org.postgresql.core

Class VisibleBufferedInputStream

java.lang.Object

java.io.InputStream

org.postgresql.core.VisibleBufferedInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class VisibleBufferedInputStream
extends InputStream

A faster version of BufferedInputStream. Does no synchronisation and allows direct access to the used byte[] buffer.

Author:

Mikko Tiihonen

Constructor Summary

Constructors

Constructor and Description
VisibleBufferedInputStream(InputStream in, int bufferSize) Creates a new buffer around the given stream.

Method Summary

Methods

Modifier and Type	Method and Description
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.
void	close() Closes this input stream and releases any system resources associated with the stream.
boolean	ensureBytes(int n) Ensures that the buffer contains at least n bytes.
byte[]	getBuffer() Returns direct handle to the used buffer.
int	getIndex() Returns the current read position in the buffer.
int	peek() Reads a byte from the buffer without advancing the index pointer.
int	read() Reads the next byte of data from the input stream.
int	read(byte[] to, int off, int len) Reads up to len bytes of data from the input stream into an array of bytes.
byte	readRaw() Reads byte from the buffer without any checks.
int	scanCStringLength() Scans the length of the next null terminated string (C-style string) from the stream.
long	skip(long n) Skips over and discards n bytes of data from this input stream.

Methods inherited from class java.io.InputStream

mark, markSupported, read, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

VisibleBufferedInputStream

public VisibleBufferedInputStream(InputStream in,
                          int bufferSize)

Creates a new buffer around the given stream.

Parameters:

in - The stream to buffer.

bufferSize - The initial size of the buffer.

Method Detail

read

public int read()
         throws 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. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

Specified by:

read in class InputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if an I/O error occurs.

peek

public int peek()
         throws IOException

Reads a byte from the buffer without advancing the index pointer.

Returns:

byte from the buffer without advancing the index pointer

Throws:

IOException - if something wrong happens

readRaw

public byte readRaw()

Reads byte from the buffer without any checks. This method never reads from the underlaying stream. Before calling this method the ensureBytes(int) method must have been called.

Returns:

The next byte from the buffer.

Throws:

ArrayIndexOutOfBoundsException - If ensureBytes was not called to make sure the buffer contains the byte.

ensureBytes

public boolean ensureBytes(int n)
                    throws IOException

Ensures that the buffer contains at least n bytes. This method invalidates the buffer and index fields.

Parameters:

n - The amount of bytes to ensure exists in buffer

Returns:

true if required bytes are available and false if EOF

Throws:

IOException - If reading of the wrapped stream failed.

read

public int read(byte[] to,
       int off,
       int len)
         throws IOException

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 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.

Overrides:

read in class InputStream

Parameters:

to - 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:

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.

See Also:

InputStream.read()

skip

public long skip(long n)
          throws 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.

The skip method of this class creates a byte array and then repeatedly reads into it until n bytes have been read or the end of the stream has been reached. Subclasses are encouraged to provide a more efficient implementation of this method. For instance, the implementation may depend on the ability to seek.

Overrides:

skip in class InputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if the stream does not support seek, or if some other I/O error occurs.

available

public int available()
              throws IOException

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.

Note that while some implementations of InputStream will return the total number of bytes in the stream, many will not. It is never correct to use the return value of this method to allocate a buffer intended to hold all data in this stream.

A subclass' implementation of this method may choose to throw an IOException if this input stream has been closed by invoking the InputStream.close() method.

The available method for class InputStream always returns 0.

This method should be overridden by subclasses.

Overrides:

available in class InputStream

Returns:

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 void close()
           throws IOException

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

The close method of InputStream does nothing.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class InputStream

Throws:

IOException - if an I/O error occurs.

getBuffer

public byte[] getBuffer()

Returns direct handle to the used buffer. Use the ensureBytes(int) to prefill required bytes the buffer and getIndex() to fetch the current position of the buffer.

Returns:

The underlaying buffer.

getIndex

public int getIndex()

Returns the current read position in the buffer.

Returns:

the current read position in the buffer.

scanCStringLength

public int scanCStringLength()
                      throws IOException

Scans the length of the next null terminated string (C-style string) from the stream.

Returns:

The length of the next null terminated string.

Throws:

IOException - If reading of stream fails.

EOFException - If the stream did not contain any null terminators.