com.flagstone.transform.coder
Class SWFDecoder

java.lang.Object
  com.flagstone.transform.coder.SWFDecoder

public final class SWFDecoder
extends Object

SWFDecoder wraps an InputStream with a buffer to reduce the amount of memory required to decode a movie and to improve efficiency by reading data from a file or external source in blocks.

Field Summary

static int

BUFFER_SIZE The default size, in bytes, for the internal buffer.

Constructor Summary

SWFDecoder(InputStream streamIn)
Create a new SWFDecoder for the underlying InputStream using the default buffer size.

SWFDecoder(InputStream streamIn, int length)
Create a new SWFDecoder for the underlying InputStream with the specified buffer size.

Method Summary

void	alignToByte() Changes the location to the next byte boundary.
int	bytesRead() Get the number of bytes read from the last saved position.
void	check(int count) Compare the number of bytes read since the last saved position and record any difference.
void	fill() Fill the internal buffer.
int	getDelta() Get the difference from the expected number of bytes from the last call to check().
int	getExpected() Get the expected number of bytes from the last call to check().
int	getLocation() Get the location recorded for the last call to check().
int	mark() Remember the current position.
int	readBits(int numberOfBits, boolean signed) Read a bit field.
int	readByte() Read an unsigned byte.
byte[]	readBytes(byte[] bytes) Reads an array of bytes.
float	readHalf() Read a single-precision floating point number.
int	readInt() Read an unsigned 32-bit integer.
int	readSignedShort() Read an unsigned 16-bit integer.
String	readString() Read a null-terminated string using the default character set defined in the decoder.
String	readString(int length) Read a string using the default character set defined in the decoder.
int	readUnsignedShort() Read an unsigned 16-bit integer.
int	readVarInt() Read a 32-bit unsigned integer, encoded using a variable number of bytes.
void	reset() Reposition the decoder to the point recorded by the last call to the mark() method.
int	scanBits(int numberOfBits, boolean signed) Read-ahead a bit field.
int	scanByte() Read an unsigned byte but do not advance the internal pointer.
int	scanUnsignedShort() Read an unsigned 16-bit integer.
void	setEncoding(CharacterEncoding enc) Sets the character encoding scheme used when encoding or decoding strings.
void	skip(int count) Skips over and discards n bytes of data.
void	unmark() Discard the last saved position.

Methods inherited from class java.lang.Object

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

Field Detail

BUFFER_SIZE

public static final int BUFFER_SIZE

The default size, in bytes, for the internal buffer.

See Also:

Constant Field Values

Constructor Detail

SWFDecoder

public SWFDecoder(InputStream streamIn,
                  int length)

Create a new SWFDecoder for the underlying InputStream with the specified buffer size.

Parameters:

streamIn - the stream from which data will be read.

length - the size in bytes of the buffer.

SWFDecoder

public SWFDecoder(InputStream streamIn)

Create a new SWFDecoder for the underlying InputStream using the default buffer size.

Parameters:

streamIn - the stream from which data will be read.

Method Detail

fill

public void fill()
          throws IOException

Fill the internal buffer. Any unread bytes are copied to the start of the buffer and the remaining space is filled with data from the underlying stream.

Throws:

IOException - if an error occurs reading from the underlying input stream.

mark

public int mark()

Remember the current position.

Returns:

the current position.

unmark

public void unmark()

Discard the last saved position.

reset

public void reset()
           throws IOException

Reposition the decoder to the point recorded by the last call to the mark() method.

Throws:

IOException - if the internal buffer was filled after mark() was called.

check

public void check(int count)

Compare the number of bytes read since the last saved position and record any difference.

Parameters:

count - the expected number of bytes read.

getLocation

public int getLocation()

Get the location recorded for the last call to check().

Returns:

the position in the buffer of the call to mark() used by check().

getExpected

public int getExpected()

Get the expected number of bytes from the last call to check().

Returns:

the difference from the expected number of bytes decoded.

getDelta

public int getDelta()

Get the difference from the expected number of bytes from the last call to check().

Returns:

the difference from the expected number of bytes decoded.

bytesRead

public int bytesRead()

Get the number of bytes read from the last saved position.

Returns:

the number of bytes read since the mark() method was last called.

alignToByte

public void alignToByte()

Changes the location to the next byte boundary.

skip

public void skip(int count)
          throws IOException

Skips over and discards n bytes of data.

Parameters:

count - the number of bytes to skip.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readBits

public int readBits(int numberOfBits,
                    boolean signed)
             throws IOException

Read a bit field.

Parameters:

numberOfBits - the number of bits to read.

signed - indicates whether the integer value read is signed.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

scanBits

public int scanBits(int numberOfBits,
                    boolean signed)
             throws IOException

Read-ahead a bit field.

Parameters:

numberOfBits - the number of bits to read.

signed - indicates whether the integer value read is signed.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

scanByte

public int scanByte()
             throws IOException

Read an unsigned byte but do not advance the internal pointer.

Returns:

an 8-bit unsigned value.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readByte

public int readByte()
             throws IOException

Read an unsigned byte.

Returns:

an 8-bit unsigned value.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readBytes

public byte[] readBytes(byte[] bytes)
                 throws IOException

Reads an array of bytes.

Parameters:

bytes - the array that will contain the bytes read.

Returns:

the array of bytes.

Throws:

IOException - if an error occurs reading from the underlying input stream.

setEncoding

public void setEncoding(CharacterEncoding enc)

Sets the character encoding scheme used when encoding or decoding strings.

Parameters:

enc - the CharacterEncoding that identifies how strings are encoded.

readString

public String readString(int length)
                  throws IOException

Read a string using the default character set defined in the decoder.

Parameters:

length - the number of bytes to read.

Returns:

the decoded string.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readString

public String readString()
                  throws IOException

Read a null-terminated string using the default character set defined in the decoder.

Returns:

the decoded string.

Throws:

IOException - if an error occurs reading from the underlying input stream.

scanUnsignedShort

public int scanUnsignedShort()
                      throws IOException

Read an unsigned 16-bit integer.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readUnsignedShort

public int readUnsignedShort()
                      throws IOException

Read an unsigned 16-bit integer.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readSignedShort

public int readSignedShort()
                    throws IOException

Read an unsigned 16-bit integer.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readInt

public int readInt()
            throws IOException

Read an unsigned 32-bit integer.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readVarInt

public int readVarInt()
               throws IOException

Read a 32-bit unsigned integer, encoded using a variable number of bytes.

Returns:

the value read.

Throws:

IOException - if an error occurs reading from the underlying input stream.

readHalf

public float readHalf()
               throws IOException

Read a single-precision floating point number.

Returns:

the value.

Throws:

IOException - if an error occurs reading from the underlying input stream.