From 49b541775a8ad74c8944ca3fe8de92f3cb066a7a Mon Sep 17 00:00:00 2001
From: Stefano Calabretti <StefanoCalabretti@outlook.it>
Date: Mon, 11 Apr 2022 15:50:22 +0200
Subject: [PATCH] Add TryReceive

---
 Inc/mmr_can.h            | 13 ++++++++++++-
 Inc/mmr_can_message_id.h |  8 ++++++--
 Inc/mmr_can_util.h       | 10 +++++-----
 Src/mmr_can_receive.c    | 22 ++++++++++++++--------
 4 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/Inc/mmr_can.h b/Inc/mmr_can.h
index f4c4c8b..b85fa92 100644
--- a/Inc/mmr_can.h
+++ b/Inc/mmr_can.h
@@ -230,9 +230,20 @@ HalStatus MMR_CAN_Send(CanHandle *hcan, MmrCanPacket packet);
  */
 HalStatus MMR_CAN_SendNoTamper(CanHandle *hcan, MmrCanPacket packet);
 
+
 /**
  * @brief
- * Receives a can message from the network.
+ * Tries to receive a message.
+ */
+MmrResult MMR_CAN_TryReceive(CanHandle *hcan, MmrCanMessage *result);
+
+/**
+ * @brief
+ * Reads a CAN message and stores it inside the
+ * given MmrCanMessage struct.
+ *
+ * If a multi-frame message is received, this function will block
+ * and read every frame for that particular message.
  */
 HalStatus MMR_CAN_Receive(CanHandle *hcan, MmrCanMessage *result);
 
diff --git a/Inc/mmr_can_message_id.h b/Inc/mmr_can_message_id.h
index 5dde863..cdeb956 100644
--- a/Inc/mmr_can_message_id.h
+++ b/Inc/mmr_can_message_id.h
@@ -10,6 +10,10 @@
  * MMR_CAN_MESSAGE_ID_POINT might be interpreted as
  * a message carrying a struct Point { int x; int y; };,
  * and thus deserialized accordingly.
+ *
+ * You can find a table with more in-depth explanations on
+ * Google Drive:
+ * https://docs.google.com/spreadsheets/d/1GIC0_FuhCjXfBOg_dUWzoEsl5TG7SEOR
  */
 
 #ifndef INC_MMR_CAN_MESSAGE_ID_H_
@@ -22,8 +26,8 @@
 /**
  * @brief
  * Message ids are 10 bits wide
- * The first 3 bits determine the message id type, while
- * the other 7 determine the subtype.
+ * The first 5 bits determine the message id type, while
+ * the other 5 determine the subtype.
  * 
  * Ids scheme:
  *
diff --git a/Inc/mmr_can_util.h b/Inc/mmr_can_util.h
index 6c3790e..c9382fe 100644
--- a/Inc/mmr_can_util.h
+++ b/Inc/mmr_can_util.h
@@ -73,11 +73,11 @@
  *
  * Asynchronous logic can be easily implemented using State Machines
  */
-typedef enum MmrAsyncResult {
-  MMR_ASYNC_RESULT_ERROR,
-  MMR_ASYNC_RESULT_PENDING,
-  MMR_ASYNC_RESULT_COMPLETED,
-} MmrAsyncResult;
+typedef enum MmrResult {
+  MMR_RESULT_ERROR,
+  MMR_RESULT_PENDING,
+  MMR_RESULT_COMPLETED,
+} MmrResult;
 
 
 #endif /* INC_MMR_CAN_UTIL_H_ */
diff --git a/Src/mmr_can_receive.c b/Src/mmr_can_receive.c
index a3639ff..8480b85 100644
--- a/Src/mmr_can_receive.c
+++ b/Src/mmr_can_receive.c
@@ -20,14 +20,20 @@ static HalStatus receiveAll(ReceptionParams *rp);
 static bool headerIsMultiFrame(MmrCanHeader header, CanId targetId);
 
 
-/**
- * @brief
- * Reads a CAN message and stores it inside the
- * given MmrCanMessage struct.
- *
- * If a multi-frame message is received, this function will block
- * and read every frame for that particular message.
- */
+MmrResult MMR_CAN_TryReceive(CanHandle *hcan, MmrCanMessage *result) {
+  size_t pendingMessages =
+    HAL_CAN_GetRxFifoFillLevel(hcan, MMR_CAN_RX_FIFO);
+
+  if (pendingMessages > 0) {
+    return MMR_CAN_Receive(hcan, result) != HAL_OK
+      ? MMR_RESULT_COMPLETED
+      : MMR_RESULT_ERROR;
+  }
+
+  return MMR_RESULT_PENDING;
+}
+
+
 HalStatus MMR_CAN_Receive(CanHandle *hcan, MmrCanMessage *result) {
   ReceptionParams rp = {
     .handle = hcan,