HAL CRC: Return early when calling compute with null or 0 size buffer

Author: Steven Cartmell

hal/crc_api.h

@@ -114,6 +114,9 @@ void hal_crc_compute_partial_start(const uint32_t polynomial);
  * To obtain the final result of the CRC calculation hal_crc_get_result() is
  * called to apply the final transformations to the data.
  *
+ * If the function is passed an undefined pointer, or the size of the buffer is
+ * specified to be 0, this function will do nothing and return.
+ *
  * This function can be call multiple times in succession, this can be used
  * to calculate the CRC result of streamed data.
  *

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/TARGET_MCU_K64F/mbed_crc_api.c

@@ -73,14 +73,21 @@ void hal_crc_compute_partial_start(const uint32_t polynomial)
     }
     default:
       MBED_ASSERT("Configuring Mbed CRC with unsupported polynomial");
-      break;
+
+      return;
   }
 
   CRC_Init(CRC0, &config);
 }
 
 void hal_crc_compute_partial(const uint8_t *data, const size_t size)
 {
+  if (data == NULL)
+    return;
+
+  if (size == 0)
+    return;
+
   CRC_WriteData(CRC0, data, size);
 }