src/base/commandlineflags.h

// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2005, Google Inc.
// All rights reserved.
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// modification, are permitted provided that the following conditions are
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// 
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// notice, this list of conditions and the following disclaimer.
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// ---
// This file is a compatibility layer that defines Google's version of
// command line flags that are used for configuration.
//
// We put flags into their own namespace.  It is purposefully
// named in an opaque way that people should have trouble typing
// directly.  The idea is that DEFINE puts the flag in the weird
// namespace, and DECLARE imports the flag from there into the
// current namespace.  The net result is to force people to use
// DECLARE to get access to a flag, rather than saying
//   extern bool FLAGS_logtostderr;
// or some such instead.  We want this so we can put extra
// functionality (like sanity-checking) in DECLARE if we want,
// and make sure it is picked up everywhere.
//
// We also put the type of the variable in the namespace, so that
// people can't DECLARE_int32 something that they DEFINE_bool'd
// elsewhere.
#ifndef BASE_COMMANDLINEFLAGS_H_
#define BASE_COMMANDLINEFLAGS_H_

#include <config.h>
#include <string>
#include <string.h>               // for memchr
#include <stdlib.h>               // for getenv
#include "base/basictypes.h"

#define DECLARE_VARIABLE(type, name)                                          \
  namespace FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead {  \
  extern PERFTOOLS_DLL_DECL type FLAGS_##name;                                \
  }                                                                           \
  using FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead::FLAGS_##name

#define DEFINE_VARIABLE(type, name, value, meaning) \
  namespace FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead {  \
  PERFTOOLS_DLL_DECL type FLAGS_##name(value);                                \
  char FLAGS_no##name;                                                        \
  }                                                                           \
  using FLAG__namespace_do_not_use_directly_use_DECLARE_##type##_instead::FLAGS_##name

// bool specialization
#define DECLARE_bool(name) \
  DECLARE_VARIABLE(bool, name)
#define DEFINE_bool(name, value, meaning) \
  DEFINE_VARIABLE(bool, name, value, meaning)

// int32 specialization
#define DECLARE_int32(name) \
  DECLARE_VARIABLE(int32, name)
#define DEFINE_int32(name, value, meaning) \
  DEFINE_VARIABLE(int32, name, value, meaning)

// int64 specialization
#define DECLARE_int64(name) \
  DECLARE_VARIABLE(int64, name)
#define DEFINE_int64(name, value, meaning) \
  DEFINE_VARIABLE(int64, name, value, meaning)

#define DECLARE_uint64(name) \
  DECLARE_VARIABLE(uint64, name)
#define DEFINE_uint64(name, value, meaning) \
  DEFINE_VARIABLE(uint64, name, value, meaning)

// double specialization
#define DECLARE_double(name) \
  DECLARE_VARIABLE(double, name)
#define DEFINE_double(name, value, meaning) \
  DEFINE_VARIABLE(double, name, value, meaning)

// Special case for string, because we have to specify the namespace
// std::string, which doesn't play nicely with our FLAG__namespace hackery.
#define DECLARE_string(name)                                          \
  namespace FLAG__namespace_do_not_use_directly_use_DECLARE_string_instead {  \
  extern std::string FLAGS_##name;                                                   \
  }                                                                           \
  using FLAG__namespace_do_not_use_directly_use_DECLARE_string_instead::FLAGS_##name
#define DEFINE_string(name, value, meaning) \
  namespace FLAG__namespace_do_not_use_directly_use_DECLARE_string_instead {  \
  std::string FLAGS_##name(value);                                                   \
  char FLAGS_no##name;                                                        \
  }                                                                           \
  using FLAG__namespace_do_not_use_directly_use_DECLARE_string_instead::FLAGS_##name

// implemented in sysinfo.cc
namespace tcmalloc {
  namespace commandlineflags {

    inline bool StringToBool(const char *value, bool def) {
      if (!value) {
        return def;
      }
      switch (value[0]) {
      case 't':
      case 'T':
      case 'y':
      case 'Y':
      case '1':
      case '\0':
        return true;
      }
      return false;
    }

    inline int StringToInt(const char *value, int def) {
      if (!value) {
        return def;
      }
      return strtol(value, NULL, 10);
    }

    inline long long StringToLongLong(const char *value, long long def) {
      if (!value) {
        return def;
      }
      return strtoll(value, NULL, 10);
    }

    inline double StringToDouble(const char *value, double def) {
      if (!value) {
        return def;
      }
      return strtod(value, NULL);
    }
  }
}

// These macros (could be functions, but I don't want to bother with a .cc
// file), make it easier to initialize flags from the environment.

#define EnvToString(envname, dflt)   \
  (!getenv(envname) ? (dflt) : getenv(envname))

#define EnvToBool(envname, dflt)   \
  tcmalloc::commandlineflags::StringToBool(getenv(envname), dflt)

#define EnvToInt(envname, dflt)  \
  tcmalloc::commandlineflags::StringToInt(getenv(envname), dflt)

#define EnvToInt64(envname, dflt)  \
  tcmalloc::commandlineflags::StringToLongLong(getenv(envname), dflt)

#define EnvToDouble(envname, dflt)  \
  tcmalloc::commandlineflags::StringToDouble(getenv(envname), dflt)

#endif  // BASE_COMMANDLINEFLAGS_H_