/*
* @(#)LittleEndianInputStream.java 1.0.2 99/05/19
*
* Copyright 1998, 1999 Elliotte Rusty Harold
*
*/
package com.macfaq.io;
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 java.io.DataInputStream class
* which this class imitates reads big-endian quantities.
*
* @author Elliotte Rusty Harold
* @version 1.0.2, 19 May 1999
* @see com.macfaq.io.LittleEndianOutputStream
* @see java.io.DataInputStream
*/
public class LittleEndianInputStream extends FilterInputStream {
/**
* Creates a new little endian input stream and chains it to the
* input stream specified by the in argument.
*
* @param in the underlying input stream.
* @see java.io.FilterInputStream#out
*/
public LittleEndianInputStream(InputStream in) {
super(in);
}
/**
* Reads a <code>boolean</code> 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 b the <code>boolean</code> value read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public boolean readBoolean() throws IOException {
int bool = in.read();
if (bool == -1) throw new EOFException();
return (bool != 0);
}
/**
* Reads a signed <code>byte</code> from the underlying input stream
* with value between -128 and 127
*
* @return the <code>byte</code> value read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public byte readByte(int b) throws IOException {
int temp = in.read();
if (temp == -1) throw new EOFException();
return (byte) temp;
}
/**
* Reads an unsigned <code>byte</code> from the underlying
* input stream with value between 0 and 255
*
* @return the <code>byte</code> value read.
* @exception EOFException if the end of the underlying input
* stream has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public int readUnsignedByte() throws IOException {
int temp = in.read();
if (temp == -1) throw new EOFException();
return temp;
}
/**
* Reads a two byte signed <code>short</code> from the underlying
* input stream in little endian order, low byte first.
*
* @return the <code>short</code> read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception 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 == -1) throw new EOFException();
return (short) ((byte2 << 8) + byte1);
}
/**
* Reads a two byte unsigned <code>short</code> from the underlying
* input stream in little endian order, low byte first.
*
* @return the int value of the unsigned short read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public int readUnsignedShort() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 == -1) throw new EOFException();
return (byte2 << 8) + byte1;
}
/**
* Reads a two byte Unicode <code>char</code> from the underlying
* input stream in little endian order, low byte first.
*
* @return the int value of the unsigned short read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public char readChar() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 == -1) throw new EOFException();
return (char) ((byte2 << 8) + byte1);
}
/**
* Reads a four byte signed <code>int</code> from the underlying
* input stream in little endian order, low byte first.
*
* @return the <code>int</code> read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception IOException if the underlying stream throws an IOException.
*/
public int readInt() throws IOException {
int byte1, byte2, byte3, byte4;
synchronized (this) {
byte1 = in.read();
byte2 = in.read();
byte3 = in.read();
byte4 = in.read();
}
if (byte4 == -1) {
throw new EOFException();
}
return (byte4 << 24) + (byte3 << 16) + (byte2 << 8) + byte1;
}
/**
* Reads an eight byte signed <code>int</code> from the underlying
* input stream in little endian order, low byte first.
*
* @return the <code>int</code> read.
* @exception EOFException if the end of the underlying input stream
* has been reached
* @exception 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 == -1) {
throw new EOFException();
}
return (byte8 << 56) + (byte7 << 48) + (byte6 << 40) + (byte5 << 32) +
(byte4 << 24) + (byte3 << 16) + (byte2 << 8) + byte1;
}
/**
* 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
* @exception UTFDataFormatException if the string cannot be decoded
* @exception IOException if the underlying stream throws an IOException.
*/
public String readUTF() throws IOException {
int byte1 = in.read();
int byte2 = in.read();
if (byte2 == -1) 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;
// look at the first four bits of c1 to determine how many
// bytes 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</code>.
* @exception EOFException if end of stream occurs before eight bytes
* have been read.
* @exception IOException if an I/O error occurs.
*/
public final double readDouble() throws IOException {
return Double.longBitsToDouble(this.readLong());
}
/**
*
* @return the next four bytes of this input stream, interpreted as a
* little endian <code>int</code>.
* @exception EOFException if end of stream occurs before four bytes
* have been read.
* @exception IOException if an I/O error occurs.
*/
public final float readFloat() throws IOException {
return Float.intBitsToFloat(this.readInt());
}
/**
* Skip exactly <code>n</code> bytes of input in the underlying
* input stream. This method blocks until all the bytes are skipped,
* the end of the stream is detected, or an exception is thrown.
*
* @param n the number of bytes to skip.
* @return the number of bytes skipped, generally n
* @exception EOFException if this input stream reaches the end before
* skipping all the bytes.
* @exception IOException if the underlying stream throws an IOException.
*/
public final int skipBytes(int n) throws IOException {
for (int i = 0; i < n; i += (int) skip(n - i));
return n;
}
}
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