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/*
* Copyright (c) 1996, 2024, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.io;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
/**
* Reads text from a character-input stream, buffering characters so as to
* provide for the efficient reading of characters, arrays, and lines.
*
* <p> The buffer size may be specified, or the default size may be used. The
* default is large enough for most purposes.
*
* <p> 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 {@code BufferedReader} around any
* {@code Reader} whose {@code read()} operations may be costly, such as
* {@code FileReader}s and {@code InputStreamReader}s. For
* example,
*
* {@snippet lang=java :
* BufferedReader in = new BufferedReader(new FileReader("foo.in"));
* }
*
* will buffer the input from the specified file. Without buffering, each
* invocation of {@code read()} or {@code readLine()} could cause bytes to be
* read from the file, converted into characters, and then returned, which can
* be very inefficient.
*
* <p> Programs that use {@code DataInputStream}s for textual input can be
* localized by replacing each {@code DataInputStream} with an appropriate
* {@code BufferedReader}.
*
* @apiNote
* Once wrapped in a {@code BufferedReader}, the underlying
* {@code Reader} should not be used directly nor wrapped with
* another reader.
*
* @see FileReader
* @see InputStreamReader
* @see java.nio.file.Files#newBufferedReader
*
* @author Mark Reinhold
* @since 1.1
*/
public class BufferedReader 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 final int DEFAULT_CHAR_BUFFER_SIZE = 8192;
private static final int DEFAULT_EXPECTED_LINE_LENGTH = 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
*
* @throws IllegalArgumentException If {@code sz <= 0}
*/
public BufferedReader(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 BufferedReader(Reader in) {
this(in, DEFAULT_CHAR_BUFFER_SIZE);
}
/** 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 ({@code 0x00-0xffff}), or -1 if the
* end of the stream has been reached
* @throws IOException If an I/O error occurs
*/
public int read() throws IOException {
synchronized (lock) {
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.
*
* <p> 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 {@code read} method of the underlying stream. This iterated
* {@code read} continues until one of the following conditions becomes
* true:
* <ul>
*
* <li> The specified number of characters have been read,
*
* <li> The {@code read} method of the underlying stream returns
* {@code -1}, indicating end-of-file, or
*
* <li> The {@code ready} method of the underlying stream
* returns {@code false}, indicating that further input requests
* would block.
*
* </ul>
* If the first {@code read} on the underlying stream returns
* {@code -1} to indicate end-of-file then this method returns
* {@code -1}. Otherwise this method returns the number of characters
* actually read.
*
* <p> Subclasses of this class are encouraged, but not required, to
* attempt to read as many characters as possible in the same fashion.
*
* <p> 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 {@code BufferedReader}s will not copy data
* unnecessarily.
*
* @param cbuf {@inheritDoc}
* @param off {@inheritDoc}
* @param len {@inheritDoc}
*
* @return {@inheritDoc}
*
* @throws IndexOutOfBoundsException {@inheritDoc}
* @throws IOException {@inheritDoc}
*/
public int read(char[] cbuf, int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
Objects.checkFromIndexSize(off, len, cbuf.length);
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'), a carriage return
* followed immediately by a line feed, or by reaching the end-of-file
* (EOF).
*
* @param ignoreLF If true, the next '\n' will be skipped
* @param term Output: Whether a line terminator was encountered
* while reading the line; may be {@code null}.
*
* @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 without reading any characters
*
* @see java.io.LineNumberReader#readLine()
*
* @throws IOException If an I/O error occurs
*/
String readLine(boolean ignoreLF, boolean[] term) throws IOException {
synchronized (lock) {
StringBuilder s = null;
int startChar;
ensureOpen();
boolean omitLF = ignoreLF || skipLF;
if (term != null) term[0] = false;
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')) {
if (term != null) term[0] = true;
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 StringBuilder(DEFAULT_EXPECTED_LINE_LENGTH);
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'), a carriage return
* followed immediately by a line feed, or by reaching the end-of-file
* (EOF).
*
* @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 without reading any characters
*
* @throws IOException If an I/O error occurs
*
* @see java.nio.file.Files#readAllLines
*/
public String readLine() throws IOException {
return readLine(false, null);
}
/**
* {@inheritDoc}
*/
public long skip(long n) throws IOException {
if (n < 0L) {
throw new IllegalArgumentException("skip value is negative");
}
synchronized (lock) {
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 += (int)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.
*
* @throws IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
synchronized (lock) {
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.
*/
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.
*
* @throws IllegalArgumentException If {@code readAheadLimit < 0}
* @throws IOException If an I/O error occurs
*/
public void mark(int readAheadLimit) throws IOException {
if (readAheadLimit < 0) {
throw new IllegalArgumentException("Read-ahead limit < 0");
}
synchronized (lock) {
ensureOpen();
this.readAheadLimit = readAheadLimit;
markedChar = nextChar;
markedSkipLF = skipLF;
}
}
/**
* Resets the stream to the most recent mark.
*
* @throws IOException If the stream has never been marked,
* or if the mark has been invalidated
*/
public void reset() throws IOException {
synchronized (lock) {
ensureOpen();
if (markedChar < 0)
throw new IOException((markedChar == INVALIDATED)
? "Mark invalid"
: "Stream not marked");
nextChar = markedChar;
skipLF = markedSkipLF;
}
}
public void close() throws IOException {
synchronized (lock) {
if (in == null)
return;
try {
in.close();
} finally {
in = null;
cb = null;
}
}
}
/**
* Returns a {@code Stream}, the elements of which are lines read from
* this {@code BufferedReader}. The {@link Stream} is lazily populated,
* i.e., read only occurs during the
* <a href="../util/stream/package-summary.html#StreamOps">terminal
* stream operation</a>.
*
* <p> The reader must not be operated on during the execution of the
* terminal stream operation. Otherwise, the result of the terminal stream
* operation is undefined.
*
* <p> After execution of the terminal stream operation there are no
* guarantees that the reader will be at a specific position from which to
* read the next character or line.
*
* <p> If an {@link IOException} is thrown when accessing the underlying
* {@code BufferedReader}, it is wrapped in an {@link
* UncheckedIOException} which will be thrown from the {@code Stream}
* method that caused the read to take place. This method will return a
* Stream if invoked on a BufferedReader that is closed. Any operation on
* that stream that requires reading from the BufferedReader after it is
* closed, will cause an UncheckedIOException to be thrown.
*
* @return a {@code Stream<String>} providing the lines of text
* described by this {@code BufferedReader}
*
* @since 1.8
*/
public Stream<String> lines() {
Iterator<String> iter = new Iterator<>() {
String nextLine = null;
@Override
public boolean hasNext() {
if (nextLine != null) {
return true;
} else {
try {
nextLine = readLine();
return (nextLine != null);
} catch (IOException e) {
throw new UncheckedIOException(e);
}
}
}
@Override
public String next() {
if (nextLine != null || hasNext()) {
String line = nextLine;
nextLine = null;
return line;
} else {
throw new NoSuchElementException();
}
}
};
return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
iter, Spliterator.ORDERED | Spliterator.NONNULL), false);
}
}