Hi all! I have a theoretical question. I want to send files from multiplatform client to serverver. I saw an example.

val result = <http://client.post|client.post><HttpResponse>("<http://127.0.0.1:$port/handler>") {
                    body = MultiPartContent.build {
                        add("user", "myuser")
                        add("password", "password")
                        add("file", byteArrayOf(1, 2, 3, 4), filename = "binary.bin")
                    }
                }

But what will doing if file is big? ByteArraySize could not be more than free RAM. How to send file from IOS and Android to multiplatform without out of memory errors?

Here’s a working snippet from my codebase:

private suspend fun doUploadFile(data: ByteReadChannel, uploadUrl: String, contentType: ContentType): Unit =
    http.put(uploadUrl) {
        body = object : OutgoingContent.ReadChannelContent() {
            override val contentType = contentType
            override fun readFrom() = data
        }
    }

Wow! Great, thank you! I'm going to try now

On Android, with the

Uri

to a local file, the

data

parameter is

appCtx.contentResolver.openInputStream(uri)?.toByteReadChannel() ?: error(...)

My regards! Thank you so much

I was about to tell you that it’s the same on iOS but after checking it was a little complex:

private fun NSURL.toByteReadChannel(errorHandler: (Throwable) -> Unit): ByteReadChannel =
        writer(CoroutineExceptionHandler { _, e -> errorHandler(e) }, true) {
            memScoped {
                val bufferSize = 8192
                val buffer = allocArray<UByteVar>(bufferSize)
                val input = NSInputStream.inputStreamWithURL(this@toByteReadChannel)
                        ?: throw Error("Failed to create NSInputStream from url ${this@toByteReadChannel}")
                var result: Int
                try {
                    input.open()
                    do {
                        @Suppress("EXPERIMENTAL_API_USAGE")
                        result = input.read(buffer, bufferSize.toULong()).toInt()
                        if (result > 0) {
                            channel.writeFully(buffer.readBytes(bufferSize))
                        }
                        if (result < 0) {
                            throw Error("Failed to read inputStream: ${input.streamError?.debugDescription}")
                        }
                    } while (result > 0)
                } finally {
                    channel.close()
                    input.close()
                }
            }
        }.channel

You just saved my day. Now I feel like a lazy ass because I haven’t tried it myself