updates go-mutexes to no longer rely on unsafe linkname (#3027)

vendor/codeberg.org/gruf/go-mutexes/hash_map.go

@@ -0,0 +1,56 @@
+package mutexes
+
+type hashmap struct {
+	m map[string]*rwmutex
+	n int
+}
+
+func (m *hashmap) init(cap int) {
+	m.m = make(map[string]*rwmutex, cap)
+	m.n = cap
+}
+
+func (m *hashmap) Get(key string) *rwmutex { return m.m[key] }
+
+func (m *hashmap) Put(key string, mu *rwmutex) {
+	m.m[key] = mu
+	if n := len(m.m); n > m.n {
+		m.n = n
+	}
+}
+
+func (m *hashmap) Delete(key string) {
+	delete(m.m, key)
+}
+
+func (m *hashmap) Compact() {
+	// Noop when hashmap size
+	// is too small to matter.
+	if m.n < 2048 {
+		return
+	}
+
+	// Difference between maximum map
+	// size and the current map size.
+	diff := m.n - len(m.m)
+
+	// Maximum load factor before
+	// runtime allocates new hmap:
+	// maxLoad = 13 / 16
+	//
+	// So we apply the inverse/2, once
+	// $maxLoad/2 % of hmap is empty we
+	// compact the map to drop buckets.
+	if 2*16*diff > m.n*13 {
+
+		// Create new map only as big as required.
+		m2 := make(map[string]*rwmutex, len(m.m))
+		for k, v := range m.m {
+			m2[k] = v
+		}
+
+		// Set new.
+		m.m = m2
+		m.n = len(m2)
+	}
+}