Better CreateRomanString() to create Roman numbers

The previous implementation of CreateRomanString() was complex and
was using various tricks and pointers to create Roman representation
of the integers.

The new implementation is simpler, and easier to understand.

Change-Id: Ibda4f8cfab02fd360e718736c957b3e04110c57a
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/131573
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

1 files changed, 11 insertions, 37 deletions

diff --git a/editeng/source/items/numitem.cxx b/editeng/source/items/numitem.cxx
index 7d6fa5fe23ae..c4220c78a4b5 100644
--- a/editeng/source/items/numitem.cxx
+++ b/editeng/source/items/numitem.cxx
@@ -539,48 +539,22 @@ Size SvxNumberFormat::GetGraphicSizeMM100(const Graphic* pGraphic)
 
 OUString SvxNumberFormat::CreateRomanString( sal_Int32 nNo, bool bUpper )
 {
-    nNo %= 4000;            // more can not be displayed
-//      i, ii, iii, iv, v, vi, vii, vii, viii, ix
-//                          (Dummy),1000,500,100,50,10,5,1
-    const char *cRomanArr = bUpper
-                        ? "MDCLXVI--"   // +2 Dummy entries!
-                        : "mdclxvi--";  // +2 Dummy entries!
-
     OUStringBuffer sRet;
-    sal_uInt16 nMask = 1000;
-    while( nMask )
-    {
-        sal_uInt8 nNumber = sal_uInt8(nNo / nMask);
-        sal_uInt8 nDiff = 1;
-        nNo %= nMask;
 
-        if( 5 < nNumber )
-        {
-            if( nNumber < 9 )
-                sRet.append(*(cRomanArr-1));
-            ++nDiff;
-            nNumber -= 5;
-        }
-        switch( nNumber )
+    constexpr char romans[][13] = {"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"};
+    constexpr sal_Int32 values[] = {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
+
+    for (size_t i = 0; i < std::size(romans); ++i)
+    {
+        while(nNo - values[i] >= 0)
         {
-        case 3:     { sRet.append(*cRomanArr); [[fallthrough]]; }
-        case 2:     { sRet.append(*cRomanArr); [[fallthrough]]; }
-        case 1:     { sRet.append(*cRomanArr); }
-                    break;
-
-        case 4:     {
-                        sRet.append(*cRomanArr);
-                        sRet.append(*(cRomanArr-nDiff));
-                    }
-                    break;
-        case 5:     { sRet.append(*(cRomanArr-nDiff)); }
-                    break;
+            sRet.appendAscii(romans[i]);
+            nNo -= values[i];
         }
-
-        nMask /= 10;            // for the next decade
-        cRomanArr += 2;
     }
-    return sRet.makeStringAndClear();
+
+    return bUpper ? sRet.makeStringAndClear()
+                  : sRet.makeStringAndClear().toAsciiLowerCase();
 }
 
 void SvxNumberFormat::SetListFormat(const OUString& rPrefix, const OUString& rSuffix, int nLevel)