open-consul/vendor/github.com/mitchellh/pointerstructure/get.go

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2020-05-12 01:59:29 +00:00
package pointerstructure
import (
"fmt"
"reflect"
)
// Get reads the value out of the total value v.
func (p *Pointer) Get(v interface{}) (interface{}, error) {
// fast-path the empty address case to avoid reflect.ValueOf below
if len(p.Parts) == 0 {
return v, nil
}
// Map for lookup of getter to call for type
funcMap := map[reflect.Kind]func(string, reflect.Value) (reflect.Value, error){
reflect.Array: p.getSlice,
reflect.Map: p.getMap,
reflect.Slice: p.getSlice,
reflect.Struct: p.getStruct,
}
currentVal := reflect.ValueOf(v)
for i, part := range p.Parts {
for currentVal.Kind() == reflect.Interface {
currentVal = currentVal.Elem()
}
for currentVal.Kind() == reflect.Ptr {
currentVal = reflect.Indirect(currentVal)
}
f, ok := funcMap[currentVal.Kind()]
if !ok {
return nil, fmt.Errorf(
"%s: at part %d, invalid value kind: %s", p, i, currentVal.Kind())
}
var err error
currentVal, err = f(part, currentVal)
if err != nil {
return nil, fmt.Errorf("%s at part %d: %s", p, i, err)
}
}
return currentVal.Interface(), nil
}
func (p *Pointer) getMap(part string, m reflect.Value) (reflect.Value, error) {
var zeroValue reflect.Value
// Coerce the string part to the correct key type
key, err := coerce(reflect.ValueOf(part), m.Type().Key())
if err != nil {
return zeroValue, err
}
// Verify that the key exists
found := false
for _, k := range m.MapKeys() {
if k.Interface() == key.Interface() {
found = true
break
}
}
if !found {
return zeroValue, fmt.Errorf("couldn't find key %#v", key.Interface())
}
// Get the key
return m.MapIndex(key), nil
}
func (p *Pointer) getSlice(part string, v reflect.Value) (reflect.Value, error) {
var zeroValue reflect.Value
// Coerce the key to an int
idxVal, err := coerce(reflect.ValueOf(part), reflect.TypeOf(42))
if err != nil {
return zeroValue, err
}
idx := int(idxVal.Int())
// Verify we're within bounds
if idx < 0 || idx >= v.Len() {
return zeroValue, fmt.Errorf(
"index %d is out of range (length = %d)", idx, v.Len())
}
// Get the key
return v.Index(idx), nil
}
func (p *Pointer) getStruct(part string, m reflect.Value) (reflect.Value, error) {
return m.FieldByName(part), nil
}