implement an actually working setErrorCell() from BIFF error codes

Not that we're currently using that, but..

Change-Id: I67b8fc324779875ba14e2d69204c40fe27cc180e

sc/source/filter/inc/unitconverter.hxx

@@ -86,6 +86,9 @@ public:
     /** Returns a BIFF error code from the passed error string. */
     sal_uInt8           calcBiffErrorCode( const OUString& rErrorCode ) const;
 
+    /** Returns an error string from the passed BIFF error code. */
+    const OUString&     calcErrorString( sal_uInt8 nErrorCode ) const;
+
 private:
     /** Adds an error code to the internal maps. */
     void                addErrorCode( sal_uInt8 nErrorCode, const OUString& rErrorCode );

sc/source/filter/oox/sheetdatabuffer.cxx

@@ -204,16 +204,7 @@ void SheetDataBuffer::setErrorCell( const CellModel& rModel, const OUString& rEr
 
 void SheetDataBuffer::setErrorCell( const CellModel& rModel, sal_uInt8 nErrorCode )
 {
-    assert(!"stringizing any NaN will only give 'nan'");
-    /* FIXME: map nErrorCode to error string and call setErrorCell() above. */
-
-    OUStringBuffer aBuf;
-    aBuf.append('{');
-    aBuf.append(BiffHelper::calcDoubleFromError(nErrorCode));
-    aBuf.append('}');
-
-    getFormulaBuffer().setCellFormula(rModel.maCellAddr, aBuf.makeStringAndClear());
-    setCellFormat( rModel );
+    setErrorCell( rModel, getUnitConverter().calcErrorString( nErrorCode));
 }
 
 void SheetDataBuffer::setDateCell( const CellModel& rModel, const OUString& rDateString )

sc/source/filter/oox/unitconverter.cxx

@@ -218,6 +218,20 @@ sal_uInt8 UnitConverter::calcBiffErrorCode( const OUString& rErrorCode ) const
     return (aIt == maOoxErrCodes.end()) ? BIFF_ERR_NA : aIt->second;
 }
 
+const OUString& UnitConverter::calcErrorString( sal_uInt8 nErrorCode ) const
+{
+    OoxErrorCodeMap::const_iterator iFail( maOoxErrCodes.end());
+    for (OoxErrorCodeMap::const_iterator aIt( maOoxErrCodes.begin()); aIt != maOoxErrCodes.end(); ++aIt)
+    {
+        if (aIt->second == nErrorCode)
+            return aIt->first;
+        if (aIt->second == BIFF_ERR_NA)
+            iFail = aIt;
+    }
+    assert(iFail != maOoxErrCodes.end());   // BIFF_ERR_NA really should be in the map..
+    return iFail->first;
+}
+
 void UnitConverter::addErrorCode( sal_uInt8 nErrorCode, const OUString& rErrorCode )
 {
     maOoxErrCodes[ rErrorCode ]  = nErrorCode;