byte[] b)
          Reads some number of bytes from the input stream and stores them into the buffer array b.
 int read(byte[] b, int off, int len)
          Reads up to len bytes of data from the input stream into an array of bytes.
 void reset()
          Repositions this stream to the position at the time the mark method was last called on this input stream.
 long skip(long n)
          Skips over and discards n bytes of data from this input stream.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

DocumentInputStream

public DocumentInputStream(DocumentEntry document)
                    throws java.io.IOException
Create an InputStream from the specified DocumentEntry

Parameters:
document - the DocumentEntry to be read
Throws:
java.io.IOException - if the DocumentEntry cannot be opened (like, maybe it has been deleted?)

DocumentInputStream

public DocumentInputStream(POIFSDocument document)
                    throws java.io.IOException
Create an InputStream from the specified Document

Parameters:
document - the Document to be read
Throws:
java.io.IOException - if the DocumentEntry cannot be opened (like, maybe it has been deleted?)
Method Detail

available

public int available()
              throws java.io.IOException
Returns the number of bytes that can be read (or skipped over) from this input stream without blocking by the next caller of a method for this input stream. The next caller might be the same thread or or another thread.

Overrides:
available in class java.io.InputStream
Returns:
the number of bytes that can be read from this input stream without blocking.
Throws:
java.io.IOException - on error (such as the stream has been closed)

close

public void close()
           throws java.io.IOException
Closes this input stream and releases any system resources associated with the stream.

Specified by:
close in interface java.io.Closeable
Overrides:
close in class java.io.InputStream
Throws:
java.io.IOException

mark

public void mark(int ignoredReadlimit)
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.

The readlimit arguments tells this input stream to allow that many bytes to be read before the mark position gets invalidated. This implementation, however, does not care.

The general contract of mark is that, if the method markSupported returns true, the stream somehow remembers all the bytes read after the call to mark and stands ready to supply those same bytes again if and whenever the method reset is called. However, the stream is not required to remember any data at all if more than readlimit bytes are read from the stream before reset is called. But this stream will.

Overrides:
mark in class java.io.InputStream
Parameters:
ignoredReadlimit - the maximum limit of bytes that can be read before the mark position becomes invalid. Ignored by this implementation.

markSupported

public boolean markSupported()
Tests if this input stream supports the mark and reset methods.

Overrides:
markSupported in class java.io.InputStream
Returns:
true

read

public int read()
         throws java.io.IOException
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. The definition of this method in java.io.InputStream allows this method to block, but it won't.

Specified by:
read in class java.io.InputStream
Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
java.io.IOException

read

public int read(byte[] b)
         throws java.io.IOException,
                java.lang.NullPointerException
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. The definition of this method in java.io.InputStream allows this method to block, but it won't.

If b is null, a NullPointerException 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 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[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.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

The read(b) method for class InputStream has the same effect as:

read(b, 0, b.length)

Overrides:
read in class java.io.InputStream
Parameters:
b - the buffer into which the data is read.
Returns:
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:
java.io.IOException
java.lang.NullPointerException

read

public int read(byte[] b,
                int off,
                int len)
         throws java.io.IOException,
                java.lang.NullPointerException,
                java.lang.IndexOutOfBoundsException
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, possibly zero. The number of bytes actually read is returned as an integer.

The definition of this method in java.io.InputStream allows it to block, but it won't.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException 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.

If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

Overrides:
read in class java.io.InputStream
Parameters:
b - the buffer into which the data is read.
off - the start offset in array b at which the data is written.
len - the maximum number of bytes to read.
Returns:
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:
java.io.IOException
java.lang.NullPointerException
java.lang.IndexOutOfBoundsException

reset

public void reset()
Repositions this stream to the position at the time the mark method was last called on this input stream.

The general contract of reset is:

All well and good ... this class's markSupported method returns true and this method does not care whether you've called mark at all, or whether you've exceeded the number of bytes specified in the last call to mark. We're basically walking a byte array ... mark and reset to your heart's content.

Overrides:
reset in class java.io.InputStream

skip

public long skip(long n)
          throws java.io.IOException
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.

Overrides:
skip in class java.io.InputStream
Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws:
java.io.IOException


Copyright 2008 The Apache Software Foundation or its licensors, as applicable.