KTOR-7518 Add ReadableByteChannel to ByteReadChannel interop util (#4358

)

ktor-io/api/ktor-io.api

@@ -466,6 +466,12 @@ public final class io/ktor/utils/io/jvm/javaio/WritingKt {
 	public static synthetic fun copyTo$default (Lio/ktor/utils/io/ByteReadChannel;Ljava/io/OutputStream;JLkotlin/coroutines/Continuation;ILjava/lang/Object;)Ljava/lang/Object;
 }
 
+public final class io/ktor/utils/io/jvm/nio/ReadingKt {
+	public static final fun asSource (Ljava/nio/channels/ReadableByteChannel;)Lkotlinx/io/RawSource;
+	public static final fun toByteReadChannel (Ljava/nio/channels/ReadableByteChannel;Lkotlin/coroutines/CoroutineContext;)Lio/ktor/utils/io/ByteReadChannel;
+	public static synthetic fun toByteReadChannel$default (Ljava/nio/channels/ReadableByteChannel;Lkotlin/coroutines/CoroutineContext;ILjava/lang/Object;)Lio/ktor/utils/io/ByteReadChannel;
+}
+
 public final class io/ktor/utils/io/jvm/nio/WriteSuspendSession {
 	public fun <init> (Lio/ktor/utils/io/ByteWriteChannel;)V
 	public final fun getChannel ()Lio/ktor/utils/io/ByteWriteChannel;

ktor-io/jvm/src/io/ktor/utils/io/jvm/javaio/Reading.kt

@@ -10,6 +10,7 @@ import kotlinx.io.EOFException
 import kotlinx.io.IOException
 import java.io.*
 import java.nio.*
+import java.nio.channels.*
 import kotlin.coroutines.*
 
 /**

ktor-io/jvm/src/io/ktor/utils/io/jvm/nio/Reading.kt

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.utils.io.jvm.nio
+
+import io.ktor.utils.io.*
+import io.ktor.utils.io.jvm.javaio.*
+import kotlinx.coroutines.*
+import kotlinx.io.*
+import kotlinx.io.Buffer
+import kotlinx.io.unsafe.*
+import java.nio.*
+import java.nio.channels.*
+import kotlin.coroutines.*
+
+/**
+ * Converts a [ReadableByteChannel] to a [ByteReadChannel], enabling asynchronous reading of bytes.
+ *
+ * @param context the [CoroutineContext] to execute the read operation. Defaults to [Dispatchers.IO].
+ * @return a [ByteReadChannel] for reading bytes asynchronously from the given [ReadableByteChannel].
+ */
+public fun ReadableByteChannel.toByteReadChannel(
+    context: CoroutineContext = Dispatchers.IO,
+): ByteReadChannel = RawSourceChannel(asSource(), context)
+
+/**
+ * Converts a [ReadableByteChannel] into a [RawSource].
+ *
+ * This extension function wraps the given [ReadableByteChannel] into a [RawSource],
+ * enabling efficient reading of bytes from the channel as a source of data.
+ *
+ * @return a [RawSource] representation of the [ReadableByteChannel].
+ */
+public fun ReadableByteChannel.asSource(): RawSource =
+    ReadableByteChannelSource(this)
+
+/**
+ * A data source that reads from a [ReadableByteChannel].
+ *
+ * This class implements the [RawSource] interface, allowing for the reading
+ * of bytes from a [ReadableByteChannel] into a [Buffer].
+ *
+ * @property channel The [ReadableByteChannel] from which bytes are read.
+ */
+private open class ReadableByteChannelSource(
+    private val channel: ReadableByteChannel,
+) : RawSource {
+    @OptIn(UnsafeIoApi::class)
+    override fun readAtMostTo(sink: Buffer, byteCount: Long): Long {
+        if (byteCount <= 0L) return 0L
+
+        var readTotal: Int
+        val actualByteCount = minOf(byteCount, Int.MAX_VALUE.toLong()).toInt()
+
+        UnsafeBufferOperations.writeToTail(sink, 1) { data, pos, limit ->
+            val maxToCopy = minOf(actualByteCount, limit - pos)
+            val buffer = ByteBuffer.wrap(data, pos, maxToCopy)
+            readTotal = channel.read(buffer)
+            maxOf(readTotal, 0)
+        }
+
+        return readTotal.toLong()
+    }
+
+    override fun close() =
+        channel.close()
+
+    override fun toString(): String =
+        "ReadableByteChannelSource($channel)"
+}

ktor-io/jvm/test/io/ktor/utils/io/jvm/nio/ReadingTest.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.utils.io.jvm.nio
+
+import io.ktor.utils.io.*
+import kotlinx.coroutines.test.*
+import java.io.*
+import java.nio.channels.*
+import java.nio.file.*
+import kotlin.io.path.*
+import kotlin.test.*
+
+class ReadingTest {
+
+    @Test
+    fun readsFromByteChannel() = runTest {
+        val expected = "This is a test string"
+        val channel = Channels.newChannel(ByteArrayInputStream(expected.encodeToByteArray()))
+        val actual = channel.toByteReadChannel().readRemaining().readText()
+        assertEquals(expected, actual)
+    }
+
+    @Test
+    fun readsFromFileChannelAndCloses() = runTest {
+        val expected = "This is a test string"
+        val temp = Files.createTempFile("file", "txt")
+        temp.writeText(expected)
+        val channel = Files.newByteChannel(temp)
+        val actual = channel.toByteReadChannel().readRemaining().readText()
+        assertEquals(expected, actual)
+        assertFalse(channel.isOpen)
+    }
+}