edu.princeton.cs.introcs.BinaryIn Maven / Gradle / Ivy
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package edu.princeton.cs.introcs;
/*************************************************************************
* Compilation: javac BinaryIn.java
* Execution: java BinaryIn input output
*
* This library is for reading binary data from an input stream.
*
* % java BinaryIn http://introcs.cs.princeton.edu/cover.jpg output.jpg
*
*************************************************************************/
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.Socket;
import java.net.URL;
import java.net.URLConnection;
/**
* Binary input. This class provides methods for reading
* in bits from a binary input stream, either
* one bit at a time (as a boolean),
* 8 bits at a time (as a byte or char),
* 16 bits at a time (as a short),
* 32 bits at a time (as an int or float), or
* 64 bits at a time (as a double or long).
*
* The binary input stream can be from standard input, a filename,
* a URL name, a Socket, or an InputStream.
*
* All primitive types are assumed to be represented using their
* standard Java representations, in big-endian (most significant
* byte first) order.
*
* The client should not intermix calls to BinaryIn with calls
* to In; otherwise unexpected behavior will result.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public final class BinaryIn {
private static final int EOF = -1; // end of file
private BufferedInputStream in; // the input stream
private int buffer; // one character buffer
private int N; // number of bits left in buffer
/**
* Create a binary input stream from standard input.
*/
public BinaryIn() {
in = new BufferedInputStream(System.in);
fillBuffer();
}
/**
* Create a binary input stream from an InputStream.
*/
public BinaryIn(InputStream is) {
in = new BufferedInputStream(is);
fillBuffer();
}
/**
* Create a binary input stream from a socket.
*/
public BinaryIn(Socket socket) {
try {
InputStream is = socket.getInputStream();
in = new BufferedInputStream(is);
fillBuffer();
}
catch (IOException ioe) {
System.err.println("Could not open " + socket);
}
}
/**
* Create a binary input stream from a URL.
*/
public BinaryIn(URL url) {
try {
URLConnection site = url.openConnection();
InputStream is = site.getInputStream();
in = new BufferedInputStream(is);
fillBuffer();
}
catch (IOException ioe) {
System.err.println("Could not open " + url);
}
}
/**
* Create a binary input stream from a filename or URL name.
*/
public BinaryIn(String s) {
try {
// first try to read file from local file system
File file = new File(s);
if (file.exists()) {
FileInputStream fis = new FileInputStream(file);
in = new BufferedInputStream(fis);
fillBuffer();
return;
}
// next try for files included in jar
URL url = getClass().getResource(s);
// or URL from web
if (url == null) { url = new URL(s); }
URLConnection site = url.openConnection();
InputStream is = site.getInputStream();
in = new BufferedInputStream(is);
fillBuffer();
}
catch (IOException ioe) {
System.err.println("Could not open " + s);
}
}
private void fillBuffer() {
try { buffer = in.read(); N = 8; }
catch (IOException e) { System.err.println("EOF"); buffer = EOF; N = -1; }
}
/**
* Does the binary input stream exist?
*/
public boolean exists() {
return in != null;
}
/**
* Returns true if the binary input stream is empty.
* @return true if and only if the binary input stream is empty
*/
public boolean isEmpty() {
return buffer == EOF;
}
/**
* Read the next bit of data from the binary input stream and return as a boolean.
* @return the next bit of data from the binary input stream as a boolean
* @throws RuntimeException if the input stream is empty
*/
public boolean readBoolean() {
if (isEmpty()) throw new RuntimeException("Reading from empty input stream");
N--;
boolean bit = ((buffer >> N) & 1) == 1;
if (N == 0) fillBuffer();
return bit;
}
/**
* Read the next 8 bits from the binary input stream and return as an 8-bit char.
* @return the next 8 bits of data from the binary input stream as a char
* @throws RuntimeException if there are fewer than 8 bits available
*/
public char readChar() {
if (isEmpty()) throw new RuntimeException("Reading from empty input stream");
// special case when aligned byte
if (N == 8) {
int x = buffer;
fillBuffer();
return (char) (x & 0xff);
}
// combine last N bits of current buffer with first 8-N bits of new buffer
int x = buffer;
x <<= (8-N);
int oldN = N;
fillBuffer();
if (isEmpty()) throw new RuntimeException("Reading from empty input stream");
N = oldN;
x |= (buffer >>> N);
return (char) (x & 0xff);
// the above code doesn't quite work for the last character if N = 8
// because buffer will be -1
}
/**
* Read the next r bits from the binary input stream and return as an r-bit character.
* @param r number of bits to read.
* @return the next r bits of data from the binary input streamt as a char
* @throws RuntimeException if there are fewer than r bits available
*/
public char readChar(int r) {
if (r < 1 || r > 16) throw new RuntimeException("Illegal value of r = " + r);
// optimize r = 8 case
if (r == 8) return readChar();
char x = 0;
for (int i = 0; i < r; i++) {
x <<= 1;
boolean bit = readBoolean();
if (bit) x |= 1;
}
return x;
}
/**
* Read the remaining bytes of data from the binary input stream and return as a string.
* @return the remaining bytes of data from the binary input stream as a String
* @throws RuntimeException if the input stream is empty or if the number of bits
* available is not a multiple of 8 (byte-aligned)
*/
public String readString() {
if (isEmpty()) throw new RuntimeException("Reading from empty input stream");
StringBuilder sb = new StringBuilder();
while (!isEmpty()) {
char c = readChar();
sb.append(c);
}
return sb.toString();
}
/**
* Read the next 16 bits from the binary input stream and return as a 16-bit short.
* @return the next 16 bits of data from the binary standard input as a short
* @throws RuntimeException if there are fewer than 16 bits available
*/
public short readShort() {
short x = 0;
for (int i = 0; i < 2; i++) {
char c = readChar();
x <<= 8;
x |= c;
}
return x;
}
/**
* Read the next 32 bits from the binary input stream and return as a 32-bit int.
* @return the next 32 bits of data from the binary input stream as a int
* @throws RuntimeException if there are fewer than 32 bits available
*/
public int readInt() {
int x = 0;
for (int i = 0; i < 4; i++) {
char c = readChar();
x <<= 8;
x |= c;
}
return x;
}
/**
* Read the next r bits from the binary input stream return as an r-bit int.
* @param r number of bits to read.
* @return the next r bits of data from the binary input stream as a int
* @throws RuntimeException if there are fewer than r bits available on standard input
*/
public int readInt(int r) {
if (r < 1 || r > 32) throw new RuntimeException("Illegal value of r = " + r);
// optimize r = 32 case
if (r == 32) return readInt();
int x = 0;
for (int i = 0; i < r; i++) {
x <<= 1;
boolean bit = readBoolean();
if (bit) x |= 1;
}
return x;
}
/**
* Read the next 64 bits from the binary input stream and return as a 64-bit long.
* @return the next 64 bits of data from the binary input stream as a long
* @throws RuntimeException if there are fewer than 64 bits available
*/
public long readLong() {
long x = 0;
for (int i = 0; i < 8; i++) {
char c = readChar();
x <<= 8;
x |= c;
}
return x;
}
/**
* Read the next 64 bits from the binary input stream and return as a 64-bit double.
* @return the next 64 bits of data from the binary input stream as a double
* @throws RuntimeException if there are fewer than 64 bits available
*/
public double readDouble() {
return Double.longBitsToDouble(readLong());
}
/**
* Read the next 32 bits from standard input and return as a 32-bit float.
* @return the next 32 bits of data from standard input as a float
* @throws RuntimeException if there are fewer than 32 bits available on standard input
*/
public float readFloat() {
return Float.intBitsToFloat(readInt());
}
/**
* Read the next 8 bits from the binary input stream and return as an 8-bit byte.
* @return the next 8 bits of data from the binary input stream as a byte
* @throws RuntimeException if there are fewer than 8 bits available
*/
public byte readByte() {
char c = readChar();
byte x = (byte) (c & 0xff);
return x;
}
/**
* Test client. Reads in the name of a file or url (first command-line
* argument) and writes it to a file (second command-line argument).
*/
public static void main(String[] args) {
BinaryIn in = new BinaryIn(args[0]);
BinaryOut out = new BinaryOut(args[1]);
// read one 8-bit char at a time
while (!in.isEmpty()) {
char c = in.readChar();
out.write(c);
}
out.flush();
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of stdlib-package.jar, which accompanies the textbook
*
* Introduction to Programming in Java: An Interdisciplinary Approach
* by R. Sedgewick and K. Wayne, Addison-Wesley, 2007. ISBN 0-321-49805-4.
*
* http://introcs.cs.princeton.edu
*
*
* stdlib-package.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* stdlib-package.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with stdlib-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/