I dont know if this is a bug or if Im using it inc...

# ktor

[Robin T]

I dont know if this is a bug or if Im using it incorrectly.
I try to read from multipart form file items like this:

when (val fileItem = call.receiveMultipart().readAllParts().single()) {
                is PartData.FileItem -> {
                    fileItem.provider().use {
                        it.readByte()
                    }
                }
                else -> error("")
            }

But it.readByte() is returning -1.
Also, it.canRead() is returning false.

However, if I first call it.tryPeek() then I am able to call readBytes. and it.canRead() is returning true again.
Does this have something to do with the chunkbuffer-pool not being setup for read yet?

[Aleksei Tirman [JB]]

is there only one part?

[Robin T]

Yes, for now there is only one part

[Robin T]

It does work to call fileItem.streamProvider().readAllBytes() but this is not what I want to do.. I need to cancel the stream after X bytes

[Aleksei Tirman [JB]]

Unfortunately, I cannot reproduce the problem using your code and by sending a single file part.

[Robin T]

Hmm, strange..
Does this look horrible?

client.submitFormWithBinaryData(
                    "/mellomlagring/fil",
                    formData {
                        append("document", Resource.read("/resources/images/bilde.jpg"),
                            Headers.build {
                                append(HttpHeaders.ContentDisposition, "filename=bilde.jpg")
                                append(HttpHeaders.ContentType, "image/jpeg")
                            })
                    },
                )

[Aleksei Tirman [JB]]

Are you able to reproduce the problem using Postman, curl or Insomnia?

[Robin T]

Yes.

fun main() {
    embeddedServer(Netty, port = 8080, module = {
        install(ContentNegotiation) { jackson {} }

        routing {
            post("/byte") {
                when (val fileItem = call.receiveMultipart().readAllParts().single()) {
                    is PartData.FileItem -> {
                        fileItem.provider().use {
                            // it.tryPeek() // uncomment to read byte
                            when (it.canRead()) {
                                true -> call.respond(it.readByte())
                                false -> call.respond(HttpStatusCode.UnprocessableEntity, "cant read stream")
                            }
                        }
                    }

                    else -> call.respond(HttpStatusCode.BadRequest, "File not found")
                }
            }
        }
    }).start(wait = true)
}

Intellij HTTP client:

POST  <http://0.0.0.0:8080/byte>
Content-Type: multipart/form-data; boundary=boundary

--boundary
Content-Disposition: form-data; name="document"; filename="bilde.jpg"

< ./bilde.jpg

Setup:
JDK 21
ktor 2.3.9
Kotlin 1.9.23

dependencies {
    implementation("io.ktor:ktor-server-core:$ktorVersion")
    implementation("io.ktor:ktor-server-netty:$ktorVersion")
    implementation("io.ktor:ktor-server-content-negotiation:$ktorVersion")
    implementation("io.ktor:ktor-serialization-jackson:$ktorVersion")
}

[Robin T]

Hmm. After debug some more, it looks lik .jpg starts with -1

Example:

object Resource {
    fun read(path: String): ByteArray = requireNotNull(this::class.java.getResource(path)).readBytes()
}

Resource.read("/resources/images/Cat03.jpg") # first byte is -1

Ref:

https://en.m.wikipedia.org/wiki/File:Cat03.jpg▾

[Robin T]

Nvm, canRead is still false with a .png that does not start with -1