smartarchive/ts/classes.gziptools.ts

import type { SmartArchive } from './classes.smartarchive.js';
import * as plugins from './plugins.js';

// This class wraps fflate's gunzip in a Node.js Transform stream
export class CompressGunzipTransform extends plugins.stream.Transform {
  constructor() {
    super();
  }

  _transform(
    chunk: Buffer,
    encoding: BufferEncoding,
    callback: plugins.stream.TransformCallback,
  ) {
    plugins.fflate.gunzip(chunk, (err, decompressed) => {
      if (err) {
        callback(err);
      } else {
        this.push(decompressed);
        callback();
      }
    });
  }
}

// DecompressGunzipTransform class that extends the Node.js Transform stream to
// create a stream that decompresses GZip-compressed data using fflate's gunzip function
export class DecompressGunzipTransform extends plugins.stream.Transform {
  private gunzip: any; // fflate.Gunzip instance
  
  constructor() {
    super();
    
    // Create a streaming Gunzip decompressor
    this.gunzip = new plugins.fflate.Gunzip((chunk, final) => {
      // Push decompressed chunks to the output stream
      this.push(Buffer.from(chunk));
      if (final) {
        // Signal end of stream when decompression is complete
        this.push(null);
      }
    });
  }

  _transform(
    chunk: Buffer,
    encoding: BufferEncoding,
    callback: plugins.stream.TransformCallback,
  ) {
    try {
      // Feed chunks to the gunzip stream
      this.gunzip.push(chunk, false);
      callback();
    } catch (err) {
      callback(err as Error);
    }
  }
  
  _flush(callback: plugins.stream.TransformCallback) {
    try {
      // Signal end of input to gunzip
      this.gunzip.push(new Uint8Array(0), true);
      callback();
    } catch (err) {
      callback(err as Error);
    }
  }
}

export class GzipTools {
  constructor() {}

  public getCompressionStream() {
    return new CompressGunzipTransform();
  }

  public getDecompressionStream() {
    return new DecompressGunzipTransform();
  }
}