org.apache.wicket.util.string.PrependingStringBuffer.java Source code

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Here is the source code for org.apache.wicket.util.string.PrependingStringBuffer.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.wicket.util.string;

/**
 * This is a prepending stringbuffer optimized for constantly prepending strings to the front of the
 * buffer.
 * 
 * @author jcompagner
 */
public class PrependingStringBuffer {
    private int size;
    private int position;

    private char[] buffer;

    /**
     * Default constructor, the internal initial buffer size will be 16
     */
    public PrependingStringBuffer() {
        this(16);
    }

    /**
     * Constructs this PrependingStringBuffer with the given buffer size.
     * 
     * @param size
     *            The initial size of the buffer.
     */
    public PrependingStringBuffer(final int size) {
        buffer = new char[size];
        position = size;
        this.size = 0;
    }

    /**
     * Constructs and direct inserts the given string. The buffer size will be string.length+16
     * 
     * @param start
     *            The string that is directly inserted.
     */
    public PrependingStringBuffer(final String start) {
        this(start.length() + 16);
        prepend(start);
    }

    /**
     * Prepends one char to this PrependingStringBuffer
     * 
     * @param ch
     *            The char that will be prepended
     * @return this
     */
    public PrependingStringBuffer prepend(final char ch) {
        int len = 1;
        if (position < len) {
            expandCapacity(size + len);
        }
        position -= len;
        buffer[position] = ch;
        size += len;
        return this;
    }

    /**
     * Prepends the string to this PrependingStringBuffer
     * 
     * @param str
     *            The string that will be prepended
     * @return this
     */
    public PrependingStringBuffer prepend(final String str) {
        int len = str.length();
        if (position < len) {
            expandCapacity(size + len);
        }
        str.getChars(0, len, buffer, position - len);
        position -= len;
        size += len;
        return this;
    }

    private void expandCapacity(final int minimumCapacity) {
        int newCapacity = (buffer.length + 1) * 2;
        if (newCapacity < 0) {
            newCapacity = Integer.MAX_VALUE;
        } else if (minimumCapacity > newCapacity) {
            newCapacity = minimumCapacity;
        }

        char newValue[] = new char[newCapacity];
        System.arraycopy(buffer, position, newValue, newCapacity - size, size);
        buffer = newValue;
        position = newCapacity - size;
    }

    /**
     * Returns the size of this PrependingStringBuffer
     * 
     * @return The size
     */
    public int length() {
        return size;
    }

    /**
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return new String(buffer, position, size);
    }

    @Override
    public boolean equals(final Object obj) {
        if (obj == this) {
            return true;
        } else if (obj == null) {
            return false;
        } else {
            return toString().equals(obj.toString());
        }
    }

    @Override
    public int hashCode() {
        return toString().hashCode();
    }
}