Add a method for converting ukm::SourceId from other ID types.

This gathers the code relating to SourceId into a new file, and adds
a conversion method from other ID types.  External ID types aren't
converted when recieving IDs from other processes.

Change-Id: I3c65406457666f9d099d654a75db7e13a53590d7
Reviewed-on: https://chromium-review.googlesource.com/596725
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Oystein Eftevaag <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491602}

components/ukm/BUILD.gn

@@ -49,12 +49,14 @@ static_library("ukm_interface") {
 
   public_deps = [
     "//base",
+    "//services/metrics/public/cpp:metrics_cpp",
     "//services/metrics/public/interfaces",
   ]
 
   deps = [
     ":ukm",
     "//mojo/public/cpp/bindings",
+    "//services/metrics/public/cpp:metrics_cpp",
   ]
 }
 

components/ukm/ukm_interface.cc

@@ -8,24 +8,11 @@
 #include "base/memory/ptr_util.h"
 #include "mojo/public/cpp/bindings/strong_binding.h"
 #include "services/metrics/public/cpp/ukm_recorder.h"
+#include "services/metrics/public/cpp/ukm_source_id.h"
 #include "url/gurl.h"
 
 namespace ukm {
 
-namespace {
-
-// Map source ids from different instances into unique namespaces, so that
-// clients can create thier own IDs without having them collide.
-// This won't be necessary once we switch to using CoordinationUnitIDs.
-int64_t ConvertSourceId(int64_t source_id, int64_t instance_id) {
-  const int64_t low_bits = (INT64_C(1) << 32) - 1;
-  // Neither ID should get large enough to cause an issue, but explicitly
-  // discard down to 32 bits anyway.
-  return ((instance_id & low_bits) << 32) | (source_id & low_bits);
-}
-
-}  // namespace
-
 UkmInterface::UkmInterface(UkmRecorder* ukm_recorder, int64_t instance_id)
     : ukm_recorder_(ukm_recorder), instance_id_(instance_id) {}
 
@@ -42,13 +29,14 @@ void UkmInterface::Create(UkmRecorder* ukm_recorder,
 }
 
 void UkmInterface::AddEntry(mojom::UkmEntryPtr ukm_entry) {
-  ukm_entry->source_id = ConvertSourceId(instance_id_, ukm_entry->source_id);
+  ukm_entry->source_id =
+      ConvertSourceIdFromInstance(instance_id_, ukm_entry->source_id);
   ukm_recorder_->AddEntry(std::move(ukm_entry));
 }
 
 void UkmInterface::UpdateSourceURL(int64_t source_id, const std::string& url) {
-  ukm_recorder_->UpdateSourceURL(ConvertSourceId(instance_id_, source_id),
-                                 GURL(url));
+  ukm_recorder_->UpdateSourceURL(
+      ConvertSourceIdFromInstance(instance_id_, source_id), GURL(url));
 }
 
 }  // namespace ukm

components/ukm/ukm_source.h

@@ -5,19 +5,17 @@
 #ifndef COMPONENTS_UKM_UKM_SOURCE_H_
 #define COMPONENTS_UKM_UKM_SOURCE_H_
 
-#include <stddef.h>
 #include <map>
 
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "services/metrics/public/cpp/ukm_source_id.h"
 #include "url/gurl.h"
 
 namespace ukm {
 
 class Source;
 
-typedef int64_t SourceId;
-
 // Contains UKM data for a single navigation entry.
 class UkmSource {
  public:

services/metrics/public/cpp/BUILD.gn

@@ -15,6 +15,8 @@ component("metrics_cpp") {
     "ukm_entry_builder_base.h",
     "ukm_recorder.cc",
     "ukm_recorder.h",
+    "ukm_source_id.cc",
+    "ukm_source_id.h",
   ]
 
   defines = [ "METRICS_IMPLEMENTATION" ]

services/metrics/public/cpp/ukm_entry_builder.h

@@ -9,12 +9,11 @@
 
 #include "base/macros.h"
 #include "services/metrics/public/cpp/metrics_export.h"
+#include "services/metrics/public/cpp/ukm_source_id.h"
 #include "services/metrics/public/interfaces/ukm_interface.mojom.h"
 
 namespace ukm {
 
-typedef int64_t SourceId;
-
 // The builder that builds UkmEntry and adds it to UkmRecorder.
 // The example usage is:
 //

services/metrics/public/cpp/ukm_recorder.cc

@@ -4,7 +4,6 @@
 
 #include "services/metrics/public/cpp/ukm_recorder.h"
 
-#include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/feature_list.h"
 #include "base/memory/ptr_util.h"
@@ -33,8 +32,7 @@ UkmRecorder* UkmRecorder::Get() {
 
 // static
 ukm::SourceId UkmRecorder::GetNewSourceID() {
-  static base::AtomicSequenceNumber seq;
-  return static_cast<ukm::SourceId>(seq.GetNext());
+  return AssignNewSourceId();
 }
 
 std::unique_ptr<UkmEntryBuilder> UkmRecorder::GetEntryBuilder(

services/metrics/public/cpp/ukm_recorder.h

@@ -5,8 +5,6 @@
 #ifndef SERVICES_METRICS_PUBLIC_CPP_UKM_RECORDER_H_
 #define SERVICES_METRICS_PUBLIC_CPP_UKM_RECORDER_H_
 
-#include <stddef.h>
-
 #include <memory>
 
 #include "base/callback.h"
@@ -15,6 +13,7 @@
 #include "base/threading/thread_checker.h"
 #include "services/metrics/public/cpp/metrics_export.h"
 #include "services/metrics/public/cpp/ukm_entry_builder.h"
+#include "services/metrics/public/cpp/ukm_source_id.h"
 #include "services/metrics/public/interfaces/ukm_interface.mojom.h"
 #include "url/gurl.h"
 
@@ -76,8 +75,6 @@ class UkmEntryBuilderBase;
 // This feature controls whether UkmService should be created.
 METRICS_EXPORT extern const base::Feature kUkmFeature;
 
-typedef int64_t SourceId;
-
 // Interface for recording UKM
 class METRICS_EXPORT UkmRecorder {
  public:

services/metrics/public/cpp/ukm_source_id.cc

+// Copyright 2017 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 "services/metrics/public/cpp/ukm_source_id.h"
+
+#include "base/atomic_sequence_num.h"
+#include "base/logging.h"
+
+namespace ukm {
+
+namespace {
+
+const int64_t kLowBitsMask = (INT64_C(1) << 32) - 1;
+const int64_t kNumTypeBits = 2;
+const int64_t kTypeMask = (INT64_C(1) << kNumTypeBits) - 1;
+
+}  // namespace
+
+SourceId AssignNewSourceId() {
+  static base::AtomicSequenceNumber seq;
+  return ConvertToSourceId(seq.GetNext() + 1, SourceIdType::UKM);
+}
+
+SourceId ConvertToSourceId(int64_t other_id, SourceIdType id_type) {
+  const int64_t type_bits = static_cast<int64_t>(id_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 (other_id << kNumTypeBits) | type_bits;
+}
+
+SourceId ConvertSourceIdFromInstance(int64_t instance_id, int64_t source_id) {
+  // Only convert source IDs from Create().
+  if ((kTypeMask & source_id) != static_cast<int64_t>(SourceIdType::UKM))
+    return source_id;
+
+  // Neither ID should get large enough to cause an issue, but explicitly
+  // discard down to 32 bits anyway.
+  return ((instance_id & kLowBitsMask) << 32) | (source_id & kLowBitsMask);
+}
+
+}  // namespace ukm

services/metrics/public/cpp/ukm_source_id.h

+// Copyright 2017 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.
+
+#ifndef SERVICES_METRICS_PUBLIC_CPP_UKM_SOURCE_ID_H_
+#define SERVICES_METRICS_PUBLIC_CPP_UKM_SOURCE_ID_H_
+
+#include <stdint.h>
+
+#include "services/metrics/public/cpp/metrics_export.h"
+
+namespace ukm {
+
+typedef int64_t SourceId;
+
+enum class SourceIdType : int64_t {
+  UKM = 0,
+  NAVIGATION_ID = 1,
+};
+
+// Get a new source ID, which is unique for the duration of a browser session.
+METRICS_EXPORT SourceId AssignNewSourceId();
+
+// Utility for converting other unique ids to source ids.
+METRICS_EXPORT SourceId ConvertToSourceId(int64_t other_id,
+                                          SourceIdType id_type);
+
+// Convert source ids from another process.
+METRICS_EXPORT SourceId ConvertSourceIdFromInstance(int64_t instance_id,
+                                                    int64_t source_id);
+
+}  // namespace ukm
+
+#endif  // SERVICES_METRICS_PUBLIC_CPP_UKM_SOURCE_ID_H_