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/*
 * 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.
 * 

* The standard {@code java.io.DataInputStream} class * which this class imitates reads big endian quantities. *

*

* 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. * *

* * @see com.twelvemonkeys.io.LittleEndianRandomAccessFile * @see java.io.DataInputStream * @see java.io.DataInput * @see java.io.DataOutput * * @author Elliotte Rusty Harold * @author Harald Kuhr * @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 big 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}. *

* 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}. *

* 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}. *

* 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}. *

* 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(); } }





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