com.greenpepper.shaded.antlr.CharQueue Maven / Gradle / Ivy
The newest version!
package antlr;
/* ANTLR Translator Generator
* Project led by Terence Parr at http://www.cs.usfca.edu
* Software rights: http://www.antlr.org/license.html
*
* $Id: //depot/code/org.antlr/release/antlr-2.7.6/antlr/CharQueue.java#1 $
*/
/** A circular buffer object used by CharBuffer */
public class CharQueue {
/** Physical circular buffer of tokens */
protected char[] buffer;
/** buffer.length-1 for quick modulos */
private int sizeLessOne;
/** physical index of front token */
private int offset;
/** number of tokens in the queue */
protected int nbrEntries;
public CharQueue(int minSize) {
// Find first power of 2 >= to requested size
int size;
if ( minSize<0 ) {
init(16); // pick some value for them
return;
}
// check for overflow
if ( minSize>=(Integer.MAX_VALUE/2) ) {
init(Integer.MAX_VALUE); // wow that's big.
return;
}
for (size = 2; size < minSize; size *= 2) {
}
init(size);
}
/** Add token to end of the queue
* @param tok The token to add
*/
public final void append(char tok) {
if (nbrEntries == buffer.length) {
expand();
}
buffer[(offset + nbrEntries) & sizeLessOne] = tok;
nbrEntries++;
}
/** Fetch a token from the queue by index
* @param idx The index of the token to fetch, where zero is the token at the front of the queue
*/
public final char elementAt(int idx) {
return buffer[(offset + idx) & sizeLessOne];
}
/** Expand the token buffer by doubling its capacity */
private final void expand() {
char[] newBuffer = new char[buffer.length * 2];
// Copy the contents to the new buffer
// Note that this will store the first logical item in the
// first physical array element.
for (int i = 0; i < buffer.length; i++) {
newBuffer[i] = elementAt(i);
}
// Re-initialize with new contents, keep old nbrEntries
buffer = newBuffer;
sizeLessOne = buffer.length - 1;
offset = 0;
}
/** Initialize the queue.
* @param size The initial size of the queue
*/
public void init(int size) {
// Allocate buffer
buffer = new char[size];
// Other initialization
sizeLessOne = size - 1;
offset = 0;
nbrEntries = 0;
}
/** Clear the queue. Leaving the previous buffer alone.
*/
public final void reset() {
offset = 0;
nbrEntries = 0;
}
/** Remove char from front of queue */
public final void removeFirst() {
offset = (offset + 1) & sizeLessOne;
nbrEntries--;
}
}