the massive refactoring effort

[chaz/yoink] / src / moof / log.hh

diff --git a/src/moof/log.hh b/src/moof/log.hh
new file mode 100644 (file)
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--- /dev/null
+++ b/src/moof/log.hh
@@ -0,0 +1,171 @@
+
+/*]  Copyright (c) 2009-2010, Charles McGarvey  [**************************
+**]  All rights reserved.
+*
+* vi:ts=4 sw=4 tw=75
+*
+* Distributable under the terms and conditions of the 2-clause BSD license;
+* see the file COPYING for a complete text of the license.
+*
+**************************************************************************/
+
+#ifndef _MOOF_LOG_HH_
+#define _MOOF_LOG_HH_
+
+/**
+ * \file log.hh
+ * Functions related to logging the process.
+ * The logging functions are log_error(), log_warning(), and log_info(),
+ * listed from most critical to least critical.
+ */
+
+#include <cstdlib>             // exit
+#include <iostream>
+
+
+#undef ASSERT
+#if NDEBUG
+#define ASSERT(X)
+#else
+/**
+ * Macro which tests an assertion and issues a log_error() and exits if the
+ * assertion is false.
+ * \param X test to perform
+ */
+#define ASSERT(X) if (!(X)) moof::log_error \
+       << "false assertion at " << __FILE__ << ":" << __LINE__ << ", " \
+       << #X, exit(1)
+#endif
+
+
+namespace moof {
+
+
+class script;
+
+
+/**
+ * A class for handling a log priority.  There are two ways to log
+ * messages: by treating a log object as a function whose parameters are
+ * printed with default spacing, or by treating a log object as an output
+ * stream.  Either way, any object can be printed to the log as long as
+ * there is an override for the ostream insertion operator.
+ */
+class log
+{
+public:
+
+       /**
+        * A type for the level or priority of a log message.
+        */
+       enum level
+       {
+               none            = 0,            ///< Disable all logging.
+               error           = 1,            ///< Log only errors.
+               warning         = 2,            ///< Log warnings and errors.
+               info            = 3,            ///< Log everything.
+       };
+
+
+       /**
+        * Set the lowest-priority log message that will be outputted to the
+        * log.  Any logging with a lower priority will be ignored.
+        * \param level The log level.
+        */
+       static void level(level level);
+
+       /**
+        * Get the current lowest-priority log level.  If unchanged, the
+        * default level is info.
+        * \return The log level.
+        */
+       static enum level level();
+
+
+       /**
+        * Import log functions to a script.
+        * \param The script.
+        */
+       static void import(script& script);
+
+
+       /**
+        * Construct a log with a certain priority and prefix string.
+        * \param level The log level.
+        * \param prefix The string printed before each log message.
+        */
+       log(enum level level, const char* prefix) :
+               level_(level),
+               prefix_(prefix) /* only pass literal strings */ {}
+
+
+       template <class A>
+       void operator () (const A& a)
+       {
+               *this << a << std::endl;
+       }
+
+       template <class A, class B>
+       void operator () (const A& a, const B& b)
+       {
+               *this << a << " " << b << std::endl;
+       }
+
+       template <class A, class B, class C>
+       void operator () (const A& a, const B& b, const C& c)
+       {
+               *this << a << " " << b << " " << c << std::endl;
+       }
+
+       template <class A, class B, class C, class D>
+       void operator () (const A& a, const B& b, const C& c, const D& d)
+       {
+               *this << a << " " << b << " " << c << " " << d << std::endl;
+       }
+
+       template <class A, class B, class C, class D, class E>
+       void operator () (const A& a,
+                                         const B& b,
+                                         const C& c,
+                                         const D& d,
+                                         const E& e)
+       {
+               *this << a << " "
+                         << b << " "
+                         << c << " "
+                         << d << " "
+                         << e << std::endl;
+       }
+
+
+private:
+
+       template <class T> friend std::ostream& operator << (log&, const T&);
+
+       static enum level       gLevel;
+
+       enum level                      level_;
+       const char*                     prefix_;
+};
+
+
+extern std::ostream&   log;
+extern std::ostream&   null_log;
+
+extern class log log_error;
+extern class log log_warning;
+extern class log log_info;
+
+
+template <class T>
+inline std::ostream& operator << (class log& log, const T& item)
+{
+       if (log::gLevel < log.level_) return null_log;
+       return moof::log << log.prefix_ << item;
+}
+
+
+} // namespace moof
+
+#endif // _MOOF_LOG_HH_
+