add function slurp(), coming from JsonAdapter

slurp.cc

@@ -0,0 +1,22 @@
+#include "slurp.hh"
+#include <fstream>
+#include <sstream>
+#include <stdexcept>
+
+namespace pEp
+{
+
+std::string slurp(const std::string& filename)
+{
+    std::ifstream input(filename.c_str(), std::ios_base::binary);
+    if(!input)
+    {
+        throw std::runtime_error("Cannot read file \"" + filename + "\"! ");
+    }
+    
+    std::stringstream sstr;
+    sstr << input.rdbuf();
+    return sstr.str();
+}
+
+} // end of namespace pEp

slurp.hh

@@ -0,0 +1,14 @@
+#ifndef PEP_LIB_SLURP_HH
+#define PEP_LIB_SLURP_HH
+
+#include <string>
+
+namespace pEp
+{
+    // reads a whole file and returns it as std::string
+    // throws std::runtime_error() if the file cannot be read. Empty file is not an error.
+    std::string slurp(const std::string& filename);
+
+} // end of namespace pEp
+
+#endif // PEP_LIB_SLURP_HH