Get Socket.inputStream and outputStream eagerly (#1669)

I was looking into migrating OkHttp to use Okio's
Socket internally and I came across a small behavior
change - previously we were getting the stream once
and reusing it on each call, but now Okio is getting
the stream on each access.

With this change the Socket.asOkioSocket() API behaves
more consistently with Socket.source() and Socket.sink().

Co-authored-by: Jesse Wilson <jwilson@squareup.com>

Author: swankjesse

okio/src/jvmMain/kotlin/okio/internal/DefaultSocket.kt

@@ -48,6 +48,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
   override fun toString() = socket.toString()
 
   inner class SocketSink : Sink {
+    private val outputStream = socket.outputStream
     private val timeout = SocketAsyncTimeout(socket)
 
     override fun write(source: Buffer, byteCount: Long) {
@@ -58,7 +59,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
         val head = source.head!!
         val toCopy = minOf(remaining, head.limit - head.pos).toInt()
         timeout.withTimeout {
-          socket.outputStream.write(head.data, head.pos, toCopy)
+          outputStream.write(head.data, head.pos, toCopy)
         }
 
         head.pos += toCopy
@@ -74,7 +75,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
 
     override fun flush() {
       timeout.withTimeout {
-        socket.outputStream.flush()
+        outputStream.flush()
       }
     }
 
@@ -90,7 +91,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
           // Close this stream only.
           else -> {
             if (socket.isClosed || socket.isOutputShutdown) return // Nothing to do.
-            socket.outputStream.flush()
+            outputStream.flush()
             socket.shutdownOutput()
           }
         }
@@ -103,6 +104,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
   }
 
   inner class SocketSource : Source {
+    private val inputStream = socket.inputStream
     private val timeout = SocketAsyncTimeout(socket)
 
     override fun read(sink: Buffer, byteCount: Long): Long {
@@ -113,7 +115,7 @@ internal class DefaultSocket(val socket: JavaNetSocket) : Socket {
       val maxToCopy = minOf(byteCount, Segment.Companion.SIZE - tail.limit).toInt()
       val bytesRead = try {
         timeout.withTimeout {
-          socket.inputStream.read(tail.data, tail.limit, maxToCopy)
+          inputStream.read(tail.data, tail.limit, maxToCopy)
         }
       } catch (e: AssertionError) {
         if (e.isAndroidGetsocknameError) throw IOException(e)

okio/src/jvmTest/kotlin/okio/SocketTest.kt

@@ -25,6 +25,7 @@ import java.io.InterruptedIOException
 import java.net.InetAddress
 import java.net.InetSocketAddress
 import java.net.ServerSocket
+import java.net.SocketException
 import java.util.concurrent.CompletableFuture
 import java.util.concurrent.TimeUnit
 import javax.net.SocketFactory
@@ -253,6 +254,24 @@ class SocketTest(val factory: Factory = Factory.Default) {
     assertThat(javaNetSocket.isClosed).isFalse()
   }
 
+  @Test
+  fun cannotCreateOkioSocketFromClosedJavaNetSocket() {
+    val javaNetSocket = (this.socket as? DefaultSocket)?.socket ?: return
+    javaNetSocket.close()
+
+    assertFailsWith<SocketException> {
+      javaNetSocket.asOkioSocket()
+    }
+  }
+
+  @Test
+  fun cannotCreateOkioSocketFromUnconnectedJavaNetSocket() {
+    val unconnected = SocketFactory.getDefault().createSocket()
+    assertFailsWith<SocketException> {
+      unconnected.asOkioSocket()
+    }
+  }
+
   @Suppress("ktlint:trailing-comma-on-declaration-site")
   enum class Factory {
     /** Implements an okio.Socket using the `java.net.Socket` API on OS sockets. */