From 9095167039592088c10c251b99c4d3ade6a59a8e Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Tue, 7 May 2019 19:54:54 +0200
Subject: [PATCH] thread/*Cond: add wait_for() overload with predicate

---
 src/lib/nfs/Blocking.hxx   |  6 +-----
 src/thread/PosixCond.hxx   | 13 +++++++++++++
 src/thread/WindowsCond.hxx | 13 +++++++++++++
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/lib/nfs/Blocking.hxx b/src/lib/nfs/Blocking.hxx
index 5d5d707e3..981d1434c 100644
--- a/src/lib/nfs/Blocking.hxx
+++ b/src/lib/nfs/Blocking.hxx
@@ -60,11 +60,7 @@ public:
 private:
 	bool LockWaitFinished() noexcept {
 		std::unique_lock<Mutex> lock(mutex);
-		while (!finished)
-			if (!cond.wait_for(lock, timeout))
-				return false;
-
-		return true;
+		return cond.wait_for(lock, timeout, [this]{ return finished; });
 	}
 
 	/**
diff --git a/src/thread/PosixCond.hxx b/src/thread/PosixCond.hxx
index d16aa2898..8ab2a3f03 100644
--- a/src/thread/PosixCond.hxx
+++ b/src/thread/PosixCond.hxx
@@ -105,6 +105,19 @@ public:
 
 		return wait_for(lock, timeout_us);
 	}
+
+	template<typename M, typename P>
+	bool wait_for(std::unique_lock<M> &lock,
+		      std::chrono::steady_clock::duration timeout,
+		      P &&predicate) noexcept {
+		while (!predicate()) {
+			// TODO: without wait_until(), this multiplies the timeout
+			if (!wait_for(lock, timeout))
+				return predicate();
+		}
+
+		return true;
+	}
 };
 
 #endif
diff --git a/src/thread/WindowsCond.hxx b/src/thread/WindowsCond.hxx
index 162a9ac7a..40389512b 100644
--- a/src/thread/WindowsCond.hxx
+++ b/src/thread/WindowsCond.hxx
@@ -70,6 +70,19 @@ public:
 						&lock.mutex()->critical_section,
 						timeout_ms);
 	}
+
+	template<typename M, typename P>
+	bool wait_for(std::unique_lock<M> &lock,
+		      std::chrono::steady_clock::duration timeout,
+		      P &&predicate) noexcept {
+		while (!predicate()) {
+			// TODO: without wait_until(), this multiplies the timeout
+			if (!wait_for(lock, timeout))
+				return predicate();
+		}
+
+		return true;
+	}
 };
 
 #endif