1 files changed, 101 insertions, 0 deletions
diff --git a/compiler/pepper-env/include/pepper/env.h b/compiler/pepper-env/include/pepper/env.h
new file mode 100644
index 000000000..233c8b421
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+++ b/compiler/pepper-env/include/pepper/env.h
@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2020 Samsung Electronics Co., Ltd. All Rights Reserved
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __PEPPER_ENV_H__
+#define __PEPPER_ENV_H__
+
+#include <string>
+
+//
+// KVStore: Key-Value Store Interface
+//
+namespace pepper // TODO Extract this section if necessary
+{
+
+enum class KVStoreTrait
+{
+  Queryable,
+};
+
+template <KVStoreTrait Trait> class KVStoreInterface;
+
+template <> class KVStoreInterface<KVStoreTrait::Queryable>
+{
+public:
+  KVStoreInterface() = default;
+
+public:
+  virtual ~KVStoreInterface() = default;
+
+public: // Core interface (PLEASE PREFER TO THE BELOW HELPERS)
+  //
+  //  "query(k)" SHOULD
+  //  - return a valid C-string if the key "k" exists in the store, or
+  //  - return nullptr otherwise.
+  //
+  // DESIGN NOTE - Why "query" instead of "get"?
+  //
+  //  Let us consider the following class declarations as an example:
+  //
+  //  struct Base {
+  //    virtual const char *get(const char *) const = 0;
+  //    const char *get(const std::string &s) const { return nullptr; }
+  //  };
+  //
+  //  struct Derived : public Base {
+  //    const char *get(const char *) const final { return nullptr; }
+  //  };
+  //
+  //  It is impossible to write the code of the following form:
+  //
+  //  Derived obj;
+  //
+  //  std::string s = ...;
+  //  obj.get(s);
+  //  ^^^^^^^^^^^
+  //  error: no viable conversion from 'std::string' (aka 'basic_string<char>') to 'const char *'
+  //
+  //  Please refer to the concept of name hiding in C++ for more details.
+  virtual const char *query(const char *k) const = 0;
+
+public: // Derived helper methods
+  const char *get(const std::string &k) const { return query(k.c_str()); }
+
+  /**
+   * NOTE
+   *
+   *  get(k, v) same as query(k) if the key "k" exists in the store.
+   *  get(k, v) returns "v" otherwise
+   */
+  std::string get(const std::string &key, const std::string &default_value) const;
+};
+
+} // namespace pepper
+
+//
+// ProcessEnvironment
+//
+namespace pepper
+{
+
+struct ProcessEnvironment final : public KVStoreInterface<KVStoreTrait::Queryable>
+{
+  const char *query(const char *k) const final;
+};
+
+} // namespace pepper
+
+#endif // __PEPPER_ENV_H__