Convert positive status values to errors.

include/cRIO/NiStatus.h

@@ -40,7 +40,8 @@ namespace cRIO {
 const char* NiStatus(int32_t status);
 
 /**
- * Log NiFpga call error.
+ * Log NiFpga call error. If status is positive, it is converted to negative
+ * number, to represent an error.
  *
  * @param msg additional message (can be __PRETTY_FUNCTION__)
  * @param status NiFpga returned status

src/LSST/cRIO/NiStatus.cpp

@@ -32,6 +32,12 @@ struct NiErrors {
     const char *desc;
 };
 
+// those values are from NI documentation:
+// https://www.ni.com/docs/en-US/bundle/fpga-interface-c-api-ref/page/capi/errors.html
+//
+// However, Ni functions return positive numbers on errors. Hence NiStatus
+// function does the conversion of positive numbers to negative.
+
 NiErrors errors[] = {
         {0, "NiFpga_Status_Success: No errors or warnings"},
         {-50400, "NiFpga_Status_FifoTimeout: The timeout expired before the FIFO operation could complete"},
@@ -195,6 +201,9 @@ NiErrors errors[] = {
         {0, nullptr}};
 
 const char *NiStatus(int32_t status) {
+    if (status > 0) {
+        status = -status;
+    }
     for (NiErrors *err = errors; err->desc != nullptr; err++) {
         if (err->status == status) return err->desc;
     }