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Dahua ICC Open API SDK for Java
package com.dahuatech.hutool.core.io;
/**
* 代码移植自blade
* 快速缓冲，将数据存放在缓冲集中，取代以往的单一数组
*
* @author biezhi, looly
* @since 1.0
*/
public class FastByteBuffer {
/** 一个缓冲区的最小字节数 */
private final int minChunkLen;
/** 缓冲集 */
private byte[][] buffers = new byte[16][];
/** 缓冲数 */
private int buffersCount;
/** 当前缓冲索引 */
private int currentBufferIndex = -1;
/** 当前缓冲 */
private byte[] currentBuffer;
/** 当前缓冲偏移量 */
private int offset;
/** 缓冲字节数 */
private int size;
public FastByteBuffer() {
this.minChunkLen = 1024;
}
public FastByteBuffer(int size) {
this.minChunkLen = Math.abs(size);
}
/**
* 分配下一个缓冲区，不会小于1024
*
* @param newSize 理想缓冲区字节数
*/
private void needNewBuffer(int newSize) {
int delta = newSize - size;
int newBufferSize = Math.max(minChunkLen, delta);
currentBufferIndex++;
currentBuffer = new byte[newBufferSize];
offset = 0;
// add buffer
if (currentBufferIndex >= buffers.length) {
int newLen = buffers.length << 1;
byte[][] newBuffers = new byte[newLen][];
System.arraycopy(buffers, 0, newBuffers, 0, buffers.length);
buffers = newBuffers;
}
buffers[currentBufferIndex] = currentBuffer;
buffersCount++;
}
/**
* 向快速缓冲加入数据
*
* @param array 数据
* @param off 偏移量
* @param len 字节数
* @return 快速缓冲自身 @see FastByteBuffer
*/
public FastByteBuffer append(byte[] array, int off, int len) {
int end = off + len;
if ((off < 0) || (len < 0) || (end > array.length)) {
throw new IndexOutOfBoundsException();
}
if (len == 0) {
return this;
}
int newSize = size + len;
int remaining = len;
if (currentBuffer != null) {
// first try to fill current buffer
int part = Math.min(remaining, currentBuffer.length - offset);
System.arraycopy(array, end - remaining, currentBuffer, offset, part);
remaining -= part;
offset += part;
size += part;
}
if (remaining > 0) {
// still some data left
// ask for new buffer
needNewBuffer(newSize);
// then copy remaining
// but this time we are sure that it will fit
int part = Math.min(remaining, currentBuffer.length - offset);
System.arraycopy(array, end - remaining, currentBuffer, offset, part);
offset += part;
size += part;
}
return this;
}
/**
* 向快速缓冲加入数据
*
* @param array 数据
* @return 快速缓冲自身 @see FastByteBuffer
*/
public FastByteBuffer append(byte[] array) {
return append(array, 0, array.length);
}
/**
* 向快速缓冲加入一个字节
*
* @param element 一个字节的数据
* @return 快速缓冲自身 @see FastByteBuffer
*/
public FastByteBuffer append(byte element) {
if ((currentBuffer == null) || (offset == currentBuffer.length)) {
needNewBuffer(size + 1);
}
currentBuffer[offset] = element;
offset++;
size++;
return this;
}
/**
* 将另一个快速缓冲加入到自身
*
* @param buff 快速缓冲
* @return 快速缓冲自身 @see FastByteBuffer
*/
public FastByteBuffer append(FastByteBuffer buff) {
if (buff.size == 0) {
return this;
}
for (int i = 0; i < buff.currentBufferIndex; i++) {
append(buff.buffers[i]);
}
append(buff.currentBuffer, 0, buff.offset);
return this;
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
/**
* 当前缓冲位于缓冲区的索引位
*
* @return {@link #currentBufferIndex}
*/
public int index() {
return currentBufferIndex;
}
public int offset() {
return offset;
}
/**
* 根据索引位返回缓冲集中的缓冲
*
* @param index 索引位
* @return 缓冲
*/
public byte[] array(int index) {
return buffers[index];
}
public void reset() {
size = 0;
offset = 0;
currentBufferIndex = -1;
currentBuffer = null;
buffersCount = 0;
}
/**
* 返回快速缓冲中的数据
*
* @return 快速缓冲中的数据
*/
public byte[] toArray() {
int pos = 0;
byte[] array = new byte[size];
if (currentBufferIndex == -1) {
return array;
}
for (int i = 0; i < currentBufferIndex; i++) {
int len = buffers[i].length;
System.arraycopy(buffers[i], 0, array, pos, len);
pos += len;
}
System.arraycopy(buffers[currentBufferIndex], 0, array, pos, offset);
return array;
}
/**
* 返回快速缓冲中的数据
*
* @param start 逻辑起始位置
* @param len 逻辑字节长
* @return 快速缓冲中的数据
*/
public byte[] toArray(int start, int len) {
int remaining = len;
int pos = 0;
byte[] array = new byte[len];
if (len == 0) {
return array;
}
int i = 0;
while (start >= buffers[i].length) {
start -= buffers[i].length;
i++;
}
while (i < buffersCount) {
byte[] buf = buffers[i];
int c = Math.min(buf.length - start, remaining);
System.arraycopy(buf, start, array, pos, c);
pos += c;
remaining -= c;
if (remaining == 0) {
break;
}
start = 0;
i++;
}
return array;
}
/**
* 根据索引位返回一个字节
*
* @param index 索引位
* @return 一个字节
*/
public byte get(int index) {
if ((index >= size) || (index < 0)) {
throw new IndexOutOfBoundsException();
}
int ndx = 0;
while (true) {
byte[] b = buffers[ndx];
if (index < b.length) {
return b[index];
}
ndx++;
index -= b.length;
}
}
}