Add format string method

Interpret printf-like format strings using std::string instead
of raw char buffers. By using std::snprintf we avoid buffer
overflows and a boost::format dependency at the price of
depending on a c++11 feature.

Perhaps we'd like to have this in dune-common

[[Imported from SVN: r13087]]

dune/fufem/CMakeLists.txt

@@ -30,6 +30,7 @@ install(FILES
     dunepython.hh
     facehierarchy.hh
     facelocalfiniteelement.hh
+    formatstring.hh
     globalintersectioniterator.hh
     improvegrid.hh
     interval.hh

dune/fufem/Makefile.am

@@ -23,6 +23,8 @@ fufem_HEADERS = any.hh \
                 dunedataio.hh \
                 dunepython.hh \
                 facehierarchy.hh \
+                facelocalfiniteelement.hh \
+                formatstring.hh \
                 globalintersectioniterator.hh \
                 improvegrid.hh \
                 indexedsliceiterator.hh \

dune/fufem/formatstring.hh

+#ifndef DUNE_FUFEM_FORMATSTRING_HH
+#define DUNE_FUFEM_FORMATSTRING_HH
+
+#include <cstdio>
+
+#include <dune/common/exceptions.hh>
+
+namespace Dune {
+namespace Fufem {
+
+/**
+ * \brief Return formated output for printf like string
+ *
+ * \param s Format string using printf syntax
+ * \param args Arguments for format string
+ * \returns Result of conversion as string
+ */
+template<class... T>
+std::string formatString(const std::string& s, const T&... args)
+{
+    static const int bufferSize=1000;
+    char buffer[bufferSize];
+
+    r = std::snprintf(buffer, s.c_str(), bufferSize, args...);
+
+    // negative return values correspond to errors
+    if (r<0)
+        DUNE_THROW(Dune::Exception,"Could not convert format string using given arguments.");
+
+    // if buffer was large enough return result as string
+    if (r<bufferSize)
+        return std::string(buffer);
+
+    // if buffer was to small allocate a larger buffer using
+    // the returned size hint +1 for the terminating 0-byte.
+    int dynamicBufferSize = r+1;
+    char* dynamicBuffer = new char[dynamicBufferSize];
+
+    // convert and check for errors again
+    r = std::snprintf(dynamicBuffer, s.c_str(), dynamicBufferSize, args...);
+    if (r<0)
+        DUNE_THROW(Dune::Exception,"Could not convert format string using given arguments.");
+
+    // the new buffer should always be large enough
+    assert(r<dynamicBufferSize);
+
+    // convert result to string, release buffer, return result
+    std::string result(dynamicBuffer);
+    delete[] dynamicBuffer;
+
+    return result;
+}
+
+}
+}
+
+#endif // DUNE_FUFEM_FORMATSTRING_HH