From 6e1f17167a91faf701996adfe6acd3c28a013733 Mon Sep 17 00:00:00 2001
From: Petr Kubanek <pkubanek@lsst.org>
Date: Fri, 3 Nov 2023 11:01:47 +0100
Subject: [PATCH] Convert positive status values to errors.

---
 include/cRIO/NiStatus.h    | 3 ++-
 src/LSST/cRIO/NiStatus.cpp | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/cRIO/NiStatus.h b/include/cRIO/NiStatus.h
index 22c11977..5711c8f3 100644
--- a/include/cRIO/NiStatus.h
+++ b/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
diff --git a/src/LSST/cRIO/NiStatus.cpp b/src/LSST/cRIO/NiStatus.cpp
index f1505849..ab741982 100644
--- a/src/LSST/cRIO/NiStatus.cpp
+++ b/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;
     }