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/*--------------------------------------------------------------------------
 *  Copyright 2009 Taro L. Saito
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *--------------------------------------------------------------------------*/
//--------------------------------------
// XerialJ
//
// FastBufferedReader.java
// Since: Jan 19, 2010 2:46:38 PM
//
// $URL$
// $Author$
//--------------------------------------
package org.xerial.util;

import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;

/*
 * @(#)BufferedReader.java  1.37 06/03/15
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

/**
 * Reads text from a character-input stream, buffering characters so as to
 * provide for the efficient reading of characters, arrays, and lines.
 * 
 * 

* The buffer size may be specified, or the default size may be used. The * default is large enough for most purposes. * *

* In general, each read request made of a Reader causes a corresponding read * request to be made of the underlying character or byte stream. It is * therefore advisable to wrap a BufferedReader around any Reader whose read() * operations may be costly, such as FileReaders and InputStreamReaders. For * example, * *

 * BufferedReader in = new BufferedReader(new FileReader("foo.in"));
 * 
* * will buffer the input from the specified file. Without buffering, each * invocation of read() or readLine() could cause bytes to be read from the * file, converted into characters, and then returned, which can be very * inefficient. * *

* Programs that use DataInputStreams for textual input can be localized by * replacing each DataInputStream with an appropriate BufferedReader. * * @see FileReader * @see InputStreamReader * * @version 1.37, 06/03/15 * @author Mark Reinhold * @since JDK1.1 */ public class FastBufferedReader extends Reader { private Reader in; private char cb[]; private int nChars, nextChar; private static final int INVALIDATED = -2; private static final int UNMARKED = -1; private int markedChar = UNMARKED; private int readAheadLimit = 0; /* Valid only when markedChar > 0 */ /** If the next character is a line feed, skip it */ private boolean skipLF = false; /** The skipLF flag when the mark was set */ private boolean markedSkipLF = false; private static int defaultCharBufferSize = 8192; private static int defaultExpectedLineLength = 80; /** * Creates a buffering character-input stream that uses an input buffer of * the specified size. * * @param in * A Reader * @param sz * Input-buffer size * * @exception IllegalArgumentException * If sz is <= 0 */ public FastBufferedReader(Reader in, int sz) { super(in); if (sz <= 0) throw new IllegalArgumentException("Buffer size <= 0"); this.in = in; cb = new char[sz]; nextChar = nChars = 0; } /** * Creates a buffering character-input stream that uses a default-sized * input buffer. * * @param in * A Reader */ public FastBufferedReader(Reader in) { this(in, defaultCharBufferSize); } /** Checks to make sure that the stream has not been closed */ private void ensureOpen() throws IOException { if (in == null) throw new IOException("Stream closed"); } /** * Fills the input buffer, taking the mark into account if it is valid. */ private void fill() throws IOException { int dst; if (markedChar <= UNMARKED) { /* No mark */ dst = 0; } else { /* Marked */ int delta = nextChar - markedChar; if (delta >= readAheadLimit) { /* Gone past read-ahead limit: Invalidate mark */ markedChar = INVALIDATED; readAheadLimit = 0; dst = 0; } else { if (readAheadLimit <= cb.length) { /* Shuffle in the current buffer */ System.arraycopy(cb, markedChar, cb, 0, delta); markedChar = 0; dst = delta; } else { /* Reallocate buffer to accommodate read-ahead limit */ char ncb[] = new char[readAheadLimit]; System.arraycopy(cb, markedChar, ncb, 0, delta); cb = ncb; markedChar = 0; dst = delta; } nextChar = nChars = delta; } } int n; do { n = in.read(cb, dst, cb.length - dst); } while (n == 0); if (n > 0) { nChars = dst + n; nextChar = dst; } } /** * Reads a single character. * * @return The character read, as an integer in the range 0 to 65535 ( * 0x00-0xffff), or -1 if the end of the stream has been * reached * @exception IOException * If an I/O error occurs */ @Override public int read() throws IOException { ensureOpen(); for (;;) { if (nextChar >= nChars) { fill(); if (nextChar >= nChars) return -1; } if (skipLF) { skipLF = false; if (cb[nextChar] == '\n') { nextChar++; continue; } } return cb[nextChar++]; } } /** * Reads characters into a portion of an array, reading from the underlying * stream if necessary. */ private int read1(char[] cbuf, int off, int len) throws IOException { if (nextChar >= nChars) { /* If the requested length is at least as large as the buffer, and if there is no mark/reset activity, and if line feeds are not being skipped, do not bother to copy the characters into the local buffer. In this way buffered streams will cascade harmlessly. */ if (len >= cb.length && markedChar <= UNMARKED && !skipLF) { return in.read(cbuf, off, len); } fill(); } if (nextChar >= nChars) return -1; if (skipLF) { skipLF = false; if (cb[nextChar] == '\n') { nextChar++; if (nextChar >= nChars) fill(); if (nextChar >= nChars) return -1; } } int n = Math.min(len, nChars - nextChar); System.arraycopy(cb, nextChar, cbuf, off, n); nextChar += n; return n; } /** * Reads characters into a portion of an array. * *

* This method implements the general contract of the corresponding * {@link Reader#read(char[], int, int) read} method of the * {@link Reader} class. As an additional convenience, it * attempts to read as many characters as possible by repeatedly invoking * the read method of the underlying stream. This iterated * read continues until one of the following conditions becomes * true: *

    * *
  • The specified number of characters have been read, * *
  • The read method of the underlying stream returns * -1, indicating end-of-file, or * *
  • The ready method of the underlying stream returns * false, indicating that further input requests would block. * *
* If the first read on the underlying stream returns * -1 to indicate end-of-file then this method returns * -1. Otherwise this method returns the number of characters * actually read. * *

* Subclasses of this class are encouraged, but not required, to attempt to * read as many characters as possible in the same fashion. * *

* Ordinarily this method takes characters from this stream's character * buffer, filling it from the underlying stream as necessary. If, however, * the buffer is empty, the mark is not valid, and the requested length is * at least as large as the buffer, then this method will read characters * directly from the underlying stream into the given array. Thus redundant * FastBufferedReaders will not copy data unnecessarily. * * @param cbuf * Destination buffer * @param off * Offset at which to start storing characters * @param len * Maximum number of characters to read * * @return The number of characters read, or -1 if the end of the stream has * been reached * * @exception IOException * If an I/O error occurs */ @Override public int read(char cbuf[], int off, int len) throws IOException { ensureOpen(); if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return 0; } int n = read1(cbuf, off, len); if (n <= 0) return n; while ((n < len) && in.ready()) { int n1 = read1(cbuf, off + n, len - n); if (n1 <= 0) break; n += n1; } return n; } /** * Reads a line of text. A line is considered to be terminated by any one of * a line feed ('\n'), a carriage return ('\r'), or a carriage return * followed immediately by a linefeed. * * @param ignoreLF * If true, the next '\n' will be skipped * * @return A String containing the contents of the line, not including any * line-termination characters, or null if the end of the stream has * been reached * * @see java.io.LineNumberReader#readLine() * * @exception IOException * If an I/O error occurs */ String readLine(boolean ignoreLF) throws IOException { StringBuffer s = null; int startChar; ensureOpen(); boolean omitLF = ignoreLF || skipLF; bufferLoop: for (;;) { if (nextChar >= nChars) fill(); if (nextChar >= nChars) { /* EOF */ if (s != null && s.length() > 0) return s.toString(); else return null; } boolean eol = false; char c = 0; int i; /* Skip a leftover '\n', if necessary */ if (omitLF && (cb[nextChar] == '\n')) nextChar++; skipLF = false; omitLF = false; charLoop: for (i = nextChar; i < nChars; i++) { c = cb[i]; if ((c == '\n') || (c == '\r')) { eol = true; break charLoop; } } startChar = nextChar; nextChar = i; if (eol) { String str; if (s == null) { str = new String(cb, startChar, i - startChar); } else { s.append(cb, startChar, i - startChar); str = s.toString(); } nextChar++; if (c == '\r') { skipLF = true; } return str; } if (s == null) s = new StringBuffer(defaultExpectedLineLength); s.append(cb, startChar, i - startChar); } } /** * Reads a line of text. A line is considered to be terminated by any one of * a line feed ('\n'), a carriage return ('\r'), or a carriage return * followed immediately by a linefeed. * * @return A String containing the contents of the line, not including any * line-termination characters, or null if the end of the stream has * been reached * * @exception IOException * If an I/O error occurs */ public String readLine() throws IOException { return readLine(false); } /** * Skips characters. * * @param n * The number of characters to skip * * @return The number of characters actually skipped * * @exception IllegalArgumentException * If n is negative. * @exception IOException * If an I/O error occurs */ @Override public long skip(long n) throws IOException { if (n < 0L) { throw new IllegalArgumentException("skip value is negative"); } ensureOpen(); long r = n; while (r > 0) { if (nextChar >= nChars) fill(); if (nextChar >= nChars) /* EOF */ break; if (skipLF) { skipLF = false; if (cb[nextChar] == '\n') { nextChar++; } } long d = nChars - nextChar; if (r <= d) { nextChar += r; r = 0; break; } else { r -= d; nextChar = nChars; } } return n - r; } /** * Tells whether this stream is ready to be read. A buffered character * stream is ready if the buffer is not empty, or if the underlying * character stream is ready. * * @exception IOException * If an I/O error occurs */ @Override public boolean ready() throws IOException { ensureOpen(); /* * If newline needs to be skipped and the next char to be read * is a newline character, then just skip it right away. */ if (skipLF) { /* Note that in.ready() will return true if and only if the next * read on the stream will not block. */ if (nextChar >= nChars && in.ready()) { fill(); } if (nextChar < nChars) { if (cb[nextChar] == '\n') nextChar++; skipLF = false; } } return (nextChar < nChars) || in.ready(); } /** * Tells whether this stream supports the mark() operation, which it does. */ @Override public boolean markSupported() { return true; } /** * Marks the present position in the stream. Subsequent calls to reset() * will attempt to reposition the stream to this point. * * @param readAheadLimit * Limit on the number of characters that may be read while still * preserving the mark. An attempt to reset the stream after * reading characters up to this limit or beyond may fail. A * limit value larger than the size of the input buffer will * cause a new buffer to be allocated whose size is no smaller * than limit. Therefore large values should be used with care. * * @exception IllegalArgumentException * If readAheadLimit is < 0 * @exception IOException * If an I/O error occurs */ @Override public void mark(int readAheadLimit) throws IOException { if (readAheadLimit < 0) { throw new IllegalArgumentException("Read-ahead limit < 0"); } ensureOpen(); this.readAheadLimit = readAheadLimit; markedChar = nextChar; markedSkipLF = skipLF; } /** * Resets the stream to the most recent mark. * * @exception IOException * If the stream has never been marked, or if the mark has * been invalidated */ @Override public void reset() throws IOException { ensureOpen(); if (markedChar < 0) throw new IOException((markedChar == INVALIDATED) ? "Mark invalid" : "Stream not marked"); nextChar = markedChar; skipLF = markedSkipLF; } @Override public void close() throws IOException { if (in == null) return; in.close(); in = null; cb = null; } }





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