ByteArrayBuffer.java
/*
* ====================================================================
* 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
*/
package com.foxinmy.weixin4j.util;
import java.io.Serializable;
/**
* A resizable byte array.
*
* @since 4.0
*/
public final class ByteArrayBuffer implements Serializable {
private static final long serialVersionUID = 4359112959524048036L;
private byte[] buffer;
private int len;
/**
* Creates an instance of {@link ByteArrayBuffer} with the given initial
* capacity.
*
* @param capacity the capacity
*/
public ByteArrayBuffer(final int capacity) {
super();
this.buffer = new byte[capacity];
}
private void expand(final int newlen) {
final byte newbuffer[] = new byte[Math.max(this.buffer.length << 1, newlen)];
System.arraycopy(this.buffer, 0, newbuffer, 0, this.len);
this.buffer = newbuffer;
}
/**
* Appends {@code len} bytes to this buffer from the given source
* array starting at index {@code off}. The capacity of the buffer
* is increased, if necessary, to accommodate all {@code len} bytes.
*
* @param b the bytes to be appended.
* @param off the index of the first byte to append.
* @param len the number of bytes to append.
* @throws IndexOutOfBoundsException if {@code off} if out of
* range, {@code len} is negative, or
* {@code off} + {@code len} is out of range.
*/
public void append(final byte[] b, final int off, final int len) {
if (b == null) {
return;
}
if ((off < 0) || (off > b.length) || (len < 0) ||
((off + len) < 0) || ((off + len) > b.length)) {
throw new IndexOutOfBoundsException("off: "+off+" len: "+len+" b.length: "+b.length);
}
if (len == 0) {
return;
}
final int newlen = this.len + len;
if (newlen > this.buffer.length) {
expand(newlen);
}
System.arraycopy(b, off, this.buffer, this.len, len);
this.len = newlen;
}
/**
* Appends {@code b} byte to this buffer. The capacity of the buffer
* is increased, if necessary, to accommodate the additional byte.
*
* @param b the byte to be appended.
*/
public void append(final int b) {
final int newlen = this.len + 1;
if (newlen > this.buffer.length) {
expand(newlen);
}
this.buffer[this.len] = (byte)b;
this.len = newlen;
}
/**
* Appends {@code len} chars to this buffer from the given source
* array starting at index {@code off}. The capacity of the buffer
* is increased if necessary to accommodate all {@code len} chars.
* <p>
* The chars are converted to bytes using simple cast.
*
* @param b the chars to be appended.
* @param off the index of the first char to append.
* @param len the number of bytes to append.
* @throws IndexOutOfBoundsException if {@code off} if out of
* range, {@code len} is negative, or
* {@code off} + {@code len} is out of range.
*/
public void append(final char[] b, final int off, final int len) {
if (b == null) {
return;
}
if ((off < 0) || (off > b.length) || (len < 0) ||
((off + len) < 0) || ((off + len) > b.length)) {
throw new IndexOutOfBoundsException("off: "+off+" len: "+len+" b.length: "+b.length);
}
if (len == 0) {
return;
}
final int oldlen = this.len;
final int newlen = oldlen + len;
if (newlen > this.buffer.length) {
expand(newlen);
}
for (int i1 = off, i2 = oldlen; i2 < newlen; i1++, i2++) {
this.buffer[i2] = (byte) b[i1];
}
this.len = newlen;
}
/**
* Appends {@code len} chars to this buffer from the given source
* char array buffer starting at index {@code off}. The capacity
* of the buffer is increased if necessary to accommodate all
* {@code len} chars.
* <p>
* The chars are converted to bytes using simple cast.
*
* @param b the chars to be appended.
* @param off the index of the first char to append.
* @param len the number of bytes to append.
* @throws IndexOutOfBoundsException if {@code off} if out of
* range, {@code len} is negative, or
* {@code off} + {@code len} is out of range.
*/
public void append(final CharArrayBuffer b, final int off, final int len) {
if (b == null) {
return;
}
append(b.buffer(), off, len);
}
/**
* Clears content of the buffer. The underlying byte array is not resized.
*/
public void clear() {
this.len = 0;
}
/**
* Converts the content of this buffer to an array of bytes.
*
* @return byte array
*/
public byte[] toByteArray() {
final byte[] b = new byte[this.len];
if (this.len > 0) {
System.arraycopy(this.buffer, 0, b, 0, this.len);
}
return b;
}
/**
* Returns the {@code byte} value in this buffer at the specified
* index. The index argument must be greater than or equal to
* {@code 0}, and less than the length of this buffer.
*
* @param i the index of the desired byte value.
* @return the byte value at the specified index.
* @throws IndexOutOfBoundsException if {@code index} is
* negative or greater than or equal to {@link #length()}.
*/
public int byteAt(final int i) {
return this.buffer[i];
}
/**
* Returns the current capacity. The capacity is the amount of storage
* available for newly appended bytes, beyond which an allocation
* will occur.
*
* @return the current capacity
*/
public int capacity() {
return this.buffer.length;
}
/**
* Returns the length of the buffer (byte count).
*
* @return the length of the buffer
*/
public int length() {
return this.len;
}
/**
* Ensures that the capacity is at least equal to the specified minimum.
* If the current capacity is less than the argument, then a new internal
* array is allocated with greater capacity. If the {@code required}
* argument is non-positive, this method takes no action.
*
* @param required the minimum required capacity.
*
* @since 4.1
*/
public void ensureCapacity(final int required) {
if (required <= 0) {
return;
}
final int available = this.buffer.length - this.len;
if (required > available) {
expand(this.len + required);
}
}
/**
* Returns reference to the underlying byte array.
*
* @return the byte array.
*/
public byte[] buffer() {
return this.buffer;
}
/**
* Sets the length of the buffer. The new length value is expected to be
* less than the current capacity and greater than or equal to
* {@code 0}.
*
* @param len the new length
* @throws IndexOutOfBoundsException if the
* {@code len} argument is greater than the current
* capacity of the buffer or less than {@code 0}.
*/
public void setLength(final int len) {
if (len < 0 || len > this.buffer.length) {
throw new IndexOutOfBoundsException("len: "+len+" < 0 or > buffer len: "+this.buffer.length);
}
this.len = len;
}
/**
* Returns {@code true} if this buffer is empty, that is, its
* {@link #length()} is equal to {@code 0}.
* @return {@code true} if this buffer is empty, {@code false}
* otherwise.
*/
public boolean isEmpty() {
return this.len == 0;
}
/**
* Returns {@code true} if this buffer is full, that is, its
* {@link #length()} is equal to its {@link #capacity()}.
* @return {@code true} if this buffer is full, {@code false}
* otherwise.
*/
public boolean isFull() {
return this.len == this.buffer.length;
}
/**
* Returns the index within this buffer of the first occurrence of the
* specified byte, starting the search at the specified
* {@code beginIndex} and finishing at {@code endIndex}.
* If no such byte occurs in this buffer within the specified bounds,
* {@code -1} is returned.
* <p>
* There is no restriction on the value of {@code beginIndex} and
* {@code endIndex}. If {@code beginIndex} is negative,
* it has the same effect as if it were zero. If {@code endIndex} is
* greater than {@link #length()}, it has the same effect as if it were
* {@link #length()}. If the {@code beginIndex} is greater than
* the {@code endIndex}, {@code -1} is returned.
*
* @param b the byte to search for.
* @param from the index to start the search from.
* @param to the index to finish the search at.
* @return the index of the first occurrence of the byte in the buffer
* within the given bounds, or {@code -1} if the byte does
* not occur.
*
* @since 4.1
*/
public int indexOf(final byte b, final int from, final int to) {
int beginIndex = from;
if (beginIndex < 0) {
beginIndex = 0;
}
int endIndex = to;
if (endIndex > this.len) {
endIndex = this.len;
}
if (beginIndex > endIndex) {
return -1;
}
for (int i = beginIndex; i < endIndex; i++) {
if (this.buffer[i] == b) {
return i;
}
}
return -1;
}
/**
* Returns the index within this buffer of the first occurrence of the
* specified byte, starting the search at {@code 0} and finishing
* at {@link #length()}. If no such byte occurs in this buffer within
* those bounds, {@code -1} is returned.
*
* @param b the byte to search for.
* @return the index of the first occurrence of the byte in the
* buffer, or {@code -1} if the byte does not occur.
*
* @since 4.1
*/
public int indexOf(final byte b) {
return indexOf(b, 0, this.len);
}
}