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/*
* Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package jdk.nashorn.internal.parser;
/**
*
*/
/**
* Handles streaming of tokens between lexer and parser.
*
*/
public class TokenStream {
/** Initial buffer size. */
private static final int INITIAL_SIZE = 256;
/** Token buffer. */
private long[] buffer;
/** Token count. */
private int count;
/** Cursor to write position in buffer */
private int in;
/** Cursor to read position in buffer */
private int out;
/** Base index in buffer */
private int base;
/**
* Constructor.
*/
public TokenStream() {
buffer = new long[INITIAL_SIZE];
count = 0;
in = 0;
out = 0;
base = 0;
}
/**
* Get the next position in the buffer.
* @param position Current position in buffer.
* @return Next position in buffer.
*/
private int next(final int position) {
// Next position.
int next = position + 1;
// If exceeds buffer length.
if (next >= buffer.length) {
// Wrap around.
next = 0;
}
return next;
}
/**
* Get the index position in the buffer.
* @param k Seek position.
* @return Position in buffer.
*/
private int index(final int k) {
// Bias k.
int index = k - (base - out);
// If wrap around.
if (index >= buffer.length) {
index -= buffer.length;
}
return index;
}
/**
* Test to see if stream is empty.
* @return True if stream is empty.
*/
public boolean isEmpty() {
return count == 0;
}
/**
* Test to see if stream is full.
* @return True if stream is full.
*/
public boolean isFull() {
return count == buffer.length;
}
/**
* Get the number of tokens in the buffer.
* @return Number of tokens.
*/
public int count() {
return count;
}
/**
* Get the index of the first token in the stream.
* @return Index of first buffered token in the stream.
*/
public int first() {
return base;
}
/**
* Get the index of the last token in the stream.
* @return Index of last buffered token in the stream.
*/
public int last() {
return base + count - 1;
}
/**
* Remove the last token in the stream.
*/
public void removeLast() {
if (count != 0) {
count--;
in--;
if (in < 0) {
in = buffer.length - 1;
}
}
}
/**
* Put a token descriptor to the stream.
* @param token Token descriptor to add.
*/
public void put(final long token) {
if (count == buffer.length) {
grow();
}
buffer[in] = token;
count++;
in = next(in);
}
/**
* Get the kth token descriptor from the stream.
* @param k index
* @return Token descriptor.
*/
public long get(final int k) {
return buffer[index(k)];
}
/**
* Advances the base of the stream.
* @param k Position of token to be the new base.
*/
public void commit(final int k) {
// Advance out.
out = index(k);
// Adjust count.
count -= k - base;
// Set base.
base = k;
}
/**
* Grow the buffer to accommodate more token descriptors.
*/
public void grow() {
// Allocate new buffer.
final long[] newBuffer = new long[buffer.length * 2];
// If single chunk.
if (in > out) {
System.arraycopy(buffer, out, newBuffer, 0, count);
} else {
final int portion = buffer.length - out;
System.arraycopy(buffer, out, newBuffer, 0, portion);
System.arraycopy(buffer, 0, newBuffer, portion, count - portion);
}
// Update buffer and indices.
out = 0;
in = count;
buffer = newBuffer;
}
}
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