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+// Copyright 2022 The Abseil 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
+//
+// https://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.
+//
+// -----------------------------------------------------------------------------
+// File: log/absl_vlog_is_on.h
+// -----------------------------------------------------------------------------
+//
+// This header defines the `ABSL_VLOG_IS_ON()` macro that controls the
+// variable-verbosity conditional logging.
+//
+// It's used by `VLOG` in log.h, or it can also be used directly like this:
+//
+// if (ABSL_VLOG_IS_ON(2)) {
+// foo_server.RecomputeStatisticsExpensive();
+// LOG(INFO) << foo_server.LastStatisticsAsString();
+// }
+//
+// Each source file has an effective verbosity level that's a non-negative
+// integer computed from the `--vmodule` and `--v` flags.
+// `ABSL_VLOG_IS_ON(n)` is true, and `VLOG(n)` logs, if that effective verbosity
+// level is greater than or equal to `n`.
+//
+// `--vmodule` takes a comma-delimited list of key=value pairs. Each key is a
+// pattern matched against filenames, and the values give the effective severity
+// level applied to matching files. '?' and '*' characters in patterns are
+// interpreted as single-character and zero-or-more-character wildcards.
+// Patterns including a slash character are matched against full pathnames,
+// while those without are matched against basenames only. One suffix (i.e. the
+// last . and everything after it) is stripped from each filename prior to
+// matching, as is the special suffix "-inl".
+//
+// Files are matched against globs in `--vmodule` in order, and the first match
+// determines the verbosity level.
+//
+// Files which do not match any pattern in `--vmodule` use the value of `--v` as
+// their effective verbosity level. The default is 0.
+//
+// SetVLOGLevel helper function is provided to do limited dynamic control over
+// V-logging by appending to `--vmodule`. Because these go at the beginning of
+// the list, they take priority over any globs previously added.
+//
+// Resetting --vmodule will override all previous modifications to `--vmodule`,
+// including via SetVLOGLevel.
+
+#ifndef ABSL_LOG_ABSL_VLOG_IS_ON_H_
+#define ABSL_LOG_ABSL_VLOG_IS_ON_H_
+
+#include "absl/base/attributes.h"
+#include "absl/base/config.h"
+#include "absl/log/internal/vlog_config.h" // IWYU pragma: export
+#include "absl/strings/string_view.h"
+
+// IWYU pragma: private, include "absl/log/log.h"
+
+// This is expanded at the callsite to allow the compiler to optimize
+// always-false cases out of the build.
+// An ABSL_MAX_VLOG_VERBOSITY of 2 means that VLOG(3) and above should never
+// log.
+#ifdef ABSL_MAX_VLOG_VERBOSITY
+#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x) \
+ ((x) <= ABSL_MAX_VLOG_VERBOSITY)&&
+#else
+#define ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(x)
+#endif
+
+// Each ABSL_VLOG_IS_ON call site gets its own VLogSite that registers with the
+// global linked list of sites to asynchronously update its verbosity level on
+// changes to --v or --vmodule. The verbosity can also be set by manually
+// calling SetVLOGLevel.
+//
+// ABSL_VLOG_IS_ON is not async signal safe, but it is guaranteed not to
+// allocate new memory.
+#define ABSL_VLOG_IS_ON(verbose_level) \
+ (ABSL_LOG_INTERNAL_MAX_LOG_VERBOSITY_CHECK(verbose_level)[]() \
+ ->::absl::log_internal::VLogSite * \
+ { \
+ ABSL_CONST_INIT static ::absl::log_internal::VLogSite site(__FILE__); \
+ return &site; \
+ }() \
+ ->IsEnabled(verbose_level))
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+// Sets the global `(ABSL_)VLOG(_IS_ON)` level to `log_level`. This level is
+// applied to any sites whose filename doesn't match any `module_pattern`.
+// Returns the prior value.
+inline int SetGlobalVLogLevel(int log_level) {
+ return absl::log_internal::UpdateGlobalVLogLevel(log_level);
+}
+
+// Sets `(ABSL_)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.
+// Calling this with `log_level` of kUseFlag will have all sites for that
+// pattern use the value of --v.
+inline int SetVLogLevel(absl::string_view module_pattern, int log_level) {
+ return absl::log_internal::PrependVModule(module_pattern, log_level);
+}
+
+ABSL_NAMESPACE_END
+} // namespace absl
+
+#endif // ABSL_LOG_ABSL_VLOG_IS_ON_H_