implement open and add FileMode

3 files changed, 62 insertions, 3 deletions

diff --git a/src/main/kotlin/Connection.kt b/src/main/kotlin/Connection.kt
index 6630567..1aeb4b1 100644
--- a/src/main/kotlin/Connection.kt
+++ b/src/main/kotlin/Connection.kt
@@ -2,8 +2,10 @@ import except.MsizeValueTooBigException
 import except.RErrorException
 import except.UnaccessibleFileException
 import except.UnknownVersionException
+import java.io.File
 import java.io.IOException
 import java.math.BigInteger
+import kotlin.io.path.Path
 
 /**
  * This class represents a 9P connection. It provides a practical implementation with networking to the 9P methods
@@ -182,8 +184,25 @@ class Connection(transLay: TransportLayer) : ProtocolTranslator {
         this.pathInfo.addPath(PathInfo.Path(wname, newfid, qids.last()))
     }
 
-    override fun open(path: String) {
-        TODO("Not yet implemented")
+    override fun open(fid: UInt, mode: FileMode): Pair<QID, UInt> {
+        val omsg = OutMessage(NinePMessageType.TOPEN, this.tagGen.generate(), listOf("fid", "mode"),
+            mapOf(
+                "fid" to BigInteger(fid.toString()),
+                "mode" to BigInteger(mode.toModeByte().toString())
+            ),
+            emptyMap(),
+            emptyMap(),
+            this.maxSize
+        )
+        omsg.write(this.tl)
+        val imsg = checkedInMessage(omsg.tag)
+        imsg.applySchema(listOf(
+            InMessage.Field("qid", InMessage.Field.Type.RAW, 13u),
+            InMessage.Field("iounit", InMessage.Field.Type.INTEGER, 4u)
+        ))
+        val qid = QID(imsg.fieldsRaw["qid"]!!.toList())
+        val iounit = imsg.fieldsInt["iounit"]!!.toInt().toUInt()
+        return Pair(qid, iounit)
     }
 
     override fun create(path: String) {
diff --git a/src/main/kotlin/FileMode.kt b/src/main/kotlin/FileMode.kt
new file mode 100644
index 0000000..81712e6
--- /dev/null
+++ b/src/main/kotlin/FileMode.kt
@@ -0,0 +1,32 @@
+/**
+ * The mode in which to open or create a file. For directories, it's illegal for directories to be written, truncated,
+ * or removed on close.
+ *
+ * @param mode The actual mode, as described by the [Mode] enum class.
+ * @param truncate Set or unset the truncation bit. It requires the write permission.
+ * @param removeClose Set or unset the "remove on close" bit. It requires the remove permission in the parent directory.
+ */
+data class FileMode(val mode: Mode, val truncate: Boolean, val removeClose: Boolean) {
+    enum class Mode(val value: UByte) {
+        READ(0u),
+        WRITE(1u),
+        READ_WRITE(2u),
+        EXECUTE(3u)
+    }
+
+    /**
+     * Turn the mode described by the [FileMode] fields into a mode byte.
+     */
+    fun toModeByte(): UByte {
+        var byte: UByte = 0u
+        byte = byte.or(this.mode.value)
+        if (truncate) {
+            byte = byte.or(0x10u)
+        }
+        if (removeClose) {
+            byte = byte.or(0x40u)
+        }
+
+        return byte
+    }
+}
\ No newline at end of file
diff --git a/src/main/kotlin/ProtocolTranslator.kt b/src/main/kotlin/ProtocolTranslator.kt
index b74eef0..b3674f1 100644
--- a/src/main/kotlin/ProtocolTranslator.kt
+++ b/src/main/kotlin/ProtocolTranslator.kt
@@ -75,8 +75,16 @@ interface ProtocolTranslator {
 
     /**
      * Prepare an FID for I/O on an existing file.
+     *
+     * @param fid The FID of the file to open.
+     * @param mode The mode in which the file is opened.
+     * @return A pair of: (1) the returned QID, and (2) a value called `iounit` that indicates, if non-zero, the maximum
+     * number of bytes that are guaranteed to be read from or written to the file without breaking the I/O transfer into
+     * multiple 9P messages.
+     * @throws except.InvalidMessageException if the received message is invalid.
+     * @throws except.RErrorException if the received message is an R-error message.
      */
-    fun open(path: String)
+    fun open(fid: UInt, mode: FileMode): Pair<QID, UInt>
 
     /**
      * Prepare an FID for I/O on a new file.