二进制标准输入工具
/****************************************************************************** * Copyright 2002-2015, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.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. * * algs4.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 algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/ /****************************************************************************** * Compilation: javac BinaryStdIn.java * Execution: java BinaryStdIn < input > output * Dependencies: none * * Supports reading binary data from standard input. * * % java BinaryStdIn < input.jpg > output.jpg * % diff input.jpg output.jpg * ******************************************************************************//*来自 nowjava*/ package edu.pucit.cs.algo; import java.io.BufferedInputStream; import java.io.IOException; /** * <i>Binary standard input</i>. This class provides methods for reading * in bits from standard input, either one bit at a time (as a <tt>boolean</tt>), * 8 bits at a time (as a <tt>byte</tt> or <tt>char</tt>), * 16 bits at a time (as a <tt>short</tt>), 32 bits at a time * (as an <tt>int</tt> or <tt>float</tt>), or 64 bits at a time (as a * <tt>double</tt> or <tt>long</tt>). * <p> * All primitive types are assumed to be represented using their * standard Java representations, in big-endian (most significant * byte first) order. * <p> * The client should not intermix calls to <tt>BinaryStdIn</tt> with calls * to <tt>StdIn</tt> or <tt>System.in</tt>; * otherwise unexpected behavior will result. * * @author Robert Sedgewick * @author Kevin Wayne */ public final class BinaryStdIn { private static BufferedInputStream in = new BufferedInputStream( System.in); private static final int EOF = -1; // end of file private static int buffer; // one character buffer private static int n; // number of bits left in buffer // static initializer/**来 自 nowjava.com - 时代Java**/ static { fillBuffer(); } // don't instantiate private BinaryStdIn() { } private static void fillBuffer() { try { buffer = in.read(); n = 8; } catch (IOException e) { System.out.println("EOF"); buffer = EOF; n = -1; } } /** * Close this input stream and release any associated system resources. */ public static void close() { try { in.close(); } catch (IOException e) { e.printStackTrace(); throw new RuntimeException("Could not close BinaryStdIn"); } } /** * Returns true if standard input is empty. * @return true if and only if standard input is empty */ public static boolean isEmpty() { return buffer == EOF; } /** * Reads the next bit of data from standard input and return as a boolean. * * @return the next bit of data from standard input as a <tt>boolean</tt> * @throws RuntimeException if standard input is empty */ public static 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; } /** * Reads the next 8 bits from standard input and return as an 8-bit char. * Note that <tt>char</tt> is a 16-bit type; * to read the next 16 bits as a char, use <tt>readChar(16)</tt>. * * @return the next 8 bits of data from standard input as a <tt>char</tt> * @throws RuntimeException if there are fewer than 8 bits available on standard input */ public static 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, so there is a special case for aligned byte } /** * Reads the next r bits from standard input and return as an r-bit character. * * @param r number of bits to read. * @return the next r bits of data from standard input as a <tt>char</tt> * @throws IllegalArgumentException if there are fewer than r bits available on standard input * @throws IllegalArgumentException unless 1 ≤ r ≤ 16 */ public static char readChar(int r) { if (r < 1 || r > 16) throw new IllegalArgumentException("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; } /** * Reads the remaining bytes of data from standard input and return as a string. * * @return the remaining bytes of data from standard input as a <tt>String</tt> * @throws RuntimeException if standard input is empty or if the number of bits * available on standard input is not a multiple of 8 (byte-aligned) */ public static 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(); } /** * Reads the next 16 bits from standard input and return as a 16-bit short. * * @return the next 16 bits of data from standard input as a <tt>short</tt> * @throws RuntimeException if there are fewer than 16 bits available on standard input */ public static short readShort() { short x = 0; for (int i = 0; i < 2; i++) { char c = readChar(); x <<= 8; x |= c; } return x; } /** * Reads the next 32 bits from standard input and return as a 32-bit int. * * @return the next 32 bits of data from standard input as a <tt>int</tt> * @throws RuntimeException if there are fewer than 32 bits available on standard input */ public static int readInt() { int x = 0; for (int i = 0; i < 4; i++) { char c = readChar(); x <<= 8; x |= c; } return x; } /** * Reads the next r bits from standard input and return as an r-bit int. * * @param r number of bits to read. * @return the next r bits of data from standard input as a <tt>int</tt> * @throws IllegalArgumentException if there are fewer than r bits available on standard input * @throws IllegalArgumentException unless 1 ≤ r ≤ 32 */ public static int readInt(int r) { if (r < 1 || r > 32) throw new IllegalArgumentException("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; } /** * Reads the next 64 bits from standard input and return as a 64-bit long. * * @return the next 64 bits of data from standard input as a <tt>long</tt> * @throws RuntimeException if there are fewer than 64 bits available on standard input */ public static long readLong() { long x = 0; for (int i = 0; i < 8; i++) {