Add support for multi-frame responses (#4)

* first test with multi-frame. storing data in handler. still need to free memory since using malloc.

* hardcode the IsoTpMessage payload size. copy the full multi-frame response into a complete isotpMessage once all frames have been received. otherwise, the returned isotpMessage is not complete.

* remove unnecessary debug statements.

* do not receive multi-frame message if it is larger than the payload buffer size.

* update changelog with multi-frame support

* fix the changelog version for proper semantic versioning. oops.

* move pointer intialization for testing purposes.

* add tests for multi-frame.

* try latest version of check

* fix syntax for version install.

* fix tests. no longer check for malloc pointer (not supported in Travis version of check.h - just test that flow control message has not been sent.

* add IsoTpMessage field for multi_frame. Need this upstream for doing timeout updates.

* add test multi_frame field.

2 files changed, 104 insertions, 13 deletions

diff --git a/src/isotp/isotp_types.h b/src/isotp/isotp_types.h
index 9d05980a..6ae3a795 100644
--- a/src/isotp/isotp_types.h
+++ b/src/isotp/isotp_types.h
@@ -9,8 +9,14 @@
 #define MAX_ISO_TP_MESSAGE_SIZE 4096
 // TODO we want to avoid malloc, and we can't be allocated 4K on the stack for
 // each IsoTpMessage, so for now we're setting an artificial max message size
-// here - since we only handle single frame messages, 8 bytes is plenty.
-#define OUR_MAX_ISO_TP_MESSAGE_SIZE 8
+// here - for most multi-frame use cases, 256 bytes is plenty.
+#define OUR_MAX_ISO_TP_MESSAGE_SIZE 256
+
+/* Private: IsoTp nibble specifics for PCI and Payload.
+ */
+#define PCI_NIBBLE_INDEX 0
+#define PAYLOAD_LENGTH_NIBBLE_INDEX 1
+#define PAYLOAD_BYTE_INDEX 1
 
 /* Private: The default timeout to use when waiting for a response during a
  * multi-frame send or receive.
@@ -30,8 +36,9 @@ extern "C" {
  * completed - An IsoTpMessage is the return value from a few functions - this
  *      attribute will be true if the message is actually completely received.
  *      If the function returns but is only partially through receiving the
- *      message, this will be false and you should not consider the other data
- *      to be valid.
+ *      message, this will be false, the multi_frame attribute will be true,
+ *      and you should not consider the other data to be valid.
+ * multi_frame - Designates the message is being built with multi-frame.
  * arbitration_id - The arbitration ID of the message.
  * payload - The optional payload of the message - don't forget to check the
  *      size!
@@ -42,6 +49,7 @@ typedef struct {
     uint8_t payload[OUR_MAX_ISO_TP_MESSAGE_SIZE];
     uint16_t size;
     bool completed;
+    bool multi_frame;
 } IsoTpMessage;
 
 /* Public: The type signature for an optional logging function, if the user
diff --git a/src/isotp/receive.c b/src/isotp/receive.c
index 2dc380bc..35b7a2a6 100644
--- a/src/isotp/receive.c
+++ b/src/isotp/receive.c
@@ -1,6 +1,10 @@
 #include <isotp/receive.h>
+#include <isotp/send.h>
 #include <bitfield/bitfield.h>
 #include <string.h>
+#include <stdlib.h>
+
+#define ARBITRATION_ID_OFFSET 0x8
 
 static void isotp_complete_receive(IsoTpReceiveHandle* handle, IsoTpMessage* message) {
     if(handle->message_received_callback != NULL) {
@@ -13,6 +17,26 @@ bool isotp_handle_single_frame(IsoTpReceiveHandle* handle, IsoTpMessage* message
     return true;
 }
 
+bool isotp_handle_multi_frame(IsoTpReceiveHandle* handle, IsoTpMessage* message) {
+    // call this once all consecutive frames have been received
+    isotp_complete_receive(handle, message);
+    return true;
+}
+
+bool isotp_send_flow_control_frame(IsoTpShims* shims, IsoTpMessage* message) {
+    uint8_t can_data[CAN_MESSAGE_BYTE_SIZE] = {0};
+
+    if(!set_nibble(PCI_NIBBLE_INDEX, PCI_FLOW_CONTROL_FRAME, can_data, sizeof(can_data))) {
+        shims->log("Unable to set PCI in CAN data");
+        return false;
+    }
+
+    shims->send_can_message(message->arbitration_id - ARBITRATION_ID_OFFSET, can_data,
+            shims->frame_padding ? 8 : 1 + message->size);
+    return true;
+}
+
+
 IsoTpReceiveHandle isotp_receive(IsoTpShims* shims,
         const uint32_t arbitration_id, IsoTpMessageReceivedHandler callback) {
     IsoTpReceiveHandle handle = {
@@ -31,6 +55,7 @@ IsoTpMessage isotp_continue_receive(IsoTpShims* shims,
     IsoTpMessage message = {
         arbitration_id: arbitration_id,
         completed: false,
+        multi_frame: false,
         payload: {0},
         size: 0
     };
@@ -53,30 +78,88 @@ IsoTpMessage isotp_continue_receive(IsoTpShims* shims,
     IsoTpProtocolControlInformation pci = (IsoTpProtocolControlInformation)
             get_nibble(data, size, 0);
 
-    uint8_t payload_length = get_nibble(data, size, 1);
-    uint8_t payload[payload_length];
-    if(payload_length > 0 && size > 0) {
-        memcpy(payload, &data[1], payload_length);
-    }
-
     // TODO this is set up to handle rx a response with a payload, but not to
     // handle flow control responses for multi frame messages that we're in the
     // process of sending
 
     switch(pci) {
         case PCI_SINGLE: {
+            uint8_t payload_length = get_nibble(data, size, 1);
+            
             if(payload_length > 0) {
-                memcpy(message.payload, payload, payload_length);
+                memcpy(message.payload, &data[1], payload_length);
             }
+            
             message.size = payload_length;
             message.completed = true;
             handle->success = true;
             handle->completed = true;
             isotp_handle_single_frame(handle, &message);
             break;
-         }
+        }
+        //If multi-frame, then the payload length is contained in the 12
+        //bits following the first nibble of Byte 0. 
+        case PCI_FIRST_FRAME: {
+            uint16_t payload_length = (get_nibble(data, size, 1) << 8) + get_byte(data, size, 1);
+
+            if(payload_length > OUR_MAX_ISO_TP_MESSAGE_SIZE) {
+                shims->log("Multi-frame response too large for receive buffer.");
+                break;
+            }
+
+            //Need to allocate memory for the combination of multi-frame
+            //messages. That way we don't have to allocate 4k of memory 
+            //for each multi-frame response.
+            uint8_t* combined_payload = NULL;
+            combined_payload = (uint8_t*)malloc(sizeof(uint8_t)*payload_length);
+
+            if(combined_payload == NULL) {
+                shims->log("Unable to allocate memory for multi-frame response.");
+                break;
+            }
+
+            memcpy(combined_payload, &data[2], CAN_MESSAGE_BYTE_SIZE - 2);
+            handle->receive_buffer = combined_payload;
+            handle->received_buffer_size = CAN_MESSAGE_BYTE_SIZE - 2;
+            handle->incoming_message_size = payload_length;
+
+            message.multi_frame = true;
+            handle->success = false;
+            handle->completed = false;
+            isotp_send_flow_control_frame(shims, &message);
+            break;
+        }
+        case PCI_CONSECUTIVE_FRAME: {
+            uint8_t start_index = handle->received_buffer_size;
+            uint8_t remaining_bytes = handle->incoming_message_size - start_index;
+            message.multi_frame = true;
+
+            if(remaining_bytes > 7) {
+                memcpy(&handle->receive_buffer[start_index], &data[1], CAN_MESSAGE_BYTE_SIZE - 1);
+                handle->received_buffer_size = start_index + 7;
+            } else {
+                memcpy(&handle->receive_buffer[start_index], &data[1], remaining_bytes);
+                handle->received_buffer_size = start_index + remaining_bytes;
+
+                if(handle->received_buffer_size != handle->incoming_message_size){
+                    free(handle->receive_buffer);
+                    handle->success = false;
+                    shims->log("Error capturing all bytes of multi-frame. Freeing memory.");
+                } else {
+                    memcpy(message.payload,&handle->receive_buffer[0],handle->incoming_message_size);
+                    free(handle->receive_buffer);
+                    message.size = handle->incoming_message_size;
+                    message.completed = true;
+                    shims->log("Successfully captured all of multi-frame. Freeing memory.");
+
+                    handle->success = true;
+                    handle->completed = true;
+                    isotp_handle_multi_frame(handle, &message);
+                }
+            }
+            break;
+        }
         default:
-            shims->log("Only single frame messages are supported");
             break;
     }
     return message;