Add lockfree::set_read_offset

danngreen · danngreen · commit 1fa9eae893c3 · 2025-07-08T22:59:10.000-07:00
diff --git a/util/lockfree_fifo_spsc.hh b/util/lockfree_fifo_spsc.hh
@@ -115,6 +115,13 @@ public:
 		tail_.store(pos, std::memory_order_release);
 	}
 
+	// Sets read head `offset` samples before write head, if possible
+	void set_read_offset(size_t offset) {
+		auto head = head_.load(std::memory_order_acquire);
+		if (offset <= head)
+			tail_.store(head - offset, std::memory_order_release);
+	}
+
 	void set_write_pos(size_t pos) {
 		head_.store(pos, std::memory_order_release);
 	}

Original file line number	Diff line number	Diff line change
`@@ -115,6 +115,13 @@ public:`
`115`	`115`	`tail_.store(pos, std::memory_order_release);`
`116`	`116`	`}`
`117`	`117`
	`118`	+ // Sets read head `offset` samples before write head, if possible
	`119`	`+ void set_read_offset(size_t offset) {`
	`120`	`+ auto head = head_.load(std::memory_order_acquire);`
	`121`	`+ if (offset <= head)`
	`122`	`+ tail_.store(head - offset, std::memory_order_release);`
	`123`	`+ }`
	`124`	`+`
`118`	`125`	`void set_write_pos(size_t pos) {`
`119`	`126`	`head_.store(pos, std::memory_order_release);`
`120`	`127`	`}`