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CharArrayReader.java
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232 lines (215 loc) · 6.51 KB
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/*
* Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.io;
/**
* This class implements a character buffer that can be used as a
* character-input stream.
*
* @author Herb Jellinek
* @since JDK1.1
*/
public class CharArrayReader extends Reader {
/** The character buffer. */
protected char buf[];
/** The current buffer position. */
protected int pos;
/** The position of mark in buffer. */
protected int markedPos = 0;
/**
* The index of the end of this buffer. There is not valid
* data at or beyond this index.
*/
protected int count;
/**
* Creates a CharArrayReader from the specified array of chars.
* @param buf Input buffer (not copied)
*/
public CharArrayReader(char buf[]) {
this.buf = buf;
this.pos = 0;
this.count = buf.length;
}
/**
* Creates a CharArrayReader from the specified array of chars.
*
* <p> The resulting reader will start reading at the given
* <tt>offset</tt>. The total number of <tt>char</tt> values that can be
* read from this reader will be either <tt>length</tt> or
* <tt>buf.length-offset</tt>, whichever is smaller.
*
* @throws IllegalArgumentException
* If <tt>offset</tt> is negative or greater than
* <tt>buf.length</tt>, or if <tt>length</tt> is negative, or if
* the sum of these two values is negative.
*
* @param buf Input buffer (not copied)
* @param offset Offset of the first char to read
* @param length Number of chars to read
*/
public CharArrayReader(char buf[], int offset, int length) {
if ((offset < 0) || (offset > buf.length) || (length < 0) ||
((offset + length) < 0)) {
throw new IllegalArgumentException();
}
this.buf = buf;
this.pos = offset;
this.count = Math.min(offset + length, buf.length);
this.markedPos = offset;
}
/** Checks to make sure that the stream has not been closed */
private void ensureOpen() throws IOException {
if (buf == null)
throw new IOException("Stream closed");
}
/**
* Reads a single character.
*
* @exception IOException If an I/O error occurs
*/
public int read() throws IOException {
synchronized (lock) {
ensureOpen();
if (pos >= count)
return -1;
else
return buf[pos++];
}
}
/**
* Reads characters into a portion of an array.
* @param b Destination buffer
* @param off Offset at which to start storing characters
* @param len Maximum number of characters to read
* @return The actual number of characters read, or -1 if
* the end of the stream has been reached
*
* @exception IOException If an I/O error occurs
*/
public int read(char b[], int off, int len) throws IOException {
synchronized (lock) {
ensureOpen();
if ((off < 0) || (off > b.length) || (len < 0) ||
((off + len) > b.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}
if (pos >= count) {
return -1;
}
if (pos + len > count) {
len = count - pos;
}
if (len <= 0) {
return 0;
}
System.arraycopy(buf, pos, b, off, len);
pos += len;
return len;
}
}
/**
* Skips characters. Returns the number of characters that were skipped.
*
* <p>The <code>n</code> parameter may be negative, even though the
* <code>skip</code> method of the {@link Reader} superclass throws
* an exception in this case. If <code>n</code> is negative, then
* this method does nothing and returns <code>0</code>.
*
* @param n The number of characters to skip
* @return The number of characters actually skipped
* @exception IOException If the stream is closed, or an I/O error occurs
*/
public long skip(long n) throws IOException {
synchronized (lock) {
ensureOpen();
if (pos + n > count) {
n = count - pos;
}
if (n < 0) {
return 0;
}
pos += n;
return n;
}
}
/**
* Tells whether this stream is ready to be read. Character-array readers
* are always ready to be read.
*
* @exception IOException If an I/O error occurs
*/
public boolean ready() throws IOException {
synchronized (lock) {
ensureOpen();
return (count - pos) > 0;
}
}
/**
* 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 reposition the stream to this point.
*
* @param readAheadLimit Limit on the number of characters that may be
* read while still preserving the mark. Because
* the stream's input comes from a character array,
* there is no actual limit; hence this argument is
* ignored.
*
* @exception IOException If an I/O error occurs
*/
public void mark(int readAheadLimit) throws IOException {
synchronized (lock) {
ensureOpen();
markedPos = pos;
}
}
/**
* Resets the stream to the most recent mark, or to the beginning if it has
* never been marked.
*
* @exception IOException If an I/O error occurs
*/
public void reset() throws IOException {
synchronized (lock) {
ensureOpen();
pos = markedPos;
}
}
/**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(), ready(),
* mark(), reset(), or skip() invocations will throw an IOException.
* Closing a previously closed stream has no effect.
*/
public void close() {
buf = null;
}
}