354 lines
11 KiB
Go
354 lines
11 KiB
Go
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// Go support for Protocol Buffers - Google's data interchange format
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//
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// Copyright 2010 The Go Authors. All rights reserved.
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// https://github.com/golang/protobuf
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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package proto
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/*
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* Types and routines for supporting protocol buffer extensions.
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*/
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import (
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"errors"
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"reflect"
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"strconv"
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"sync"
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)
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// ErrMissingExtension is the error returned by GetExtension if the named extension is not in the message.
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var ErrMissingExtension = errors.New("proto: missing extension")
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// ExtensionRange represents a range of message extensions for a protocol buffer.
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// Used in code generated by the protocol compiler.
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type ExtensionRange struct {
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Start, End int32 // both inclusive
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}
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// extendableProto is an interface implemented by any protocol buffer that may be extended.
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type extendableProto interface {
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Message
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ExtensionRangeArray() []ExtensionRange
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ExtensionMap() map[int32]Extension
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}
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var extendableProtoType = reflect.TypeOf((*extendableProto)(nil)).Elem()
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// ExtensionDesc represents an extension specification.
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// Used in generated code from the protocol compiler.
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type ExtensionDesc struct {
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ExtendedType Message // nil pointer to the type that is being extended
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ExtensionType interface{} // nil pointer to the extension type
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Field int32 // field number
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Name string // fully-qualified name of extension, for text formatting
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Tag string // protobuf tag style
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}
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func (ed *ExtensionDesc) repeated() bool {
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t := reflect.TypeOf(ed.ExtensionType)
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return t.Kind() == reflect.Slice && t.Elem().Kind() != reflect.Uint8
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}
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// Extension represents an extension in a message.
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type Extension struct {
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// When an extension is stored in a message using SetExtension
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// only desc and value are set. When the message is marshaled
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// enc will be set to the encoded form of the message.
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//
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// When a message is unmarshaled and contains extensions, each
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// extension will have only enc set. When such an extension is
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// accessed using GetExtension (or GetExtensions) desc and value
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// will be set.
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desc *ExtensionDesc
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value interface{}
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enc []byte
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}
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// SetRawExtension is for testing only.
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func SetRawExtension(base extendableProto, id int32, b []byte) {
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base.ExtensionMap()[id] = Extension{enc: b}
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}
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// isExtensionField returns true iff the given field number is in an extension range.
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func isExtensionField(pb extendableProto, field int32) bool {
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for _, er := range pb.ExtensionRangeArray() {
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if er.Start <= field && field <= er.End {
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return true
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}
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}
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return false
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}
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// checkExtensionTypes checks that the given extension is valid for pb.
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func checkExtensionTypes(pb extendableProto, extension *ExtensionDesc) error {
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// Check the extended type.
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if a, b := reflect.TypeOf(pb), reflect.TypeOf(extension.ExtendedType); a != b {
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return errors.New("proto: bad extended type; " + b.String() + " does not extend " + a.String())
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}
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// Check the range.
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if !isExtensionField(pb, extension.Field) {
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return errors.New("proto: bad extension number; not in declared ranges")
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}
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return nil
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}
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// extPropKey is sufficient to uniquely identify an extension.
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type extPropKey struct {
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base reflect.Type
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field int32
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}
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var extProp = struct {
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sync.RWMutex
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m map[extPropKey]*Properties
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}{
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m: make(map[extPropKey]*Properties),
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}
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func extensionProperties(ed *ExtensionDesc) *Properties {
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key := extPropKey{base: reflect.TypeOf(ed.ExtendedType), field: ed.Field}
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extProp.RLock()
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if prop, ok := extProp.m[key]; ok {
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extProp.RUnlock()
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return prop
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}
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extProp.RUnlock()
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extProp.Lock()
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defer extProp.Unlock()
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// Check again.
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if prop, ok := extProp.m[key]; ok {
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return prop
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}
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prop := new(Properties)
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prop.Init(reflect.TypeOf(ed.ExtensionType), "unknown_name", ed.Tag, nil)
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extProp.m[key] = prop
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return prop
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}
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// encodeExtensionMap encodes any unmarshaled (unencoded) extensions in m.
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func encodeExtensionMap(m map[int32]Extension) error {
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for k, e := range m {
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if e.value == nil || e.desc == nil {
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// Extension is only in its encoded form.
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continue
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}
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// We don't skip extensions that have an encoded form set,
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// because the extension value may have been mutated after
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// the last time this function was called.
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et := reflect.TypeOf(e.desc.ExtensionType)
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props := extensionProperties(e.desc)
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p := NewBuffer(nil)
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// If e.value has type T, the encoder expects a *struct{ X T }.
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// Pass a *T with a zero field and hope it all works out.
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x := reflect.New(et)
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x.Elem().Set(reflect.ValueOf(e.value))
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if err := props.enc(p, props, toStructPointer(x)); err != nil {
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return err
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}
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e.enc = p.buf
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m[k] = e
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}
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return nil
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}
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func sizeExtensionMap(m map[int32]Extension) (n int) {
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for _, e := range m {
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if e.value == nil || e.desc == nil {
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// Extension is only in its encoded form.
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n += len(e.enc)
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continue
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}
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// We don't skip extensions that have an encoded form set,
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// because the extension value may have been mutated after
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// the last time this function was called.
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et := reflect.TypeOf(e.desc.ExtensionType)
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props := extensionProperties(e.desc)
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// If e.value has type T, the encoder expects a *struct{ X T }.
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// Pass a *T with a zero field and hope it all works out.
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x := reflect.New(et)
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x.Elem().Set(reflect.ValueOf(e.value))
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n += props.size(props, toStructPointer(x))
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}
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return
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}
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// HasExtension returns whether the given extension is present in pb.
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func HasExtension(pb extendableProto, extension *ExtensionDesc) bool {
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// TODO: Check types, field numbers, etc.?
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_, ok := pb.ExtensionMap()[extension.Field]
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return ok
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}
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// ClearExtension removes the given extension from pb.
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func ClearExtension(pb extendableProto, extension *ExtensionDesc) {
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// TODO: Check types, field numbers, etc.?
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delete(pb.ExtensionMap(), extension.Field)
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}
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// GetExtension parses and returns the given extension of pb.
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// If the extension is not present it returns ErrMissingExtension.
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func GetExtension(pb extendableProto, extension *ExtensionDesc) (interface{}, error) {
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if err := checkExtensionTypes(pb, extension); err != nil {
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return nil, err
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}
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emap := pb.ExtensionMap()
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e, ok := emap[extension.Field]
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if !ok {
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return nil, ErrMissingExtension
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}
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if e.value != nil {
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// Already decoded. Check the descriptor, though.
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if e.desc != extension {
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// This shouldn't happen. If it does, it means that
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// GetExtension was called twice with two different
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// descriptors with the same field number.
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return nil, errors.New("proto: descriptor conflict")
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}
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return e.value, nil
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}
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v, err := decodeExtension(e.enc, extension)
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if err != nil {
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return nil, err
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}
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// Remember the decoded version and drop the encoded version.
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// That way it is safe to mutate what we return.
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e.value = v
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e.desc = extension
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e.enc = nil
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emap[extension.Field] = e
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return e.value, nil
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}
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// decodeExtension decodes an extension encoded in b.
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func decodeExtension(b []byte, extension *ExtensionDesc) (interface{}, error) {
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o := NewBuffer(b)
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t := reflect.TypeOf(extension.ExtensionType)
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rep := extension.repeated()
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props := extensionProperties(extension)
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// t is a pointer to a struct, pointer to basic type or a slice.
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// Allocate a "field" to store the pointer/slice itself; the
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// pointer/slice will be stored here. We pass
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// the address of this field to props.dec.
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// This passes a zero field and a *t and lets props.dec
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// interpret it as a *struct{ x t }.
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value := reflect.New(t).Elem()
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for {
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// Discard wire type and field number varint. It isn't needed.
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if _, err := o.DecodeVarint(); err != nil {
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return nil, err
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}
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if err := props.dec(o, props, toStructPointer(value.Addr())); err != nil {
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return nil, err
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}
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if !rep || o.index >= len(o.buf) {
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break
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}
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}
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return value.Interface(), nil
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}
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// GetExtensions returns a slice of the extensions present in pb that are also listed in es.
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// The returned slice has the same length as es; missing extensions will appear as nil elements.
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func GetExtensions(pb Message, es []*ExtensionDesc) (extensions []interface{}, err error) {
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epb, ok := pb.(extendableProto)
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if !ok {
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err = errors.New("proto: not an extendable proto")
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return
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}
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extensions = make([]interface{}, len(es))
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for i, e := range es {
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extensions[i], err = GetExtension(epb, e)
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if err == ErrMissingExtension {
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err = nil
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}
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if err != nil {
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return
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}
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}
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return
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}
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// SetExtension sets the specified extension of pb to the specified value.
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func SetExtension(pb extendableProto, extension *ExtensionDesc, value interface{}) error {
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if err := checkExtensionTypes(pb, extension); err != nil {
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return err
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}
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typ := reflect.TypeOf(extension.ExtensionType)
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if typ != reflect.TypeOf(value) {
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return errors.New("proto: bad extension value type")
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}
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pb.ExtensionMap()[extension.Field] = Extension{desc: extension, value: value}
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return nil
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}
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// A global registry of extensions.
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// The generated code will register the generated descriptors by calling RegisterExtension.
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var extensionMaps = make(map[reflect.Type]map[int32]*ExtensionDesc)
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// RegisterExtension is called from the generated code.
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func RegisterExtension(desc *ExtensionDesc) {
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st := reflect.TypeOf(desc.ExtendedType).Elem()
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m := extensionMaps[st]
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if m == nil {
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m = make(map[int32]*ExtensionDesc)
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extensionMaps[st] = m
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}
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if _, ok := m[desc.Field]; ok {
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panic("proto: duplicate extension registered: " + st.String() + " " + strconv.Itoa(int(desc.Field)))
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}
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m[desc.Field] = desc
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}
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// RegisteredExtensions returns a map of the registered extensions of a
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// protocol buffer struct, indexed by the extension number.
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// The argument pb should be a nil pointer to the struct type.
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func RegisteredExtensions(pb Message) map[int32]*ExtensionDesc {
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return extensionMaps[reflect.TypeOf(pb).Elem()]
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}
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