text: // Copyright (c) 1999, 2007, Google Inc.
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  //
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  //
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  // notice, this list of conditions and the following disclaimer.
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  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
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  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Author: Ray Sidney and many others
  //
  // Defines the VLOG_IS_ON macro that controls the variable-verbosity
  // conditional logging.
  //
  // It's used by VLOG and VLOG_IF in logging.h
  // and by RAW_VLOG in raw_logging.h to trigger the logging.
  //
  // It can also be used directly e.g. like this:
  //   if (VLOG_IS_ON(2)) {
  //     // do some logging preparation and logging
  //     // that can't be accomplished e.g. via just VLOG(2) << ...;
  //   }
  //
  // The truth value that VLOG_IS_ON(level) returns is determined by 
  // the three verbosity level flags:
  //   --v=<n>  Gives the default maximal active V-logging level;
  //            0 is the default.
  //            Normally positive values are used for V-logging levels.
  //   --vmodule=<str>  Gives the per-module maximal V-logging levels to override
  //                    the value given by --v.
  //                    E.g. "my_module=2,foo*=3" would change the logging level
  //                    for all code in source files "my_module.*" and "foo*.*"
  //                    ("-inl" suffixes are also disregarded for this matching).
  //
  // SetVLOGLevel helper function is provided to do limited dynamic control over
  // V-logging by overriding the per-module settings given via --vmodule flag.
  //
  // CAVEAT: --vmodule functionality is not available in non gcc compilers.
  //
  
  #ifndef BASE_VLOG_IS_ON_H_
  #define BASE_VLOG_IS_ON_H_
  
  #include "glog/log_severity.h"
  
  // Annoying stuff for windows -- makes sure clients can import these functions
  #ifndef GOOGLE_GLOG_DLL_DECL
  # if defined(_WIN32) && !defined(__CYGWIN__)
  #   define GOOGLE_GLOG_DLL_DECL  __declspec(dllimport)
  # else
  #   define GOOGLE_GLOG_DLL_DECL
  # endif
  #endif
  
  #if defined(__GNUC__)
  // We emit an anonymous static int* variable at every VLOG_IS_ON(n) site.
  // (Normally) the first time every VLOG_IS_ON(n) site is hit,
  // we determine what variable will dynamically control logging at this site:
  // it's either FLAGS_v or an appropriate internal variable
  // matching the current source file that represents results of
  // parsing of --vmodule flag and/or SetVLOGLevel calls.
  #define VLOG_IS_ON(verboselevel)                                \
    __extension__  \
    ({ static google::int32* vlocal__ = &google::kLogSiteUninitialized;           \
       google::int32 verbose_level__ = (verboselevel);                    \
       (*vlocal__ >= verbose_level__) &&                          \
       ((vlocal__ != &google::kLogSiteUninitialized) ||                   \
        (google::InitVLOG3__(&vlocal__, &FLAGS_v,                         \
                     __FILE__, verbose_level__))); })
  #else
  // GNU extensions not available, so we do not support --vmodule.
  // Dynamic value of FLAGS_v always controls the logging level.
  #define VLOG_IS_ON(verboselevel) (FLAGS_v >= (verboselevel))
  #endif
  
  // Set VLOG(_IS_ON) level for module_pattern to log_level.
  // This lets us dynamically control what is normally set by the --vmodule flag.
  // Returns the level that previously applied to module_pattern.
  // NOTE: To change the log level for VLOG(_IS_ON) sites
  //	 that have already executed after/during InitGoogleLogging,
  //	 one needs to supply the exact --vmodule pattern that applied to them.
  //       (If no --vmodule pattern applied to them
  //       the value of FLAGS_v will continue to control them.)
  extern GOOGLE_GLOG_DLL_DECL int SetVLOGLevel(const char* module_pattern,
                                               int log_level);
  
  // Various declarations needed for VLOG_IS_ON above: =========================
  
  // Special value used to indicate that a VLOG_IS_ON site has not been
  // initialized.  We make this a large value, so the common-case check
  // of "*vlocal__ >= verbose_level__" in VLOG_IS_ON definition
  // passes in such cases and InitVLOG3__ is then triggered.
  extern google::int32 kLogSiteUninitialized;
  
  // Helper routine which determines the logging info for a particalur VLOG site.
  //   site_flag     is the address of the site-local pointer to the controlling
  //                 verbosity level
  //   site_default  is the default to use for *site_flag
  //   fname         is the current source file name
  //   verbose_level is the argument to VLOG_IS_ON
  // We will return the return value for VLOG_IS_ON
  // and if possible set *site_flag appropriately.
  extern GOOGLE_GLOG_DLL_DECL bool InitVLOG3__(
      google::int32** site_flag,
      google::int32* site_default,
      const char* fname,
      google::int32 verbose_level);
  
  #endif  // BASE_VLOG_IS_ON_H_
  