added wxCStrData::operator- for compatibility with expressions like 'c_str() + n...

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45124 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

diff --git a/include/wx/string.h b/include/wx/string.h
index f1be0afe8956b9835c3891a01d5f78f2b1dccad2..735e75ef7709c6de6338e8110d286b0cfb499c84 100644 (file)
--- a/include/wx/string.h
+++ b/include/wx/string.h
@@ -220,6 +220,26 @@ public:
     wxCStrData operator+(size_t n) const
         { return wxCStrData(m_str, m_offset + n, m_owned); }
 
+    // and these for "str.c_str() + n - 2":
+    wxCStrData operator-(int n) const
+    {
+        wxASSERT_MSG( n <= (int)m_offset,
+                      _T("attempt to construct address before the beginning of the string") );
+        return wxCStrData(m_str, m_offset - n, m_owned);
+    }
+    wxCStrData operator-(long n) const
+    {
+        wxASSERT_MSG( n <= (int)m_offset,
+                      _T("attempt to construct address before the beginning of the string") );
+        return wxCStrData(m_str, m_offset - n, m_owned);
+    }
+    wxCStrData operator-(size_t n) const
+    {
+        wxASSERT_MSG( n <= (int)m_offset,
+                      _T("attempt to construct address before the beginning of the string") );
+        return wxCStrData(m_str, m_offset - n, m_owned);
+    }
+
     // this operator is needed to make expressions like "*c_str()" or
     // "*(c_str() + 2)" work
     wxUniChar operator*() const;