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com.google.common.io
Class LittleEndianDataInputStream

java.lang.Object
  extended by java.io.InputStream
      extended by java.io.FilterInputStream
          extended by com.google.common.io.LittleEndianDataInputStream
All Implemented Interfaces:
Closeable, DataInput
@Beta
public final class LittleEndianDataInputStream
extends FilterInputStream
implements DataInput

An implementation of DataInput that uses little-endian byte ordering for reading short, int, float, double, and long values.

Note: This class intentionally violates the specification of its supertype DataInput, which explicitly requires big-endian byte order.

Since:
8
Author:
chrisn@google.com (Chris Nokleberg), kbottner@google.com (Keith Bottner)

Field Summary
 
Fields inherited from class java.io.FilterInputStream
in
 
Constructor Summary
LittleEndianDataInputStream(InputStream in)
          Creates a LittleEndianDataInputStream that wraps the given stream.
 
Method Summary
 boolean readBoolean()
          Reads one input byte and returns true if that byte is nonzero, false if that byte is zero.
 byte readByte()
          Reads and returns one input byte.
 char readChar()
          Reads a char as specified by DataInputStream.readChar(), except using little-endian byte order.
 double readDouble()
          Reads a double as specified by DataInputStream.readDouble(), except using little-endian byte order.
 float readFloat()
          Reads a float as specified by DataInputStream.readFloat(), except using little-endian byte order.
 void readFully(byte[] b)
          Reads some bytes from an input stream and stores them into the buffer array b.
 void readFully(byte[] b, int off, int len)
          Reads len bytes from an input stream.
 int readInt()
          Reads an integer as specified by DataInputStream.readInt(), except using little-endian byte order.
 String readLine()
          This method will throw a UnsupportedOperationException.
 long readLong()
          Reads a long as specified by DataInputStream.readLong(), except using little-endian byte order.
 short readShort()
          Reads a short as specified by DataInputStream.readShort(), except using little-endian byte order.
 int readUnsignedByte()
          Reads one input byte, zero-extends it to type int, and returns the result, which is therefore in the range 0 through 255.
 int readUnsignedShort()
          Reads an unsigned short as specified by DataInputStream.readUnsignedShort(), except using little-endian byte order.
 String readUTF()
          Reads in a string that has been encoded using a modified UTF-8 format.
 int skipBytes(int n)
          Makes an attempt to skip over n bytes of data from the input stream, discarding the skipped bytes.
 
Methods inherited from class java.io.FilterInputStream
available, close, mark, markSupported, read, read, read, reset, skip
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

LittleEndianDataInputStream

public LittleEndianDataInputStream(InputStream in)
Creates a LittleEndianDataInputStream that wraps the given stream.

Parameters:
in - the stream to delegate to
Method Detail

readLine

public String readLine()
This method will throw a UnsupportedOperationException.

Specified by:
readLine in interface DataInput
Returns:
the next line of text from the input stream, or null if the end of file is encountered before a byte can be read.

readFully

public void readFully(byte[] b)
               throws IOException
Description copied from interface: java.io.DataInput
Reads some bytes from an input stream and stores them into the buffer array b. The number of bytes read is equal to the length of b.

This method blocks until one of the following conditions occurs:

If b is null, a NullPointerException is thrown. If b.length is zero, then no bytes are read. Otherwise, the first byte read is stored into element b[0], the next one into b[1], and so on. If an exception is thrown from this method, then it may be that some but not all bytes of b have been updated with data from the input stream.

Specified by:
readFully in interface DataInput
Parameters:
b - the buffer into which the data is read.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

readFully

public void readFully(byte[] b,
                      int off,
                      int len)
               throws IOException
Description copied from interface: java.io.DataInput
Reads len bytes from an input stream.

This method blocks until one of the following conditions occurs:

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. Otherwise, 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.

Specified by:
readFully in interface DataInput
Parameters:
b - the buffer into which the data is read.
off - an int specifying the offset into the data.
len - an int specifying the number of bytes to read.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

skipBytes

public int skipBytes(int n)
              throws IOException
Description copied from interface: java.io.DataInput
Makes an attempt to skip over n bytes of data from the input stream, discarding the skipped bytes. However, it may skip over some smaller number of bytes, possibly zero. This may result from any of a number of conditions; reaching end of file before n bytes have been skipped is only one possibility. This method never throws an EOFException. The actual number of bytes skipped is returned.

Specified by:
skipBytes in interface DataInput
Parameters:
n - the number of bytes to be skipped.
Returns:
the number of bytes actually skipped.
Throws:
IOException - if an I/O error occurs.

readUnsignedByte

public int readUnsignedByte()
                     throws IOException
Description copied from interface: java.io.DataInput
Reads one input byte, zero-extends it to type int, and returns the result, which is therefore in the range 0 through 255. This method is suitable for reading the byte written by the writeByte method of interface DataOutput if the argument to writeByte was intended to be a value in the range 0 through 255.

Specified by:
readUnsignedByte in interface DataInput
Returns:
the unsigned 8-bit value read.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

readUnsignedShort

public int readUnsignedShort()
                      throws IOException
Reads an unsigned short as specified by DataInputStream.readUnsignedShort(), except using little-endian byte order.

Specified by:
readUnsignedShort in interface DataInput
Returns:
the next two bytes of the input stream, interpreted as an int in little-endian byte order
Throws:
IOException - if an I/O error occurs

readInt

public int readInt()
            throws IOException
Reads an integer as specified by DataInputStream.readInt(), except using little-endian byte order.

Specified by:
readInt in interface DataInput
Returns:
the next four bytes of the input stream, interpreted as an int in little-endian byte order
Throws:
IOException - if an I/O error occurs

readLong

public long readLong()
              throws IOException
Reads a long as specified by DataInputStream.readLong(), except using little-endian byte order.

Specified by:
readLong in interface DataInput
Returns:
the next eight bytes of the input stream, interpreted as a long in little-endian byte order
Throws:
IOException - if an I/O error occurs

readFloat

public float readFloat()
                throws IOException
Reads a float as specified by DataInputStream.readFloat(), except using little-endian byte order.

Specified by:
readFloat in interface DataInput
Returns:
the next four bytes of the input stream, interpreted as an float in little-endian byte order
Throws:
IOException - if an I/O error occurs

readDouble

public double readDouble()
                  throws IOException
Reads a double as specified by DataInputStream.readDouble(), except using little-endian byte order.

Specified by:
readDouble in interface DataInput
Returns:
the next eight bytes of the input stream, interpreted as an int in little-endian byte order
Throws:
IOException - if an I/O error occurs

readUTF

public String readUTF()
               throws IOException
Description copied from interface: java.io.DataInput
Reads in a string that has been encoded using a modified UTF-8 format. The general contract of readUTF is that it reads a representation of a Unicode character string encoded in modified UTF-8 format; this string of characters is then returned as a String.

First, two bytes are read and used to construct an unsigned 16-bit integer in exactly the manner of the readUnsignedShort method . This integer value is called the UTF length and specifies the number of additional bytes to be read. These bytes are then converted to characters by considering them in groups. The length of each group is computed from the value of the first byte of the group. The byte following a group, if any, is the first byte of the next group.

If the first byte of a group matches the bit pattern 0xxxxxxx (where x means "may be 0 or 1"), then the group consists of just that byte. The byte is zero-extended to form a character.

If the first byte of a group matches the bit pattern 110xxxxx, then the group consists of that byte a and a second byte b. If there is no byte b (because byte a was the last of the bytes to be read), or if byte b does not match the bit pattern 10xxxxxx, then a UTFDataFormatException is thrown. Otherwise, the group is converted to the character:

(char)(((a& 0x1F) << 6) | (b & 0x3F))
If the first byte of a group matches the bit pattern 1110xxxx, then the group consists of that byte a and two more bytes b and c. If there is no byte c (because byte a was one of the last two of the bytes to be read), or either byte b or byte c does not match the bit pattern 10xxxxxx, then a UTFDataFormatException is thrown. Otherwise, the group is converted to the character:


 (char)(((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F))
If the first byte of a group matches the pattern 1111xxxx or the pattern 10xxxxxx, then a UTFDataFormatException is thrown.

If end of file is encountered at any time during this entire process, then an EOFException is thrown.

After every group has been converted to a character by this process, the characters are gathered, in the same order in which their corresponding groups were read from the input stream, to form a String, which is returned.

The writeUTF method of interface DataOutput may be used to write data that is suitable for reading by this method.

Specified by:
readUTF in interface DataInput
Returns:
a Unicode string.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

readShort

public short readShort()
                throws IOException
Reads a short as specified by DataInputStream.readShort(), except using little-endian byte order.

Specified by:
readShort in interface DataInput
Returns:
the next two bytes of the input stream, interpreted as an short in little-endian byte order.
Throws:
IOException - if an I/O error occurs.

readChar

public char readChar()
              throws IOException
Reads a char as specified by DataInputStream.readChar(), except using little-endian byte order.

Specified by:
readChar in interface DataInput
Returns:
the next two bytes of the input stream, interpreted as an char in little-endian byte order
Throws:
IOException - if an I/O error occurs

readByte

public byte readByte()
              throws IOException
Description copied from interface: java.io.DataInput
Reads and returns one input byte. The byte is treated as a signed value in the range -128 through 127, inclusive. This method is suitable for reading the byte written by the writeByte method of interface DataOutput.

Specified by:
readByte in interface DataInput
Returns:
the 8-bit value read.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

readBoolean

public boolean readBoolean()
                    throws IOException
Description copied from interface: java.io.DataInput
Reads one input byte and returns true if that byte is nonzero, false if that byte is zero. This method is suitable for reading the byte written by the writeBoolean method of interface DataOutput.

Specified by:
readBoolean in interface DataInput
Returns:
the boolean value read.
Throws:
EOFException - if this stream reaches the end before reading all the bytes.
IOException - if an I/O error occurs.
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