add read_value method

very simple functionality, but I gain two lines per value in the useful
file, which I consider a big deal.

bfps/cpp/hdf5_tools.cpp

 #include "hdf5_tools.hpp"
+#include <cfloat>
+#include <climits>
 
 int hdf5_tools::require_size_single_dataset(hid_t dset, int tsize)
 {
@@ -136,6 +138,37 @@ std::vector<number> hdf5_tools::read_vector(
     return result;
 }
 
+template <typename number>
+std::vector<number> hdf5_tools::read_value(
+        const hid_t group,
+        const std::string dset_name)
+{
+    number result;
+    hid_t dset;
+    hid_t mem_dtype;
+    if (typeid(number) == typeid(int))
+        mem_dtype = H5Tcopy(H5T_NATIVE_INT);
+    else if (typeid(number) == typeid(double))
+        mem_dtype = H5Tcopy(H5T_NATIVE_DOUBLE);
+    if (H5Lexists(group, dset_name.c_str(), H5P_DEFAULT))
+    {
+        dset = H5Dopen(group, dset_name.c_str(), H5P_DEFAULT);
+        H5Dread(dset, mem_dtype, H5S_ALL, H5S_ALL, H5P_DEFAULT, &result);
+        H5Dclose(dset);
+    }
+    else
+    {
+        DEBUG_MSG("attempted to read dataset %s which does not exist.\n",
+                dset_name.c_str());
+        if (typeid(number) == typeid(int))
+            result = INT_MAX;
+        else if (typeid(number) == typeid(double))
+            result = DBL_MAX;
+    }
+    H5Tclose(mem_dtype);
+    return result;
+}
+
 template <typename dtype>
 std::vector<dtype> hdf5_tools::read_vector_with_single_rank(
         const int myrank,

bfps/cpp/hdf5_tools.hpp

@@ -79,6 +79,11 @@ namespace hdf5_tools
     std::string read_string(
             const hid_t group,
             const std::string dset_name);
+
+    template <typename number>
+    number read_value(
+            const hid_t group,
+            const std::string dset_name);
 }
 
 #endif//HDF5_TOOLS_HPP