compression-stream.js

/* original */
// threshold
if (threshold && ctx.response.length < threshold) return

/* fork */
// threshold
if (threshold) {
  if (ctx.body instanceof Readable) {
    const st = /** @type {!stream.Readable} */ (ctx.body)
    let totalLength = 0
    let resolved = false
    let error
    const { newStream, callback } = await new Promise((re, j) => {
      const r = new Transform(/** @type {!stream.TransformOptions} */({
        transform(data, enc, cb) {
          this.push(data)
          if (resolved) {
            cb()
            return
          }
          totalLength += data.length
          if (totalLength > threshold) {
            resolved = true
            re({ newStream: this, callback: cb })
          } else cb()
        },
      }))
      r.once('finish', () => re({ newStream: r }))
      st.once('error', (err) => {
        error = err
        re({})
      })
      r.once('error', j)
      st.pipe(r)
      r.pause()
    })

    if (error) return // handled by Koa
    body = newStream
    body.resume()
    if (!callback) {
      ctx.body = body
      return
    }
    callback()
  } else if (ctx.response.length < threshold) return
}

/* common end of middleware */
ctx.set('Content-Encoding', encoding)
ctx.res.removeHeader('Content-Length')

const stream = ctx.body = encodingMethods[encoding](options)

if (body instanceof Stream) {
  body.pipe(stream)
} else {
  stream.end(body)
}