bluetooth: Implement hardware filtering on macOS

device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm

Index: device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
diff --git a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
index eeb1ace3beb1996e17dc2abb39103a7ffc787899..ec3afbccb834da73087094055ba33479ef0673d8 100644
--- a/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
+++ b/device/bluetooth/bluetooth_low_energy_discovery_manager_mac.mm
@@ -23,11 +23,25 @@ bool BluetoothLowEnergyDiscoveryManagerMac::IsDiscovering() const {
 }
 
 void BluetoothLowEnergyDiscoveryManagerMac::StartDiscovery(
-    BluetoothDevice::UUIDList services_uuids) {
-  discovering_ = true;
-  pending_ = true;
-  services_uuids_ = services_uuids;
-  TryStartDiscovery();
+    std::set<BluetoothUUID> services_uuids) {

[Jeffrey Yasskin, 2016/08/23 21:37:04]

Since this doesn't modify the input argument, it should probably take a const
std::set<BluetoothUUID>& instead of by-value. Also, a vector<> or
unordered_set<> would be more efficient: do they make sense as the argument
type?

+  // Update Scan UUIDs.
+  bool should_update_scan = false;
+  for (const auto& uuid : services_uuids) {
+    size_t& count = scan_uuids_to_filter_count_[uuid];
+    count++;
+
+    if (count == 1) {
+      should_update_scan = true;
+    }
+  }
+
+  // Try to scan only if there are new services or we haven't
+  // started discovery yet.
+  if (should_update_scan || !discovering_) {

[Jeffrey Yasskin, 2016/08/23 21:37:04]

If we're not discovering, but there are no services to scan for, shouldn't we
keep not discovering?

+    pending_ = true;
+    discovering_ = true;
+    TryStartDiscovery();
+  }
 }
 
 void BluetoothLowEnergyDiscoveryManagerMac::TryStartDiscovery() {
@@ -53,11 +67,13 @@ void BluetoothLowEnergyDiscoveryManagerMac::TryStartDiscovery() {
 
   // Converts the services UUIDs to a CoreBluetooth data structure.
   NSMutableArray* services = nil;
-  if (!services_uuids_.empty()) {
+  if (!scan_uuids_to_filter_count_.empty()) {
     services = [NSMutableArray array];
-    for (auto& service_uuid : services_uuids_) {
-      NSString* uuidString =
-          base::SysUTF8ToNSString(service_uuid.canonical_value().c_str());
+    VLOG(1) << "Scanning for UUIDs: ";
+    for (const auto& uuid_to_count : scan_uuids_to_filter_count_) {
+      const std::string& uuid_str = uuid_to_count.first.canonical_value();
+      VLOG(1) << uuid_str;
+      NSString* uuidString = base::SysUTF8ToNSString(uuid_str.c_str());
       CBUUID* uuid = [CBUUID UUIDWithString:uuidString];
       [services addObject:uuid];
     }
@@ -76,8 +92,28 @@ void BluetoothLowEnergyDiscoveryManagerMac::TryStartDiscovery() {
   pending_ = false;
 }
 
+void BluetoothLowEnergyDiscoveryManagerMac::RemoveDiscoveryUUIDs(
+    std::set<BluetoothUUID> uuids_to_remove) {
+  bool did_remove_service = false;
+  for (const auto& uuid_to_remove : uuids_to_remove) {
+    auto it = scan_uuids_to_filter_count_.find(uuid_to_remove);
+    DCHECK(it != scan_uuids_to_filter_count_.end());
+    DCHECK_LT(0u, it->second);
+    it->second--;
+    if (it->second == 0) {
+      scan_uuids_to_filter_count_.erase(it);
+      did_remove_service = true;
+    }
+  }
+  if (did_remove_service) {
+    pending_ = true;
+    TryStartDiscovery();

[Jeffrey Yasskin, 2016/08/23 21:37:04]

Shouldn't RemoveDiscoveryUUIDs stop discovery when no UUIDs are left?

+  }
+}
+
 void BluetoothLowEnergyDiscoveryManagerMac::StopDiscovery() {
   VLOG(1) << "StopDiscovery";
+  scan_uuids_to_filter_count_.clear();
   if (discovering_ && !pending_) {
     [central_manager_ stopScan];
   }