encourage the use of CopyCharSpanToMutableCharSpanWithTruncation (project-chip#35444)

* Updated the service area documentation to encourage the use of CopyCharSpanToMutableCharSpanWithTruncation for memory safety. Updated the rvc-app example to use this method.

* Restyled by whitespace

---------

Co-authored-by: Restyled.io <commits@restyled.io>

Author: hicklin

examples/rvc-app/rvc-common/src/rvc-device.cpp

@@ -168,7 +168,7 @@ bool RvcDevice::SaIsSetSelectedAreasAllowed(MutableCharSpan & statusText)
 {
     if (mOperationalStateInstance.GetCurrentOperationalState() == to_underlying(OperationalState::OperationalStateEnum::kRunning))
     {
-        CopyCharSpanToMutableCharSpan("cannot set the Selected Areas while the device is running"_span, statusText);
+        CopyCharSpanToMutableCharSpanWithTruncation("cannot set the Selected Areas while the device is running"_span, statusText);
         return false;
     }
     return true;
@@ -179,14 +179,14 @@ bool RvcDevice::SaHandleSkipArea(uint32_t skippedArea, MutableCharSpan & skipSta
     if (mServiceAreaInstance.GetCurrentArea() != skippedArea)
     {
         // This device only supports skipping the current location.
-        CopyCharSpanToMutableCharSpan("the skipped area does not match the current area"_span, skipStatusText);
+        CopyCharSpanToMutableCharSpanWithTruncation("the skipped area does not match the current area"_span, skipStatusText);
         return false;
     }
 
     if (mOperationalStateInstance.GetCurrentOperationalState() != to_underlying(OperationalState::OperationalStateEnum::kRunning))
     {
         // This device only accepts the skip are command while in the running state
-        CopyCharSpanToMutableCharSpan("skip area is only accepted when the device is running"_span, skipStatusText);
+        CopyCharSpanToMutableCharSpanWithTruncation("skip area is only accepted when the device is running"_span, skipStatusText);
         return false;
     }
 

examples/rvc-app/rvc-common/src/rvc-service-area-delegate.cpp

@@ -134,7 +134,7 @@ bool RvcServiceAreaDelegate::IsValidSelectAreasSet(const Span<const uint32_t> &
         if (!GetInstance()->GetSupportedAreaById(selectedAreas[0], ignoredIndex, tempArea))
         {
             areaStatus = SelectAreasStatus::kUnsupportedArea;
-            CopyCharSpanToMutableCharSpan("unable to find selected area in supported areas"_span, statusText);
+            CopyCharSpanToMutableCharSpanWithTruncation("unable to find selected area in supported areas"_span, statusText);
             return false;
         }
 
@@ -145,14 +145,14 @@ bool RvcServiceAreaDelegate::IsValidSelectAreasSet(const Span<const uint32_t> &
             if (!GetInstance()->GetSupportedAreaById(areaId, ignoredIndex, tempArea))
             {
                 areaStatus = SelectAreasStatus::kUnsupportedArea;
-                CopyCharSpanToMutableCharSpan("unable to find selected area in supported areas"_span, statusText);
+                CopyCharSpanToMutableCharSpanWithTruncation("unable to find selected area in supported areas"_span, statusText);
                 return false;
             }
 
             if (tempArea.mapID.Value() != mapId)
             {
                 areaStatus = SelectAreasStatus::kInvalidSet;
-                CopyCharSpanToMutableCharSpan("all selected areas must be in the same map"_span, statusText);
+                CopyCharSpanToMutableCharSpanWithTruncation("all selected areas must be in the same map"_span, statusText);
                 return false;
             }
         }

src/app/clusters/service-area-server/service-area-delegate.h

@@ -55,9 +55,10 @@ class Delegate
      * @brief Can the selected locations be set by the client in the current operating mode?
      * @param[out] statusText text describing why the selected locations cannot be set (if return is false).
      * Max size kMaxSizeStatusText.
-     * Note: If the return is false and statusText is not successfully set, for example due to a string that can be longer than
-     * kMaxSizeStatusText, the size of this value should be set to 0 with .reduce_size(0) to avoid callers using un-initialized
-     * memory.
+     * Note: statusText must be successfully set if the return is false. Use CopyCharSpanToMutableCharSpanWithTruncation to
+     * ensure that a message is copied successfully. Otherwise, ensure that if setting the statusText can fail (e.g., due
+     * to exceeding kMaxSizeStatusText) the size of this value is set to 0 with .reduce_size(0) to avoid callers using
+     * un-initialized memory.
      * @return true if the current device state allows selected locations to be set by user.
      *
      * @note The statusText field SHOULD indicate why the request is not allowed, given the current mode
@@ -77,9 +78,10 @@ class Delegate
      * @param[in] selectedAreas List of new selected locations.
      * @param[out] locationStatus Success if all checks pass, error code if failure.
      * @param[out] statusText text describing failure (see description above). Max size kMaxSizeStatusText.
-     * Note: If the return is false and statusText is not successfully set, for example due to a string that can be longer than
-     * kMaxSizeStatusText, the size of this value should be set to 0 with .reduce_size(0) to avoid callers using un-initialized
-     * memory.
+     * Note: statusText must be successfully set if the return is false. Use CopyCharSpanToMutableCharSpanWithTruncation to
+     * ensure that a message is copied successfully. Otherwise, ensure that if setting the statusText can fail (e.g., due
+     * to exceeding kMaxSizeStatusText) the size of this value is set to 0 with .reduce_size(0) to avoid callers using
+     * un-initialized memory.
      * @return true if success.
      *
      * @note If the SelectAreas command is allowed when the device is operating and the selected locations change to none, the
@@ -93,9 +95,10 @@ class Delegate
      * calling this method.
      * @param[in] skippedArea the area ID to skip.
      * @param[out] skipStatusText text describing why the current location cannot be skipped. Max size kMaxSizeStatusText.
-     * Note: If the return is false and skipStatusText is not successfully set, for example due to a string that can be longer than
-     * kMaxSizeStatusText, the size of this value should be set to 0 with .reduce_size(0) to avoid callers using un-initialized
-     * memory.
+     * Note: skipStatusText must be successfully set if the return is false. Use CopyCharSpanToMutableCharSpanWithTruncation to
+     * ensure that a message is copied successfully. Otherwise, ensure that if setting the skipStatusText can fail (e.g., due
+     * to exceeding kMaxSizeStatusText) the size of this value is set to 0 with .reduce_size(0) to avoid callers using
+     * un-initialized memory.
      * @return true if command is successful, false if the received skip request cannot be handled due to the current mode of the
      * device.
      *
@@ -120,7 +123,7 @@ class Delegate
     virtual bool HandleSkipArea(uint32_t skippedArea, MutableCharSpan & skipStatusText)
     {
         // device support of this command is optional
-        CopyCharSpanToMutableCharSpan("Skip Current Area command not supported by device"_span, skipStatusText);
+        CopyCharSpanToMutableCharSpanWithTruncation("Skip Current Area command not supported by device"_span, skipStatusText);
         return false;
     }