global_config_env.h

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/*
 *
 * Copyright 2019 gRPC authors.
 *
 * 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 GRPC_CORE_LIB_GPRPP_GLOBAL_CONFIG_ENV_H
#define GRPC_CORE_LIB_GPRPP_GLOBAL_CONFIG_ENV_H
 
#include <grpc/support/port_platform.h>
 
#include <stdint.h>
 
#include "src/core/lib/gprpp/global_config_generic.h"  // IWYU pragma: export
#include "src/core/lib/gprpp/memory.h"
 
namespace grpc_core {
 
typedef void (*GlobalConfigEnvErrorFunctionType)(const char* error_message);
 
/*
 * Set global_config_env_error_function which is called when config system
 * encounters errors such as parsing error. What the default function does
 * is logging error message.
 */
void SetGlobalConfigEnvErrorFunction(GlobalConfigEnvErrorFunctionType func);
 
// Base class for all classes to access environment variables.
class GlobalConfigEnv {
 protected:
  // `name` should be writable and alive after constructor is called.
  constexpr explicit GlobalConfigEnv(char* name) : name_(name) {}
 
 public:
  // Returns the value of `name` variable.
  UniquePtr<char> GetValue();
 
  // Sets the value of `name` variable.
  void SetValue(const char* value);
 
  // Unsets `name` variable.
  void Unset();
 
 protected:
  char* GetName();
 
 private:
  char* name_;
};
 
class GlobalConfigEnvBool : public GlobalConfigEnv {
 public:
  constexpr GlobalConfigEnvBool(char* name, bool default_value)
      : GlobalConfigEnv(name), default_value_(default_value) {}
 
  bool Get();
  void Set(bool value);
 
 private:
  bool default_value_;
};
 
class GlobalConfigEnvInt32 : public GlobalConfigEnv {
 public:
  constexpr GlobalConfigEnvInt32(char* name, int32_t default_value)
      : GlobalConfigEnv(name), default_value_(default_value) {}
 
  int32_t Get();
  void Set(int32_t value);
 
 private:
  int32_t default_value_;
};
 
class GlobalConfigEnvString : public GlobalConfigEnv {
 public:
  constexpr GlobalConfigEnvString(char* name, const char* default_value)
      : GlobalConfigEnv(name), default_value_(default_value) {}
 
  UniquePtr<char> Get();
  void Set(const char* value);
 
 private:
  const char* default_value_;
};
 
}  // namespace grpc_core
 
// Macros for defining global config instances using environment variables.
// This defines a GlobalConfig*Type* instance with arguments for
// mutable variable name and default value.
// Mutable name (g_env_str_##name) is here for having an array
// for the canonical name without dynamic allocation.
// `help` argument is ignored for this implementation.
 
#define GPR_GLOBAL_CONFIG_DEFINE_BOOL(name, default_value, help)         \
  static char g_env_str_##name[] = #name;                                \
  static ::grpc_core::GlobalConfigEnvBool g_env_##name(g_env_str_##name, \
                                                       default_value);   \
  bool gpr_global_config_get_##name() { return g_env_##name.Get(); }     \
  void gpr_global_config_set_##name(bool value) { g_env_##name.Set(value); }
 
#define GPR_GLOBAL_CONFIG_DEFINE_INT32(name, default_value, help)         \
  static char g_env_str_##name[] = #name;                                 \
  static ::grpc_core::GlobalConfigEnvInt32 g_env_##name(g_env_str_##name, \
                                                        default_value);   \
  int32_t gpr_global_config_get_##name() { return g_env_##name.Get(); }   \
  void gpr_global_config_set_##name(int32_t value) { g_env_##name.Set(value); }
 
#define GPR_GLOBAL_CONFIG_DEFINE_STRING(name, default_value, help)         \
  static char g_env_str_##name[] = #name;                                  \
  static ::grpc_core::GlobalConfigEnvString g_env_##name(g_env_str_##name, \
                                                         default_value);   \
  ::grpc_core::UniquePtr<char> gpr_global_config_get_##name() {            \
    return g_env_##name.Get();                                             \
  }                                                                        \
  void gpr_global_config_set_##name(const char* value) {                   \
    g_env_##name.Set(value);                                               \
  }
 
#endif /* GRPC_CORE_LIB_GPRPP_GLOBAL_CONFIG_ENV_H */