source: code/trunk/vendor/google.golang.org/protobuf/internal/impl/encode.go@ 822

// Copyright 2019 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 impl

import (
        "math"
        "sort"
        "sync/atomic"

        "google.golang.org/protobuf/internal/flags"
        proto "google.golang.org/protobuf/proto"
        piface "google.golang.org/protobuf/runtime/protoiface"
)

type marshalOptions struct {
        flags piface.MarshalInputFlags
}

func (o marshalOptions) Options() proto.MarshalOptions {
        return proto.MarshalOptions{
                AllowPartial:  true,
                Deterministic: o.Deterministic(),
                UseCachedSize: o.UseCachedSize(),
        }
}

func (o marshalOptions) Deterministic() bool { return o.flags&piface.MarshalDeterministic != 0 }
func (o marshalOptions) UseCachedSize() bool { return o.flags&piface.MarshalUseCachedSize != 0 }

// size is protoreflect.Methods.Size.
func (mi *MessageInfo) size(in piface.SizeInput) piface.SizeOutput {
        var p pointer
        if ms, ok := in.Message.(*messageState); ok {
                p = ms.pointer()
        } else {
                p = in.Message.(*messageReflectWrapper).pointer()
        }
        size := mi.sizePointer(p, marshalOptions{
                flags: in.Flags,
        })
        return piface.SizeOutput{Size: size}
}

func (mi *MessageInfo) sizePointer(p pointer, opts marshalOptions) (size int) {
        mi.init()
        if p.IsNil() {
                return 0
        }
        if opts.UseCachedSize() && mi.sizecacheOffset.IsValid() {
                if size := atomic.LoadInt32(p.Apply(mi.sizecacheOffset).Int32()); size >= 0 {
                        return int(size)
                }
        }
        return mi.sizePointerSlow(p, opts)
}

func (mi *MessageInfo) sizePointerSlow(p pointer, opts marshalOptions) (size int) {
        if flags.ProtoLegacy && mi.isMessageSet {
                size = sizeMessageSet(mi, p, opts)
                if mi.sizecacheOffset.IsValid() {
                        atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
                }
                return size
        }
        if mi.extensionOffset.IsValid() {
                e := p.Apply(mi.extensionOffset).Extensions()
                size += mi.sizeExtensions(e, opts)
        }
        for _, f := range mi.orderedCoderFields {
                if f.funcs.size == nil {
                        continue
                }
                fptr := p.Apply(f.offset)
                if f.isPointer && fptr.Elem().IsNil() {
                        continue
                }
                size += f.funcs.size(fptr, f, opts)
        }
        if mi.unknownOffset.IsValid() {
                if u := mi.getUnknownBytes(p); u != nil {
                        size += len(*u)
                }
        }
        if mi.sizecacheOffset.IsValid() {
                if size > math.MaxInt32 {
                        // The size is too large for the int32 sizecache field.
                        // We will need to recompute the size when encoding;
                        // unfortunately expensive, but better than invalid output.
                        atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), -1)
                } else {
                        atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
                }
        }
        return size
}

// marshal is protoreflect.Methods.Marshal.
func (mi *MessageInfo) marshal(in piface.MarshalInput) (out piface.MarshalOutput, err error) {
        var p pointer
        if ms, ok := in.Message.(*messageState); ok {
                p = ms.pointer()
        } else {
                p = in.Message.(*messageReflectWrapper).pointer()
        }
        b, err := mi.marshalAppendPointer(in.Buf, p, marshalOptions{
                flags: in.Flags,
        })
        return piface.MarshalOutput{Buf: b}, err
}

func (mi *MessageInfo) marshalAppendPointer(b []byte, p pointer, opts marshalOptions) ([]byte, error) {
        mi.init()
        if p.IsNil() {
                return b, nil
        }
        if flags.ProtoLegacy && mi.isMessageSet {
                return marshalMessageSet(mi, b, p, opts)
        }
        var err error
        // The old marshaler encodes extensions at beginning.
        if mi.extensionOffset.IsValid() {
                e := p.Apply(mi.extensionOffset).Extensions()
                // TODO: Special handling for MessageSet?
                b, err = mi.appendExtensions(b, e, opts)
                if err != nil {
                        return b, err
                }
        }
        for _, f := range mi.orderedCoderFields {
                if f.funcs.marshal == nil {
                        continue
                }
                fptr := p.Apply(f.offset)
                if f.isPointer && fptr.Elem().IsNil() {
                        continue
                }
                b, err = f.funcs.marshal(b, fptr, f, opts)
                if err != nil {
                        return b, err
                }
        }
        if mi.unknownOffset.IsValid() && !mi.isMessageSet {
                if u := mi.getUnknownBytes(p); u != nil {
                        b = append(b, (*u)...)
                }
        }
        return b, nil
}

func (mi *MessageInfo) sizeExtensions(ext *map[int32]ExtensionField, opts marshalOptions) (n int) {
        if ext == nil {
                return 0
        }
        for _, x := range *ext {
                xi := getExtensionFieldInfo(x.Type())
                if xi.funcs.size == nil {
                        continue
                }
                n += xi.funcs.size(x.Value(), xi.tagsize, opts)
        }
        return n
}

func (mi *MessageInfo) appendExtensions(b []byte, ext *map[int32]ExtensionField, opts marshalOptions) ([]byte, error) {
        if ext == nil {
                return b, nil
        }

        switch len(*ext) {
        case 0:
                return b, nil
        case 1:
                // Fast-path for one extension: Don't bother sorting the keys.
                var err error
                for _, x := range *ext {
                        xi := getExtensionFieldInfo(x.Type())
                        b, err = xi.funcs.marshal(b, x.Value(), xi.wiretag, opts)
                }
                return b, err
        default:
                // Sort the keys to provide a deterministic encoding.
                // Not sure this is required, but the old code does it.
                keys := make([]int, 0, len(*ext))
                for k := range *ext {
                        keys = append(keys, int(k))
                }
                sort.Ints(keys)
                var err error
                for _, k := range keys {
                        x := (*ext)[int32(k)]
                        xi := getExtensionFieldInfo(x.Type())
                        b, err = xi.funcs.marshal(b, x.Value(), xi.wiretag, opts)
                        if err != nil {
                                return b, err
                        }
                }
                return b, nil
        }
}