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// Copyright 2017, The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package function provides functionality for identifying function types.
package function
import (
"reflect"
"regexp"
"runtime"
"strings"
)
type funcType int
const (
_ funcType = iota
tbFunc // func(T) bool
ttbFunc // func(T, T) bool
trbFunc // func(T, R) bool
tibFunc // func(T, I) bool
trFunc // func(T) R
Equal = ttbFunc // func(T, T) bool
EqualAssignable = tibFunc // func(T, I) bool; encapsulates func(T, T) bool
Transformer = trFunc // func(T) R
ValueFilter = ttbFunc // func(T, T) bool
Less = ttbFunc // func(T, T) bool
ValuePredicate = tbFunc // func(T) bool
KeyValuePredicate = trbFunc // func(T, R) bool
)
var boolType = reflect.TypeOf(true)
// IsType reports whether the reflect.Type is of the specified function type.
func IsType(t reflect.Type, ft funcType) bool {
if t == nil || t.Kind() != reflect.Func || t.IsVariadic() {
return false
}
ni, no := t.NumIn(), t.NumOut()
switch ft {
case tbFunc: // func(T) bool
if ni == 1 && no == 1 && t.Out(0) == boolType {
return true
}
case ttbFunc: // func(T, T) bool
if ni == 2 && no == 1 && t.In(0) == t.In(1) && t.Out(0) == boolType {
return true
}
case trbFunc: // func(T, R) bool
if ni == 2 && no == 1 && t.Out(0) == boolType {
return true
}
case tibFunc: // func(T, I) bool
if ni == 2 && no == 1 && t.In(0).AssignableTo(t.In(1)) && t.Out(0) == boolType {
return true
}
case trFunc: // func(T) R
if ni == 1 && no == 1 {
return true
}
}
return false
}
var lastIdentRx = regexp.MustCompile(`[_\p{L}][_\p{L}\p{N}]*$`)
// NameOf returns the name of the function value.
func NameOf(v reflect.Value) string {
fnc := runtime.FuncForPC(v.Pointer())
if fnc == nil {
return "<unknown>"
}
fullName := fnc.Name() // e.g., "long/path/name/mypkg.(*MyType).(long/path/name/mypkg.myMethod)-fm"
// Method closures have a "-fm" suffix.
fullName = strings.TrimSuffix(fullName, "-fm")
var name string
for len(fullName) > 0 {
inParen := strings.HasSuffix(fullName, ")")
fullName = strings.TrimSuffix(fullName, ")")
s := lastIdentRx.FindString(fullName)
if s == "" {
break
}
name = s + "." + name
fullName = strings.TrimSuffix(fullName, s)
if i := strings.LastIndexByte(fullName, '('); inParen && i >= 0 {
fullName = fullName[:i]
}
fullName = strings.TrimSuffix(fullName, ".")
}
return strings.TrimSuffix(name, ".")
}
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