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读写操作。可以通过 ArrayBuffer 和 DataView 来实现。

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，自动扩容以避免数据丢失。

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

  let newCapacity = Math.max(this.capacity * 2, requiredCapacity);
  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;
}

写入基本数据类型

实现各种基本数据类型的写入方法，包括整数、浮点数等。

writeInt8(value) {
  this.ensureCapacity(this.position + 1);
  this.view.setInt8(this.position, value);
  this.position += 1;
}

writeInt32(value) {
  this.ensureCapacity(this.position + 4);
  this.view.setInt32(this.position, value);
  this.position += 4;
}

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

读取基本数据类型

实现从缓冲区读取各种基本数据类型的方法。

readInt8() {
  const value = this.view.getInt8(this.position);
  this.position += 1;
  return value;
}

readInt32() {
  const value = this.view.getInt32(this.position);
  this.position += 4;
  return value;
}

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

字节序控制

添加对字节序的支持，允许指定大端或小端模式。

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

writeInt32(value) {
  this.ensureCapacity(this.position + 4);
  this.view.setInt32(this.position, value, this.littleEndian);
  this.position += 4;
}

缓冲区操作

添加对缓冲区整体操作的支持，如切片、合并等。

slice(start, end) {
  return new Uint8Array(this.buffer).slice(start, end);
}

concat(otherBuffer) {
  const newBuffer = new Uint8Array(this.position + otherBuffer.position);
  newBuffer.set(new Uint8Array(this.buffer), 0);
  newBuffer.set(new Uint8Array(otherBuffer.buffer), this.position);

  const result = new ByteBuffer();
  result.buffer = newBuffer.buffer;
  result.position = newBuffer.length;
  return result;
}

实用工具方法

添加一些实用方法，如重置位置、获取剩余空间等。

reset() {
  this.position = 0;
}

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

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

使用示例

const buffer = new ByteBuffer();
buffer.writeInt32(123456);
buffer.writeFloat(3.14159);
buffer.reset();
console.log(buffer.readInt32());  // 123456
console.log(buffer.readFloat());  // 3.14159

这种方法提供了基本的 ByteBuffer 功能，可以根据需要进一步扩展，如添加对字符串的支持、更复杂的数据结构等。