Add an experimental way to whitelist calls

A call list is a way of grouping a number of packages and function calls
into a blacklist or whitelist. Could be useful to exclude certain
functions from results or looking for a specific set of functions.

core/call_list.go

@@ -0,0 +1,65 @@
+//
+// 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 core
+
+type set map[string]bool
+
+type calls struct {
+	matchAny  bool
+	functions set
+}
+
+/// CallList is used to check for usage of specific packages
+/// and functions.
+type CallList map[string]*calls
+
+/// NewCallList creates a new empty CallList
+func NewCallList() CallList {
+	return make(CallList)
+}
+
+/// NewCallListFor createse a call list using the package path
+func NewCallListFor(pkg string, funcs ...string) CallList {
+	c := NewCallList()
+	if len(funcs) == 0 {
+		c[pkg] = &calls{true, make(set)}
+	} else {
+		for _, fn := range funcs {
+			c.Add(pkg, fn)
+		}
+	}
+	return c
+}
+
+/// Add a new package and function to the call list
+func (c CallList) Add(pkg, fn string) {
+	if cl, ok := c[pkg]; ok {
+		if cl.matchAny {
+			cl.matchAny = false
+		}
+	} else {
+		c[pkg] = &calls{false, make(set)}
+	}
+	c[pkg].functions[fn] = true
+}
+
+/// Contains returns true if the package and function are
+/// members of this call list.
+func (c CallList) Contains(pkg, fn string) bool {
+	if funcs, ok := c[pkg]; ok {
+		_, ok = funcs.functions[fn]
+		return ok || funcs.matchAny
+	}
+	return false
+}