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# coroutines
j
u
hmm why does that work? does okhttp check for java thread interrupts implicitly?
j
yes
u
does that in any chance add some overhead versus 
while (bytes >= 0 && coroutineContext.isActive) {
? (I’m measuring download speed)
j
Seems unlikely. If you're going for speed you shouldn't be using 
byteStream()
but should instead be using Okio for the whole way to the file.
u
how would that help? I only read a 8K buffer each time and throw it away
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val start = System.currentTimeMillis()
body.use { it.byteStream().use { iss -> iss.justIterateUntilEnd() } }
val end = System.currentTimeMillis()
would okio’s stream implementation be faster?
j
Well, maybe. You're not really doing anything with the bytes there. So calling 
it.skip(Long.MAX_VALUE)
would be even faster, but then you're measuring even less.
Are you trying to measure the speed of the network?
Or the speed of copying bytes?
u
speed of the network via downloading some bigger static file
I figured stream reading would be negligible but yes less overhead is preferable
let me revise that, I do count the bytes read to calculate the speed
j
What you have is probably fine, then. It would be slightly faster to operate on the 
BufferedSource
and call 
skip()
since it avoids copying the bytes one extra time.
u
so this is what I have
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val totalBytesRead = runInterruptible {
    body.source().use {
        val buffer = ByteArray(DEFAULT_BUFFER_SIZE)
        var bytesRead = 0L
        while (!it.exhausted()) {
            bytesRead += it.read(buffer)
        }
        bytesRead
    }
}
how would I factor the 
skip
into it?
.skip(buffer.size)
?
j
skip BUFFER_LENGTH at a time, delete all the byte array stuff
u
right but what about the last “buffer”, skip doesnt return anything
j
do you have a content length?
u
most likely no
j
otherwise you'd need to do request+skip
u
I still don’t get how will I get the total bytes?
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var bytesRead = 0
while (!it.request(bufferSize)) {
    it.skip(bufferSize)
    bytesRead += bufferSize
}
I mean the last buffer length
j
if 
request
returns false the count of bytes is available at 
it.buffer.size()
which ideally you should still skip so that the internal segment becomes empty and is returned to the pool
u
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body.source().use {
    var bytesRead = 0L
    while (true) {
        if (!it.request(BUFFER_SIZE)) {
            val lastBufferSize = it.buffer.size
            bytesRead += lastBufferSize
            it.skip(lastBufferSize)
            break
        }
        it.skip(BUFFER_SIZE)
        bytesRead += BUFFER_SIZE
    }
    bytesRead
}
like this?
j
do you only want the total byte count?
or are you reporting timings after each buffer read?
u
just the total download size, to figure out speed
j
i see. sorry we never really talked about exactly what you were doing. you can do that with a oneliner like:
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val bytesRead = it.source().use { it.readAll(blackholeSink()) }
u
oh, my bad, sweet!
and this is all more efficient, because okhttp is okio buffers underneath anyways, and using 
byteStream()
makes it transform back to inputstreams + byteArray allocations?
j
that's right. we're avoiding intermediate copies between byte arrays.
u
got it, thank you so much!
btw if I use the 
runInterruptible
and cancel the job then I get 
java.io.InterruptedIOException: interrupted
which is then reported as a regular error, should I just filter it away? It seems that I cannot treat it as 
CancellationException
and rethrow it
j
Hmm I would have thought that 
runCatching
would handle that, but looks like it only handles 
InterruptedException
.
u
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private fun <T> runInterruptibleInExpectedContext(coroutineContext: CoroutineContext, block: () -> T): T {
    try {
        val threadState = ThreadState(coroutineContext.job)
        threadState.setup()
        try {
            return block()
        } finally {
            threadState.clearInterrupt()
        }
    } catch (e: InterruptedException) {
        throw CancellationException("Blocking call was interrupted due to parent cancellation").initCause(e)
    }
}
yes exactly, not the IO one
j
Probably worth a bug to discuss on the coroutines repo.
u
but in meantime I should be able to just
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try {
    runInterruptible { ... }
} catch (ex: InterruptedIOException) {
    throw CancellationException().initCause(ex)
}
right?
j
yes
u
btw it does behave a bit oddly, if I wrap it with 
withTimeoutOrNull
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private suspend fun readTotalBytes(body: ResponseBody): Long {
    return body.use { b ->
        withTimeoutOrNull(timeMillis = 1000) {
            runIoInterruptible {
                simulateWork(5000)
                44
            }
        } ?: -1L
    }
}

fun simulateWork(delayMillis: Long) {
    val start = System.currentTimeMillis()
    @Suppress("ControlFlowWithEmptyBody")
    while (true) {
        if (System.currentTimeMillis() - start >= delayMillis) {
            break
        }
        if (Thread.interrupted()) {
            LOG.d("INTERRUPTED")
            break
        }
    }
}
this works as expected, timout kicks in, and 
-1L
is returned
if I use what we said to use
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private suspend fun readTotalBytes(body: ResponseBody): Long {
    return body.use { b ->
        withTimeoutOrNull(timeMillis = 1000) {
            runIoInterruptible {
                b.source().use {
                    it.readAll(blackholeSink())
                }
            }
        } ?: -1L
    }
}

suspend fun <T> runIoInterruptible(block: () -> T): T {
    return try {
        runInterruptible(block = block)
    } catch (ex: InterruptedIOException) {
        throw CancellationException().initCause(ex)
    }
}
then, I see the InterruptedIO get caught, and cancellation thrown, however, it messes up the 
withTimeoutOrNull
, it never returns, as if it threw
and I’m not sure why it doesn’t work, when 
runInterriptible
uses the same mechanism of throwing CancellationException
only this seems to work as expected
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runInterruptible {
    try {
        b.source().use {
            it.readAll(blackholeSink())
        }
    } catch (ex: InterruptedIOException) { <-----------------
        throw InterruptedException().initCause(ex)
    }
}
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