Hello! Can `RawSource.readAtMostTo(sink, byteCount...

# io

[Zhang Zihan]

Hello! Can RawSource.readAtMostTo(sink, byteCount) read at most 8192 bytes at a time? How to read more at once?

[Zhang Zihan]

I created a function to do this. Is there a simpler way?

fun RawSource.readRecursivelyAtMostTo(sink: Buffer, byteCount: Long): Long {
    var read = 0L
    while (read != byteCount) {
        val count = readAtMostTo(sink, byteCount)
        read += count
        if (count == -1L) {
            if (read == 0L)
                return -1L
            break
        }
    }
    return read
}

[Filipp Zhinkin]

Hi! If you need to work with RawSource , there's no way to do that out of the box.
I don't think a simpler way exists (however, read should only be incremented only after checking count value, otherwise for a source containing only a single byte, the implementation may return -1).

Could you please elaborate on your particular use case?
In scenarios where I personally stumbled the lack of a more exhaustive reading routine, it was usually fine to wrap a RawSource into a Source by calling buffered(), then fill the buffer using require(byteCount) and then processing data out of `Source`'s buffer.

[Zhang Zihan]

@Filipp Zhinkin Use case:

val path = Path("D:\\Pictures\\Pixiv\\73597952_p0.jpg")
val source = SystemFileSystem.source(path).buffered()
val buffer = Buffer()

val count = source.readAtMostTo(buffer, 16384)
println(count)
val count2 = source.readAtMostTo(buffer, 16384)
println(count2)

// 8192
// 8192

I expected to get 16384 bytes in one go, but it only returns 8192 every time.
This is different from FileInputStream.readNBytes(len) and confuses me.
Based on your reply, I discovered the require() and request() functions, which can solve this problem, thank you!

[Filipp Zhinkin]

Thank you for details!

This is different from FileInputStream.readNBytes(len) and confuses me.

Perhaps, kotlinx-io should provide similar extension for reading into a buffer, especially given the readByteArray overload with exactly N bytes semantics is already there.