/*
* 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/>
* <em>Warning:
* <!-- Beware of little indians! -->
* 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>
*
* @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.
*
* @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.
*
* @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()
* @noinspection deprecation
*/
public
String readLine() throws
IOException {
DataInputStream ds = new
DataInputStream(
in);
return
ds.
readLine();
}
}