js实现bytebuffer

实现 ByteBuffer 的基本结构

在 JavaScript 中实现 ByteBuffer 需要处理二进制数据的存储和操作。可以使用 ArrayBuffer 和 DataView 作为基础。

class ByteBuffer {
  constructor(initialCapacity = 1024) {
    this.buffer = new ArrayBuffer(initialCapacity);
    this.view = new DataView(this.buffer);
    this.position = 0;
    this.capacity = initialCapacity;
  }
}

动态扩容机制

当写入数据超过当前容量时自动扩展缓冲区大小。

ensureCapacity(requiredCapacity) {
  if (requiredCapacity <= this.capacity) return;

  let newCapacity = this.capacity * 2;
  while (newCapacity < requiredCapacity) {
    newCapacity *= 2;
  }

  const newBuffer = new ArrayBuffer(newCapacity);
  new Uint8Array(newBuffer).set(new Uint8Array(this.buffer));
  this.buffer = newBuffer;
  this.view = new DataView(this.buffer);
  this.capacity = newCapacity;
}

基本写入方法

实现常见数据类型的写入操作。

putInt8(value) {
  this.ensureCapacity(this.position + 1);
  this.view.setInt8(this.position, value);
  this.position += 1;
}

putInt16(value) {
  this.ensureCapacity(this.position + 2);
  this.view.setInt16(this.position, value);
  this.position += 2;
}

putInt32(value) {
  this.ensureCapacity(this.position + 4);
  this.view.setInt32(this.position, value);
  this.position += 4;
}

putFloat32(value) {
  this.ensureCapacity(this.position + 4);
  this.view.setFloat32(this.position, value);
  this.position += 4;
}

putFloat64(value) {
  this.ensureCapacity(this.position + 8);
  this.view.setFloat64(this.position, value);
  this.position += 8;
}

基本读取方法

实现常见数据类型的读取操作。

getInt8() {
  const value = this.view.getInt8(this.position);
  this.position += 1;
  return value;
}

getInt16() {
  const value = this.view.getInt16(this.position);
  this.position += 2;
  return value;
}

getInt32() {
  const value = this.view.getInt32(this.position);
  this.position += 4;
  return value;
}

getFloat32() {
  const value = this.view.getFloat32(this.position);
  this.position += 4;
  return value;
}

getFloat64() {
  const value = this.view.getFloat64(this.position);
  this.position += 8;
  return value;
}

字节顺序控制

添加字节序（Endianness）支持。

setEndian(littleEndian) {
  this.littleEndian = littleEndian;
}

// 修改写入方法示例
putInt32(value) {
  this.ensureCapacity(this.position + 4);
  this.view.setInt32(this.position, value, this.littleEndian);
  this.position += 4;
}

实用工具方法

添加常用的辅助功能。

reset() {
  this.position = 0;
}

remaining() {
  return this.capacity - this.position;
}

flip() {
  const newBuffer = new ArrayBuffer(this.position);
  new Uint8Array(newBuffer).set(new Uint8Array(this.buffer, 0, this.position));
  this.buffer = newBuffer;
  this.view = new DataView(this.buffer);
  this.capacity = this.position;
  this.position = 0;
}

toArray() {
  return new Uint8Array(this.buffer, 0, this.position);
}

字符串处理方法

实现字符串的编码和解码。

putString(str, encoding = 'utf-8') {
  const encoder = new TextEncoder(encoding);
  const encoded = encoder.encode(str);
  this.putInt32(encoded.length);
  this.ensureCapacity(this.position + encoded.length);
  new Uint8Array(this.buffer).set(encoded, this.position);
  this.position += encoded.length;
}

getString(encoding = 'utf-8') {
  const length = this.getInt32();
  const bytes = new Uint8Array(this.buffer, this.position, length);
  this.position += length;
  const decoder = new TextDecoder(encoding);
  return decoder.decode(bytes);
}

使用示例

const buffer = new ByteBuffer();
buffer.putInt32(123456);
buffer.putFloat32(3.14159);
buffer.putString("Hello World");

buffer.reset();
console.log(buffer.getInt32());    // 123456
console.log(buffer.getFloat32());  // 3.14159
console.log(buffer.getString());   // "Hello World"

性能优化建议

对于高性能场景，可以考虑以下优化：

• 预分配更大的初始缓冲区减少扩容次数
• 使用类型化数组（TypedArray）直接操作而非 DataView
• 实现批量写入方法减少函数调用开销
• 添加缓冲区池重用已分配的 ArrayBuffer

// 批量写入示例
putInt32Array(values) {
  this.ensureCapacity(this.position + values.length * 4);
  const view = new Int32Array(this.buffer, this.position, values.length);
  view.set(values);
  this.position += values.length * 4;
}