compiler/generator/generator.go

// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 Google Inc.  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"
	"log"
	"os"
	"path"
	"strconv"
	"strings"

	"goprotobuf.googlecode.com/hg/proto"
	plugin "goprotobuf.googlecode.com/hg/compiler/plugin"
	descriptor "goprotobuf.googlecode.com/hg/compiler/descriptor"
)

// 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) }

// 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.
}

// 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] = proto.GetString(parent.Name)
	}
	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.
}

// 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 := proto.GetString(e.Name)
	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 proto.GetString(c.Name) == name {
			return fmt.Sprint(proto.GetInt32(c.Number))
		}
	}
	log.Exit("cannot find value for enum constant")
	return ""
}

// ExtensionDescriptor desribes 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 := proto.GetString(e.Name)
	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
}

// 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.
}

// 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) }

// The package named defined in the input for this file, possibly dotted.
// If the file does not define a package, use the base of the file name.
func (d *FileDescriptor) originalPackageName() string {
	// Does the file have a package clause?
	pkg := proto.GetString(d.Package)
	if pkg != "" {
		return pkg
	}
	// Use the file base name.
	return BaseName(proto.GetString(d.Name))
}

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

// Each package name we generate must be unique. The package we're generating
// gets its own name but every other package must have a unqiue 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.Exit("internal error: no package name defined for", proto.GetString(fd.Name))
	}
	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.
	ImportPrefix string            // String to prefix to imported package file names.
	ImportMap    map[string]string // Mapping from import name to generated name

	ProtoPkg string // The name under which we import the library's package proto.

	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 os.Error, and exits the program.
func (g *Generator) Error(err os.Error, msgs ...string) {
	s := strings.Join(msgs, " ") + ":" + err.String()
	log.Println("protoc-gen-go: error:", s)
	g.Response.Error = proto.String(s)
	os.Exit(1)
}

// Fail reports a problem and exits the program.
func (g *Generator) Fail(msgs ...string) {
	s := strings.Join(msgs, " ")
	log.Println("protoc-gen-go: error:", s)
	g.Response.Error = proto.String(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, ",", -1) {
		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 {
		if k == "import_prefix" {
			g.ImportPrefix = v
		} else 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 {
	for i, orig := 1, pkg; pkgNamesInUse[pkg]; i++ {
		// It's a duplicate; must rename.
		pkg = orig + strconv.Itoa(i)
	}
	// Install it.
	pkgNamesInUse[pkg] = true
	pkg = strings.Map(DotToUnderscore, pkg)
	if f != nil {
		uniquePackageName[f.FileDescriptorProto] = pkg
	}
	return pkg
}

// 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 := g.genFiles[0].originalPackageName()
	g.packageName = RegisterUniquePackageName(pkg, g.genFiles[0])
	// Register the proto package name.  It might collide with the
	// name of a package we import.
	g.ProtoPkg = RegisterUniquePackageName("proto", nil)
	for _, f := range g.genFiles {
		thisPkg := f.originalPackageName()
		if thisPkg != pkg {
			g.Fail("inconsistent package names:", thisPkg, pkg)
		}
	}
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
			}
		}
		RegisterUniquePackageName(f.originalPackageName(), 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)
		g.allFiles[i] = &FileDescriptor{
			FileDescriptorProto: f,
			desc:                descs,
			enum:                enums,
			ext:                 exts,
		}
	}

	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 == proto.GetString(file.Name) {
				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", proto.GetString(desc.Name))
			}
		}
	}
}

// Construct the Descriptor and add it to the slice
func addDescriptor(sl []*Descriptor, desc *descriptor.DescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto) []*Descriptor {
	d := &Descriptor{common{File: file}, desc, parent, nil, nil, nil}

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

	return append(sl, 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 _, desc := range file.MessageType {
		sl = wrapThisDescriptor(sl, desc, nil, file)
	}
	return sl
}

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

// Construct the EnumDescriptor and add it to the slice
func addEnumDescriptor(sl []*EnumDescriptor, desc *descriptor.EnumDescriptorProto, parent *Descriptor, file *descriptor.FileDescriptorProto) []*EnumDescriptor {
	return append(sl, &EnumDescriptor{common{File: file}, desc, parent, nil})
}

// 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 _, enum := range file.EnumType {
		sl = addEnumDescriptor(sl, enum, nil, file)
	}
	// Enums within messages. Enums within embedded messages appear in the outer-most message.
	for _, nested := range descs {
		for _, enum := range nested.EnumType {
			sl = addEnumDescriptor(sl, enum, nested, file)
		}
	}
	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: file}, field, nil}
	}
	return sl
}

// 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 := "." + proto.GetString(f.Package)
		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 {
	f, ok := g.typeNameToObject[typeName]
	if !ok {
		g.Fail("can't find object with type", typeName)
	}
	return f
}

// 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 *int32:
			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.
	for i, file := range g.genFiles {
		g.Reset()
		g.generate(file)
		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())
	}
}

// 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:", proto.GetString(fd.Name))
	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 _, 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())
}

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

// Generate the header, including package definition and 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 os package.
	g.P("import " + g.ProtoPkg + " " + Quote(g.ImportPrefix+"goprotobuf.googlecode.com/hg/proto"))
	g.P(`import "os"`)
	for _, s := range g.file.Dependency {
		// Need to find the descriptor for this file
		for _, fd := range g.allFiles {
			// Do not import our own package.
			if fd.PackageName() == g.packageName {
				continue
			}
			if proto.GetString(fd.Name) == s {
				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]
				}
				if _, ok := g.usedPackages[fd.PackageName()]; ok {
					g.P("import ", fd.PackageName(), " ", Quote(filename))
				} else {
					log.Println("protoc-gen-go: discarding unused import:", filename)
				}
				break
			}
		}
	}
	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 & os imports to suppress error if it's not otherwise used.")
	g.P("var _ = ", g.ProtoPkg, ".GetString")
	g.P("var _ os.Error")
	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.P("type ", ccTypeName, " int32")
	g.P("const (")
	g.In()
	for _, e := range enum.Value {
		g.P(ccPrefix+*e.Name, " = ", e.Number)
	}
	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, ": ", 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(Quote(*e.Name), ": ", e.Number, ",")
	}
	g.Out()
	g.P("}")
	g.P("func New", ccTypeName, "(x int32) *", ccTypeName, " {")
	g.In()
	g.P("e := ", ccTypeName, "(x)")
	g.P("return &e")
	g.Out()
	g.P("}")
	g.P()
}

// The tag is a string like "PB(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
//	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 := proto.GetString(field.DefaultValue)
	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:
			// Protect frogs.
			defaultValue = Quote(defaultValue)
			// Don't need the quotes
			defaultValue = defaultValue[1 : len(defaultValue)-1]
		case descriptor.FieldDescriptorProto_TYPE_ENUM:
			// For enums we need to provide the integer constant.
			obj := g.ObjectNamed(proto.GetString(field.TypeName))
			enum, ok := obj.(*EnumDescriptor)
			if !ok {
				g.Fail("enum type inconsistent for", CamelCaseSlice(obj.TypeName()))
			}
			defaultValue = enum.integerValueAsString(defaultValue)
		}
		defaultValue = ",def=" + defaultValue
	}
	enum := ""
	if *field.Type == descriptor.FieldDescriptorProto_TYPE_ENUM {
		obj := g.ObjectNamed(proto.GetString(field.TypeName))
		enum = ",enum=" + obj.PackageName() + "." + CamelCaseSlice(obj.TypeName())
	}
	name := proto.GetString(field.Name)
	if name == CamelCase(name) {
		name = ""
	} else {
		name = ",name=" + name
	}
	return Quote(fmt.Sprintf("PB(%s,%d,%s%s%s%s)",
		wiretype,
		proto.GetInt32(field.Number),
		optrepreq,
		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(proto.GetString(field.TypeName))
		typ, wire = "*"+g.TypeName(desc), "group"
	case descriptor.FieldDescriptorProto_TYPE_MESSAGE:
		desc := g.ObjectNamed(proto.GetString(field.TypeName))
		typ, wire = "*"+g.TypeName(desc), "bytes"
	case descriptor.FieldDescriptorProto_TYPE_BYTES:
		typ, wire = "[]byte", "bytes"
	case descriptor.FieldDescriptorProto_TYPE_ENUM:
		desc := g.ObjectNamed(proto.GetString(field.TypeName))
		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", proto.GetString(field.Name))
	}
	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 {
		g.usedPackages[obj.PackageName()] = true
	}
}

// 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)

	g.P("type ", ccTypeName, " struct {")
	g.In()
	for _, field := range message.Field {
		fieldname := CamelCase(*field.Name)
		typename, wiretype := g.GoType(message, field)
		tag := g.goTag(field, wiretype)
		g.P(fieldname, "\t", typename, "\t", tag)
		g.RecordTypeUse(proto.GetString(field.TypeName))
	}
	if len(message.ExtensionRange) > 0 {
		g.P("XXX_extensions\t\tmap[int32][]byte")
	}
	g.P("XXX_unrecognized\t[]byte")
	g.Out()
	g.P("}")

	// Reset function
	g.P("func (this *", ccTypeName, ") Reset() {")
	g.In()
	g.P("*this = ", ccTypeName, "{}")
	g.Out()
	g.P("}")

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

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

	// Default constants
	for _, field := range message.Field {
		def := proto.GetString(field.DefaultValue)
		if def == "" {
			continue
		}
		fieldname := "Default_" + ccTypeName + "_" + CamelCase(*field.Name)
		typename, _ := g.GoType(message, field)
		if typename[0] == '*' {
			typename = typename[1:]
		}
		kind := "const "
		switch {
		case typename == "bool":
		case typename == "string":
			def = Quote(def)
		case typename == "[]byte":
			def = "[]byte(" + Quote(def) + ")"
			kind = "var "
		case *field.Type == descriptor.FieldDescriptorProto_TYPE_ENUM:
			// Must be an enum.  Need to construct the prefixed name.
			obj := g.ObjectNamed(proto.GetString(field.TypeName))
			enum, ok := obj.(*EnumDescriptor)
			if !ok {
				log.Println("don't know how to generate constant for", fieldname)
				continue
			}
			def = g.DefaultPackageName(enum) + enum.prefix() + def
		}
		g.P(kind, fieldname, " ", typename, " = ", def)
	}
	g.P()

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

func (g *Generator) generateExtension(ext *ExtensionDescriptor) {
	// The full type name
	typeName := ext.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)
	}
	ccTypeName := "E_" + strings.Join(typeName, "_")

	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)

	g.P("var ", ccTypeName, " = &", g.ProtoPkg, ".ExtensionDesc{")
	g.In()
	g.P("ExtendedType: (", extendedType, ")(nil),")
	g.P("ExtensionType: (", fieldType, ")(nil),")
	g.P("Field: ", field.Number, ",")
	g.P("Tag: ", tag, ",")

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

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

func (g *Generator) generateEnumRegistration(enum *EnumDescriptor) {
	pkg := g.packageName + "." // We always print the full package name here.
	// The full type name
	typeName := enum.TypeName()
	// The full type name, CamelCased.
	ccTypeName := CamelCaseSlice(typeName)
	g.P(g.ProtoPkg+".RegisterEnum(", Quote(pkg+ccTypeName), ", ", ccTypeName+"_name, ", ccTypeName+"_value)")
}

// 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 XMyFieldName2.
func CamelCase(s string) string {
	if s == "" {
		return ""
	}
	t := make([]byte, 0, 32)
	oneC := make([]byte, 1)
	i := 0
	if s[0] == '_' {
		// Need a capital letter; drop the '_'.
		oneC[0] = 'X'
		t = bytes.Add(t, oneC)
		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]
		oneC[0] = c
		if c == '_' && i+1 < len(s) && isASCIILower(s[i+1]) {
			continue // Skip the underscore in s.
		}
		if isASCIIDigit(c) {
			t = bytes.Add(t, oneC)
			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) {
			oneC[0] ^= ' ' // Make it a capital letter.
		}
		t = bytes.Add(t, oneC) // Guaranteed not lower case.
		// Accept lower case sequence that follows.
		for i+1 < len(s) && isASCIILower(s[i+1]) {
			i++
			oneC[0] = s[i]
			t = bytes.Add(t, oneC)
		}
	}
	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, ".") }

// Quote returns a Go-source quoted string representation of s.
func Quote(s string) string { return fmt.Sprintf("%q", s) }

// 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
}

// DotToUnderscore is the mapping function used to generate Go names from package names,
// which can be dotted in the input .proto file.  It maps dots to underscores.
// Because we also get here from package names generated from file names, it also maps
// minus signs to underscores.
func DotToUnderscore(rune int) int {
	switch rune {
	case '.', '-':
		return '_'
	}
	return rune
}

// 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
}