51 lines
1.8 KiB
C++
51 lines
1.8 KiB
C++
// Copyright 2018 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.
|
|
|
|
#include "base/metrics/ukm_source_id.h"
|
|
|
|
#include "base/atomic_sequence_num.h"
|
|
#include "base/logging.h"
|
|
#include "base/rand_util.h"
|
|
|
|
namespace base {
|
|
|
|
namespace {
|
|
|
|
const int64_t kLowBitsMask = (INT64_C(1) << 32) - 1;
|
|
const int64_t kNumTypeBits = static_cast<int64_t>(UkmSourceId::Type::kMaxValue);
|
|
const int64_t kTypeMask = (INT64_C(1) << kNumTypeBits) - 1;
|
|
|
|
} // namespace
|
|
|
|
// static
|
|
UkmSourceId UkmSourceId::New() {
|
|
// Generate some bits which are unique to this process, so we can generate
|
|
// IDs independently in different processes. IDs generated by this method may
|
|
// collide, but it should be sufficiently rare enough to not impact data
|
|
// quality.
|
|
const static int64_t process_id_bits =
|
|
static_cast<int64_t>(RandUint64()) & ~kLowBitsMask;
|
|
// Generate some bits which are unique within the process, using a counter.
|
|
static AtomicSequenceNumber seq;
|
|
UkmSourceId local_id = FromOtherId(seq.GetNext() + 1, UkmSourceId::Type::UKM);
|
|
// Combine the local and process bits to generate a unique ID.
|
|
return UkmSourceId((local_id.value_ & kLowBitsMask) | process_id_bits);
|
|
}
|
|
|
|
// static
|
|
UkmSourceId UkmSourceId::FromOtherId(int64_t other_id, UkmSourceId::Type type) {
|
|
const int64_t type_bits = static_cast<int64_t>(type);
|
|
DCHECK_EQ(type_bits, type_bits & kTypeMask);
|
|
// Stores the the type ID in the low bits of the source id, and shift the rest
|
|
// of the ID to make room. This could cause the original ID to overflow, but
|
|
// that should be rare enough that it won't matter for UKM's purposes.
|
|
return UkmSourceId((other_id << kNumTypeBits) | type_bits);
|
|
}
|
|
|
|
UkmSourceId::Type UkmSourceId::GetType() const {
|
|
return static_cast<UkmSourceId::Type>(value_ & kTypeMask);
|
|
}
|
|
|
|
} // namespace base
|