org.xerial.util.FastBufferedReader Maven / Gradle / Ivy
/*--------------------------------------------------------------------------
* 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;
}
}