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// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_WIN_SCOPED_PDH_QUERY_H_
#define BASE_WIN_SCOPED_PDH_QUERY_H_
#include "base/base_export.h"
#include "base/scoped_generic.h"
#include "base/win/pdh_shim.h"
namespace base::win {
namespace internal {
struct ScopedPdhQueryTraits {
static PDH_HQUERY InvalidValue() { return nullptr; }
static void Free(PDH_HQUERY query) { ::PdhCloseQuery(query); }
};
} // namespace internal
// ScopedPdhQuery is a wrapper around a PDH_HQUERY, the handle used by
// Performance Counters functions (see
// https://learn.microsoft.com/en-us/windows/win32/api/_perf/.) Prefer this to
// using PDH_HQUERY directly to make sure that handles are always closed when
// going out of scope.
//
// Example use:
//
// ScopedPdhQuery pdh_query = ScopedPdhQuery::Create();
// if (pdh_query.is_valid()) {
// ::PdhCollectQueryData(pdh_query.get(), ...);
// }
//
// To adopt an already-open handle:
//
// PDH_HQUERY pdh_handle;
// PDH_STATUS status = ::PdhOpenQuery(..., &pdh_handle);
// if (status == ERROR_SUCCESS) {
// ScopedPdhQuery pdh_query(pdh_handle);
// ::PdhCollectCollectQueryData(pdh_query.get(), ...);
// }
class BASE_EXPORT ScopedPdhQuery
: public ScopedGeneric<PDH_HQUERY, internal::ScopedPdhQueryTraits> {
public:
// Constructs a ScopedPdhQuery from a PDH_HQUERY, and takes ownership of
// `pdh_query` if it is not null.
explicit ScopedPdhQuery(PDH_HQUERY pdh_query = nullptr)
: ScopedGeneric(pdh_query) {}
// Returns a ScopedPdhQuery to the default real-time data source. Equivalent
// to ::PdhOpenQuery(nullptr, nullptr, &pdh_query).
static ScopedPdhQuery Create();
};
} // namespace base::win
#endif // BASE_WIN_SCOPED_PDH_QUERY_H_
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