source: code/trunk/vendor/github.com/golang/protobuf/proto/extensions.go@ 822

// Copyright 2010 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 proto

import (
        "errors"
        "fmt"
        "reflect"

        "google.golang.org/protobuf/encoding/protowire"
        "google.golang.org/protobuf/proto"
        "google.golang.org/protobuf/reflect/protoreflect"
        "google.golang.org/protobuf/reflect/protoregistry"
        "google.golang.org/protobuf/runtime/protoiface"
        "google.golang.org/protobuf/runtime/protoimpl"
)

type (
        // ExtensionDesc represents an extension descriptor and
        // is used to interact with an extension field in a message.
        //
        // Variables of this type are generated in code by protoc-gen-go.
        ExtensionDesc = protoimpl.ExtensionInfo

        // ExtensionRange represents a range of message extensions.
        // Used in code generated by protoc-gen-go.
        ExtensionRange = protoiface.ExtensionRangeV1

        // Deprecated: Do not use; this is an internal type.
        Extension = protoimpl.ExtensionFieldV1

        // Deprecated: Do not use; this is an internal type.
        XXX_InternalExtensions = protoimpl.ExtensionFields
)

// ErrMissingExtension reports whether the extension was not present.
var ErrMissingExtension = errors.New("proto: missing extension")

var errNotExtendable = errors.New("proto: not an extendable proto.Message")

// HasExtension reports whether the extension field is present in m
// either as an explicitly populated field or as an unknown field.
func HasExtension(m Message, xt *ExtensionDesc) (has bool) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() {
                return false
        }

        // Check whether any populated known field matches the field number.
        xtd := xt.TypeDescriptor()
        if isValidExtension(mr.Descriptor(), xtd) {
                has = mr.Has(xtd)
        } else {
                mr.Range(func(fd protoreflect.FieldDescriptor, _ protoreflect.Value) bool {
                        has = int32(fd.Number()) == xt.Field
                        return !has
                })
        }

        // Check whether any unknown field matches the field number.
        for b := mr.GetUnknown(); !has && len(b) > 0; {
                num, _, n := protowire.ConsumeField(b)
                has = int32(num) == xt.Field
                b = b[n:]
        }
        return has
}

// ClearExtension removes the extension field from m
// either as an explicitly populated field or as an unknown field.
func ClearExtension(m Message, xt *ExtensionDesc) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() {
                return
        }

        xtd := xt.TypeDescriptor()
        if isValidExtension(mr.Descriptor(), xtd) {
                mr.Clear(xtd)
        } else {
                mr.Range(func(fd protoreflect.FieldDescriptor, _ protoreflect.Value) bool {
                        if int32(fd.Number()) == xt.Field {
                                mr.Clear(fd)
                                return false
                        }
                        return true
                })
        }
        clearUnknown(mr, fieldNum(xt.Field))
}

// ClearAllExtensions clears all extensions from m.
// This includes populated fields and unknown fields in the extension range.
func ClearAllExtensions(m Message) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() {
                return
        }

        mr.Range(func(fd protoreflect.FieldDescriptor, _ protoreflect.Value) bool {
                if fd.IsExtension() {
                        mr.Clear(fd)
                }
                return true
        })
        clearUnknown(mr, mr.Descriptor().ExtensionRanges())
}

// GetExtension retrieves a proto2 extended field from m.
//
// If the descriptor is type complete (i.e., ExtensionDesc.ExtensionType is non-nil),
// then GetExtension parses the encoded field and returns a Go value of the specified type.
// If the field is not present, then the default value is returned (if one is specified),
// otherwise ErrMissingExtension is reported.
//
// If the descriptor is type incomplete (i.e., ExtensionDesc.ExtensionType is nil),
// then GetExtension returns the raw encoded bytes for the extension field.
func GetExtension(m Message, xt *ExtensionDesc) (interface{}, error) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() || mr.Descriptor().ExtensionRanges().Len() == 0 {
                return nil, errNotExtendable
        }

        // Retrieve the unknown fields for this extension field.
        var bo protoreflect.RawFields
        for bi := mr.GetUnknown(); len(bi) > 0; {
                num, _, n := protowire.ConsumeField(bi)
                if int32(num) == xt.Field {
                        bo = append(bo, bi[:n]...)
                }
                bi = bi[n:]
        }

        // For type incomplete descriptors, only retrieve the unknown fields.
        if xt.ExtensionType == nil {
                return []byte(bo), nil
        }

        // If the extension field only exists as unknown fields, unmarshal it.
        // This is rarely done since proto.Unmarshal eagerly unmarshals extensions.
        xtd := xt.TypeDescriptor()
        if !isValidExtension(mr.Descriptor(), xtd) {
                return nil, fmt.Errorf("proto: bad extended type; %T does not extend %T", xt.ExtendedType, m)
        }
        if !mr.Has(xtd) && len(bo) > 0 {
                m2 := mr.New()
                if err := (proto.UnmarshalOptions{
                        Resolver: extensionResolver{xt},
                }.Unmarshal(bo, m2.Interface())); err != nil {
                        return nil, err
                }
                if m2.Has(xtd) {
                        mr.Set(xtd, m2.Get(xtd))
                        clearUnknown(mr, fieldNum(xt.Field))
                }
        }

        // Check whether the message has the extension field set or a default.
        var pv protoreflect.Value
        switch {
        case mr.Has(xtd):
                pv = mr.Get(xtd)
        case xtd.HasDefault():
                pv = xtd.Default()
        default:
                return nil, ErrMissingExtension
        }

        v := xt.InterfaceOf(pv)
        rv := reflect.ValueOf(v)
        if isScalarKind(rv.Kind()) {
                rv2 := reflect.New(rv.Type())
                rv2.Elem().Set(rv)
                v = rv2.Interface()
        }
        return v, nil
}

// extensionResolver is a custom extension resolver that stores a single
// extension type that takes precedence over the global registry.
type extensionResolver struct{ xt protoreflect.ExtensionType }

func (r extensionResolver) FindExtensionByName(field protoreflect.FullName) (protoreflect.ExtensionType, error) {
        if xtd := r.xt.TypeDescriptor(); xtd.FullName() == field {
                return r.xt, nil
        }
        return protoregistry.GlobalTypes.FindExtensionByName(field)
}

func (r extensionResolver) FindExtensionByNumber(message protoreflect.FullName, field protoreflect.FieldNumber) (protoreflect.ExtensionType, error) {
        if xtd := r.xt.TypeDescriptor(); xtd.ContainingMessage().FullName() == message && xtd.Number() == field {
                return r.xt, nil
        }
        return protoregistry.GlobalTypes.FindExtensionByNumber(message, field)
}

// GetExtensions returns a list of the extensions values present in m,
// corresponding with the provided list of extension descriptors, xts.
// If an extension is missing in m, the corresponding value is nil.
func GetExtensions(m Message, xts []*ExtensionDesc) ([]interface{}, error) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() {
                return nil, errNotExtendable
        }

        vs := make([]interface{}, len(xts))
        for i, xt := range xts {
                v, err := GetExtension(m, xt)
                if err != nil {
                        if err == ErrMissingExtension {
                                continue
                        }
                        return vs, err
                }
                vs[i] = v
        }
        return vs, nil
}

// SetExtension sets an extension field in m to the provided value.
func SetExtension(m Message, xt *ExtensionDesc, v interface{}) error {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() || mr.Descriptor().ExtensionRanges().Len() == 0 {
                return errNotExtendable
        }

        rv := reflect.ValueOf(v)
        if reflect.TypeOf(v) != reflect.TypeOf(xt.ExtensionType) {
                return fmt.Errorf("proto: bad extension value type. got: %T, want: %T", v, xt.ExtensionType)
        }
        if rv.Kind() == reflect.Ptr {
                if rv.IsNil() {
                        return fmt.Errorf("proto: SetExtension called with nil value of type %T", v)
                }
                if isScalarKind(rv.Elem().Kind()) {
                        v = rv.Elem().Interface()
                }
        }

        xtd := xt.TypeDescriptor()
        if !isValidExtension(mr.Descriptor(), xtd) {
                return fmt.Errorf("proto: bad extended type; %T does not extend %T", xt.ExtendedType, m)
        }
        mr.Set(xtd, xt.ValueOf(v))
        clearUnknown(mr, fieldNum(xt.Field))
        return nil
}

// SetRawExtension inserts b into the unknown fields of m.
//
// Deprecated: Use Message.ProtoReflect.SetUnknown instead.
func SetRawExtension(m Message, fnum int32, b []byte) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() {
                return
        }

        // Verify that the raw field is valid.
        for b0 := b; len(b0) > 0; {
                num, _, n := protowire.ConsumeField(b0)
                if int32(num) != fnum {
                        panic(fmt.Sprintf("mismatching field number: got %d, want %d", num, fnum))
                }
                b0 = b0[n:]
        }

        ClearExtension(m, &ExtensionDesc{Field: fnum})
        mr.SetUnknown(append(mr.GetUnknown(), b...))
}

// ExtensionDescs returns a list of extension descriptors found in m,
// containing descriptors for both populated extension fields in m and
// also unknown fields of m that are in the extension range.
// For the later case, an type incomplete descriptor is provided where only
// the ExtensionDesc.Field field is populated.
// The order of the extension descriptors is undefined.
func ExtensionDescs(m Message) ([]*ExtensionDesc, error) {
        mr := MessageReflect(m)
        if mr == nil || !mr.IsValid() || mr.Descriptor().ExtensionRanges().Len() == 0 {
                return nil, errNotExtendable
        }

        // Collect a set of known extension descriptors.
        extDescs := make(map[protoreflect.FieldNumber]*ExtensionDesc)
        mr.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
                if fd.IsExtension() {
                        xt := fd.(protoreflect.ExtensionTypeDescriptor)
                        if xd, ok := xt.Type().(*ExtensionDesc); ok {
                                extDescs[fd.Number()] = xd
                        }
                }
                return true
        })

        // Collect a set of unknown extension descriptors.
        extRanges := mr.Descriptor().ExtensionRanges()
        for b := mr.GetUnknown(); len(b) > 0; {
                num, _, n := protowire.ConsumeField(b)
                if extRanges.Has(num) && extDescs[num] == nil {
                        extDescs[num] = nil
                }
                b = b[n:]
        }

        // Transpose the set of descriptors into a list.
        var xts []*ExtensionDesc
        for num, xt := range extDescs {
                if xt == nil {
                        xt = &ExtensionDesc{Field: int32(num)}
                }
                xts = append(xts, xt)
        }
        return xts, nil
}

// isValidExtension reports whether xtd is a valid extension descriptor for md.
func isValidExtension(md protoreflect.MessageDescriptor, xtd protoreflect.ExtensionTypeDescriptor) bool {
        return xtd.ContainingMessage() == md && md.ExtensionRanges().Has(xtd.Number())
}

// isScalarKind reports whether k is a protobuf scalar kind (except bytes).
// This function exists for historical reasons since the representation of
// scalars differs between v1 and v2, where v1 uses *T and v2 uses T.
func isScalarKind(k reflect.Kind) bool {
        switch k {
        case reflect.Bool, reflect.Int32, reflect.Int64, reflect.Uint32, reflect.Uint64, reflect.Float32, reflect.Float64, reflect.String:
                return true
        default:
                return false
        }
}

// clearUnknown removes unknown fields from m where remover.Has reports true.
func clearUnknown(m protoreflect.Message, remover interface {
        Has(protoreflect.FieldNumber) bool
}) {
        var bo protoreflect.RawFields
        for bi := m.GetUnknown(); len(bi) > 0; {
                num, _, n := protowire.ConsumeField(bi)
                if !remover.Has(num) {
                        bo = append(bo, bi[:n]...)
                }
                bi = bi[n:]
        }
        if bi := m.GetUnknown(); len(bi) != len(bo) {
                m.SetUnknown(bo)
        }
}

type fieldNum protoreflect.FieldNumber

func (n1 fieldNum) Has(n2 protoreflect.FieldNumber) bool {
        return protoreflect.FieldNumber(n1) == n2
}