/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.io;
/**
* A character-stream reader that allows characters to be pushed back into the
* stream.
*
* @author Mark Reinhold
* @since JDK1.1
*/
public class
PushbackReader extends
FilterReader {
/** Pushback buffer */
private char[]
buf;
/** Current position in buffer */
private int
pos;
/**
* Creates a new pushback reader with a pushback buffer of the given size.
*
* @param in The reader from which characters will be read
* @param size The size of the pushback buffer
* @exception IllegalArgumentException if {@code size <= 0}
*/
public
PushbackReader(
Reader in, int
size) {
super(
in);
if (
size <= 0) {
throw new
IllegalArgumentException("size <= 0");
}
this.
buf = new char[
size];
this.
pos =
size;
}
/**
* Creates a new pushback reader with a one-character pushback buffer.
*
* @param in The reader from which characters will be read
*/
public
PushbackReader(
Reader in) {
this(
in, 1);
}
/** 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.
*
* @return The character read, or -1 if the end of the stream has been
* reached
*
* @exception IOException If an I/O error occurs
*/
public int
read() throws
IOException {
synchronized (
lock) {
ensureOpen();
if (
pos <
buf.length)
return
buf[
pos++];
else
return super.read();
}
}
/**
* Reads characters into a portion of an array.
*
* @param cbuf Destination buffer
* @param off Offset at which to start writing 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
*/
public int
read(char
cbuf[], int
off, int
len) throws
IOException {
synchronized (
lock) {
ensureOpen();
try {
if (
len <= 0) {
if (
len < 0) {
throw new
IndexOutOfBoundsException();
} else if ((
off < 0) || (
off >
cbuf.length)) {
throw new
IndexOutOfBoundsException();
}
return 0;
}
int
avail =
buf.length -
pos;
if (
avail > 0) {
if (
len <
avail)
avail =
len;
System.
arraycopy(
buf,
pos,
cbuf,
off,
avail);
pos +=
avail;
off +=
avail;
len -=
avail;
}
if (
len > 0) {
len = super.read(
cbuf,
off,
len);
if (
len == -1) {
return (
avail == 0) ? -1 :
avail;
}
return
avail +
len;
}
return
avail;
} catch (
ArrayIndexOutOfBoundsException e) {
throw new
IndexOutOfBoundsException();
}
}
}
/**
* Pushes back a single character by copying it to the front of the
* pushback buffer. After this method returns, the next character to be read
* will have the value <code>(char)c</code>.
*
* @param c The int value representing a character to be pushed back
*
* @exception IOException If the pushback buffer is full,
* or if some other I/O error occurs
*/
public void
unread(int
c) throws
IOException {
synchronized (
lock) {
ensureOpen();
if (
pos == 0)
throw new
IOException("Pushback buffer overflow");
buf[--
pos] = (char)
c;
}
}
/**
* Pushes back a portion of an array of characters by copying it to the
* front of the pushback buffer. After this method returns, the next
* character to be read will have the value <code>cbuf[off]</code>, the
* character after that will have the value <code>cbuf[off+1]</code>, and
* so forth.
*
* @param cbuf Character array
* @param off Offset of first character to push back
* @param len Number of characters to push back
*
* @exception IOException If there is insufficient room in the pushback
* buffer, or if some other I/O error occurs
*/
public void
unread(char
cbuf[], int
off, int
len) throws
IOException {
synchronized (
lock) {
ensureOpen();
if (
len >
pos)
throw new
IOException("Pushback buffer overflow");
pos -=
len;
System.
arraycopy(
cbuf,
off,
buf,
pos,
len);
}
}
/**
* Pushes back an array of characters by copying it to the front of the
* pushback buffer. After this method returns, the next character to be
* read will have the value <code>cbuf[0]</code>, the character after that
* will have the value <code>cbuf[1]</code>, and so forth.
*
* @param cbuf Character array to push back
*
* @exception IOException If there is insufficient room in the pushback
* buffer, or if some other I/O error occurs
*/
public void
unread(char
cbuf[]) throws
IOException {
unread(
cbuf, 0,
cbuf.length);
}
/**
* Tells whether this stream is ready to be read.
*
* @exception IOException If an I/O error occurs
*/
public boolean
ready() throws
IOException {
synchronized (
lock) {
ensureOpen();
return (
pos <
buf.length) || super.ready();
}
}
/**
* Marks the present position in the stream. The <code>mark</code>
* for class <code>PushbackReader</code> always throws an exception.
*
* @exception IOException Always, since mark is not supported
*/
public void
mark(int
readAheadLimit) throws
IOException {
throw new
IOException("mark/reset not supported");
}
/**
* Resets the stream. The <code>reset</code> method of
* <code>PushbackReader</code> always throws an exception.
*
* @exception IOException Always, since reset is not supported
*/
public void
reset() throws
IOException {
throw new
IOException("mark/reset not supported");
}
/**
* Tells whether this stream supports the mark() operation, which it does
* not.
*/
public boolean
markSupported() {
return false;
}
/**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(),
* unread(), ready(), or skip() invocations will throw an IOException.
* Closing a previously closed stream has no effect.
*
* @exception IOException If an I/O error occurs
*/
public void
close() throws
IOException {
super.close();
buf = null;
}
/**
* Skips characters. This method will block until some characters are
* available, an I/O error occurs, or the end of the stream is reached.
*
* @param n The number of characters to skip
*
* @return The number of characters actually skipped
*
* @exception IllegalArgumentException If <code>n</code> is negative.
* @exception IOException If an I/O error occurs
*/
public long
skip(long
n) throws
IOException {
if (
n < 0L)
throw new
IllegalArgumentException("skip value is negative");
synchronized (
lock) {
ensureOpen();
int
avail =
buf.length -
pos;
if (
avail > 0) {
if (
n <=
avail) {
pos +=
n;
return
n;
} else {
pos =
buf.length;
n -=
avail;
}
}
return
avail + super.skip(
n);
}
}
}