hugo/tpl/collections/reflect_helpers.go

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// Copyright 2017 The Hugo Authors. All rights reserved.
//
// 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 collections
import (
"fmt"
"reflect"
"time"
"github.com/pkg/errors"
)
var (
zero reflect.Value
errorType = reflect.TypeOf((*error)(nil)).Elem()
timeType = reflect.TypeOf((*time.Time)(nil)).Elem()
)
func numberToFloat(v reflect.Value) (float64, error) {
switch kind := v.Kind(); {
case isFloat(kind):
return v.Float(), nil
case isInt(kind):
return float64(v.Int()), nil
case isUint(kind):
return float64(v.Uint()), nil
case kind == reflect.Interface:
return numberToFloat(v.Elem())
default:
return 0, fmt.Errorf("Invalid kind %s in numberToFloat", kind)
}
}
// normalizes different numeric types to make them comparable.
func normalize(v reflect.Value) interface{} {
k := v.Kind()
switch {
case isNumber(k):
f, err := numberToFloat(v)
if err == nil {
return f
}
}
return v.Interface()
}
// collects identities from the slices in seqs into a set. Numeric values are normalized,
// pointers unwrapped.
func collectIdentities(seqs ...interface{}) (map[interface{}]bool, error) {
seen := make(map[interface{}]bool)
for _, seq := range seqs {
v := reflect.ValueOf(seq)
switch v.Kind() {
case reflect.Array, reflect.Slice:
for i := 0; i < v.Len(); i++ {
ev, _ := indirectInterface(v.Index(i))
if !ev.Type().Comparable() {
return nil, errors.New("elements must be comparable")
}
seen[normalize(ev)] = true
}
default:
return nil, fmt.Errorf("arguments must be slices or arrays")
}
}
return seen, nil
}
// We have some different numeric and string types that we try to behave like
// they were the same.
func convertValue(v reflect.Value, to reflect.Type) (reflect.Value, error) {
if v.Type().AssignableTo(to) {
return v, nil
}
switch kind := to.Kind(); {
case kind == reflect.String:
s, err := toString(v)
return reflect.ValueOf(s), err
case isNumber(kind):
return convertNumber(v, kind)
default:
return reflect.Value{}, errors.Errorf("%s is not assignable to %s", v.Type(), to)
}
}
// There are potential overflows in this function, but the downconversion of
// int64 etc. into int8 etc. is coming from the synthetic unit tests for Union etc.
// TODO(bep) We should consider normalizing the slices to int64 etc.
func convertNumber(v reflect.Value, to reflect.Kind) (reflect.Value, error) {
var n reflect.Value
if isFloat(to) {
f, err := toFloat(v)
if err != nil {
return n, err
}
switch to {
case reflect.Float32:
n = reflect.ValueOf(float32(f))
default:
n = reflect.ValueOf(float64(f))
}
} else if isInt(to) {
i, err := toInt(v)
if err != nil {
return n, err
}
switch to {
case reflect.Int:
n = reflect.ValueOf(int(i))
case reflect.Int8:
n = reflect.ValueOf(int8(i))
case reflect.Int16:
n = reflect.ValueOf(int16(i))
case reflect.Int32:
n = reflect.ValueOf(int32(i))
case reflect.Int64:
n = reflect.ValueOf(int64(i))
}
} else if isUint(to) {
i, err := toUint(v)
if err != nil {
return n, err
}
switch to {
case reflect.Uint:
n = reflect.ValueOf(uint(i))
case reflect.Uint8:
n = reflect.ValueOf(uint8(i))
case reflect.Uint16:
n = reflect.ValueOf(uint16(i))
case reflect.Uint32:
n = reflect.ValueOf(uint32(i))
case reflect.Uint64:
n = reflect.ValueOf(uint64(i))
}
}
if !n.IsValid() {
return n, errors.New("invalid values")
}
return n, nil
}
func newSliceElement(items interface{}) interface{} {
tp := reflect.TypeOf(items)
if tp == nil {
return nil
}
switch tp.Kind() {
case reflect.Array, reflect.Slice:
tp = tp.Elem()
if tp.Kind() == reflect.Ptr {
tp = tp.Elem()
}
return reflect.New(tp).Interface()
}
return nil
}
func isNumber(kind reflect.Kind) bool {
return isInt(kind) || isUint(kind) || isFloat(kind)
}
func isInt(kind reflect.Kind) bool {
switch kind {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return true
default:
return false
}
}
func isUint(kind reflect.Kind) bool {
switch kind {
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return true
default:
return false
}
}
func isFloat(kind reflect.Kind) bool {
switch kind {
case reflect.Float32, reflect.Float64:
return true
default:
return false
}
}