/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
package java.io;
import java.util.Arrays;
/**
* Wraps an existing {@link Reader} and <em>buffers</em> the input. Expensive
* interaction with the underlying reader is minimized, since most (smaller)
* requests can be satisfied by accessing the buffer alone. The drawback is that
* some extra space is required to hold the buffer and that copying takes place
* when filling that buffer, but this is usually outweighed by the performance
* benefits.
*
* <p/>A typical application pattern for the class looks like this:<p/>
*
* <pre>
* BufferedReader buf = new BufferedReader(new FileReader("file.java"));
* </pre>
*
* @see BufferedWriter
* @since 1.1
*/
public class BufferedReader extends Reader {
private Reader in;
/**
* The characters that can be read and refilled in bulk. We maintain three
* indices into this buffer:<pre>
* { X X X X X X X X X X X X - - }
* ^ ^ ^
* | | |
* mark pos end</pre>
* Pos points to the next readable character. End is one greater than the
* last readable character. When {@code pos == end}, the buffer is empty and
* must be {@link #fillBuf() filled} before characters can be read.
*
* <p>Mark is the value pos will be set to on calls to {@link #reset}. Its
* value is in the range {@code [0...pos]}. If the mark is {@code -1}, the
* buffer cannot be reset.
*
* <p>MarkLimit limits the distance between the mark and the pos. When this
* limit is exceeded, {@link #reset} is permitted (but not required) to
* throw an exception. For shorter distances, {@link #reset} shall not throw
* (unless the reader is closed).
*/
private char[] buf;
private int pos;
private int end;
private int mark = -1;
private int markLimit = -1;
/**
* Constructs a new {@code BufferedReader}, providing {@code in} with a buffer
* of 8192 characters.
*
* @param in the {@code Reader} the buffer reads from.
*/
public BufferedReader(Reader in) {
this(in, 8192);
}
/**
* Constructs a new {@code BufferedReader}, providing {@code in} with {@code size} characters
* of buffer.
*
* @param in the {@code InputStream} the buffer reads from.
* @param size the size of buffer in characters.
* @throws IllegalArgumentException if {@code size <= 0}.
*/
public BufferedReader(Reader in, int size) {
super(in);
if (size <= 0) {
throw new IllegalArgumentException("size <= 0");
}
this.in = in;
buf = new char[size];
}
/**
* Closes this reader. This implementation closes the buffered source reader
* and releases the buffer. Nothing is done if this reader has already been
* closed.
*
* @throws IOException
* if an error occurs while closing this reader.
*/
@Override
public void close() throws IOException {
synchronized (lock) {
if (!isClosed()) {
in.close();
buf = null;
}
}
}
/**
* Populates the buffer with data. It is an error to call this method when
* the buffer still contains data; ie. if {@code pos < end}.
*
* @return the number of bytes read into the buffer, or -1 if the end of the
* source stream has been reached.
*/
private int fillBuf() throws IOException {
// assert(pos == end);
if (mark == -1 || (pos - mark >= markLimit)) {
/* mark isn't set or has exceeded its limit. use the whole buffer */
int result = in.read(buf, 0, buf.length);
if (result > 0) {
mark = -1;
pos = 0;
end = result;
}
return result;
}
if (mark == 0 && markLimit > buf.length) {
/* the only way to make room when mark=0 is by growing the buffer */
int newLength = buf.length * 2;
if (newLength > markLimit) {
newLength = markLimit;
}
char[] newbuf = new char[newLength];
System.arraycopy(buf, 0, newbuf, 0, buf.length);
buf = newbuf;
} else if (mark > 0) {
/* make room by shifting the buffered data to left mark positions */
System.arraycopy(buf, mark, buf, 0, buf.length - mark);
pos -= mark;
end -= mark;
mark = 0;
}
/* Set the new position and mark position */
int count = in.read(buf, pos, buf.length - pos);
if (count != -1) {
end += count;
}
return count;
}
/**
* Indicates whether or not this reader is closed.
*
* @return {@code true} if this reader is closed, {@code false}
* otherwise.
*/
private boolean isClosed() {
return buf == null;
}
/**
* Sets a mark position in this reader. The parameter {@code markLimit}
* indicates how many characters can be read before the mark is invalidated.
* Calling {@code reset()} will reposition the reader back to the marked
* position if {@code markLimit} has not been surpassed.
*
* @param markLimit
* the number of characters that can be read before the mark is
* invalidated.
* @throws IllegalArgumentException
* if {@code markLimit < 0}.
* @throws IOException
* if an error occurs while setting a mark in this reader.
* @see #markSupported()
* @see #reset()
*/
@Override
public void mark(int markLimit) throws IOException {
if (markLimit < 0) {
throw new IllegalArgumentException();
}
synchronized (lock) {
checkNotClosed();
this.markLimit = markLimit;
mark = pos;
}
}
private void checkNotClosed() throws IOException {
if (isClosed()) {
throw new IOException("BufferedReader is closed");
}
}
/**
* Indicates whether this reader supports the {@code mark()} and
* {@code reset()} methods. This implementation returns {@code true}.
*
* @return {@code true} for {@code BufferedReader}.
* @see #mark(int)
* @see #reset()
*/
@Override
public boolean markSupported() {
return true;
}
/**
* Reads a single character from this reader and returns it with the two
* higher-order bytes set to 0. If possible, BufferedReader returns a
* character from the buffer. If there are no characters available in the
* buffer, it fills the buffer and then returns a character. It returns -1
* if there are no more characters in the source reader.
*
* @return the character read or -1 if the end of the source reader has been
* reached.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
@Override
public int read() throws IOException {
synchronized (lock) {
checkNotClosed();
/* Are there buffered characters available? */
if (pos < end || fillBuf() != -1) {
return buf[pos++];
}
return -1;
}
}
/**
* Reads at most {@code length} characters from this reader and stores them
* at {@code offset} in the character array {@code buffer}. Returns the
* number of characters actually read or -1 if the end of the source reader
* has been reached. If all the buffered characters have been used, a mark
* has not been set and the requested number of characters is larger than
* this readers buffer size, BufferedReader bypasses the buffer and simply
* places the results directly into {@code buffer}.
*
* @param buffer
* the character array to store the characters read.
* @param offset
* the initial position in {@code buffer} to store the bytes read
* from this reader.
* @param length
* the maximum number of characters to read, must be
* non-negative.
* @return number of characters read or -1 if the end of the source reader
* has been reached.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code length < 0}, or if
* {@code offset + length} is greater than the size of
* {@code buffer}.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
@Override
public int read(char[] buffer, int offset, int length) throws IOException {
synchronized (lock) {
checkNotClosed();
Arrays.checkOffsetAndCount(buffer.length, offset, length);
int outstanding = length;
while (outstanding > 0) {
/*
* If there are bytes in the buffer, grab those first.
*/
int available = end - pos;
if (available > 0) {
int count = available >= outstanding ? outstanding : available;
System.arraycopy(buf, pos, buffer, offset, count);
pos += count;
offset += count;
outstanding -= count;
}
/*
* Before attempting to read from the underlying stream, make
* sure we really, really want to. We won't bother if we're
* done, or if we've already got some bytes and reading from the
* underlying stream would block.
*/
if (outstanding == 0 || (outstanding < length && !in.ready())) {
break;
}
// assert(pos == end);
/*
* If we're unmarked and the requested size is greater than our
* buffer, read the bytes directly into the caller's buffer. We
* don't read into smaller buffers because that could result in
* a many reads.
*/
if ((mark == -1 || (pos - mark >= markLimit)) && outstanding >= buf.length) {
int count = in.read(buffer, offset, outstanding);
if (count > 0) {
outstanding -= count;
mark = -1;
}
break; // assume the source stream gave us all that it could
}
if (fillBuf() == -1) {
break; // source is exhausted
}
}
int count = length - outstanding;
return (count > 0 || count == length) ? count : -1;
}
}
/**
* Peeks at the next input character, refilling the buffer if necessary. If
* this character is a newline character ("\n"), it is discarded.
*/
final void chompNewline() throws IOException {
if ((pos != end || fillBuf() != -1)
&& buf[pos] == '\n') {
pos++;
}
}
/**
* Returns the next line of text available from this reader. A line is
* represented by zero or more characters followed by {@code '\n'},
* {@code '\r'}, {@code "\r\n"} or the end of the reader. The string does
* not include the newline sequence.
*
* @return the contents of the line or {@code null} if no characters were
* read before the end of the reader has been reached.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
*/
public String readLine() throws IOException {
synchronized (lock) {
checkNotClosed();
/* has the underlying stream been exhausted? */
if (pos == end && fillBuf() == -1) {
return null;
}
for (int charPos = pos; charPos < end; charPos++) {
char ch = buf[charPos];
if (ch > '\r') {
continue;
}
if (ch == '\n') {
String res = new String(buf, pos, charPos - pos);
pos = charPos + 1;
return res;
} else if (ch == '\r') {
String res = new String(buf, pos, charPos - pos);
pos = charPos + 1;
if (((pos < end) || (fillBuf() != -1))
&& (buf[pos] == '\n')) {
pos++;
}
return res;
}
}
char eol = '\0';
StringBuilder result = new StringBuilder(80);
/* Typical Line Length */
result.append(buf, pos, end - pos);
while (true) {
pos = end;
/* Are there buffered characters available? */
if (eol == '\n') {
return result.toString();
}
// attempt to fill buffer
if (fillBuf() == -1) {
// characters or null.
return result.length() > 0 || eol != '\0'
? result.toString()
: null;
}
for (int charPos = pos; charPos < end; charPos++) {
char c = buf[charPos];
if (eol == '\0') {
if ((c == '\n' || c == '\r')) {
eol = c;
}
} else if (eol == '\r' && c == '\n') {
if (charPos > pos) {
result.append(buf, pos, charPos - pos - 1);
}
pos = charPos + 1;
return result.toString();
} else {
if (charPos > pos) {
result.append(buf, pos, charPos - pos - 1);
}
pos = charPos;
return result.toString();
}
}
if (eol == '\0') {
result.append(buf, pos, end - pos);
} else {
result.append(buf, pos, end - pos - 1);
}
}
}
}
/**
* Indicates whether this reader is ready to be read without blocking.
*
* @return {@code true} if this reader will not block when {@code read} is
* called, {@code false} if unknown or blocking will occur.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
* @see #read()
* @see #read(char[], int, int)
* @see #readLine()
*/
@Override
public boolean ready() throws IOException {
synchronized (lock) {
checkNotClosed();
return ((end - pos) > 0) || in.ready();
}
}
/**
* Resets this reader's position to the last {@code mark()} location.
* Invocations of {@code read()} and {@code skip()} will occur from this new
* location.
*
* @throws IOException
* if this reader is closed or no mark has been set.
* @see #mark(int)
* @see #markSupported()
*/
@Override
public void reset() throws IOException {
synchronized (lock) {
checkNotClosed();
if (mark == -1) {
throw new IOException("Invalid mark");
}
pos = mark;
}
}
/**
* Skips {@code byteCount} bytes in this stream. Subsequent calls to
* {@code read} will not return these bytes unless {@code reset} is
* used.
* Skipping characters may invalidate a mark if {@code markLimit}
* is surpassed.
*
* @param byteCount
* the maximum number of characters to skip.
* @return the number of characters actually skipped.
* @throws IllegalArgumentException
* if {@code byteCount < 0}.
* @throws IOException
* if this reader is closed or some other I/O error occurs.
* @see #mark(int)
* @see #markSupported()
* @see #reset()
*/
@Override
public long skip(long byteCount) throws IOException {
if (byteCount < 0) {
throw new IllegalArgumentException("byteCount < 0: " + byteCount);
}
synchronized (lock) {
checkNotClosed();
if (byteCount < 1) {
return 0;
}
if (end - pos >= byteCount) {
pos += byteCount;
return byteCount;
}
long read = end - pos;
pos = end;
while (read < byteCount) {
if (fillBuf() == -1) {
return read;
}
if (end - pos >= byteCount - read) {
pos += byteCount - read;
return byteCount;
}
// Couldn't get all the characters, skip what we read
read += (end - pos);
pos = end;
}
return byteCount;
}
}
}