[chromium-reviews] Add Compact Language Detection (CLD) library to Chrome. This works in Windows...

third_party/cld/base/vlog_is_on.h

Index: third_party/cld/base/vlog_is_on.h
===================================================================
--- third_party/cld/base/vlog_is_on.h	(revision 0)
+++ third_party/cld/base/vlog_is_on.h	(revision 0)
@@ -0,0 +1,141 @@
+// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// 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).
+//   --silent_init  When true has the effect of increasing
+//                  the argument of VLOG_IS_ON by 1,
+//                  thus suppressing one more level of verbose logging.
+//
+// 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 "base/atomicops.h"
+#include "base/basictypes.h"
+#include "base/port.h"
+#include "third_party/cld/base/commandlineflags.h"
+#include "third_party/cld/base/log_severity.h"
+
+DECLARE_int32(v);  // in vlog_is_on.cc
+DECLARE_bool(silent_init);  // in google.cc
+
+#if defined(__GNUC__)
+// We pack an int16 verbosity level and an int16 epoch into an
+// Atomic32 at every VLOG_IS_ON() call site.  The level determines
+// whether the site should log, and the epoch determines whether the
+// site is stale and should be reinitialized.  A verbosity level of
+// kUseFlag (-1) indicates that the value of FLAGS_v should be used as
+// the verbosity level.  When the site is (re)initialized, a verbosity
+// level for the current source file is retrieved from an internal
+// list.  This list is mutated through calls to SetVLOGLevel() and
+// mutations to the --vmodule flag.  New log sites are initialized
+// with a stale epoch and a verbosity level of kUseFlag.
+//
+// TODO(llansing): Investigate using GCC's __builtin_constant_p() to
+// generate less code at call sites where verbositylevel is known to
+// be a compile-time constant.
+#define VLOG_IS_ON(verboselevel)                                               \
+  ({ static Atomic32 site__ = ::base::internal::kDefaultSite;                  \
+     ::base::internal::VLogEnabled(&site__, (verboselevel), __FILE__); })
+#else
+// GNU extensions not available, so we do not support --vmodule.
+// Dynamic value of FLAGS_v always controls the logging level.
+//
+// TODO(llansing): Investigate supporting --vmodule on other platforms.
+#define VLOG_IS_ON(verboselevel)                                               \
+  (FLAGS_v >= (verboselevel) + FLAGS_silent_init)
+#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 InitGoogle,
+//       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.)
+int SetVLOGLevel(const char* module_pattern, int log_level);
+
+// Private implementation details.  No user-serviceable parts inside.
+namespace base {
+namespace internal {
+
+// Each log site determines whether its log level is up to date by
+// comparing its epoch to this global epoch.  Whenever the program's
+// vmodule configuration changes (ex: SetVLOGLevel is called), the
+// global epoch is advanced, invalidating all site epochs.
+extern Atomic32 vlog_epoch;
+
+// A log level of kUseFlag means "read the logging level from FLAGS_v."
+const int kUseFlag = -1;
+
+// Log sites use FLAGS_v by default, and have an initial epoch of 0.
+const Atomic32 kDefaultSite = kUseFlag << 16;
+
+// The global epoch is the least significant half of an Atomic32, and
+// may only be accessed through atomic operations.
+inline Atomic32 GlobalEpoch() { return Acquire_Load(&vlog_epoch) & 0x0000FFFF; }
+
+// The least significant half of a site is the epoch.
+inline int SiteEpoch(Atomic32 site) { return site & 0x0000FFFF; }
+
+// The most significant half of a site is the logging level.
+inline int SiteLevel(Atomic32 site) { return site >> 16; }
+
+// Construct a logging site from a logging level and epoch.
+inline Atomic32 Site(int level, int epoch) {
+  return ((level & 0x0000FFFF) << 16) | (epoch & 0x0000FFFF);
+}
+
+// Attempt to initialize or reinitialize a VLOG site.  Returns the
+// level of the log site, regardless of whether the attempt succeeds
+// or fails.
+//   site: The address of the log site's state.
+//   fname: The filename of the current source file.
+int InitVLOG(Atomic32* site, const char* fname);
+
+// Determine whether verbose logging should occur at a given log site.
+//
+// TODO(llansing): Find a way to eliminate FLAGS_silent_init from this
+// function while preserving the silent initialization behavior.  The
+// common-case code path shouldn't pay for silent initialization.
+inline bool VLogEnabled(Atomic32* site, int32 level, const char* const file) {
+  const Atomic32 site_copy = Acquire_Load(site);
+  const int32 site_level =
+      PREDICT_TRUE(SiteEpoch(site_copy) == GlobalEpoch()) ?
+      SiteLevel(site_copy) : InitVLOG(site, file);
+  return (site_level == kUseFlag ? FLAGS_v : site_level) >=
+      (level + FLAGS_silent_init);
+}
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_VLOG_IS_ON_H_
Property changes on: third_party\cld\base\vlog_is_on.h
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Added: svn:eol-style
   + LF