LittleEndianDataInputStream.java
/*
* Copyright (c) 2008, Harald Kuhr
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* * Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* From http://www.cafeaulait.org/books/javaio/ioexamples/index.html:
*
* Please feel free to use any fragment of this code you need in your own work.
* As far as I am concerned, it's in the public domain. No permission is necessary
* or required. Credit is always appreciated if you use a large chunk or base a
* significant product on one of my examples, but that's not required either.
*
* Elliotte Rusty Harold
*/
package com.twelvemonkeys.io;
import com.twelvemonkeys.lang.Validate;
import java.io.*;
/**
* A little endian input stream reads two's complement,
* little endian integers, floating point numbers, and characters
* and returns them as Java primitive types.
* <p>
* The standard {@code java.io.DataInputStream} class
* which this class imitates reads big endian quantities.
* </p>
* <p>
* <em>Warning:
* The {@code DataInput} and {@code DataOutput} interfaces
* specifies big endian byte order in their documentation.
* This means that this class is, strictly speaking, not a proper
* implementation. However, I don't see a reason for the these interfaces to
* specify the byte order of their underlying representations.
* </em>
* </p>
*
* @see com.twelvemonkeys.io.LittleEndianRandomAccessFile
* @see java.io.DataInputStream
* @see java.io.DataInput
* @see java.io.DataOutput
*
* @author Elliotte Rusty Harold
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @version 2
*/
public class LittleEndianDataInputStream extends FilterInputStream implements DataInput {
// TODO: Optimize by reading into a fixed size (8 bytes) buffer instead of individual read operations?
/**
* Creates a new little endian input stream and chains it to the
* input stream specified by the {@code pStream} argument.
*
* @param pStream the underlying input stream.
* @see java.io.FilterInputStream#in
*/
public LittleEndianDataInputStream(final InputStream pStream) {
super(Validate.notNull(pStream, "stream"));
}
/**
* Reads a {@code boolean} from the underlying input stream by
* reading a single byte. If the byte is zero, false is returned.
* If the byte is positive, true is returned.
*
* @return the {@code boolean} value read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public boolean readBoolean() throws IOException {
int b = in.read();
if (b < 0) {
throw new EOFException();
}
return b != 0;
}
/**
* Reads a signed {@code byte} from the underlying input stream
* with value between -128 and 127
*
* @return the {@code byte} value read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public byte readByte() throws IOException {
int b = in.read();
if (b < 0) {
throw new EOFException();
}
return (byte) b;
}
/**
* Reads an unsigned {@code byte} from the underlying
* input stream with value between 0 and 255
*
* @return the {@code byte} value read.
* @throws EOFException if the end of the underlying input
* stream has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public int readUnsignedByte() throws IOException {
int b = in.read();
if (b < 0) {
throw new EOFException();
}
return b;
}
/**
* Reads a two byte signed {@code short} from the underlying
* input stream in little endian order, low byte first.
*
* @return the {@code short} read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public short readShort() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
// only need to test last byte read
// if byte1 is -1 so is byte2
if (byte2 < 0) {
throw new EOFException();
}
return (short) (((byte2 << 24) >>> 16) | (byte1 << 24) >>> 24);
}
/**
* Reads a two byte unsigned {@code short} from the underlying
* input stream in little endian order, low byte first.
*
* @return the int value of the unsigned short read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public int readUnsignedShort() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 < 0) {
throw new EOFException();
}
return (byte2 << 8) + byte1;
}
/**
* Reads a two byte Unicode {@code char} from the underlying
* input stream in little endian order, low byte first.
*
* @return the int value of the unsigned short read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public char readChar() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 < 0) {
throw new EOFException();
}
return (char) (((byte2 << 24) >>> 16) | ((byte1 << 24) >>> 24));
}
/**
* Reads a four byte signed {@code int} from the underlying
* input stream in little endian order, low byte first.
*
* @return the {@code int} read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public int readInt() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
int byte3 = in.read();
int byte4 = in.read();
if (byte4 < 0) {
throw new EOFException();
}
return (byte4 << 24) | ((byte3 << 24) >>> 8)
| ((byte2 << 24) >>> 16) | ((byte1 << 24) >>> 24);
}
/**
* Reads an eight byte signed {@code int} from the underlying
* input stream in little endian order, low byte first.
*
* @return the {@code int} read.
* @throws EOFException if the end of the underlying input stream
* has been reached
* @throws IOException if the underlying stream throws an IOException.
*/
public long readLong() throws IOException {
long byte1 = in.read();
long byte2 = in.read();
long byte3 = in.read();
long byte4 = in.read();
long byte5 = in.read();
long byte6 = in.read();
long byte7 = in.read();
long byte8 = in.read();
if (byte8 < 0) {
throw new EOFException();
}
return (byte8 << 56) | ((byte7 << 56) >>> 8)
| ((byte6 << 56) >>> 16) | ((byte5 << 56) >>> 24)
| ((byte4 << 56) >>> 32) | ((byte3 << 56) >>> 40)
| ((byte2 << 56) >>> 48) | ((byte1 << 56) >>> 56);
}
/**
* Reads a string of no more than 65,535 characters
* from the underlying input stream using UTF-8
* encoding. This method first reads a two byte short
* in <b>big</b> endian order as required by the
* UTF-8 specification. This gives the number of bytes in
* the UTF-8 encoded version of the string.
* Next this many bytes are read and decoded as UTF-8
* encoded characters.
*
* @return the decoded string
* @throws UTFDataFormatException if the string cannot be decoded
* @throws IOException if the underlying stream throws an IOException.
*/
public String readUTF() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 < 0) {
throw new EOFException();
}
int numbytes = (byte1 << 8) + byte2;
char result[] = new char[numbytes];
int numread = 0;
int numchars = 0;
while (numread < numbytes) {
int c1 = readUnsignedByte();
int c2, c3;
// The first four bits of c1 determine how many bytes are in this char
int test = c1 >> 4;
if (test < 8) { // one byte
numread++;
result[numchars++] = (char) c1;
}
else if (test == 12 || test == 13) { // two bytes
numread += 2;
if (numread > numbytes) {
throw new UTFDataFormatException();
}
c2 = readUnsignedByte();
if ((c2 & 0xC0) != 0x80) {
throw new UTFDataFormatException();
}
result[numchars++] = (char) (((c1 & 0x1F) << 6) | (c2 & 0x3F));
}
else if (test == 14) { // three bytes
numread += 3;
if (numread > numbytes) {
throw new UTFDataFormatException();
}
c2 = readUnsignedByte();
c3 = readUnsignedByte();
if (((c2 & 0xC0) != 0x80) || ((c3 & 0xC0) != 0x80)) {
throw new UTFDataFormatException();
}
result[numchars++] = (char) (((c1 & 0x0F) << 12) | ((c2 & 0x3F) << 6) | (c3 & 0x3F));
}
else { // malformed
throw new UTFDataFormatException();
}
} // end while
return new String(result, 0, numchars);
}
/**
* @return the next eight bytes of this input stream, interpreted as a
* little endian {@code double}.
* @throws EOFException if end of stream occurs before eight bytes
* have been read.
* @throws IOException if an I/O error occurs.
*/
public final double readDouble() throws IOException {
return Double.longBitsToDouble(readLong());
}
/**
* @return the next four bytes of this input stream, interpreted as a
* little endian {@code int}.
* @throws EOFException if end of stream occurs before four bytes
* have been read.
* @throws IOException if an I/O error occurs.
*/
public final float readFloat() throws IOException {
return Float.intBitsToFloat(readInt());
}
/**
* See the general contract of the {@code skipBytes}
* method of {@code DataInput}.
* <p>
* Bytes for this operation are read from the contained input stream.
*
* @param pLength the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @exception IOException if an I/O error occurs.
*/
public final int skipBytes(int pLength) throws IOException {
// NOTE: There was probably a bug in ERH's original code here, as skip
// never returns -1, but returns 0 if no more bytes can be skipped...
int total = 0;
int skipped;
while ((total < pLength) && ((skipped = (int) in.skip(pLength - total)) > 0)) {
total += skipped;
}
return total;
}
/**
* See the general contract of the {@code readFully} method of {@code DataInput}.
* <p>
* Bytes for this operation are read from the contained input stream.
* </p>
*
* @param pBytes the buffer into which the data is read.
* @throws EOFException if this input stream reaches the end before
* reading all the bytes.
* @throws IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public final void readFully(byte pBytes[]) throws IOException {
readFully(pBytes, 0, pBytes.length);
}
/**
* See the general contract of the {@code readFully} method of {@code DataInput}.
* <p>
* Bytes for this operation are read from the contained input stream.
* </p>
*
* @param pBytes the buffer into which the data is read.
* @param pOffset the start offset of the data.
* @param pLength the number of bytes to read.
* @throws EOFException if this input stream reaches the end before
* reading all the bytes.
* @throws IOException if an I/O error occurs.
* @see java.io.FilterInputStream#in
*/
public final void readFully(byte pBytes[], int pOffset, int pLength) throws IOException {
if (pLength < 0) {
throw new IndexOutOfBoundsException();
}
int count = 0;
while (count < pLength) {
int read = in.read(pBytes, pOffset + count, pLength - count);
if (read < 0) {
throw new EOFException();
}
count += read;
}
}
/**
* See the general contract of the {@code readLine}
* method of {@code DataInput}.
* <p>
* Bytes for this operation are read from the contained input stream.
*
* @deprecated This method does not properly convert bytes to characters.
*
* @return the next line of text from this input stream.
* @exception IOException if an I/O error occurs.
* @see java.io.BufferedReader#readLine()
* @see java.io.DataInputStream#readLine()
*/
@Deprecated
public String readLine() throws IOException {
DataInputStream ds = new DataInputStream(in);
return ds.readLine();
}
}