/*
* 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 whose source is a string.
*
* @author Mark Reinhold
* @since JDK1.1
*/
public class
StringReader extends
Reader {
private
String str;
private int
length;
private int
next = 0;
private int
mark = 0;
/**
* Creates a new string reader.
*
* @param s String providing the character stream.
*/
public
StringReader(
String s) {
this.
str =
s;
this.
length =
s.
length();
}
/** Check to make sure that the stream has not been closed */
private void
ensureOpen() throws
IOException {
if (
str == 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 (
next >=
length)
return -1;
return
str.
charAt(
next++);
}
}
/**
* 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();
if ((
off < 0) || (
off >
cbuf.length) || (
len < 0) ||
((
off +
len) >
cbuf.length) || ((
off +
len) < 0)) {
throw new
IndexOutOfBoundsException();
} else if (
len == 0) {
return 0;
}
if (
next >=
length)
return -1;
int
n =
Math.
min(
length -
next,
len);
str.
getChars(
next,
next +
n,
cbuf,
off);
next +=
n;
return
n;
}
}
/**
* Skips the specified number of characters in the stream. Returns
* the number of characters that were skipped.
*
* <p>The <code>ns</code> parameter may be negative, even though the
* <code>skip</code> method of the {@link Reader} superclass throws
* an exception in this case. Negative values of <code>ns</code> cause the
* stream to skip backwards. Negative return values indicate a skip
* backwards. It is not possible to skip backwards past the beginning of
* the string.
*
* <p>If the entire string has been read or skipped, then this method has
* no effect and always returns 0.
*
* @exception IOException If an I/O error occurs
*/
public long
skip(long
ns) throws
IOException {
synchronized (
lock) {
ensureOpen();
if (
next >=
length)
return 0;
// Bound skip by beginning and end of the source
long
n =
Math.
min(
length -
next,
ns);
n =
Math.
max(-
next,
n);
next +=
n;
return
n;
}
}
/**
* Tells whether this stream is ready to be read.
*
* @return True if the next read() is guaranteed not to block for input
*
* @exception IOException If the stream is closed
*/
public boolean
ready() throws
IOException {
synchronized (
lock) {
ensureOpen();
return true;
}
}
/**
* 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 string, there
* is no actual limit, so this argument must not
* be negative, but is otherwise ignored.
*
* @exception IllegalArgumentException If {@code readAheadLimit < 0}
* @exception 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();
mark =
next;
}
}
/**
* Resets the stream to the most recent mark, or to the beginning of the
* string if it has never been marked.
*
* @exception IOException If an I/O error occurs
*/
public void
reset() throws
IOException {
synchronized (
lock) {
ensureOpen();
next =
mark;
}
}
/**
* Closes the stream and releases any system resources associated with
* it. Once the stream has been closed, further read(),
* ready(), mark(), or reset() invocations will throw an IOException.
* Closing a previously closed stream has no effect.
*/
public void
close() {
str = null;
}
}