org.openl.util.fast.FastStringReader Maven / Gradle / Ivy
package org.openl.util.fast;
import java.io.IOException;
import java.io.Reader;
public class FastStringReader extends Reader {
private static final IOException$1 IO_EXC = new IOException$1();
private String str;
private final int length;
private int next = 0;
private int mark = 0;
/**
* Creates a new string reader.
*
* @param s String providing the character stream.
*/
public FastStringReader(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 IO_EXC;
}
}
private static final class IOException$1 extends IOException {
private static final long serialVersionUID = 4942784446367469908L;
@Override
public Throwable fillInStackTrace() {
return this;
}
}
/**
* Reads a single character.
*
* @return The character read, or -1 if the end of the stream has been reached
* @throws IOException If an I/O error occurs
*/
@Override
public int read() throws IOException {
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
* @throws IOException If an I/O error occurs
*/
@Override
public int read(char cbuf[], int off, int len) throws IOException {
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.
*
*
* The ns parameter may be negative, even though the skip method of the {@link Reader}
* superclass throws an exception in this case. Negative values of ns 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.
*
*
* If the entire string has been read or skipped, then this method has no effect and always returns 0.
*
* @throws IOException If an I/O error occurs
*/
@Override
public long skip(long ns) throws IOException {
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
* @throws IOException If the stream is closed
*/
@Override
public boolean ready() throws IOException {
ensureOpen();
return true;
}
/**
* Tells whether this stream supports the mark() operation, which it does.
*/
@Override
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.
* @throws IllegalArgumentException If readAheadLimit is < 0
* @throws IOException If an I/O error occurs
*/
@Override
public void mark(int readAheadLimit) throws IOException {
if (readAheadLimit < 0) {
throw new IllegalArgumentException("Read-ahead limit < 0");
}
ensureOpen();
mark = next;
}
/**
* Resets the stream to the most recent mark, or to the beginning of the string if it has never been marked.
*
* @throws IOException If an I/O error occurs
*/
@Override
public void reset() throws IOException {
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.
*/
@Override
public void close() {
str = null;
}
}