Handling HTTP Uploads

Ktor supports handling HTTP Uploads. As well as receiving any other kind of content.

You can check out the Youkube example for a full example of this in action.

Receiving files using multipart

  1. val multipart = call.receiveMultipart()
  2. multipart.forEachPart { part ->
  3.     when (part) {
  4.         is PartData.FormItem -> {
  5.             if (part.name == "title") {
  6.                 title = part.value
  7.             }
  8.         }
  9.         is PartData.FileItem -> {
  10.             val ext = File(part.originalFileName).extension
  11.             val file = File(uploadDir, "upload-${System.currentTimeMillis()}-${session.userId.hashCode()}-${title.hashCode()}.$ext")
  12.             part.streamProvider().use { input -> file.outputStream().buffered().use { output -> input.copyToSuspend(output) } }
  13.             videoFile = file
  14.         }
  15.     }
  17.     part.dispose()
  18. }
  21. suspend fun InputStream.copyToSuspend(
  22.     out: OutputStream,
  23.     bufferSize: Int = DEFAULT_BUFFER_SIZE,
  24.     yieldSize: Int = 4 * 1024 * 1024,
  25.     dispatcher: CoroutineDispatcher = Dispatchers.IO
  26. ): Long {
  27.     return withContext(dispatcher) {
  28.         val buffer = ByteArray(bufferSize)
  29.         var bytesCopied = 0L
  30.         var bytesAfterYield = 0L
  31.         while (true) {
  32.             val bytes = read(buffer).takeIf { it >= 0 } ?: break
  33.             out.write(buffer, 0, bytes)
  34.             if (bytesAfterYield >= yieldSize) {
  35.                 yield()
  36.                 bytesAfterYield %= yieldSize
  37.             }
  38.             bytesCopied += bytes
  39.             bytesAfterYield += bytes
  40.         }
  41.         return@withContext bytesCopied
  42.     }
  43. }