protoc-gen-go/generator/generator.go

// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 The Go Authors.  All rights reserved.
// http://code.google.com/p/goprotobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

/*
	The code generator for the plugin for the Google protocol buffer compiler.
	It generates Go code from the protocol buffer description files read by the
	main routine.
*/
package generator

import (
	"bytes"
	"fmt"
	"go/parser"
	"go/printer"
	"go/token"
	"log"
	"os"
	"path"
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"

	"code.google.com/p/goprotobuf/proto"
	descriptor "code.google.com/p/goprotobuf/protoc-gen-go/descriptor"
	plugin "code.google.com/p/goprotobuf/protoc-gen-go/plugin"
)

// A Plugin provides functionality to add to the output during Go code generation,
// such as to produce RPC stubs.
type Plugin interface {
	// Name identifies the plugin.
	Name() string
	// Init is called once after data structures are built but before
	// code generation begins.
	Init(g *Generator)
	// Generate produces the code generated by the plugin for this file,
	// except for the imports, by calling the generator's methods P, In, and Out.
	Generate(file *FileDescriptor)
	// GenerateImports produces the import declarations for this file.
	// It is called after Generate.
	GenerateImports(file *FileDescriptor)
}

var plugins []Plugin

// RegisterPlugin installs a (second-order) plugin to be run when the Go output is generated.
// It is typically called during initialization.
func RegisterPlugin(p Plugin) {
	plugins = append(plugins, p)
}

// Each type we import as a protocol buffer (other than FileDescriptorProto) needs
// a pointer to the FileDescriptorProto that represents it.  These types achieve that
// wrapping by placing each Proto inside a struct with the pointer to its File. The
// structs have the same names as their contents, with "Proto" removed.
// FileDescriptor is used to store the things that it points to.

// The file and package name method are common to messages and enums.
type common struct {
	file *descriptor.FileDescriptorProto // File this object comes from.
}

// PackageName is name in the package clause in the generated file.
func (c *common) PackageName() string { return uniquePackageOf(c.file) }

func (c *common) File() *descriptor.FileDescriptorProto { return c.file }

// Descriptor represents a protocol buffer message.
type Descriptor struct {
	common
	*descriptor.DescriptorProto
	parent   *Descriptor            // The containing message, if any.
	nested   []*Descriptor          // Inner messages, if any.
	ext      []*ExtensionDescriptor // Extensions, if any.
	typename []string               // Cached typename vector.
	index    int                    // The index into the container, whether the file or another message.
	path     string                 // The SourceCodeInfo path as comma-separated integers.
	group    bool
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (d *Descriptor) TypeName() []string {
	if d.typename != nil {
		return d.typename
	}
	n := 0
	for parent := d; parent != nil; parent = parent.parent {
		n++
	}
	s := make([]string, n, n)
	for parent := d; parent != nil; parent = parent.parent {
		n--
		s[n] = parent.GetName()
	}
	d.typename = s
	return s
}

// EnumDescriptor describes an enum. If it's at top level, its parent will be nil.
// Otherwise it will be the descriptor of the message in which it is defined.
type EnumDescriptor struct {
	common
	*descriptor.EnumDescriptorProto
	parent   *Descriptor // The containing message, if any.
	typename []string    // Cached typename vector.
	path     string      // The SourceCodeInfo path as comma-separated integers.
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (e *EnumDescriptor) TypeName() (s []string) {
	if e.typename != nil {
		return e.typename
	}
	name := e.GetName()
	if e.parent == nil {
		s = make([]string, 1)
	} else {
		pname := e.parent.TypeName()
		s = make([]string, len(pname)+1)
		copy(s, pname)
	}
	s[len(s)-1] = name
	e.typename = s
	return s
}

// Everything but the last element of the full type name, CamelCased.
// The values of type Foo.Bar are call Foo_value1... not Foo_Bar_value1... .
func (e *EnumDescriptor) prefix() string {
	typeName := e.TypeName()
	ccPrefix := CamelCaseSlice(typeName[0:len(typeName)-1]) + "_"
	if e.parent == nil {
		// If the enum is not part of a message, the prefix is just the type name.
		ccPrefix = CamelCase(*e.Name) + "_"
	}
	return ccPrefix
}

// The integer value of the named constant in this enumerated type.
func (e *EnumDescriptor) integerValueAsString(name string) string {
	for _, c := range e.Value {
		if c.GetName() == name {
			return fmt.Sprint(c.GetNumber())
		}
	}
	log.Fatal("cannot find value for enum constant")
	return ""
}

// ExtensionDescriptor describes an extension. If it's at top level, its parent will be nil.
// Otherwise it will be the descriptor of the message in which it is defined.
type ExtensionDescriptor struct {
	common
	*descriptor.FieldDescriptorProto
	parent *Descriptor // The containing message, if any.
}

// TypeName returns the elements of the dotted type name.
// The package name is not part of this name.
func (e *ExtensionDescriptor) TypeName() (s []string) {
	name := e.GetName()
	if e.parent == nil {
		// top-level extension
		s = make([]string, 1)
	} else {
		pname := e.parent.TypeName()
		s = make([]string, len(pname)+1)
		copy(s, pname)
	}
	s[len(s)-1] = name
	return s
}

// DescName returns the variable name used for the generated descriptor.
func (e *ExtensionDescriptor) DescName() string {
	// The full type name.
	typeName := e.TypeName()
	// Each scope of the extension is individually CamelCased, and all are joined with "_" with an "E_" prefix.
	for i, s := range typeName {
		typeName[i] = CamelCase(s)
	}
	return "E_" + strings.Join(typeName, "_")
}

// ImportedDescriptor describes a type that has been publicly imported from another file.
type ImportedDescriptor struct {
	common
	o Object
}

func (id *ImportedDescriptor) TypeName() []string { return id.o.TypeName() }

// FileDescriptor describes an protocol buffer descriptor file (.proto).
// It includes slices of all the messages and enums defined within it.
// Those slices are constructed by WrapTypes.
type FileDescriptor struct {
	*descriptor.FileDescriptorProto
	desc []*Descriptor          // All the messages defined in this file.
	enum []*EnumDescriptor      // All the enums defined in this file.
	ext  []*ExtensionDescriptor // All the top-level extensions defined in this file.
	imp  []*ImportedDescriptor  // All types defined in files publicly imported by this file.

	// Comments, stored as a map of path (comma-separated integers) to the comment.
	comments map[string]*descriptor.SourceCodeInfo_Location

	// The full list of symbols that are exported,
	// as a map from the exported object to its symbols.
	// This is used for supporting public imports.
	exported map[Object][]symbol
}

// PackageName is the package name we'll use in the generated code to refer to this file.
func (d *FileDescriptor) PackageName() string { return uniquePackageOf(d.FileDescriptorProto) }

// goPackageName returns the Go package name to use in the
// generated Go file.  The result explicit reports whether the name
// came from an option go_package statement.  If explicit is false,
// the name was derived from the protocol buffer's package statement
// or the input file name.
func (d *FileDescriptor) goPackageName() (name string, explicit bool) {
	// Does the file have a "go_package" option?
	if opts := d.Options; opts != nil {
		if pkg := opts.GetGoPackage(); pkg != "" {
			return pkg, true
		}
	}

	// Does the file have a package clause?
	if pkg := d.GetPackage(); pkg != "" {
		return pkg, false
	}
	// Use the file base name.
	return baseName(d.GetName()), false
}

func (d *FileDescriptor) addExport(obj Object, sym symbol) {
	d.exported[obj] = append(d.exported[obj], sym)
}

// symbol is an interface representing an exported Go symbol.
type symbol interface {
	// GenerateAlias should generate an appropriate alias
	// for the symbol from the named package.
	GenerateAlias(g *Generator, pkg string)
}

type messageSymbol struct {
	sym                         string
	hasExtensions, isMessageSet bool
	getters                     []getterSymbol
}

type getterSymbol struct {
	name     string
	typ      string
	typeName string // canonical name in proto world; empty for proto.Message and similar
	genType  bool   // whether typ is a generated type (message/group/enum)
}

func (ms *messageSymbol) GenerateAlias(g *Generator, pkg string) {
	remoteSym := pkg + "." + ms.sym

	g.P("type ", ms.sym, " ", remoteSym)
	g.P("func (m *", ms.sym, ") Reset() { (*", remoteSym, ")(m).Reset() }")
	g.P("func (m *", ms.sym, ") String() string { return (*", remoteSym, ")(m).String() }")
	g.P("func (*", ms.sym, ") ProtoMessage() {}")
	if ms.hasExtensions {
		g.P("func (*", ms.sym, ") ExtensionRangeArray() []", g.Pkg["proto"], ".ExtensionRange ",
			"{ return (*", remoteSym, ")(nil).ExtensionRangeArray() }")
		g.P("func (m *", ms.sym, ") ExtensionMap() map[int32]", g.Pkg["proto"], ".Extension ",
			"{ return (*", remoteSym, ")(m).ExtensionMap() }")
		if ms.isMessageSet {
			g.P("func (m *", ms.sym, ") Marshal() ([]byte, error) ",
				"{ return (*", remoteSym, ")(m).Marshal() }")
			g.P("func (m *", ms.sym, ") Unmarshal(buf []byte) error ",
				"{ return (*", remoteSym, ")(m).Unmarshal(buf) }")
		}
	}
	for _, get := range ms.getters {
		if get.typeName != "" {
			g.RecordTypeUse(get.typeName)
		}
		typ := get.typ
		val := "(*" + remoteSym + ")(m)." + get.name + "()"
		if get.genType {
			// typ will be "*pkg.T" (message/group) or "pkg.T" (enum).
			// Either of those might have a "[]" prefix if it is repeated.
			// Drop the package qualifier since we have hoisted the type into this package.
			rep := strings.HasPrefix(typ, "[]")
			if rep {
				typ = typ[2:]
			}
			star := typ[0] == '*'
			typ = typ[strings.Index(typ, ".")+1:]
			if star {
				typ = "*" + typ
			}
			if rep {
				// Go does not permit conversion between slice types where both
				// element types are named. That means we need to generate a bit
				// of code in this situation.
				// typ is the element type.
				// val is the expression to get the slice from the imported type.

				ctyp := typ // conversion type expression; "Foo" or "(*Foo)"
				if star {
					ctyp = "(" + typ + ")"
				}

				g.P("func (m *", ms.sym, ") ", get.name, "() []", typ, " {")
				g.In()
				g.P("o := ", val)
				g.P("if o == nil {")
				g.In()
				g.P("return nil")
				g.Out()
				g.P("}")
				g.P("s := make([]", typ, ", len(o))")
				g.P("for i, x := range o {")
				g.In()
				g.P("s[i] = ", ctyp, "(x)")
				g.Out()
				g.P("}")
				g.P("return s")
				g.Out()
				g.P("}")
				continue
			}
			// Convert imported type into the forwarding type.
			val = "(" + typ + ")(" + val + ")"
		}

		g.P("func (m *", ms.sym, ") ", get.name, "() ", typ, " { return ", val, " }")
	}
}

type enumSymbol string

func (es enumSymbol) GenerateAlias(g *Generator, pkg string) {
	s := string(es)
	g.P("type ", s, " ", pkg, ".", s)
	g.P("var ", s, "_name = ", pkg, ".", s, "_name")
	g.P("var ", s, "_value = ", pkg, ".", s, "_value")
	g.P("func New", s, "(x ", s, ") *", s, " { e := ", s, "(x); return &e }")
}

type constOrVarSymbol struct {
	sym  string
	typ  string // either "const" or "var"
	cast string // if non-empty, a type cast is required (used for enums)
}

func (cs constOrVarSymbol) GenerateAlias(g *Generator, pkg string) {
	v := pkg + "." + cs.sym
	if cs.cast != "" {
		v = cs.cast + "(" + v + ")"
	}
	g.P(cs.typ, " ", cs.sym, " = ", v)
}

// Object is an interface abstracting the abilities shared by enums, messages, extensions and imported objects.
type Object interface {
	PackageName() string // The name we use in our output (a_b_c), possibly renamed for uniqueness.
	TypeName() []string
	File() *descriptor.FileDescriptorProto
}

// Each package name we generate must be unique. The package we're generating
// gets its own name but every other package must have a unique name that does
// not conflict in the code we generate.  These names are chosen globally (although
// they don't have to be, it simplifies things to do them globally).
func uniquePackageOf(fd *descriptor.FileDescriptorProto) string {
	s, ok := uniquePackageName[fd]
	if !ok {
		log.Fatal("internal error: no package name defined for " + fd.GetName())
	}
	return s
}

// Generator is the type whose methods generate the output, stored in the associated response structure.
type Generator struct {
	*bytes.Buffer

	Request  *plugin.CodeGeneratorRequest  // The input.
	Response *plugin.CodeGeneratorResponse // The output.

	Param             map[string]string // Command-line parameters.
	PackageImportPath string            // Go import path of the package we're generating code for
	ImportPrefix      string            // String to prefix to imported package file names.
	ImportMap         map[string]string // Mapping from import name to generated name

	Pkg map[string]string // The names under which we import support packages

	packageName      string            // What we're calling ourselves.
	allFiles         []*FileDescriptor // All files in the tree
	genFiles         []*FileDescriptor // Those files we will generate output for.
	file             *FileDescriptor   // The file we are compiling now.
	usedPackages     map[string]bool   // Names of packages used in current file.
	typeNameToObject map[string]Object // Key is a fully-qualified name in input syntax.
	indent           string
}

// New creates a new generator and allocates the request and response protobufs.
func New() *Generator {
	g := new(Generator)
	g.Buffer = new(bytes.Buffer)
	g.Request = new(plugin.CodeGeneratorRequest)
	g.Response = new(plugin.CodeGeneratorResponse)
	return g
}

// Error reports a problem, including an error, and exits the program.
func (g *Generator) Error(err error, msgs ...string) {
	s := strings.Join(msgs, " ") + ":" + err.Error()
	log.Print("protoc-gen-go: error:", s)
	os.Exit(1)
}

// Fail reports a problem and exits the program.
func (g *Generator) Fail(msgs ...string) {
	s := strings.Join(msgs, " ")
	log.Print("protoc-gen-go: error:", s)
	os.Exit(1)
}

// CommandLineParameters breaks the comma-separated list of key=value pairs
// in the parameter (a member of the request protobuf) into a key/value map.
// It then sets file name mappings defined by those entries.
func (g *Generator) CommandLineParameters(parameter string) {
	g.Param = make(map[string]string)
	for _, p := range strings.Split(parameter, ",") {
		if i := strings.Index(p, "="); i < 0 {
			g.Param[p] = ""
		} else {
			g.Param[p[0:i]] = p[i+1:]
		}
	}

	g.ImportMap = make(map[string]string)
	for k, v := range g.Param {
		switch k {
		case "import_prefix":
			g.ImportPrefix = v
		case "import_path":
			g.PackageImportPath = v
		default:
			if len(k) > 0 && k[0] == 'M' {
				g.ImportMap[k[1:]] = v
			}
		}
	}
}

// DefaultPackageName returns the package name printed for the object.
// If its file is in a different package, it returns the package name we're using for this file, plus ".".
// Otherwise it returns the empty string.
func (g *Generator) DefaultPackageName(obj Object) string {
	pkg := obj.PackageName()
	if pkg == g.packageName {
		return ""
	}
	return pkg + "."
}

// For each input file, the unique package name to use, underscored.
var uniquePackageName = make(map[*descriptor.FileDescriptorProto]string)

// Package names already registered.  Key is the name from the .proto file;
// value is the name that appears in the generated code.
var pkgNamesInUse = make(map[string]bool)

// Create and remember a guaranteed unique package name for this file descriptor.
// Pkg is the candidate name.  If f is nil, it's a builtin package like "proto" and
// has no file descriptor.
func RegisterUniquePackageName(pkg string, f *FileDescriptor) string {
	// Convert dots to underscores before finding a unique alias.
	pkg = strings.Map(badToUnderscore, pkg)

	for i, orig := 1, pkg; pkgNamesInUse[pkg]; i++ {
		// It's a duplicate; must rename.
		pkg = orig + strconv.Itoa(i)
	}
	// Install it.
	pkgNamesInUse[pkg] = true
	if f != nil {
		uniquePackageName[f.FileDescriptorProto] = pkg
	}
	return pkg
}

var isGoKeyword = map[string]bool{
	"break":       true,
	"case":        true,
	"chan":        true,
	"const":       true,
	"continue":    true,
	"default":     true,
	"else":        true,
	"defer":       true,
	"fallthrough": true,
	"for":         true,
	"func":        true,
	"go":          true,
	"goto":        true,
	"if":          true,
	"import":      true,
	"interface":   true,
	"map":         true,
	"package":     true,
	"range":       true,
	"return":      true,
	"select":      true,
	"struct":      true,
	"switch":      true,
	"type":        true,
	"var":         true,
}

// defaultGoPackage returns the package name to use,
// derived from the import path of the package we're building code for.
func (g *Generator) defaultGoPackage() string {
	p := g.PackageImportPath
	if i := strings.LastIndex(p, "/"); i >= 0 {
		p = p[i+1:]
	}
	if p == "" {
		return ""
	}

	p = strings.Map(badToUnderscore, p)
	// Identifier must not be keyword: insert _.
	if isGoKeyword[p] {
		p = "_" + p
	}
	// Identifier must not begin with digit: insert _.
	if r, _ := utf8.DecodeRuneInString(p); unicode.IsDigit(r) {
		p = "_" + p
	}
	return p
}

// SetPackageNames sets the package name for this run.
// The package name must agree across all files being generated.
// It also defines unique package names for all imported files.
func (g *Generator) SetPackageNames() {
	// Register the name for this package.  It will be the first name
	// registered so is guaranteed to be unmodified.
	pkg, explicit := g.genFiles[0].goPackageName()

	// Check all files for an explicit go_package option.
	for _, f := range g.genFiles {
		thisPkg, thisExplicit := f.goPackageName()
		if thisExplicit {
			if !explicit {
				// Let this file's go_package option serve for all input files.
				pkg, explicit = thisPkg, true
			} else if thisPkg != pkg {
				g.Fail("inconsistent package names:", thisPkg, pkg)
			}
		}
	}

	// If we don't have an explicit go_package option but we have an
	// import path, use that.
	if !explicit {
		p := g.defaultGoPackage()
		if p != "" {
			pkg, explicit = p, true
		}
	}

	// If there was no go_package and no import path to use,
	// double-check that all the inputs have the same implicit
	// Go package name.
	if !explicit {
		for _, f := range g.genFiles {
			thisPkg, _ := f.goPackageName()
			if thisPkg != pkg {
				g.Fail("inconsistent package names:", thisPkg, pkg)
			}
		}
	}

	g.packageName = RegisterUniquePackageName(pkg, g.genFiles[0])

	// Register the support package names. They might collide with the
	// name of a package we import.
	g.Pkg = map[string]string{
		"json":  RegisterUniquePackageName("json", nil),
		"math":  RegisterUniquePackageName("math", nil),
		"proto": RegisterUniquePackageName("proto", nil),
	}

AllFiles:
	for _, f := range g.allFiles {
		for _, genf := range g.genFiles {
			if f == genf {
				// In this package already.
				uniquePackageName[f.FileDescriptorProto] = g.packageName
				continue AllFiles
			}
		}
		// The file is a dependency, so we want to ignore its go_package option
		// because that is only relevant for its specific generated output.
		pkg := f.GetPackage()
		if pkg == "" {
			pkg = baseName(*f.Name)
		}
		RegisterUniquePackageName(pkg, f)
	}
}

// WrapTypes walks the incoming data, wrapping DescriptorProtos, EnumDescriptorProtos
// and FileDescriptorProtos into file-referenced objects within the Generator.
// It also creates the list of files to generate and so should be called before GenerateAllFiles.
func (g *Generator) WrapTypes() {
	g.allFiles = make([]*FileDescriptor, len(g.Request.ProtoFile))
	for i, f := range g.Request.ProtoFile {
		// We must wrap the descriptors before we wrap the enums
		descs := wrapDescriptors(f)
		g.buildNestedDescriptors(descs)
		enums := wrapEnumDescriptors(f, descs)
		exts := wrapExtensions(f)
		imps := wrapImported(f, g)
		fd := &FileDescriptor{
			FileDescriptorProto: f,
			desc:                descs,
			enum:                enums,
			ext:                 exts,
			imp:                 imps,
			exported:            make(map[Object][]symbol),
		}
		extractComments(fd)
		g.allFiles[i] = fd
	}

	g.genFiles = make([]*FileDescriptor, len(g.Request.FileToGenerate))
FindFiles:
	for i, fileName := range g.Request.FileToGenerate {
		// Search the list.  This algorithm is n^2 but n is tiny.
		for _, file := range g.allFiles {
			if fileName == file.GetName() {
				g.genFiles[i] = file
				continue FindFiles
			}
		}
		g.Fail("could not find file named", fileName)
	}
	g.Response.File = make([]*plugin.CodeGeneratorResponse_File, len(g.genFiles))
}

// Scan the descriptors in this file.  For each one, build the slice of nested descriptors
func (g *Generator) buildNestedDescriptors(descs []*Descriptor) {
	for _, desc := range descs {
		if len(desc.NestedType) != 0 {
			desc.nested = make([]*Descriptor, len(desc.NestedType))
			n := 0
			for _, nest := range descs {
				if nest.parent == desc {
					desc.nested[n] = nest
					n++
				}
			}
			if n != len(desc.NestedType) {
				g.Fail("internal error: nesting failure for", desc.GetName())
			}
		}
	}
}

// Construct the Descriptor
func newDescriptor(desc *descriptor.DescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) *Descriptor {
	d := &Descriptor{
		common:          common{file},
		DescriptorProto: desc,
		parent:          parent,
		index:           index,
	}
	if parent == nil {
		d.path = fmt.Sprintf("%d,%d", messagePath, index)
	} else {
		d.path = fmt.Sprintf("%s,%d,%d", parent.path, messageMessagePath, index)
	}

	// The only way to distinguish a group from a message is whether
	// the containing message has a TYPE_GROUP field that matches.
	if parent != nil {
		parts := d.TypeName()
		if file.Package != nil {
			parts = append([]string{*file.Package}, parts...)
		}
		exp := "." + strings.Join(parts, ".")
		for _, field := range parent.Field {
			if field.GetType() == descriptor.FieldDescriptorProto_TYPE_GROUP && field.GetTypeName() == exp {
				d.group = true
				break
			}
		}
	}

	d.ext = make([]*ExtensionDescriptor, len(desc.Extension))
	for i, field := range desc.Extension {
		d.ext[i] = &ExtensionDescriptor{common{file}, field, d}
	}

	return d
}

// Return a slice of all the Descriptors defined within this file
func wrapDescriptors(file *descriptor.FileDescriptorProto) []*Descriptor {
	sl := make([]*Descriptor, 0, len(file.MessageType)+10)
	for i, desc := range file.MessageType {
		sl = wrapThisDescriptor(sl, desc, nil, file, i)
	}
	return sl
}

// Wrap this Descriptor, recursively
func wrapThisDescriptor(sl []*Descriptor, desc *descriptor.DescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) []*Descriptor {
	sl = append(sl, newDescriptor(desc, parent, file, index))
	me := sl[len(sl)-1]
	for i, nested := range desc.NestedType {
		sl = wrapThisDescriptor(sl, nested, me, file, i)
	}
	return sl
}

// Construct the EnumDescriptor
func newEnumDescriptor(desc *descriptor.EnumDescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto, index int) *EnumDescriptor {
	ed := &EnumDescriptor{
		common:              common{file},
		EnumDescriptorProto: desc,
		parent:              parent,
	}
	if parent == nil {
		ed.path = fmt.Sprintf("%d,%d", enumPath, index)
	} else {
		ed.path = fmt.Sprintf("%s,%d,%d", parent.path, messageEnumPath, index)
	}
	return ed
}

// Return a slice of all the EnumDescriptors defined within this file
func wrapEnumDescriptors(file *descriptor.FileDescriptorProto, descs []*Descriptor) []*EnumDescriptor {
	sl := make([]*EnumDescriptor, 0, len(file.EnumType)+10)
	// Top-level enums.
	for i, enum := range file.EnumType {
		sl = append(sl, newEnumDescriptor(enum, nil, file, i))
	}
	// Enums within messages. Enums within embedded messages appear in the outer-most message.
	for _, nested := range descs {
		for i, enum := range nested.EnumType {
			sl = append(sl, newEnumDescriptor(enum, nested, file, i))
		}
	}
	return sl
}

// Return a slice of all the top-level ExtensionDescriptors defined within this file.
func wrapExtensions(file *descriptor.FileDescriptorProto) []*ExtensionDescriptor {
	sl := make([]*ExtensionDescriptor, len(file.Extension))
	for i, field := range file.Extension {
		sl[i] = &ExtensionDescriptor{common{file}, field, nil}
	}
	return sl
}

// Return a slice of all the types that are publicly imported into this file.
func wrapImported(file *descriptor.FileDescriptorProto, g *Generator) (sl []*ImportedDescriptor) {
	for _, index := range file.PublicDependency {
		df := g.fileByName(file.Dependency[index])
		for _, d := range df.desc {
			sl = append(sl, &ImportedDescriptor{common{file}, d})
		}
		for _, e := range df.enum {
			sl = append(sl, &ImportedDescriptor{common{file}, e})
		}
		for _, ext := range df.ext {
			sl = append(sl, &ImportedDescriptor{common{file}, ext})
		}
	}
	return
}

func extractComments(file *FileDescriptor) {
	file.comments = make(map[string]*descriptor.SourceCodeInfo_Location)
	for _, loc := range file.GetSourceCodeInfo().GetLocation() {
		if loc.LeadingComments == nil {
			continue
		}
		var p []string
		for _, n := range loc.Path {
			p = append(p, strconv.Itoa(int(n)))
		}
		file.comments[strings.Join(p, ",")] = loc
	}
}

// BuildTypeNameMap builds the map from fully qualified type names to objects.
// The key names for the map come from the input data, which puts a period at the beginning.
// It should be called after SetPackageNames and before GenerateAllFiles.
func (g *Generator) BuildTypeNameMap() {
	g.typeNameToObject = make(map[string]Object)
	for _, f := range g.allFiles {
		// The names in this loop are defined by the proto world, not us, so the
		// package name may be empty.  If so, the dotted package name of X will
		// be ".X"; otherwise it will be ".pkg.X".
		dottedPkg := "." + f.GetPackage()
		if dottedPkg != "." {
			dottedPkg += "."
		}
		for _, enum := range f.enum {
			name := dottedPkg + dottedSlice(enum.TypeName())
			g.typeNameToObject[name] = enum
		}
		for _, desc := range f.desc {
			name := dottedPkg + dottedSlice(desc.TypeName())
			g.typeNameToObject[name] = desc
		}
	}
}

// ObjectNamed, given a fully-qualified input type name as it appears in the input data,
// returns the descriptor for the message or enum with that name.
func (g *Generator) ObjectNamed(typeName string) Object {
	o, ok := g.typeNameToObject[typeName]
	if !ok {
		g.Fail("can't find object with type", typeName)
	}

	// If the file of this object isn't a direct dependency of the current file,
	// or in the current file, then this object has been publicly imported into
	// a dependency of the current file.
	// We should return the ImportedDescriptor object for it instead.
	direct := *o.File().Name == *g.file.Name
	if !direct {
		for _, dep := range g.file.Dependency {
			if *g.fileByName(dep).Name == *o.File().Name {
				direct = true
				break
			}
		}
	}
	if !direct {
		found := false
	Loop:
		for _, dep := range g.file.Dependency {
			df := g.fileByName(*g.fileByName(dep).Name)
			for _, td := range df.imp {
				if td.o == o {
					// Found it!
					o = td
					found = true
					break Loop
				}
			}
		}
		if !found {
			log.Printf("protoc-gen-go: WARNING: failed finding publicly imported dependency for %v, used in %v", typeName, *g.file.Name)
		}
	}

	return o
}

// P prints the arguments to the generated output.  It handles strings and int32s, plus
// handling indirections because they may be *string, etc.
func (g *Generator) P(str ...interface{}) {
	g.WriteString(g.indent)
	for _, v := range str {
		switch s := v.(type) {
		case string:
			g.WriteString(s)
		case *string:
			g.WriteString(*s)
		case bool:
			g.WriteString(fmt.Sprintf("%t", s))
		case *bool:
			g.WriteString(fmt.Sprintf("%t", *s))
		case int:
			g.WriteString(fmt.Sprintf("%d", s))
		case *int32:
			g.WriteString(fmt.Sprintf("%d", *s))
		case *int64:
			g.WriteString(fmt.Sprintf("%d", *s))
		case float64:
			g.WriteString(fmt.Sprintf("%g", s))
		case *float64:
			g.WriteString(fmt.Sprintf("%g", *s))
		default:
			g.Fail(fmt.Sprintf("unknown type in printer: %T", v))
		}
	}
	g.WriteByte('\n')
}

// In Indents the output one tab stop.
func (g *Generator) In() { g.indent += "\t" }

// Out unindents the output one tab stop.
func (g *Generator) Out() {
	if len(g.indent) > 0 {
		g.indent = g.indent[1:]
	}
}

// GenerateAllFiles generates the output for all the files we're outputting.
func (g *Generator) GenerateAllFiles() {
	// Initialize the plugins
	for _, p := range plugins {
		p.Init(g)
	}
	// Generate the output. The generator runs for every file, even the files
	// that we don't generate output for, so that we can collate the full list
	// of exported symbols to support public imports.
	genFileMap := make(map[*FileDescriptor]bool, len(g.genFiles))
	for _, file := range g.genFiles {
		genFileMap[file] = true
	}
	i := 0
	for _, file := range g.allFiles {
		g.Reset()
		g.generate(file)
		if _, ok := genFileMap[file]; !ok {
			continue
		}
		g.Response.File[i] = new(plugin.CodeGeneratorResponse_File)
		g.Response.File[i].Name = proto.String(goFileName(*file.Name))
		g.Response.File[i].Content = proto.String(g.String())
		i++
	}
}

// Run all the plugins associated with the file.
func (g *Generator) runPlugins(file *FileDescriptor) {
	for _, p := range plugins {
		p.Generate(file)
	}
}

// FileOf return the FileDescriptor for this FileDescriptorProto.
func (g *Generator) FileOf(fd *descriptor.FileDescriptorProto) *FileDescriptor {
	for _, file := range g.allFiles {
		if file.FileDescriptorProto == fd {
			return file
		}
	}
	g.Fail("could not find file in table:", fd.GetName())
	return nil
}

// Fill the response protocol buffer with the generated output for all the files we're
// supposed to generate.
func (g *Generator) generate(file *FileDescriptor) {
	g.file = g.FileOf(file.FileDescriptorProto)
	g.usedPackages = make(map[string]bool)

	for _, td := range g.file.imp {
		g.generateImported(td)
	}
	for _, enum := range g.file.enum {
		g.generateEnum(enum)
	}
	for _, desc := range g.file.desc {
		g.generateMessage(desc)
	}
	for _, ext := range g.file.ext {
		g.generateExtension(ext)
	}
	g.generateInitFunction()

	// Run the plugins before the imports so we know which imports are necessary.
	g.runPlugins(file)

	// Generate header and imports last, though they appear first in the output.
	rem := g.Buffer
	g.Buffer = new(bytes.Buffer)
	g.generateHeader()
	g.generateImports()
	g.Write(rem.Bytes())

	// Reformat generated code.
	fset := token.NewFileSet()
	ast, err := parser.ParseFile(fset, "", g, parser.ParseComments)
	if err != nil {
		g.Fail("bad Go source code was generated:", err.Error())
		return
	}
	g.Reset()
	err = (&printer.Config{Mode: printer.TabIndent | printer.UseSpaces, Tabwidth: 8}).Fprint(g, fset, ast)
	if err != nil {
		g.Fail("generated Go source code could not be reformatted:", err.Error())
	}
}

// Generate the header, including package definition
func (g *Generator) generateHeader() {
	g.P("// Code generated by protoc-gen-go.")
	g.P("// source: ", *g.file.Name)
	g.P("// DO NOT EDIT!")
	g.P()
	g.P("package ", g.file.PackageName())
	g.P()
}

// PrintComments prints any comments from the source .proto file.
// The path is a comma-separated list of integers.
// See descriptor.proto for its format.
func (g *Generator) PrintComments(path string) {
	if loc, ok := g.file.comments[path]; ok {
		text := strings.TrimSuffix(loc.GetLeadingComments(), "\n")
		for _, line := range strings.Split(text, "\n") {
			g.P("// ", strings.TrimPrefix(line, " "))
		}
	}
}

func (g *Generator) fileByName(filename string) *FileDescriptor {
	for _, fd := range g.allFiles {
		if fd.GetName() == filename {
			return fd
		}
	}
	return nil
}

// weak returns whether the ith import of the current file is a weak import.
func (g *Generator) weak(i int32) bool {
	for _, j := range g.file.WeakDependency {
		if j == i {
			return true
		}
	}
	return false
}

// Generate the imports
func (g *Generator) generateImports() {
	// We almost always need a proto import.  Rather than computing when we
	// do, which is tricky when there's a plugin, just import it and
	// reference it later. The same argument applies to the math package,
	// for handling bit patterns for floating-point numbers, and to the
	// json package, for symbolic names of enum values for JSON marshaling.
	g.P("import " + g.Pkg["proto"] + " " + strconv.Quote(g.ImportPrefix+"code.google.com/p/goprotobuf/proto"))
	g.P("import " + g.Pkg["json"] + ` "encoding/json"`)
	g.P("import " + g.Pkg["math"] + ` "math"`)
	for i, s := range g.file.Dependency {
		fd := g.fileByName(s)
		// Do not import our own package.
		if fd.PackageName() == g.packageName {
			continue
		}
		filename := goFileName(s)
		if substitution, ok := g.ImportMap[s]; ok {
			filename = substitution
		}
		filename = g.ImportPrefix + filename
		if strings.HasSuffix(filename, ".go") {
			filename = filename[0 : len(filename)-3]
		}
		// Skip weak imports.
		if g.weak(int32(i)) {
			g.P("// skipping weak import ", fd.PackageName(), " ", strconv.Quote(filename))
			continue
		}
		if _, ok := g.usedPackages[fd.PackageName()]; ok {
			g.P("import ", fd.PackageName(), " ", strconv.Quote(filename))
		} else {
			// TODO: Re-enable this when we are more feature-complete.
			// For instance, some protos use foreign field extensions, which we don't support.
			// Until then, this is just annoying spam.
			//log.Printf("protoc-gen-go: discarding unused import from %v: %v", *g.file.Name, s)
			g.P("// discarding unused import ", fd.PackageName(), " ", strconv.Quote(filename))
		}
	}
	g.P()
	// TODO: may need to worry about uniqueness across plugins
	for _, p := range plugins {
		p.GenerateImports(g.file)
		g.P()
	}
	g.P("// Reference proto, json, and math imports to suppress error if they are not otherwise used.")
	g.P("var _ = ", g.Pkg["proto"], ".Marshal")
	g.P("var _ = &", g.Pkg["json"], ".SyntaxError{}")
	g.P("var _ = ", g.Pkg["math"], ".Inf")
	g.P()
}

func (g *Generator) generateImported(id *ImportedDescriptor) {
	// Don't generate public import symbols for files that we are generating
	// code for, since those symbols will already be in this package.
	// We can't simply avoid creating the ImportedDescriptor objects,
	// because g.genFiles isn't populated at that stage.
	tn := id.TypeName()
	sn := tn[len(tn)-1]
	df := g.FileOf(id.o.File())
	filename := *df.Name
	for _, fd := range g.genFiles {
		if *fd.Name == filename {
			g.P("// Ignoring public import of ", sn, " from ", filename)
			g.P()
			return
		}
	}
	g.P("// ", sn, " from public import ", filename)
	g.usedPackages[df.PackageName()] = true

	for _, sym := range df.exported[id.o] {
		sym.GenerateAlias(g, df.PackageName())
	}

	g.P()
}

// Generate the enum definitions for this EnumDescriptor.
func (g *Generator) generateEnum(enum *EnumDescriptor) {
	// The full type name
	typeName := enum.TypeName()
	// The full type name, CamelCased.
	ccTypeName := CamelCaseSlice(typeName)
	ccPrefix := enum.prefix()

	g.PrintComments(enum.path)
	g.P("type ", ccTypeName, " int32")
	g.file.addExport(enum, enumSymbol(ccTypeName))
	g.P("const (")
	g.In()
	for i, e := range enum.Value {
		g.PrintComments(fmt.Sprintf("%s,%d,%d", enum.path, enumValuePath, i))

		name := ccPrefix + *e.Name
		g.P(name, " ", ccTypeName, " = ", e.Number)
		g.file.addExport(enum, constOrVarSymbol{name, "const", ccTypeName})
	}
	g.Out()
	g.P(")")
	g.P("var ", ccTypeName, "_name = map[int32]string{")
	g.In()
	generated := make(map[int32]bool) // avoid duplicate values
	for _, e := range enum.Value {
		duplicate := ""
		if _, present := generated[*e.Number]; present {
			duplicate = "// Duplicate value: "
		}
		g.P(duplicate, e.Number, ": ", strconv.Quote(*e.Name), ",")
		generated[*e.Number] = true
	}
	g.Out()
	g.P("}")
	g.P("var ", ccTypeName, "_value = map[string]int32{")
	g.In()
	for _, e := range enum.Value {
		g.P(strconv.Quote(*e.Name), ": ", e.Number, ",")
	}
	g.Out()
	g.P("}")

	g.P("func (x ", ccTypeName, ") Enum() *", ccTypeName, " {")
	g.In()
	g.P("p := new(", ccTypeName, ")")
	g.P("*p = x")
	g.P("return p")
	g.Out()
	g.P("}")

	g.P("func (x ", ccTypeName, ") String() string {")
	g.In()
	g.P("return ", g.Pkg["proto"], ".EnumName(", ccTypeName, "_name, int32(x))")
	g.Out()
	g.P("}")

	g.P("func (x ", ccTypeName, ") MarshalJSON() ([]byte, error) {")
	g.In()
	g.P("return json.Marshal(x.String())")
	g.Out()
	g.P("}")

	g.P("func (x *", ccTypeName, ") UnmarshalJSON(data []byte) error {")
	g.In()
	g.P("value, err := ", g.Pkg["proto"], ".UnmarshalJSONEnum(", ccTypeName, `_value, data, "`, ccTypeName, `")`)
	g.P("if err != nil {")
	g.In()
	g.P("return err")
	g.Out()
	g.P("}")
	g.P("*x = ", ccTypeName, "(value)")
	g.P("return nil")
	g.Out()
	g.P("}")

	g.P()
}

// The tag is a string like "varint,2,opt,name=fieldname,def=7" that
// identifies details of the field for the protocol buffer marshaling and unmarshaling
// code.  The fields are:
//	wire encoding
//	protocol tag number
//	opt,req,rep for optional, required, or repeated
//	packed whether the encoding is "packed" (optional; repeated primitives only)
//	name= the original declared name
//	enum= the name of the enum type if it is an enum-typed field.
//	def= string representation of the default value, if any.
// The default value must be in a representation that can be used at run-time
// to generate the default value. Thus bools become 0 and 1, for instance.
func (g *Generator) goTag(field *descriptor.FieldDescriptorProto, wiretype string) string {
	optrepreq := ""
	switch {
	case isOptional(field):
		optrepreq = "opt"
	case isRequired(field):
		optrepreq = "req"
	case isRepeated(field):
		optrepreq = "rep"
	}
	defaultValue := field.GetDefaultValue()
	if defaultValue != "" {
		switch *field.Type {
		case descriptor.FieldDescriptorProto_TYPE_BOOL:
			if defaultValue == "true" {
				defaultValue = "1"
			} else {
				defaultValue = "0"
			}
		case descriptor.FieldDescriptorProto_TYPE_STRING,
			descriptor.FieldDescriptorProto_TYPE_BYTES:
			// Nothing to do. Quoting is done for the whole tag.
		case descriptor.FieldDescriptorProto_TYPE_ENUM:
			// For enums we need to provide the integer constant.
			obj := g.ObjectNamed(field.GetTypeName())
			if id, ok := obj.(*ImportedDescriptor); ok {
				// It is an enum that was publicly imported.
				// We need the underlying type.
				obj = id.o
			}
			enum, ok := obj.(*EnumDescriptor)
			if !ok {
				log.Printf("obj is a %T", obj)
				if id, ok := obj.(*ImportedDescriptor); ok {
					log.Printf("id.o is a %T", id.o)
				}
				g.Fail("unknown enum type", CamelCaseSlice(obj.TypeName()))
			}
			defaultValue = enum.integerValueAsString(defaultValue)
		}
		defaultValue = ",def=" + defaultValue
	}
	enum := ""
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_ENUM {
		// We avoid using obj.PackageName(), because we want to use the
		// original (proto-world) package name.
		obj := g.ObjectNamed(field.GetTypeName())
		if id, ok := obj.(*ImportedDescriptor); ok {
			obj = id.o
		}
		enum = ",enum="
		if pkg := obj.File().GetPackage(); pkg != "" {
			enum += pkg + "."
		}
		enum += CamelCaseSlice(obj.TypeName())
	}
	packed := ""
	if field.Options != nil && field.Options.GetPacked() {
		packed = ",packed"
	}
	fieldName := field.GetName()
	name := fieldName
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_GROUP {
		// We must use the type name for groups instead of
		// the field name to preserve capitalization.
		// type_name in FieldDescriptorProto is fully-qualified,
		// but we only want the local part.
		name = *field.TypeName
		if i := strings.LastIndex(name, "."); i >= 0 {
			name = name[i+1:]
		}
	}
	if name == CamelCase(fieldName) {
		name = ""
	} else {
		name = ",name=" + name
	}
	return strconv.Quote(fmt.Sprintf("%s,%d,%s%s%s%s%s",
		wiretype,
		field.GetNumber(),
		optrepreq,
		packed,
		name,
		enum,
		defaultValue))
}

func needsStar(typ descriptor.FieldDescriptorProto_Type) bool {
	switch typ {
	case descriptor.FieldDescriptorProto_TYPE_GROUP:
		return false
	case descriptor.FieldDescriptorProto_TYPE_MESSAGE:
		return false
	case descriptor.FieldDescriptorProto_TYPE_BYTES:
		return false
	}
	return true
}

// TypeName is the printed name appropriate for an item. If the object is in the current file,
// TypeName drops the package name and underscores the rest.
// Otherwise the object is from another package; and the result is the underscored
// package name followed by the item name.
// The result always has an initial capital.
func (g *Generator) TypeName(obj Object) string {
	return g.DefaultPackageName(obj) + CamelCaseSlice(obj.TypeName())
}

// TypeNameWithPackage is like TypeName, but always includes the package
// name even if the object is in our own package.
func (g *Generator) TypeNameWithPackage(obj Object) string {
	return obj.PackageName() + CamelCaseSlice(obj.TypeName())
}

// GoType returns a string representing the type name, and the wire type
func (g *Generator) GoType(message *Descriptor, field *descriptor.FieldDescriptorProto) (typ string, wire string) {
	// TODO: Options.
	switch *field.Type {
	case descriptor.FieldDescriptorProto_TYPE_DOUBLE:
		typ, wire = "float64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_FLOAT:
		typ, wire = "float32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_INT64:
		typ, wire = "int64", "varint"
	case descriptor.FieldDescriptorProto_TYPE_UINT64:
		typ, wire = "uint64", "varint"
	case descriptor.FieldDescriptorProto_TYPE_INT32:
		typ, wire = "int32", "varint"
	case descriptor.FieldDescriptorProto_TYPE_UINT32:
		typ, wire = "uint32", "varint"
	case descriptor.FieldDescriptorProto_TYPE_FIXED64:
		typ, wire = "uint64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_FIXED32:
		typ, wire = "uint32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_BOOL:
		typ, wire = "bool", "varint"
	case descriptor.FieldDescriptorProto_TYPE_STRING:
		typ, wire = "string", "bytes"
	case descriptor.FieldDescriptorProto_TYPE_GROUP:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = "*"+g.TypeName(desc), "group"
	case descriptor.FieldDescriptorProto_TYPE_MESSAGE:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = "*"+g.TypeName(desc), "bytes"
	case descriptor.FieldDescriptorProto_TYPE_BYTES:
		typ, wire = "[]byte", "bytes"
	case descriptor.FieldDescriptorProto_TYPE_ENUM:
		desc := g.ObjectNamed(field.GetTypeName())
		typ, wire = g.TypeName(desc), "varint"
	case descriptor.FieldDescriptorProto_TYPE_SFIXED32:
		typ, wire = "int32", "fixed32"
	case descriptor.FieldDescriptorProto_TYPE_SFIXED64:
		typ, wire = "int64", "fixed64"
	case descriptor.FieldDescriptorProto_TYPE_SINT32:
		typ, wire = "int32", "zigzag32"
	case descriptor.FieldDescriptorProto_TYPE_SINT64:
		typ, wire = "int64", "zigzag64"
	default:
		g.Fail("unknown type for", field.GetName())
	}
	if isRepeated(field) {
		typ = "[]" + typ
	} else if needsStar(*field.Type) {
		typ = "*" + typ
	}
	return
}

func (g *Generator) RecordTypeUse(t string) {
	if obj, ok := g.typeNameToObject[t]; ok {
		// Call ObjectNamed to get the true object to record the use.
		obj = g.ObjectNamed(t)
		g.usedPackages[obj.PackageName()] = true
	}
}

// Method names that may be generated.  Fields with these names get an
// underscore appended.
var methodNames = [...]string{
	"Reset",
	"String",
	"ProtoMessage",
	"Marshal",
	"Unmarshal",
	"ExtensionRangeArray",
	"ExtensionMap",
	"Descriptor",
}

// Generate the type and default constant definitions for this Descriptor.
func (g *Generator) generateMessage(message *Descriptor) {
	// The full type name
	typeName := message.TypeName()
	// The full type name, CamelCased.
	ccTypeName := CamelCaseSlice(typeName)

	usedNames := make(map[string]bool)
	for _, n := range methodNames {
		usedNames[n] = true
	}
	fieldNames := make(map[*descriptor.FieldDescriptorProto]string)
	fieldGetterNames := make(map[*descriptor.FieldDescriptorProto]string)

	g.PrintComments(message.path)
	g.P("type ", ccTypeName, " struct {")
	g.In()

	for i, field := range message.Field {
		g.PrintComments(fmt.Sprintf("%s,%d,%d", message.path, messageFieldPath, i))

		fieldName := CamelCase(*field.Name)
		for usedNames[fieldName] {
			fieldName += "_"
		}
		fieldGetterName := fieldName
		usedNames[fieldName] = true
		typename, wiretype := g.GoType(message, field)
		jsonName := *field.Name
		tag := fmt.Sprintf("protobuf:%s json:%q", g.goTag(field, wiretype), jsonName+",omitempty")
		fieldNames[field] = fieldName
		fieldGetterNames[field] = fieldGetterName
		g.P(fieldName, "\t", typename, "\t`", tag, "`")
		g.RecordTypeUse(field.GetTypeName())
	}
	if len(message.ExtensionRange) > 0 {
		g.P("XXX_extensions\t\tmap[int32]", g.Pkg["proto"], ".Extension `json:\"-\"`")
	}
	g.P("XXX_unrecognized\t[]byte `json:\"-\"`")
	g.Out()
	g.P("}")

	// Reset, String and ProtoMessage methods.
	g.P("func (m *", ccTypeName, ") Reset() { *m = ", ccTypeName, "{} }")
	g.P("func (m *", ccTypeName, ") String() string { return ", g.Pkg["proto"], ".CompactTextString(m) }")
	g.P("func (*", ccTypeName, ") ProtoMessage() {}")

	// Extension support methods
	var hasExtensions, isMessageSet bool
	if len(message.ExtensionRange) > 0 {
		hasExtensions = true
		// message_set_wire_format only makes sense when extensions are defined.
		if opts := message.Options; opts != nil && opts.GetMessageSetWireFormat() {
			isMessageSet = true
			g.P()
			g.P("func (m *", ccTypeName, ") Marshal() ([]byte, error) {")
			g.In()
			g.P("return ", g.Pkg["proto"], ".MarshalMessageSet(m.ExtensionMap())")
			g.Out()
			g.P("}")
			g.P("func (m *", ccTypeName, ") Unmarshal(buf []byte) error {")
			g.In()
			g.P("return ", g.Pkg["proto"], ".UnmarshalMessageSet(buf, m.ExtensionMap())")
			g.Out()
			g.P("}")
			g.P("// ensure ", ccTypeName, " satisfies proto.Marshaler and proto.Unmarshaler")
			g.P("var _ ", g.Pkg["proto"], ".Marshaler = (*", ccTypeName, ")(nil)")
			g.P("var _ ", g.Pkg["proto"], ".Unmarshaler = (*", ccTypeName, ")(nil)")
		}

		g.P()
		g.P("var extRange_", ccTypeName, " = []", g.Pkg["proto"], ".ExtensionRange{")
		g.In()
		for _, r := range message.ExtensionRange {
			end := fmt.Sprint(*r.End - 1) // make range inclusive on both ends
			g.P("{", r.Start, ", ", end, "},")
		}
		g.Out()
		g.P("}")
		g.P("func (*", ccTypeName, ") ExtensionRangeArray() []", g.Pkg["proto"], ".ExtensionRange {")
		g.In()
		g.P("return extRange_", ccTypeName)
		g.Out()
		g.P("}")
		g.P("func (m *", ccTypeName, ") ExtensionMap() map[int32]", g.Pkg["proto"], ".Extension {")
		g.In()
		g.P("if m.XXX_extensions == nil {")
		g.In()
		g.P("m.XXX_extensions = make(map[int32]", g.Pkg["proto"], ".Extension)")
		g.Out()
		g.P("}")
		g.P("return m.XXX_extensions")
		g.Out()
		g.P("}")
	}

	// Default constants
	defNames := make(map[*descriptor.FieldDescriptorProto]string)
	for _, field := range message.Field {
		def := field.GetDefaultValue()
		if def == "" {
			continue
		}
		fieldname := "Default_" + ccTypeName + "_" + CamelCase(*field.Name)
		defNames[field] = fieldname
		typename, _ := g.GoType(message, field)
		if typename[0] == '*' {
			typename = typename[1:]
		}
		kind := "const "
		switch {
		case typename == "bool":
		case typename == "string":
			def = strconv.Quote(def)
		case typename == "[]byte":
			def = "[]byte(" + strconv.Quote(def) + ")"
			kind = "var "
		case def == "inf", def == "-inf", def == "nan":
			// These names are known to, and defined by, the protocol language.
			switch def {
			case "inf":
				def = "math.Inf(1)"
			case "-inf":
				def = "math.Inf(-1)"
			case "nan":
				def = "math.NaN()"
			}
			if *field.Type == descriptor.FieldDescriptorProto_TYPE_FLOAT {
				def = "float32(" + def + ")"
			}
			kind = "var "
		case *field.Type == descriptor.FieldDescriptorProto_TYPE_ENUM:
			// Must be an enum.  Need to construct the prefixed name.
			obj := g.ObjectNamed(field.GetTypeName())
			var enum *EnumDescriptor
			if id, ok := obj.(*ImportedDescriptor); ok {
				// The enum type has been publicly imported.
				enum, _ = id.o.(*EnumDescriptor)
			} else {
				enum, _ = obj.(*EnumDescriptor)
			}
			if enum == nil {
				log.Printf("don't know how to generate constant for %s", fieldname)
				continue
			}
			def = g.DefaultPackageName(obj) + enum.prefix() + def
		}
		g.P(kind, fieldname, " ", typename, " = ", def)
		g.file.addExport(message, constOrVarSymbol{fieldname, kind, ""})
	}
	g.P()

	// Field getters
	var getters []getterSymbol
	for _, field := range message.Field {
		fname := fieldNames[field]
		typename, _ := g.GoType(message, field)
		mname := "Get" + fieldGetterNames[field]
		star := ""
		if needsStar(*field.Type) && typename[0] == '*' {
			typename = typename[1:]
			star = "*"
		}

		// Only export getter symbols for basic types,
		// and for messages and enums in the same package.
		// Groups are not exported.
		// Foreign types can't be hoisted through a public import because
		// the importer may not already be importing the defining .proto.
		// As an example, imagine we have an import tree like this:
		//   A.proto -> B.proto -> C.proto
		// If A publicly imports B, we need to generate the getters from B in A's output,
		// but if one such getter returns something from C then we cannot do that
		// because A is not importing C already.
		var getter, genType bool
		switch *field.Type {
		case descriptor.FieldDescriptorProto_TYPE_GROUP:
			getter = false
		case descriptor.FieldDescriptorProto_TYPE_MESSAGE, descriptor.FieldDescriptorProto_TYPE_ENUM:
			// Only export getter if its return type is in this package.
			getter = g.ObjectNamed(field.GetTypeName()).PackageName() == message.PackageName()
			genType = true
		default:
			getter = true
		}
		if getter {
			getters = append(getters, getterSymbol{
				name:     mname,
				typ:      typename,
				typeName: field.GetTypeName(),
				genType:  genType,
			})
		}

		g.P("func (m *", ccTypeName, ") "+mname+"() "+typename+" {")
		g.In()
		def, hasDef := defNames[field]
		typeDefaultIsNil := false // whether this field type's default value is a literal nil unless specified
		switch *field.Type {
		case descriptor.FieldDescriptorProto_TYPE_BYTES:
			typeDefaultIsNil = !hasDef
		case descriptor.FieldDescriptorProto_TYPE_GROUP, descriptor.FieldDescriptorProto_TYPE_MESSAGE:
			typeDefaultIsNil = true
		}
		if isRepeated(field) {
			typeDefaultIsNil = true
		}
		if typeDefaultIsNil {
			// A bytes field with no explicit default needs less generated code,
			// as does a message or group field, or a repeated field.
			g.P("if m != nil {")
			g.In()
			g.P("return m." + fname)
			g.Out()
			g.P("}")
			g.P("return nil")
			g.Out()
			g.P("}")
			g.P()
			continue
		}
		g.P("if m != nil && m." + fname + " != nil {")
		g.In()
		g.P("return " + star + "m." + fname)
		g.Out()
		g.P("}")
		if hasDef {
			if *field.Type != descriptor.FieldDescriptorProto_TYPE_BYTES {
				g.P("return " + def)
			} else {
				// The default is a []byte var.
				// Make a copy when returning it to be safe.
				g.P("return append([]byte(nil), ", def, "...)")
			}
		} else {
			switch *field.Type {
			case descriptor.FieldDescriptorProto_TYPE_BOOL:
				g.P("return false")
			case descriptor.FieldDescriptorProto_TYPE_STRING:
				g.P(`return ""`)
			default:
				g.P("return 0")
			}
		}
		g.Out()
		g.P("}")
		g.P()
	}

	if !message.group {
		g.file.addExport(message, &messageSymbol{ccTypeName, hasExtensions, isMessageSet, getters})
	}

	for _, ext := range message.ext {
		g.generateExtension(ext)
	}

}

func (g *Generator) generateExtension(ext *ExtensionDescriptor) {
	ccTypeName := ext.DescName()

	extendedType := "*" + g.TypeName(g.ObjectNamed(*ext.Extendee))
	field := ext.FieldDescriptorProto
	fieldType, wireType := g.GoType(ext.parent, field)
	tag := g.goTag(field, wireType)
	g.RecordTypeUse(*ext.Extendee)
	if n := ext.FieldDescriptorProto.TypeName; n != nil {
		// foreign extension type
		g.RecordTypeUse(*n)
	}

	typeName := ext.TypeName()

	// Special case for proto2 message sets: If this extension is extending
	// proto2_bridge.MessageSet, and its final name component is "message_set_extension",
	// then drop that last component.
	if extendedType == "*proto2_bridge.MessageSet" && typeName[len(typeName)-1] == "message_set_extension" {
		typeName = typeName[:len(typeName)-1]
	}

	// For text formatting, the package must be exactly what the .proto file declares,
	// ignoring overrides such as the go_package option, and with no dot/underscore mapping.
	extName := strings.Join(typeName, ".")
	if g.file.Package != nil {
		extName = *g.file.Package + "." + extName
	}

	g.P("var ", ccTypeName, " = &", g.Pkg["proto"], ".ExtensionDesc{")
	g.In()
	g.P("ExtendedType: (", extendedType, ")(nil),")
	g.P("ExtensionType: (", fieldType, ")(nil),")
	g.P("Field: ", field.Number, ",")
	g.P(`Name: "`, extName, `",`)
	g.P("Tag: ", tag, ",")

	g.Out()
	g.P("}")
	g.P()

	g.file.addExport(ext, constOrVarSymbol{ccTypeName, "var", ""})
}

func (g *Generator) generateInitFunction() {
	g.P("func init() {")
	g.In()
	for _, enum := range g.file.enum {
		g.generateEnumRegistration(enum)
	}
	for _, d := range g.file.desc {
		for _, ext := range d.ext {
			g.generateExtensionRegistration(ext)
		}
	}
	for _, ext := range g.file.ext {
		g.generateExtensionRegistration(ext)
	}
	g.Out()
	g.P("}")
}

func (g *Generator) generateEnumRegistration(enum *EnumDescriptor) {
	// // We always print the full (proto-world) package name here.
	pkg := enum.File().GetPackage()
	if pkg != "" {
		pkg += "."
	}
	// The full type name
	typeName := enum.TypeName()
	// The full type name, CamelCased.
	ccTypeName := CamelCaseSlice(typeName)
	g.P(g.Pkg["proto"]+".RegisterEnum(", strconv.Quote(pkg+ccTypeName), ", ", ccTypeName+"_name, ", ccTypeName+"_value)")
}

func (g *Generator) generateExtensionRegistration(ext *ExtensionDescriptor) {
	g.P(g.Pkg["proto"]+".RegisterExtension(", ext.DescName(), ")")
}

// And now lots of helper functions.

// Is c an ASCII lower-case letter?
func isASCIILower(c byte) bool {
	return 'a' <= c && c <= 'z'
}

// Is c an ASCII digit?
func isASCIIDigit(c byte) bool {
	return '0' <= c && c <= '9'
}

// CamelCase returns the CamelCased name.
// If there is an interior underscore followed by a lower case letter,
// drop the underscore and convert the letter to upper case.
// There is a remote possibility of this rewrite causing a name collision,
// but it's so remote we're prepared to pretend it's nonexistent - since the
// C++ generator lowercases names, it's extremely unlikely to have two fields
// with different capitalizations.
// In short, _my_field_name_2 becomes XMyFieldName_2.
func CamelCase(s string) string {
	if s == "" {
		return ""
	}
	t := make([]byte, 0, 32)
	i := 0
	if s[0] == '_' {
		// Need a capital letter; drop the '_'.
		t = append(t, 'X')
		i++
	}
	// Invariant: if the next letter is lower case, it must be converted
	// to upper case.
	// That is, we process a word at a time, where words are marked by _ or
	// upper case letter. Digits are treated as words.
	for ; i < len(s); i++ {
		c := s[i]
		if c == '_' && i+1 < len(s) && isASCIILower(s[i+1]) {
			continue // Skip the underscore in s.
		}
		if isASCIIDigit(c) {
			t = append(t, c)
			continue
		}
		// Assume we have a letter now - if not, it's a bogus identifier.
		// The next word is a sequence of characters that must start upper case.
		if isASCIILower(c) {
			c ^= ' ' // Make it a capital letter.
		}
		t = append(t, c) // Guaranteed not lower case.
		// Accept lower case sequence that follows.
		for i+1 < len(s) && isASCIILower(s[i+1]) {
			i++
			t = append(t, s[i])
		}
	}
	return string(t)
}

// CamelCaseSlice is like CamelCase, but the argument is a slice of strings to
// be joined with "_".
func CamelCaseSlice(elem []string) string { return CamelCase(strings.Join(elem, "_")) }

// dottedSlice turns a sliced name into a dotted name.
func dottedSlice(elem []string) string { return strings.Join(elem, ".") }

// Given a .proto file name, return the output name for the generated Go program.
func goFileName(name string) string {
	ext := path.Ext(name)
	if ext == ".proto" || ext == ".protodevel" {
		name = name[0 : len(name)-len(ext)]
	}
	return name + ".pb.go"
}

// Is this field optional?
func isOptional(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_OPTIONAL
}

// Is this field required?
func isRequired(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_REQUIRED
}

// Is this field repeated?
func isRepeated(field *descriptor.FieldDescriptorProto) bool {
	return field.Label != nil && *field.Label == descriptor.FieldDescriptorProto_LABEL_REPEATED
}

// badToUnderscore is the mapping function used to generate Go names from package names,
// which can be dotted in the input .proto file.  It replaces non-identifier characters such as
// dot or dash with underscore.
func badToUnderscore(r rune) rune {
	if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' {
		return r
	}
	return '_'
}

// baseName returns the last path element of the name, with the last dotted suffix removed.
func baseName(name string) string {
	// First, find the last element
	if i := strings.LastIndex(name, "/"); i >= 0 {
		name = name[i+1:]
	}
	// Now drop the suffix
	if i := strings.LastIndex(name, "."); i >= 0 {
		name = name[0:i]
	}
	return name
}

// The SourceCodeInfo message describes the location of elements of a parsed
// .proto file by way of a "path", which is a sequence of integers that
// describe the route from a FileDescriptorProto to the relevant submessage.
// The path alternates between a field number of a repeated field, and an index
// into that repeated field. The constants below define the field numbers that
// are used.
//
// See descriptor.proto for more information about this.
const (
	// tag numbers in FileDescriptorProto
	messagePath = 4 // message_type
	enumPath    = 5 // enum_type
	// tag numbers in DescriptorProto
	messageFieldPath   = 2 // field
	messageMessagePath = 3 // nested_type
	messageEnumPath    = 4 // enum_type
	// tag numbers in EnumDescriptorProto
	enumValuePath = 2 // value
)