react-native-esc-pos-printer/src/printer/utils/BufferHelper.ts

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import { Buffer } from 'buffer';

export class BufferHelper {
  buffers: Buffer[];
  size: number;

  constructor() {
    this.buffers = [];
    this.size = 0;
  }

  get length() {
    return this.size;
  }

  concat(buffer: Buffer): BufferHelper {
    this.buffers.push(buffer);
    this.size += buffer.length;
    return this;
  }

  empty(): BufferHelper {
    this.buffers = [];
    this.size = 0;
    return this;
  }

  toBuffer(): Buffer {
    // @ts-ignore
    return Buffer.concat(this.buffers, this.size);
  }

  toString(encoding: BufferEncoding): string {
    return this.toBuffer().toString(encoding);
  }

  load(stream: any, callback: any) {
    stream.on('data', (trunk: Buffer) => {
      this.concat(trunk);
    });
    stream.on('end', () => {
      callback(null, this.toBuffer());
    });
    stream.once('error', callback);
  }

  bytesToString(data: Uint8Array, type: 'base64' | 'hex') {
    this.concat(Buffer.from(data));
    const buffer = this.toBuffer();
    return buffer.toString(type);
  }
}