Add some useful extensions

[e5l]

Let's consider to add some useful extensions:

• fun String.toByteReadChannel(charset)
• interface Closeable
• ObjectPool<T>.use(block):R
• readUntil for primitive types and ByteArray
• readLine with CharsetDecoder
• readLine until delimiter
• Input.skip(count) (Input.discard)
• ByteReadChannel.skip(count)
• ByteReadPacket(ByteArray)
• Input.lines(): Sequence | List
• revert ByteReadChannel.totalBytesRead
• Input.copyTo(Output) + joinTo
• ByteWriteChannel.writeFully(Input)

Jvm integration

• Input.asStream(): InputStream
• InputStream.asInput(): Input

Charset shortcuts:

• ISO_8859_1

Input/Output

• BE and LE API for reading and writing(including primitive types)

[soywiz]

Wishlist from my side (maybe all, or some of them are already included):

ByteArray -> ByteReadChannel (with optional range)
String -> ByteReadChannel providing a Charset
ByteReadChannel -> read to ByteArray (the last time I tried I think it required to read a packet first) maybe an argument to specify max length to limit memory usage throwing an exception if it is bigger
ByteReadChannel -> read to String providing a Charset
ByteArray.toString(charset)
String.toByteArray(charset)

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java.nio.channels.AsynchronousByteChannel bidirectional conversion with ReadByteChannel and WriteByteChannel

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Would be nice to provide them as extension functions to allow easily writing and discovery.

[sandwwraith]

ByteReadChannel.readText(charset: Charset = Charsets.UTF_8): String

[clarfonthey]

AsynchronousFileChannel -> ReadByteChannel and WriteByteChannel would also be nice

[ksimons]

Not sure if this is the right issue to request this, but would it make sense to move the goodies from https://github.com/ktorio/ktor/blob/7da470df9c5f067605503badf1a0d31ab9272c56/ktor-utils/ktor-utils-jvm/src/io/ktor/util/cio/FileChannels.kt into kotlinx-io?

[fzhinkin]

We're rebooting the kotlinx-io development (see #131), all issues related to the previous versions will be closed. Consider reopening it if the issue remains (or the feature is still missing) in a new version.