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96 lines
2.7 KiB
96 lines
2.7 KiB
5 years ago
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package com.fr.third.antlr;
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/* ANTLR Translator Generator
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* Project led by Terence Parr at http://www.cs.usfca.edu
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* Software rights: http://www.antlr.org/license.html
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*
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* $Id: //depot/code/org.antlr/release/antlr-2.7.7/antlr/CharQueue.java#2 $
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*/
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/** A circular buffer object used by CharBuffer */
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public class CharQueue {
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/** Physical circular buffer of tokens */
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protected char[] buffer;
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/** buffer.length-1 for quick modulos */
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private int sizeLessOne;
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/** physical index of front token */
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private int offset;
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/** number of tokens in the queue */
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protected int nbrEntries;
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public CharQueue(int minSize) {
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// Find first power of 2 >= to requested size
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int size;
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if ( minSize<0 ) {
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init(16); // pick some value for them
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return;
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}
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// check for overflow
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if ( minSize>=(Integer.MAX_VALUE/2) ) {
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init(Integer.MAX_VALUE); // wow that's big.
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return;
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}
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for (size = 2; size < minSize; size *= 2) {
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}
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init(size);
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}
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/** Add token to end of the queue
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* @param tok The token to add
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*/
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public final void append(char tok) {
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if (nbrEntries == buffer.length) {
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expand();
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}
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buffer[(offset + nbrEntries) & sizeLessOne] = tok;
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nbrEntries++;
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}
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/** Fetch a token from the queue by index
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* @param idx The index of the token to fetch, where zero is the token at the front of the queue
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*/
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public final char elementAt(int idx) {
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return buffer[(offset + idx) & sizeLessOne];
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}
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/** Expand the token buffer by doubling its capacity */
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private final void expand() {
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char[] newBuffer = new char[buffer.length * 2];
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// Copy the contents to the new buffer
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// Note that this will store the first logical item in the
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// first physical array element.
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for (int i = 0; i < buffer.length; i++) {
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newBuffer[i] = elementAt(i);
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}
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// Re-initialize with new contents, keep old nbrEntries
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buffer = newBuffer;
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sizeLessOne = buffer.length - 1;
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offset = 0;
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}
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/** Initialize the queue.
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* @param size The initial size of the queue
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*/
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public void init(int size) {
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// Allocate buffer
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buffer = new char[size];
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// Other initialization
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sizeLessOne = size - 1;
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offset = 0;
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nbrEntries = 0;
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}
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/** Clear the queue. Leaving the previous buffer alone.
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*/
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public final void reset() {
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offset = 0;
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nbrEntries = 0;
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}
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/** Remove char from front of queue */
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public final void removeFirst() {
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offset = (offset + 1) & sizeLessOne;
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nbrEntries--;
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}
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}
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