attributes: add Equal method; resolver: add AddressMap and State.BalancerAttributes (#4855)

resolver/map.go

@@ -0,0 +1,103 @@
+/*
+ *
+ * Copyright 2021 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package resolver
+
+type addressMapEntry struct {
+	addr  Address
+	value interface{}
+}
+
+// AddressMap is a map of addresses to arbitrary values taking into account
+// Attributes.  BalancerAttributes are ignored, as are Metadata and Type.
+// Multiple accesses may not be performed concurrently.  Must be created via
+// NewAddressMap; do not construct directly.
+type AddressMap struct {
+	m map[string]addressMapEntryList
+}
+
+type addressMapEntryList []*addressMapEntry
+
+// NewAddressMap creates a new AddressMap.
+func NewAddressMap() *AddressMap {
+	return &AddressMap{m: make(map[string]addressMapEntryList)}
+}
+
+// find returns the index of addr in the addressMapEntry slice, or -1 if not
+// present.
+func (l addressMapEntryList) find(addr Address) int {
+	if len(l) == 0 {
+		return -1
+	}
+	for i, entry := range l {
+		if entry.addr.ServerName == addr.ServerName &&
+			entry.addr.Attributes.Equal(addr.Attributes) {
+			return i
+		}
+	}
+	return -1
+}
+
+// Get returns the value for the address in the map, if present.
+func (a *AddressMap) Get(addr Address) (value interface{}, ok bool) {
+	entryList := a.m[addr.Addr]
+	if entry := entryList.find(addr); entry != -1 {
+		return entryList[entry].value, true
+	}
+	return nil, false
+}
+
+// Set updates or adds the value to the address in the map.
+func (a *AddressMap) Set(addr Address, value interface{}) {
+	entryList := a.m[addr.Addr]
+	if entry := entryList.find(addr); entry != -1 {
+		a.m[addr.Addr][entry].value = value
+		return
+	}
+	a.m[addr.Addr] = append(a.m[addr.Addr], &addressMapEntry{addr: addr, value: value})
+}
+
+// Delete removes addr from the map.
+func (a *AddressMap) Delete(addr Address) {
+	entryList := a.m[addr.Addr]
+	entry := entryList.find(addr)
+	if entry == -1 {
+		return
+	}
+	if len(entryList) == 1 {
+		entryList = nil
+	} else {
+		copy(entryList[entry:], entryList[entry+1:])
+		entryList = entryList[:len(entryList)-1]
+	}
+	a.m[addr.Addr] = entryList
+}
+
+// Len returns the number of entries in the map.
+func (a *AddressMap) Len() int {
+	return len(a.m)
+}
+
+// Range invokes f for each entry in the map.
+func (a *AddressMap) Range(f func(addr Address, value interface{})) {
+	for _, entryList := range a.m {
+		for _, entry := range entryList {
+			f(entry.addr, entry.value)
+		}
+	}
+}