Refactor ports

controls-core/src/commonMain/kotlin/space/kscience/controls/ports/SynchronousPort.kt

@@ -2,8 +2,11 @@ package space.kscience.controls.ports
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.takeWhile
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
+import kotlinx.io.Buffer
+import kotlinx.io.readByteArray
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.context.ContextAware
 
@@ -25,6 +28,22 @@ public interface SynchronousPort : ContextAware, AutoCloseable {
         request: ByteArray,
         transform: suspend Flow<ByteArray>.() -> R,
     ): R
+
+    /**
+     * Synchronously read fixed size response to a given [request]. Discard additional response bytes.
+     */
+    public suspend fun respondFixedMessageSize(
+        request: ByteArray,
+        responseSize: Int,
+    ): ByteArray = respond(request) {
+        val buffer = Buffer()
+        takeWhile {
+            buffer.size < responseSize
+        }.collect {
+            buffer.write(it)
+        }
+        buffer.readByteArray(responseSize)
+    }
 }
 
 private class SynchronousOverAsynchronousPort(

controls-pi/src/main/kotlin/space/kscience/controls/pi/SynchronousPiPort.kt

@@ -7,6 +7,7 @@ import com.pi4j.ktx.io.serial
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.runInterruptible
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 import space.kscience.controls.ports.SynchronousPort
@@ -55,6 +56,14 @@ public class SynchronousPiPort(
         }.transform()
     }
 
+    override suspend fun respondFixedMessageSize(request: ByteArray, responseSize: Int): ByteArray = mutex.withLock {
+        runInterruptible {
+            serial.drain()
+            serial.write(request)
+            serial.readNBytes(responseSize)
+        }
+    }
+
     override fun close() {
         serial.close()
     }

controls-serial/src/main/kotlin/space/kscience/controls/serial/SynchronousSerialPort.kt

@@ -4,6 +4,7 @@ import com.fazecast.jSerialComm.SerialPort
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.runInterruptible
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
 import space.kscience.controls.ports.SynchronousPort
@@ -44,8 +45,10 @@ public class SynchronousSerialPort(
 
     private val mutex = Mutex()
 
-    override suspend fun <R> respond(request: ByteArray, transform: suspend Flow<ByteArray>.() -> R): R =
+    override suspend fun <R> respond(
-        mutex.withLock {
+        request: ByteArray,
+        transform: suspend Flow<ByteArray>.() -> R,
+    ): R = mutex.withLock {
         comPort.flushIOBuffers()
         comPort.writeBytes(request, request.size)
         flow<ByteArray> {
@@ -65,6 +68,16 @@ public class SynchronousSerialPort(
         }.transform()
     }
 
+    override suspend fun respondFixedMessageSize(request: ByteArray, responseSize: Int): ByteArray = mutex.withLock {
+        runInterruptible {
+            comPort.flushIOBuffers()
+            comPort.writeBytes(request, request.size)
+            val buffer = ByteArray(responseSize)
+            comPort.readBytes(buffer, responseSize)
+            buffer
+        }
+    }
+
     public companion object : Factory<SynchronousPort> {
 
         public fun build(