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

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2020-05-12 01:59:29 +00:00
package pointerstructure
import (
"fmt"
"reflect"
)
// Delete deletes the value specified by the pointer p in structure s.
//
// When deleting a slice index, all other elements will be shifted to
// the left. This is specified in RFC6902 (JSON Patch) and not RFC6901 since
// RFC6901 doesn't specify operations on pointers. If you don't want to
// shift elements, you should use Set to set the slice index to the zero value.
//
// The structures s must have non-zero values set up to this pointer.
// For example, if deleting "/bob/0/name", then "/bob/0" must be set already.
//
// The returned value is potentially a new value if this pointer represents
// the root document. Otherwise, the returned value will always be s.
func (p *Pointer) Delete(s interface{}) (interface{}, error) {
// if we represent the root doc, we've deleted everything
if len(p.Parts) == 0 {
return nil, nil
}
// Save the original since this is going to be our return value
originalS := s
// Get the parent value
var err error
s, err = p.Parent().Get(s)
if err != nil {
return nil, err
}
// Map for lookup of getter to call for type
funcMap := map[reflect.Kind]deleteFunc{
reflect.Array: p.deleteSlice,
reflect.Map: p.deleteMap,
reflect.Slice: p.deleteSlice,
}
val := reflect.ValueOf(s)
for val.Kind() == reflect.Interface {
val = val.Elem()
}
for val.Kind() == reflect.Ptr {
val = reflect.Indirect(val)
}
f, ok := funcMap[val.Kind()]
if !ok {
return nil, fmt.Errorf("delete %s: invalid value kind: %s", p, val.Kind())
}
result, err := f(originalS, val)
if err != nil {
return nil, fmt.Errorf("delete %s: %s", p, err)
}
return result, nil
}
type deleteFunc func(interface{}, reflect.Value) (interface{}, error)
func (p *Pointer) deleteMap(root interface{}, m reflect.Value) (interface{}, error) {
part := p.Parts[len(p.Parts)-1]
key, err := coerce(reflect.ValueOf(part), m.Type().Key())
if err != nil {
return root, err
}
// Delete the key
var elem reflect.Value
m.SetMapIndex(key, elem)
return root, nil
}
func (p *Pointer) deleteSlice(root interface{}, s reflect.Value) (interface{}, error) {
// Coerce the key to an int
part := p.Parts[len(p.Parts)-1]
idxVal, err := coerce(reflect.ValueOf(part), reflect.TypeOf(42))
if err != nil {
return root, err
}
idx := int(idxVal.Int())
// Verify we're within bounds
if idx < 0 || idx >= s.Len() {
return root, fmt.Errorf(
"index %d is out of range (length = %d)", idx, s.Len())
}
// Mimicing the following with reflection to do this:
//
// copy(a[i:], a[i+1:])
// a[len(a)-1] = nil // or the zero value of T
// a = a[:len(a)-1]
// copy(a[i:], a[i+1:])
reflect.Copy(s.Slice(idx, s.Len()), s.Slice(idx+1, s.Len()))
// a[len(a)-1] = nil // or the zero value of T
s.Index(s.Len() - 1).Set(reflect.Zero(s.Type().Elem()))
// a = a[:len(a)-1]
s = s.Slice(0, s.Len()-1)
// set the slice back on the parent
return p.Parent().Set(root, s.Interface())
}