added postgres backend

include/matador/sql/to_value.hpp

@@ -0,0 +1,84 @@
+#ifndef QUERY_TO_VALUE_HPP
+#define QUERY_TO_VALUE_HPP
+
+#include <cerrno>
+#include <climits>
+#include <cstring>
+#include <cfloat>
+#include <cstdlib>
+#include <stdexcept>
+#include <type_traits>
+
+namespace matador::sql {
+
+template < class Type >
+void to_value(Type &value, const char *str, typename std::enable_if<std::is_integral<Type>::value && std::is_signed<Type>::value>::type* = nullptr)
+{
+  if (strlen(str) == 0) {
+    return;
+  }
+  char *end;
+  errno = 0;
+  auto result = strtoll(str, &end, 10);
+
+  // Check for various possible errors
+  if ((errno == ERANGE && (result == LLONG_MAX || result == LLONG_MIN)) || (errno != 0 && result == 0)) {
+    throw std::logic_error(strerror(errno));
+    // Handle error
+  } else if (end == str) {
+    // No digits found
+    throw std::logic_error("failed to convert value to signed number: no digits were found");
+  }
+
+  value = static_cast<Type>(result);
+}
+
+template < class Type >
+void to_value(Type &value, const char *str, typename std::enable_if<std::is_integral<Type>::value && std::is_unsigned<Type>::value>::type* = nullptr)
+{
+  if (strlen(str) == 0) {
+    return;
+  }
+
+  char *end;
+  errno = 0;
+  auto result = strtoull(str, &end, 10);
+
+  // Check for various possible errors
+  if ((errno == ERANGE && (result == LLONG_MAX || result == LLONG_MIN)) || (errno != 0 && result == 0)) {
+    throw std::logic_error(strerror(errno));
+    // Handle error
+  } else if (end == str) {
+    // No digits found
+    throw std::logic_error("failed to convert value to unsigned number: no digits were found");
+  }
+
+  value = static_cast<Type>(result);
+}
+
+template < class Type >
+void to_value(Type &value, const char *str, typename std::enable_if<std::is_floating_point<Type>::value>::type* = nullptr)
+{
+  if (strlen(str) == 0) {
+    return;
+  }
+
+  char *end;
+  errno = 0;
+  auto result = strtold(str, &end);
+
+  // Check for various possible errors
+  if ((errno == ERANGE && (result == LDBL_MAX || result == LDBL_MIN)) || (errno != 0 && result == 0)) {
+    throw std::logic_error(strerror(errno));
+    // Handle error
+  } else if (end == str) {
+    // No digits found
+    throw std::logic_error("failed to convert value to floating point number: no digits were found");
+  }
+
+  value = static_cast<Type>(result);
+}
+
+}
+
+#endif //QUERY_TO_VALUE_HPP