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io.scala
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io.scala
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/*
* Copyright (c) 2013 Functional Streams for Scala
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package fs2
import cats._
import cats.effect.kernel.{Async, Outcome, Resource, Sync}
import cats.effect.kernel.implicits._
import cats.effect.kernel.Deferred
import cats.syntax.all._
import java.io.{InputStream, OutputStream, PipedInputStream, PipedOutputStream}
import java.nio.charset.Charset
/** Provides various ways to work with streams that perform IO.
*/
package object io {
private val utf8Charset = Charset.forName("UTF-8")
/** Reads all bytes from the specified `InputStream` with a buffer size of `chunkSize`.
* Set `closeAfterUse` to false if the `InputStream` should not be closed after use.
*/
def readInputStream[F[_]](
fis: F[InputStream],
chunkSize: Int,
closeAfterUse: Boolean = true
)(implicit F: Sync[F]): Stream[F, Byte] =
readInputStreamGeneric(
fis,
F.delay(new Array[Byte](chunkSize)),
closeAfterUse
)
/** Reads all bytes from the specified `InputStream` with a buffer size of `chunkSize`.
* Set `closeAfterUse` to false if the `InputStream` should not be closed after use.
*
* Recycles an underlying input buffer for performance. It is safe to call
* this as long as whatever consumes this `Stream` does not store the `Chunk`
* returned or pipe it to a combinator that does (e.g. `buffer`). Use
* `readInputStream` for a safe version.
*/
def unsafeReadInputStream[F[_]](
fis: F[InputStream],
chunkSize: Int,
closeAfterUse: Boolean = true
)(implicit F: Sync[F]): Stream[F, Byte] =
readInputStreamGeneric(
fis,
F.pure(new Array[Byte](chunkSize)),
closeAfterUse
)
private def readBytesFromInputStream[F[_]](is: InputStream, buf: Array[Byte])(implicit
F: Sync[F]
): F[Option[Chunk[Byte]]] =
F.blocking(is.read(buf)).map { numBytes =>
if (numBytes < 0) None
else if (numBytes == 0) Some(Chunk.empty)
else if (numBytes < buf.size) Some(Chunk.array(buf.slice(0, numBytes)))
else Some(Chunk.array(buf))
}
private def readInputStreamGeneric[F[_]](
fis: F[InputStream],
buf: F[Array[Byte]],
closeAfterUse: Boolean
)(implicit F: Sync[F]): Stream[F, Byte] = {
def useIs(is: InputStream) =
Stream
.eval(buf.flatMap(b => readBytesFromInputStream(is, b)))
.repeat
.unNoneTerminate
.flatMap(c => Stream.chunk(c))
if (closeAfterUse)
Stream.bracket(fis)(is => Sync[F].blocking(is.close())).flatMap(useIs)
else
Stream.eval(fis).flatMap(useIs)
}
/** Writes all bytes to the specified `OutputStream`. Set `closeAfterUse` to false if
* the `OutputStream` should not be closed after use.
*
* Each write operation is performed on the supplied execution context. Writes are
* blocking so the execution context should be configured appropriately.
*/
def writeOutputStream[F[_]](
fos: F[OutputStream],
closeAfterUse: Boolean = true
)(implicit F: Sync[F]): Pipe[F, Byte, INothing] =
s => {
def useOs(os: OutputStream): Stream[F, INothing] =
s.chunks.foreach(c => F.blocking(os.write(c.toArray)))
val os =
if (closeAfterUse) Stream.bracket(fos)(os => F.blocking(os.close()))
else Stream.eval(fos)
os.flatMap(os => useOs(os) ++ Stream.exec(F.blocking(os.flush())))
}
/** Take a function that emits to an [[java.io.OutputStream OutputStream]] effectfully,
* and return a stream which, when run, will perform that function and emit
* the bytes recorded in the OutputStream as an fs2.Stream
*
* The stream produced by this will terminate if:
* - `f` returns
* - `f` calls `OutputStream#close`
*
* If none of those happens, the stream will run forever.
*/
def readOutputStream[F[_]: Async](
chunkSize: Int
)(
f: OutputStream => F[Unit]
): Stream[F, Byte] = {
val mkOutput: Resource[F, (OutputStream, InputStream)] =
Resource.make(Sync[F].delay {
val os = new PipedOutputStream()
val is = new PipedInputStream(os)
(os: OutputStream, is: InputStream)
})(ois =>
Sync[F].blocking {
// Piped(I/O)Stream implementations cant't throw on close, no need to nest the handling here.
ois._2.close()
ois._1.close()
}
)
Stream.resource(mkOutput).flatMap { case (os, is) =>
Stream.eval(Deferred[F, Option[Throwable]]).flatMap { err =>
// We need to close the output stream regardless of how `f` finishes
// to ensure an outstanding blocking read on the input stream completes.
// In such a case, there's a race between completion of the read
// stream and finalization of the write stream, so we capture the error
// that occurs when writing and rethrow it.
val write = f(os).guaranteeCase((outcome: Outcome[F, Throwable, Unit]) =>
Sync[F].blocking(os.close()) *> err
.complete(outcome match {
case Outcome.Errored(t) => Some(t)
case _ => None
})
.void
)
val read = readInputStream(is.pure[F], chunkSize, closeAfterUse = false)
read.concurrently(Stream.eval(write)) ++ Stream.eval(err.get).flatMap {
case None => Stream.empty
case Some(t) => Stream.raiseError[F](t)
}
}
}
}
//
// STDIN/STDOUT Helpers
/** Stream of bytes read asynchronously from standard input. */
def stdin[F[_]: Sync](bufSize: Int): Stream[F, Byte] =
readInputStream(Sync[F].blocking(System.in), bufSize, false)
/** Pipe of bytes that writes emitted values to standard output asynchronously. */
def stdout[F[_]: Sync]: Pipe[F, Byte, INothing] =
writeOutputStream(Sync[F].blocking(System.out), false)
/** Writes this stream to standard output asynchronously, converting each element to
* a sequence of bytes via `Show` and the given `Charset`.
*
* Each write operation is performed on the supplied execution context. Writes are
* blocking so the execution context should be configured appropriately.
*/
def stdoutLines[F[_]: Sync, O: Show](
charset: Charset = utf8Charset
): Pipe[F, O, INothing] =
_.map(_.show).through(text.encode(charset)).through(stdout)
/** Stream of `String` read asynchronously from standard input decoded in UTF-8. */
def stdinUtf8[F[_]: Sync](bufSize: Int): Stream[F, String] =
stdin(bufSize).through(text.utf8Decode)
/** Pipe that converts a stream of bytes to a stream that will emit a single `java.io.InputStream`,
* that is closed whenever the resulting stream terminates.
*
* If the `close` of resulting input stream is invoked manually, then this will await until the
* original stream completely terminates.
*
* Because all `InputStream` methods block (including `close`), the resulting `InputStream`
* should be consumed on a different thread pool than the one that is backing the effect.
*
* Note that the implementation is not thread safe -- only one thread is allowed at any time
* to operate on the resulting `java.io.InputStream`.
*/
def toInputStream[F[_]: Async]: Pipe[F, Byte, InputStream] =
source => Stream.resource(toInputStreamResource(source))
/** Like [[toInputStream]] but returns a `Resource` rather than a single element stream.
*/
def toInputStreamResource[F[_]: Async](
source: Stream[F, Byte]
): Resource[F, InputStream] =
JavaInputOutputStream.toInputStream(source)
}