add base::WaitForPropertyCreation
- unlike base::WaitForProperty, which waits for specific value to
be set, this one only waits until the property is created.
bug: 35178781
Test: added unit test
Change-Id: Idbf98c2152fe768357302f6b69310c55305f5d54
diff --git a/base/properties.cpp b/base/properties.cpp
index acd6c0f..32c0128 100644
--- a/base/properties.cpp
+++ b/base/properties.cpp
@@ -108,8 +108,10 @@
ts.tv_nsec = ns.count();
}
+using AbsTime = std::chrono::time_point<std::chrono::steady_clock>;
+
static void UpdateTimeSpec(timespec& ts,
- const std::chrono::time_point<std::chrono::steady_clock>& timeout) {
+ const AbsTime& timeout) {
auto now = std::chrono::steady_clock::now();
auto remaining_timeout = std::chrono::duration_cast<std::chrono::nanoseconds>(timeout - now);
if (remaining_timeout < 0ns) {
@@ -119,13 +121,16 @@
}
}
-bool WaitForProperty(const std::string& key,
- const std::string& expected_value,
- std::chrono::milliseconds relative_timeout) {
+// Waits for the system property `key` to be created.
+// Times out after `relative_timeout`.
+// Sets absolute_timeout which represents absolute time for the timeout.
+// Returns nullptr on timeout.
+static const prop_info* WaitForPropertyCreation(const std::string& key,
+ const std::chrono::milliseconds& relative_timeout,
+ AbsTime& absolute_timeout) {
// TODO: boot_clock?
auto now = std::chrono::steady_clock::now();
- std::chrono::time_point<std::chrono::steady_clock> absolute_timeout = now + relative_timeout;
- timespec ts;
+ absolute_timeout = now + relative_timeout;
// Find the property's prop_info*.
const prop_info* pi;
@@ -133,14 +138,25 @@
while ((pi = __system_property_find(key.c_str())) == nullptr) {
// The property doesn't even exist yet.
// Wait for a global change and then look again.
+ timespec ts;
UpdateTimeSpec(ts, absolute_timeout);
- if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return false;
+ if (!__system_property_wait(nullptr, global_serial, &global_serial, &ts)) return nullptr;
}
+ return pi;
+}
+
+bool WaitForProperty(const std::string& key,
+ const std::string& expected_value,
+ std::chrono::milliseconds relative_timeout) {
+ AbsTime absolute_timeout;
+ const prop_info* pi = WaitForPropertyCreation(key, relative_timeout, absolute_timeout);
+ if (pi == nullptr) return false;
WaitForPropertyData data;
data.expected_value = &expected_value;
data.done = false;
while (true) {
+ timespec ts;
// Check whether the property has the value we're looking for?
__system_property_read_callback(pi, WaitForPropertyCallback, &data);
if (data.done) return true;
@@ -152,5 +168,11 @@
}
}
+bool WaitForPropertyCreation(const std::string& key,
+ std::chrono::milliseconds relative_timeout) {
+ AbsTime absolute_timeout;
+ return (WaitForPropertyCreation(key, relative_timeout, absolute_timeout) != nullptr);
+}
+
} // namespace base
} // namespace android