internal/strs: unify string manipulation functionality

Create a new internal/strs package that unifies common functionality:
* Since protobuf itself pseudo-specifies at least 4 different camel-case
and snake-case conversion functions, we define all variants in one place.
* We move the internal/filedesc.nameBuilder function to this package.
We simplify its implementation to not depend on a strings.Builder fork
under the hood since the semantics we desire is simpler than what
strings.Builder provides.
* We use strs.Builder in reflect/protodesc in its construction of all
the full names. This is perfect use case of strs.Builder since all
full names within a file descriptor share the same lifetime.
* Add an UnsafeString and UnsafeBytes cast function that will be useful
in the near future for optimizing encoding/prototext and encoding/protojson.

Change-Id: I2cf07cbaf6f72e5f9fd6ae3d37b0d46f6af2ad59
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/185198
Reviewed-by: Damien Neil <dneil@google.com>

encoding/protojson/well_known_types.go

@@ -14,6 +14,7 @@ import (
 	"google.golang.org/protobuf/internal/encoding/json"
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/fieldnum"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/proto"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
 )
@@ -888,8 +889,8 @@ func (o MarshalOptions) marshalFieldMask(m pref.Message) error {
 	for i := 0; i < list.Len(); i++ {
 		s := list.Get(i).String()
 		// Return error if conversion to camelCase is not reversible.
-		cc := camelCase(s)
-		if s != snakeCase(cc) {
+		cc := strs.JSONCamelCase(s)
+		if s != strs.JSONSnakeCase(cc) {
 			return errors.New("%s.paths contains irreversible value %q", m.Descriptor().FullName(), s)
 		}
 		paths = append(paths, cc)
@@ -920,53 +921,7 @@ func (o UnmarshalOptions) unmarshalFieldMask(m pref.Message) error {
 		s = strings.TrimSpace(s)
 		// Convert to snake_case. Unlike encoding, no validation is done because
 		// it is not possible to know the original path names.
-		list.Append(pref.ValueOf(snakeCase(s)))
+		list.Append(pref.ValueOf(strs.JSONSnakeCase(s)))
 	}
 	return nil
 }
-
-// camelCase converts given string into camelCase where ASCII character after _
-// is turned into uppercase and _'s are removed.
-func camelCase(s string) string {
-	var b []byte
-	var afterUnderscore bool
-	for i := 0; i < len(s); i++ {
-		c := s[i]
-		if afterUnderscore {
-			if isASCIILower(c) {
-				c -= 'a' - 'A'
-			}
-		}
-		if c == '_' {
-			afterUnderscore = true
-			continue
-		}
-		afterUnderscore = false
-		b = append(b, c)
-	}
-	return string(b)
-}
-
-// snakeCase converts given string into snake_case where ASCII uppercase
-// character is turned into _ + lowercase.
-func snakeCase(s string) string {
-	var b []byte
-	for i := 0; i < len(s); i++ {
-		c := s[i]
-		if isASCIIUpper(c) {
-			c += 'a' - 'A'
-			b = append(b, '_', c)
-		} else {
-			b = append(b, c)
-		}
-	}
-	return string(b)
-}
-
-func isASCIILower(c byte) bool {
-	return 'a' <= c && c <= 'z'
-}
-
-func isASCIIUpper(c byte) bool {
-	return 'A' <= c && c <= 'Z'
-}

internal/filedesc/desc.go

@@ -14,6 +14,7 @@ import (
 	"google.golang.org/protobuf/internal/descopts"
 	"google.golang.org/protobuf/internal/encoding/defval"
 	"google.golang.org/protobuf/internal/pragma"
+	"google.golang.org/protobuf/internal/strs"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
 )
 
@@ -465,30 +466,12 @@ type jsonName struct {
 func (js *jsonName) get(fd pref.FieldDescriptor) string {
 	if !js.has {
 		js.once.Do(func() {
-			js.name = makeJSONName(fd.Name())
+			js.name = strs.JSONCamelCase(string(fd.Name()))
 		})
 	}
 	return js.name
 }
 
-// makeJSONName creates a JSON name from the protobuf short name.
-func makeJSONName(s pref.Name) string {
-	var b []byte
-	var wasUnderscore bool
-	for i := 0; i < len(s); i++ { // proto identifiers are always ASCII
-		c := s[i]
-		if c != '_' {
-			isLower := 'a' <= c && c <= 'z'
-			if wasUnderscore && isLower {
-				c -= 'a' - 'A'
-			}
-			b = append(b, c)
-		}
-		wasUnderscore = c == '_'
-	}
-	return string(b)
-}
-
 func DefaultValue(v pref.Value, ev pref.EnumValueDescriptor) defaultValue {
 	dv := defaultValue{has: v.IsValid(), val: v, enum: ev}
 	if b, ok := v.Interface().([]byte); ok {

internal/filedesc/desc_init.go

@@ -5,8 +5,11 @@
 package filedesc
 
 import (
+	"sync"
+
 	"google.golang.org/protobuf/internal/encoding/wire"
 	"google.golang.org/protobuf/internal/fieldnum"
+	"google.golang.org/protobuf/internal/strs"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
 )
 
@@ -89,8 +92,8 @@ func (fd *File) checkDecls() {
 }
 
 func (fd *File) unmarshalSeed(b []byte) {
-	nb := getNameBuilder()
-	defer putNameBuilder(nb)
+	sb := getBuilder()
+	defer putBuilder(sb)
 
 	var prevField pref.FieldNumber
 	var numEnums, numMessages, numExtensions, numServices int
@@ -114,9 +117,9 @@ func (fd *File) unmarshalSeed(b []byte) {
 					panic("invalid syntax")
 				}
 			case fieldnum.FileDescriptorProto_Name:
-				fd.L1.Path = nb.MakeString(v)
+				fd.L1.Path = sb.MakeString(v)
 			case fieldnum.FileDescriptorProto_Package:
-				fd.L1.Package = pref.FullName(nb.MakeString(v))
+				fd.L1.Package = pref.FullName(sb.MakeString(v))
 			case fieldnum.FileDescriptorProto_EnumType:
 				if prevField != fieldnum.FileDescriptorProto_EnumType {
 					if numEnums > 0 {
@@ -183,7 +186,7 @@ func (fd *File) unmarshalSeed(b []byte) {
 		for i := range fd.L1.Enums.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			fd.L1.Enums.List[i].unmarshalSeed(v, nb, fd, fd, i)
+			fd.L1.Enums.List[i].unmarshalSeed(v, sb, fd, fd, i)
 			b = b[n+m:]
 		}
 	}
@@ -192,7 +195,7 @@ func (fd *File) unmarshalSeed(b []byte) {
 		for i := range fd.L1.Messages.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			fd.L1.Messages.List[i].unmarshalSeed(v, nb, fd, fd, i)
+			fd.L1.Messages.List[i].unmarshalSeed(v, sb, fd, fd, i)
 			b = b[n+m:]
 		}
 	}
@@ -201,7 +204,7 @@ func (fd *File) unmarshalSeed(b []byte) {
 		for i := range fd.L1.Extensions.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			fd.L1.Extensions.List[i].unmarshalSeed(v, nb, fd, fd, i)
+			fd.L1.Extensions.List[i].unmarshalSeed(v, sb, fd, fd, i)
 			b = b[n+m:]
 		}
 	}
@@ -210,13 +213,13 @@ func (fd *File) unmarshalSeed(b []byte) {
 		for i := range fd.L1.Services.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			fd.L1.Services.List[i].unmarshalSeed(v, nb, fd, fd, i)
+			fd.L1.Services.List[i].unmarshalSeed(v, sb, fd, fd, i)
 			b = b[n+m:]
 		}
 	}
 }
 
-func (ed *Enum) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (ed *Enum) unmarshalSeed(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	ed.L0.ParentFile = pf
 	ed.L0.Parent = pd
 	ed.L0.Index = i
@@ -231,7 +234,7 @@ func (ed *Enum) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descr
 			b = b[m:]
 			switch num {
 			case fieldnum.EnumDescriptorProto_Name:
-				ed.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				ed.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.EnumDescriptorProto_Value:
 				numValues++
 			}
@@ -258,7 +261,7 @@ func (ed *Enum) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descr
 			b = b[m:]
 			switch num {
 			case fieldnum.EnumDescriptorProto_Value:
-				ed.L2.Values.List[i].unmarshalFull(v, nb, pf, ed, i)
+				ed.L2.Values.List[i].unmarshalFull(v, sb, pf, ed, i)
 				i++
 			}
 		default:
@@ -268,7 +271,7 @@ func (ed *Enum) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descr
 	}
 }
 
-func (md *Message) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (md *Message) unmarshalSeed(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	md.L0.ParentFile = pf
 	md.L0.Parent = pd
 	md.L0.Index = i
@@ -286,7 +289,7 @@ func (md *Message) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 			b = b[m:]
 			switch num {
 			case fieldnum.DescriptorProto_Name:
-				md.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				md.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.DescriptorProto_EnumType:
 				if prevField != fieldnum.DescriptorProto_EnumType {
 					if numEnums > 0 {
@@ -337,7 +340,7 @@ func (md *Message) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 		for i := range md.L1.Enums.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			md.L1.Enums.List[i].unmarshalSeed(v, nb, pf, md, i)
+			md.L1.Enums.List[i].unmarshalSeed(v, sb, pf, md, i)
 			b = b[n+m:]
 		}
 	}
@@ -346,7 +349,7 @@ func (md *Message) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 		for i := range md.L1.Messages.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			md.L1.Messages.List[i].unmarshalSeed(v, nb, pf, md, i)
+			md.L1.Messages.List[i].unmarshalSeed(v, sb, pf, md, i)
 			b = b[n+m:]
 		}
 	}
@@ -355,13 +358,13 @@ func (md *Message) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 		for i := range md.L1.Extensions.List {
 			_, n := wire.ConsumeVarint(b)
 			v, m := wire.ConsumeBytes(b[n:])
-			md.L1.Extensions.List[i].unmarshalSeed(v, nb, pf, md, i)
+			md.L1.Extensions.List[i].unmarshalSeed(v, sb, pf, md, i)
 			b = b[n+m:]
 		}
 	}
 }
 
-func (xd *Extension) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (xd *Extension) unmarshalSeed(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	xd.L0.ParentFile = pf
 	xd.L0.Parent = pd
 	xd.L0.Index = i
@@ -384,9 +387,9 @@ func (xd *Extension) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.
 			b = b[m:]
 			switch num {
 			case fieldnum.FieldDescriptorProto_Name:
-				xd.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				xd.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.FieldDescriptorProto_Extendee:
-				xd.L1.Extendee = PlaceholderMessage(nb.MakeFullName(v))
+				xd.L1.Extendee = PlaceholderMessage(makeFullName(sb, v))
 			}
 		default:
 			m := wire.ConsumeFieldValue(num, typ, b)
@@ -395,7 +398,7 @@ func (xd *Extension) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.
 	}
 }
 
-func (sd *Service) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (sd *Service) unmarshalSeed(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	sd.L0.ParentFile = pf
 	sd.L0.Parent = pd
 	sd.L0.Index = i
@@ -409,7 +412,7 @@ func (sd *Service) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 			b = b[m:]
 			switch num {
 			case fieldnum.ServiceDescriptorProto_Name:
-				sd.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				sd.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			}
 		default:
 			m := wire.ConsumeFieldValue(num, typ, b)
@@ -417,3 +420,27 @@ func (sd *Service) unmarshalSeed(b []byte, nb *nameBuilder, pf *File, pd pref.De
 		}
 	}
 }
+
+var nameBuilderPool = sync.Pool{
+	New: func() interface{} { return new(strs.Builder) },
+}
+
+func getBuilder() *strs.Builder {
+	return nameBuilderPool.Get().(*strs.Builder)
+}
+func putBuilder(b *strs.Builder) {
+	nameBuilderPool.Put(b)
+}
+
+// makeFullName converts b to a protoreflect.FullName,
+// where b must start with a leading dot.
+func makeFullName(sb *strs.Builder, b []byte) pref.FullName {
+	if len(b) == 0 || b[0] != '.' {
+		panic("name reference must be fully qualified")
+	}
+	return pref.FullName(sb.MakeString(b[1:]))
+}
+
+func appendFullName(sb *strs.Builder, prefix pref.FullName, suffix []byte) pref.FullName {
+	return sb.AppendFullName(prefix, pref.Name(strs.UnsafeString(suffix)))
+}

internal/filedesc/desc_lazy.go

@@ -11,6 +11,7 @@ import (
 	"google.golang.org/protobuf/internal/descopts"
 	"google.golang.org/protobuf/internal/encoding/wire"
 	"google.golang.org/protobuf/internal/fieldnum"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/proto"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
 )
@@ -132,8 +133,8 @@ func (file *File) resolveMessageDependency(md pref.MessageDescriptor, i, j int32
 }
 
 func (fd *File) unmarshalFull(b []byte) {
-	nb := getNameBuilder()
-	defer putNameBuilder(nb)
+	sb := getBuilder()
+	defer putBuilder(sb)
 
 	var enumIdx, messageIdx, extensionIdx, serviceIdx int
 	var rawOptions []byte
@@ -156,23 +157,23 @@ func (fd *File) unmarshalFull(b []byte) {
 			b = b[m:]
 			switch num {
 			case fieldnum.FileDescriptorProto_Dependency:
-				path := nb.MakeString(v)
+				path := sb.MakeString(v)
 				imp, _ := fd.builder.FileRegistry.FindFileByPath(path)
 				if imp == nil {
 					imp = PlaceholderFile(path)
 				}
 				fd.L2.Imports = append(fd.L2.Imports, pref.FileImport{FileDescriptor: imp})
 			case fieldnum.FileDescriptorProto_EnumType:
-				fd.L1.Enums.List[enumIdx].unmarshalFull(v, nb)
+				fd.L1.Enums.List[enumIdx].unmarshalFull(v, sb)
 				enumIdx++
 			case fieldnum.FileDescriptorProto_MessageType:
-				fd.L1.Messages.List[messageIdx].unmarshalFull(v, nb)
+				fd.L1.Messages.List[messageIdx].unmarshalFull(v, sb)
 				messageIdx++
 			case fieldnum.FileDescriptorProto_Extension:
-				fd.L1.Extensions.List[extensionIdx].unmarshalFull(v, nb)
+				fd.L1.Extensions.List[extensionIdx].unmarshalFull(v, sb)
 				extensionIdx++
 			case fieldnum.FileDescriptorProto_Service:
-				fd.L1.Services.List[serviceIdx].unmarshalFull(v, nb)
+				fd.L1.Services.List[serviceIdx].unmarshalFull(v, sb)
 				serviceIdx++
 			case fieldnum.FileDescriptorProto_Options:
 				rawOptions = appendOptions(rawOptions, v)
@@ -185,7 +186,7 @@ func (fd *File) unmarshalFull(b []byte) {
 	fd.L2.Options = fd.builder.optionsUnmarshaler(descopts.File, rawOptions)
 }
 
-func (ed *Enum) unmarshalFull(b []byte, nb *nameBuilder) {
+func (ed *Enum) unmarshalFull(b []byte, sb *strs.Builder) {
 	var rawValues [][]byte
 	var rawOptions []byte
 	if !ed.L1.eagerValues {
@@ -202,7 +203,7 @@ func (ed *Enum) unmarshalFull(b []byte, nb *nameBuilder) {
 			case fieldnum.EnumDescriptorProto_Value:
 				rawValues = append(rawValues, v)
 			case fieldnum.EnumDescriptorProto_ReservedName:
-				ed.L2.ReservedNames.List = append(ed.L2.ReservedNames.List, pref.Name(nb.MakeString(v)))
+				ed.L2.ReservedNames.List = append(ed.L2.ReservedNames.List, pref.Name(sb.MakeString(v)))
 			case fieldnum.EnumDescriptorProto_ReservedRange:
 				ed.L2.ReservedRanges.List = append(ed.L2.ReservedRanges.List, unmarshalEnumReservedRange(v))
 			case fieldnum.EnumDescriptorProto_Options:
@@ -216,7 +217,7 @@ func (ed *Enum) unmarshalFull(b []byte, nb *nameBuilder) {
 	if !ed.L1.eagerValues && len(rawValues) > 0 {
 		ed.L2.Values.List = make([]EnumValue, len(rawValues))
 		for i, b := range rawValues {
-			ed.L2.Values.List[i].unmarshalFull(b, nb, ed.L0.ParentFile, ed, i)
+			ed.L2.Values.List[i].unmarshalFull(b, sb, ed.L0.ParentFile, ed, i)
 		}
 	}
 	ed.L2.Options = ed.L0.ParentFile.builder.optionsUnmarshaler(descopts.Enum, rawOptions)
@@ -244,7 +245,7 @@ func unmarshalEnumReservedRange(b []byte) (r [2]pref.EnumNumber) {
 	return r
 }
 
-func (vd *EnumValue) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (vd *EnumValue) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	vd.L0.ParentFile = pf
 	vd.L0.Parent = pd
 	vd.L0.Index = i
@@ -267,7 +268,7 @@ func (vd *EnumValue) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.
 			switch num {
 			case fieldnum.EnumValueDescriptorProto_Name:
 				// NOTE: Enum values are in the same scope as the enum parent.
-				vd.L0.FullName = nb.AppendFullName(pd.Parent().FullName(), v)
+				vd.L0.FullName = appendFullName(sb, pd.Parent().FullName(), v)
 			case fieldnum.EnumValueDescriptorProto_Options:
 				rawOptions = appendOptions(rawOptions, v)
 			}
@@ -279,7 +280,7 @@ func (vd *EnumValue) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.
 	vd.L1.Options = pf.builder.optionsUnmarshaler(descopts.EnumValue, rawOptions)
 }
 
-func (md *Message) unmarshalFull(b []byte, nb *nameBuilder) {
+func (md *Message) unmarshalFull(b []byte, sb *strs.Builder) {
 	var rawFields, rawOneofs [][]byte
 	var enumIdx, messageIdx, extensionIdx int
 	var rawOptions []byte
@@ -297,7 +298,7 @@ func (md *Message) unmarshalFull(b []byte, nb *nameBuilder) {
 			case fieldnum.DescriptorProto_OneofDecl:
 				rawOneofs = append(rawOneofs, v)
 			case fieldnum.DescriptorProto_ReservedName:
-				md.L2.ReservedNames.List = append(md.L2.ReservedNames.List, pref.Name(nb.MakeString(v)))
+				md.L2.ReservedNames.List = append(md.L2.ReservedNames.List, pref.Name(sb.MakeString(v)))
 			case fieldnum.DescriptorProto_ReservedRange:
 				md.L2.ReservedRanges.List = append(md.L2.ReservedRanges.List, unmarshalMessageReservedRange(v))
 			case fieldnum.DescriptorProto_ExtensionRange:
@@ -306,13 +307,13 @@ func (md *Message) unmarshalFull(b []byte, nb *nameBuilder) {
 				md.L2.ExtensionRanges.List = append(md.L2.ExtensionRanges.List, r)
 				md.L2.ExtensionRangeOptions = append(md.L2.ExtensionRangeOptions, opts)
 			case fieldnum.DescriptorProto_EnumType:
-				md.L1.Enums.List[enumIdx].unmarshalFull(v, nb)
+				md.L1.Enums.List[enumIdx].unmarshalFull(v, sb)
 				enumIdx++
 			case fieldnum.DescriptorProto_NestedType:
-				md.L1.Messages.List[messageIdx].unmarshalFull(v, nb)
+				md.L1.Messages.List[messageIdx].unmarshalFull(v, sb)
 				messageIdx++
 			case fieldnum.DescriptorProto_Extension:
-				md.L1.Extensions.List[extensionIdx].unmarshalFull(v, nb)
+				md.L1.Extensions.List[extensionIdx].unmarshalFull(v, sb)
 				extensionIdx++
 			case fieldnum.DescriptorProto_Options:
 				md.unmarshalOptions(v)
@@ -328,14 +329,14 @@ func (md *Message) unmarshalFull(b []byte, nb *nameBuilder) {
 		md.L2.Oneofs.List = make([]Oneof, len(rawOneofs))
 		for i, b := range rawFields {
 			fd := &md.L2.Fields.List[i]
-			fd.unmarshalFull(b, nb, md.L0.ParentFile, md, i)
+			fd.unmarshalFull(b, sb, md.L0.ParentFile, md, i)
 			if fd.L1.Cardinality == pref.Required {
 				md.L2.RequiredNumbers.List = append(md.L2.RequiredNumbers.List, fd.L1.Number)
 			}
 		}
 		for i, b := range rawOneofs {
 			od := &md.L2.Oneofs.List[i]
-			od.unmarshalFull(b, nb, md.L0.ParentFile, md, i)
+			od.unmarshalFull(b, sb, md.L0.ParentFile, md, i)
 		}
 	}
 	md.L2.Options = md.L0.ParentFile.builder.optionsUnmarshaler(descopts.Message, rawOptions)
@@ -413,7 +414,7 @@ func unmarshalMessageExtensionRange(b []byte) (r [2]pref.FieldNumber, rawOptions
 	return r, rawOptions
 }
 
-func (fd *Field) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (fd *Field) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	fd.L0.ParentFile = pf
 	fd.L0.Parent = pd
 	fd.L0.Index = i
@@ -450,9 +451,9 @@ func (fd *Field) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Desc
 			b = b[m:]
 			switch num {
 			case fieldnum.FieldDescriptorProto_Name:
-				fd.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				fd.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.FieldDescriptorProto_JsonName:
-				fd.L1.JSONName = JSONName(nb.MakeString(v))
+				fd.L1.JSONName = JSONName(sb.MakeString(v))
 			case fieldnum.FieldDescriptorProto_DefaultValue:
 				fd.L1.Default.val = pref.ValueOf(v) // temporarily store as bytes; later resolved in resolveMessages
 			case fieldnum.FieldDescriptorProto_TypeName:
@@ -467,7 +468,7 @@ func (fd *Field) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Desc
 		}
 	}
 	if rawTypeName != nil {
-		name := nb.MakeFullName(rawTypeName)
+		name := makeFullName(sb, rawTypeName)
 		switch fd.L1.Kind {
 		case pref.EnumKind:
 			fd.L1.Enum = PlaceholderEnum(name)
@@ -500,7 +501,7 @@ func (fd *Field) unmarshalOptions(b []byte) {
 	}
 }
 
-func (od *Oneof) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (od *Oneof) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	od.L0.ParentFile = pf
 	od.L0.Parent = pd
 	od.L0.Index = i
@@ -515,7 +516,7 @@ func (od *Oneof) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Desc
 			b = b[m:]
 			switch num {
 			case fieldnum.OneofDescriptorProto_Name:
-				od.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				od.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.OneofDescriptorProto_Options:
 				rawOptions = appendOptions(rawOptions, v)
 			}
@@ -527,7 +528,7 @@ func (od *Oneof) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Desc
 	od.L1.Options = pf.builder.optionsUnmarshaler(descopts.Oneof, rawOptions)
 }
 
-func (xd *Extension) unmarshalFull(b []byte, nb *nameBuilder) {
+func (xd *Extension) unmarshalFull(b []byte, sb *strs.Builder) {
 	var rawTypeName []byte
 	var rawOptions []byte
 	xd.L2 = new(ExtensionL2)
@@ -547,7 +548,7 @@ func (xd *Extension) unmarshalFull(b []byte, nb *nameBuilder) {
 			b = b[m:]
 			switch num {
 			case fieldnum.FieldDescriptorProto_JsonName:
-				xd.L2.JSONName = JSONName(nb.MakeString(v))
+				xd.L2.JSONName = JSONName(sb.MakeString(v))
 			case fieldnum.FieldDescriptorProto_DefaultValue:
 				xd.L2.Default.val = pref.ValueOf(v) // temporarily store as bytes; later resolved in resolveExtensions
 			case fieldnum.FieldDescriptorProto_TypeName:
@@ -562,7 +563,7 @@ func (xd *Extension) unmarshalFull(b []byte, nb *nameBuilder) {
 		}
 	}
 	if rawTypeName != nil {
-		name := nb.MakeFullName(rawTypeName)
+		name := makeFullName(sb, rawTypeName)
 		switch xd.L1.Kind {
 		case pref.EnumKind:
 			xd.L2.Enum = PlaceholderEnum(name)
@@ -592,7 +593,7 @@ func (xd *Extension) unmarshalOptions(b []byte) {
 	}
 }
 
-func (sd *Service) unmarshalFull(b []byte, nb *nameBuilder) {
+func (sd *Service) unmarshalFull(b []byte, sb *strs.Builder) {
 	var rawMethods [][]byte
 	var rawOptions []byte
 	sd.L2 = new(ServiceL2)
@@ -617,13 +618,13 @@ func (sd *Service) unmarshalFull(b []byte, nb *nameBuilder) {
 	if len(rawMethods) > 0 {
 		sd.L2.Methods.List = make([]Method, len(rawMethods))
 		for i, b := range rawMethods {
-			sd.L2.Methods.List[i].unmarshalFull(b, nb, sd.L0.ParentFile, sd, i)
+			sd.L2.Methods.List[i].unmarshalFull(b, sb, sd.L0.ParentFile, sd, i)
 		}
 	}
 	sd.L2.Options = sd.L0.ParentFile.builder.optionsUnmarshaler(descopts.Service, rawOptions)
 }
 
-func (md *Method) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Descriptor, i int) {
+func (md *Method) unmarshalFull(b []byte, sb *strs.Builder, pf *File, pd pref.Descriptor, i int) {
 	md.L0.ParentFile = pf
 	md.L0.Parent = pd
 	md.L0.Index = i
@@ -647,11 +648,11 @@ func (md *Method) unmarshalFull(b []byte, nb *nameBuilder, pf *File, pd pref.Des
 			b = b[m:]
 			switch num {
 			case fieldnum.MethodDescriptorProto_Name:
-				md.L0.FullName = nb.AppendFullName(pd.FullName(), v)
+				md.L0.FullName = appendFullName(sb, pd.FullName(), v)
 			case fieldnum.MethodDescriptorProto_InputType:
-				md.L1.Input = PlaceholderMessage(nb.MakeFullName(v))
+				md.L1.Input = PlaceholderMessage(makeFullName(sb, v))
 			case fieldnum.MethodDescriptorProto_OutputType:
-				md.L1.Output = PlaceholderMessage(nb.MakeFullName(v))
+				md.L1.Output = PlaceholderMessage(makeFullName(sb, v))
 			case fieldnum.MethodDescriptorProto_Options:
 				rawOptions = appendOptions(rawOptions, v)
 			}

internal/filedesc/name_pure.go

@@ -1,34 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build purego appengine
-
-package filedesc
-
-import pref "google.golang.org/protobuf/reflect/protoreflect"
-
-func getNameBuilder() *nameBuilder { return nil }
-func putNameBuilder(*nameBuilder)  {}
-
-type nameBuilder struct{}
-
-// MakeFullName converts b to a protoreflect.FullName,
-// where b must start with a leading dot.
-func (*nameBuilder) MakeFullName(b []byte) pref.FullName {
-	if len(b) == 0 || b[0] != '.' {
-		panic("name reference must be fully qualified")
-	}
-	return pref.FullName(b[1:])
-}
-
-// AppendFullName is equivalent to protoreflect.FullName.Append.
-func (*nameBuilder) AppendFullName(prefix pref.FullName, name []byte) pref.FullName {
-	return prefix.Append(pref.Name(name))
-}
-
-// MakeString is equivalent to string(b), but optimized for large batches
-// with a shared lifetime.
-func (*nameBuilder) MakeString(b []byte) string {
-	return string(b)
-}

internal/filedesc/name_unsafe.go

@@ -1,124 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !purego,!appengine
-
-package filedesc
-
-import (
-	"sync"
-	"unsafe"
-
-	pref "google.golang.org/protobuf/reflect/protoreflect"
-)
-
-var nameBuilderPool = sync.Pool{
-	New: func() interface{} { return new(nameBuilder) },
-}
-
-func getNameBuilder() *nameBuilder {
-	return nameBuilderPool.Get().(*nameBuilder)
-}
-func putNameBuilder(b *nameBuilder) {
-	nameBuilderPool.Put(b)
-}
-
-type nameBuilder struct {
-	sb stringBuilder
-}
-
-// MakeFullName converts b to a protoreflect.FullName,
-// where b must start with a leading dot.
-func (nb *nameBuilder) MakeFullName(b []byte) pref.FullName {
-	if len(b) == 0 || b[0] != '.' {
-		panic("name reference must be fully qualified")
-	}
-	return pref.FullName(nb.MakeString(b[1:]))
-}
-
-// AppendFullName is equivalent to protoreflect.FullName.Append,
-// but optimized for large batches where each name has a shared lifetime.
-func (nb *nameBuilder) AppendFullName(prefix pref.FullName, name []byte) pref.FullName {
-	n := len(prefix) + len(".") + len(name)
-	if len(prefix) == 0 {
-		n -= len(".")
-	}
-	nb.grow(n)
-	nb.sb.WriteString(string(prefix))
-	nb.sb.WriteByte('.')
-	nb.sb.Write(name)
-	return pref.FullName(nb.last(n))
-}
-
-// MakeString is equivalent to string(b), but optimized for large batches
-// with a shared lifetime.
-func (nb *nameBuilder) MakeString(b []byte) string {
-	nb.grow(len(b))
-	nb.sb.Write(b)
-	return nb.last(len(b))
-}
-
-func (nb *nameBuilder) last(n int) string {
-	s := nb.sb.String()
-	return s[len(s)-n:]
-}
-
-func (nb *nameBuilder) grow(n int) {
-	const batchSize = 1 << 16
-	if nb.sb.Cap()-nb.sb.Len() < n {
-		nb.sb.Reset()
-		nb.sb.Grow(batchSize)
-	}
-}
-
-// stringsBuilder is a simplified copy of the strings.Builder from Go1.12:
-//	* removed the shallow copy check
-//	* removed methods that we do not use (e.g. WriteRune)
-//
-// A forked version is used:
-//	* to enable Go1.9 support, but strings.Builder was added in Go1.10
-//	* for the Cap method, which was missing until Go1.12
-//
-// TODO: Remove this when Go1.12 is the minimally supported toolchain version.
-type stringBuilder struct {
-	buf []byte
-}
-
-func (b *stringBuilder) String() string {
-	return *(*string)(unsafe.Pointer(&b.buf))
-}
-func (b *stringBuilder) Len() int {
-	return len(b.buf)
-}
-func (b *stringBuilder) Cap() int {
-	return cap(b.buf)
-}
-func (b *stringBuilder) Reset() {
-	b.buf = nil
-}
-func (b *stringBuilder) grow(n int) {
-	buf := make([]byte, len(b.buf), 2*cap(b.buf)+n)
-	copy(buf, b.buf)
-	b.buf = buf
-}
-func (b *stringBuilder) Grow(n int) {
-	if n < 0 {
-		panic("stringBuilder.Grow: negative count")
-	}
-	if cap(b.buf)-len(b.buf) < n {
-		b.grow(n)
-	}
-}
-func (b *stringBuilder) Write(p []byte) (int, error) {
-	b.buf = append(b.buf, p...)
-	return len(p), nil
-}
-func (b *stringBuilder) WriteByte(c byte) error {
-	b.buf = append(b.buf, c)
-	return nil
-}
-func (b *stringBuilder) WriteString(s string) (int, error) {
-	b.buf = append(b.buf, s...)
-	return len(s), nil
-}

internal/impl/legacy_message.go

@@ -14,6 +14,7 @@ import (
 	"google.golang.org/protobuf/internal/descopts"
 	ptag "google.golang.org/protobuf/internal/encoding/tag"
 	"google.golang.org/protobuf/internal/filedesc"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	pref "google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/prototype"
@@ -248,7 +249,7 @@ func aberrantAppendField(md *filedesc.Message, goType reflect.Type, tag, tagKey,
 				n := len(md.L1.Messages.List)
 				md.L1.Messages.List = append(md.L1.Messages.List, filedesc.Message{L2: new(filedesc.MessageL2)})
 				md2 := &md.L1.Messages.List[n]
-				md2.L0.FullName = md.FullName().Append(aberrantMapEntryName(fd.Name()))
+				md2.L0.FullName = md.FullName().Append(pref.Name(strs.MapEntryName(string(fd.Name()))))
 				md2.L0.ParentFile = md.L0.ParentFile
 				md2.L0.Parent = md
 				md2.L0.Index = n

internal/strs/strings.go

@@ -0,0 +1,111 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package strs provides string manipulation functionality specific to protobuf.
+package strs
+
+import (
+	"strings"
+	"unicode"
+)
+
+// JSONCamelCase converts a snake_case identifier to a camelCase identifier,
+// according to the protobuf JSON specification.
+func JSONCamelCase(s string) string {
+	var b []byte
+	var wasUnderscore bool
+	for i := 0; i < len(s); i++ { // proto identifiers are always ASCII
+		c := s[i]
+		if c != '_' {
+			isLower := 'a' <= c && c <= 'z'
+			if wasUnderscore && isLower {
+				c -= 'a' - 'A' // convert to uppercase
+			}
+			b = append(b, c)
+		}
+		wasUnderscore = c == '_'
+	}
+	return string(b)
+}
+
+// JSONSnakeCase converts a camelCase identifier to a snake_case identifier,
+// according to the protobuf JSON specification.
+func JSONSnakeCase(s string) string {
+	var b []byte
+	for i := 0; i < len(s); i++ { // proto identifiers are always ASCII
+		c := s[i]
+		isUpper := 'A' <= c && c <= 'Z'
+		if isUpper {
+			b = append(b, '_')
+			c += 'a' - 'A' // convert to lowercase
+		}
+		b = append(b, c)
+	}
+	return string(b)
+}
+
+// MapEntryName derives the name of the map entry message given the field name.
+// See protoc v3.8.0: src/google/protobuf/descriptor.cc:254-276,6057
+func MapEntryName(s string) string {
+	var b []byte
+	upperNext := true
+	for _, c := range s {
+		switch {
+		case c == '_':
+			upperNext = true
+		case upperNext:
+			b = append(b, byte(unicode.ToUpper(c)))
+			upperNext = false
+		default:
+			b = append(b, byte(c))
+		}
+	}
+	b = append(b, "Entry"...)
+	return string(b)
+}
+
+// EnumValueName derives the camel-cased enum value name.
+// See protoc v3.8.0: src/google/protobuf/descriptor.cc:297-313
+func EnumValueName(s string) string {
+	var b []byte
+	upperNext := true
+	for _, c := range s {
+		switch {
+		case c == '_':
+			upperNext = true
+		case upperNext:
+			b = append(b, byte(unicode.ToUpper(c)))
+			upperNext = false
+		default:
+			b = append(b, byte(unicode.ToLower(c)))
+			upperNext = false
+		}
+	}
+	return string(b)
+}
+
+// TrimEnumPrefix trims the enum name prefix from an enum value name,
+// where the prefix is all lowercase without underscores.
+// See protoc v3.8.0: src/google/protobuf/descriptor.cc:330-375
+func TrimEnumPrefix(s, prefix string) string {
+	s0 := s // original input
+	for len(s) > 0 && len(prefix) > 0 {
+		if s[0] == '_' {
+			s = s[1:]
+			continue
+		}
+		if unicode.ToLower(rune(s[0])) != rune(prefix[0]) {
+			return s0 // no prefix match
+		}
+		s, prefix = s[1:], prefix[1:]
+	}
+	if len(prefix) > 0 {
+		return s0 // no prefix match
+	}
+	s = strings.TrimLeft(s, "_")
+	if len(s) == 0 {
+		return s0 // avoid returning empty string
+	}
+	return s
+}

internal/strs/strings_pure.go

@@ -0,0 +1,27 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build purego appengine
+
+package strs
+
+import pref "google.golang.org/protobuf/reflect/protoreflect"
+
+func UnsafeString(b []byte) string {
+	return string(b)
+}
+
+func UnsafeBytes(s string) []byte {
+	return []byte(s)
+}
+
+type Builder struct{}
+
+func (*Builder) AppendFullName(prefix pref.FullName, name pref.Name) pref.FullName {
+	return prefix.Append(name)
+}
+
+func (*Builder) MakeString(b []byte) string {
+	return string(b)
+}

internal/strs/strings_test.go

@@ -0,0 +1,108 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package strs
+
+import (
+	"strconv"
+	"testing"
+)
+
+func TestName(t *testing.T) {
+	tests := []struct {
+		in                string
+		inEnumPrefix      string
+		wantMapEntry      string
+		wantEnumValue     string
+		wantTrimValue     string
+		wantJSONCamelCase string
+		wantJSONSnakeCase string
+	}{{
+		in:                "abc",
+		inEnumPrefix:      "",
+		wantMapEntry:      "AbcEntry",
+		wantEnumValue:     "Abc",
+		wantTrimValue:     "abc",
+		wantJSONCamelCase: "abc",
+		wantJSONSnakeCase: "abc",
+	}, {
+		in:                "foo_baR_",
+		inEnumPrefix:      "foo_bar",
+		wantMapEntry:      "FooBaREntry",
+		wantEnumValue:     "FooBar",
+		wantTrimValue:     "foo_baR_",
+		wantJSONCamelCase: "fooBaR",
+		wantJSONSnakeCase: "foo_ba_r_",
+	}, {
+		in:                "snake_caseCamelCase",
+		inEnumPrefix:      "snakecasecamel",
+		wantMapEntry:      "SnakeCaseCamelCaseEntry",
+		wantEnumValue:     "SnakeCasecamelcase",
+		wantTrimValue:     "Case",
+		wantJSONCamelCase: "snakeCaseCamelCase",
+		wantJSONSnakeCase: "snake_case_camel_case",
+	}, {
+		in:                "FiZz_BuZz",
+		inEnumPrefix:      "fizz",
+		wantMapEntry:      "FiZzBuZzEntry",
+		wantEnumValue:     "FizzBuzz",
+		wantTrimValue:     "BuZz",
+		wantJSONCamelCase: "FiZzBuZz",
+		wantJSONSnakeCase: "_fi_zz__bu_zz",
+	}}
+
+	for _, tt := range tests {
+		if got := MapEntryName(tt.in); got != tt.wantMapEntry {
+			t.Errorf("MapEntryName(%q) = %q, want %q", tt.in, got, tt.wantMapEntry)
+		}
+		if got := EnumValueName(tt.in); got != tt.wantEnumValue {
+			t.Errorf("EnumValueName(%q) = %q, want %q", tt.in, got, tt.wantEnumValue)
+		}
+		if got := TrimEnumPrefix(tt.in, tt.inEnumPrefix); got != tt.wantTrimValue {
+			t.Errorf("ErimEnumPrefix(%q, %q) = %q, want %q", tt.in, tt.inEnumPrefix, got, tt.wantTrimValue)
+		}
+		if got := JSONCamelCase(tt.in); got != tt.wantJSONCamelCase {
+			t.Errorf("JSONCamelCase(%q) = %q, want %q", tt.in, got, tt.wantJSONCamelCase)
+		}
+		if got := JSONSnakeCase(tt.in); got != tt.wantJSONSnakeCase {
+			t.Errorf("JSONSnakeCase(%q) = %q, want %q", tt.in, got, tt.wantJSONSnakeCase)
+		}
+	}
+}
+
+var (
+	srcString = "1234"
+	srcBytes  = []byte(srcString)
+	dst       uint64
+)
+
+func BenchmarkCast(b *testing.B) {
+	b.Run("Ideal", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			dst, _ = strconv.ParseUint(srcString, 0, 64)
+		}
+		if dst != 1234 {
+			b.Errorf("got %d, want %s", dst, srcString)
+		}
+	})
+	b.Run("Copy", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			dst, _ = strconv.ParseUint(string(srcBytes), 0, 64)
+		}
+		if dst != 1234 {
+			b.Errorf("got %d, want %s", dst, srcString)
+		}
+	})
+	b.Run("Cast", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			dst, _ = strconv.ParseUint(UnsafeString(srcBytes), 0, 64)
+		}
+		if dst != 1234 {
+			b.Errorf("got %d, want %s", dst, srcString)
+		}
+	})
+}

internal/strs/strings_unsafe.go

@@ -0,0 +1,94 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !purego,!appengine
+
+package strs
+
+import (
+	"unsafe"
+
+	pref "google.golang.org/protobuf/reflect/protoreflect"
+)
+
+type (
+	stringHeader struct {
+		Data unsafe.Pointer
+		Len  int
+	}
+	sliceHeader struct {
+		Data unsafe.Pointer
+		Len  int
+		Cap  int
+	}
+)
+
+// UnsafeString returns an unsafe string reference of b.
+// The caller must treat the input slice as immutable.
+//
+// WARNING: Use carefully. The returned result must not leak to the end user
+// unless the input slice is provably immutable.
+func UnsafeString(b []byte) (s string) {
+	src := (*sliceHeader)(unsafe.Pointer(&b))
+	dst := (*stringHeader)(unsafe.Pointer(&s))
+	dst.Data = src.Data
+	dst.Len = src.Len
+	return s
+}
+
+// UnsafeBytes returns an unsafe bytes slice reference of s.
+// The caller must treat returned slice as immutable.
+//
+// WARNING: Use carefully. The returned result must not leak to the end user.
+func UnsafeBytes(s string) (b []byte) {
+	src := (*stringHeader)(unsafe.Pointer(&s))
+	dst := (*sliceHeader)(unsafe.Pointer(&b))
+	dst.Data = src.Data
+	dst.Len = src.Len
+	dst.Cap = src.Len
+	return b
+}
+
+// Builder builds a set of strings with shared lifetime.
+// This differs from strings.Builder, which is for building a single string.
+type Builder struct {
+	buf []byte
+}
+
+// AppendFullName is equivalent to protoreflect.FullName.Append,
+// but optimized for large batches where each name has a shared lifetime.
+func (sb *Builder) AppendFullName(prefix pref.FullName, name pref.Name) pref.FullName {
+	n := len(prefix) + len(".") + len(name)
+	if len(prefix) == 0 {
+		n -= len(".")
+	}
+	sb.grow(n)
+	sb.buf = append(sb.buf, prefix...)
+	sb.buf = append(sb.buf, '.')
+	sb.buf = append(sb.buf, name...)
+	return pref.FullName(sb.last(n))
+}
+
+// MakeString is equivalent to string(b), but optimized for large batches
+// with a shared lifetime.
+func (sb *Builder) MakeString(b []byte) string {
+	sb.grow(len(b))
+	sb.buf = append(sb.buf, b...)
+	return sb.last(len(b))
+}
+
+func (sb *Builder) grow(n int) {
+	if cap(sb.buf)-len(sb.buf) >= n {
+		return
+	}
+
+	// Unlike strings.Builder, we do not need to copy over the contents
+	// of the old buffer since our builder provides no API for
+	// retrieving previously created strings.
+	sb.buf = make([]byte, 2*(cap(sb.buf)+n))
+}
+
+func (sb *Builder) last(n int) string {
+	return UnsafeString(sb.buf[len(sb.buf)-n:])
+}

reflect/protodesc/desc.go

@@ -10,6 +10,7 @@ import (
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/filedesc"
 	"google.golang.org/protobuf/internal/pragma"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/protoregistry"
 
@@ -144,17 +145,18 @@ func newFile(fd *descriptorpb.FileDescriptorProto, r Resolver, opts ...option) (
 	//	google.protobuf.MethodDescriptorProto.input
 	//	google.protobuf.MethodDescriptorProto.output
 	var err error
+	sb := new(strs.Builder)
 	r1 := make(descsByName)
-	if f.L1.Enums.List, err = r1.initEnumDeclarations(fd.GetEnumType(), f); err != nil {
+	if f.L1.Enums.List, err = r1.initEnumDeclarations(fd.GetEnumType(), f, sb); err != nil {
 		return nil, err
 	}
-	if f.L1.Messages.List, err = r1.initMessagesDeclarations(fd.GetMessageType(), f); err != nil {
+	if f.L1.Messages.List, err = r1.initMessagesDeclarations(fd.GetMessageType(), f, sb); err != nil {
 		return nil, err
 	}
-	if f.L1.Extensions.List, err = r1.initExtensionDeclarations(fd.GetExtension(), f); err != nil {
+	if f.L1.Extensions.List, err = r1.initExtensionDeclarations(fd.GetExtension(), f, sb); err != nil {
 		return nil, err
 	}
-	if f.L1.Services.List, err = r1.initServiceDeclarations(fd.GetService(), f); err != nil {
+	if f.L1.Services.List, err = r1.initServiceDeclarations(fd.GetService(), f, sb); err != nil {
 		return nil, err
 	}
 

reflect/protodesc/desc_init.go

@@ -7,6 +7,7 @@ package protodesc
 import (
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/filedesc"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/reflect/protoreflect"
 
 	"google.golang.org/protobuf/types/descriptorpb"
@@ -14,12 +15,12 @@ import (
 
 type descsByName map[protoreflect.FullName]protoreflect.Descriptor
 
-func (r descsByName) initEnumDeclarations(eds []*descriptorpb.EnumDescriptorProto, parent protoreflect.Descriptor) (es []filedesc.Enum, err error) {
+func (r descsByName) initEnumDeclarations(eds []*descriptorpb.EnumDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (es []filedesc.Enum, err error) {
 	es = make([]filedesc.Enum, len(eds)) // allocate up-front to ensure stable pointers
 	for i, ed := range eds {
 		e := &es[i]
 		e.L2 = new(filedesc.EnumL2)
-		if e.L0, err = r.makeBase(e, parent, ed.GetName(), i); err != nil {
+		if e.L0, err = r.makeBase(e, parent, ed.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := ed.GetOptions(); opts != nil {
@@ -35,18 +36,18 @@ func (r descsByName) initEnumDeclarations(eds []*descriptorpb.EnumDescriptorProt
 				protoreflect.EnumNumber(rr.GetEnd()),
 			})
 		}
-		if e.L2.Values.List, err = r.initEnumValuesFromDescriptorProto(ed.GetValue(), e); err != nil {
+		if e.L2.Values.List, err = r.initEnumValuesFromDescriptorProto(ed.GetValue(), e, sb); err != nil {
 			return nil, err
 		}
 	}
 	return es, nil
 }
 
-func (r descsByName) initEnumValuesFromDescriptorProto(vds []*descriptorpb.EnumValueDescriptorProto, parent protoreflect.Descriptor) (vs []filedesc.EnumValue, err error) {
+func (r descsByName) initEnumValuesFromDescriptorProto(vds []*descriptorpb.EnumValueDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (vs []filedesc.EnumValue, err error) {
 	vs = make([]filedesc.EnumValue, len(vds)) // allocate up-front to ensure stable pointers
 	for i, vd := range vds {
 		v := &vs[i]
-		if v.L0, err = r.makeBase(v, parent, vd.GetName(), i); err != nil {
+		if v.L0, err = r.makeBase(v, parent, vd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := vd.GetOptions(); opts != nil {
@@ -58,12 +59,12 @@ func (r descsByName) initEnumValuesFromDescriptorProto(vds []*descriptorpb.EnumV
 	return vs, nil
 }
 
-func (r descsByName) initMessagesDeclarations(mds []*descriptorpb.DescriptorProto, parent protoreflect.Descriptor) (ms []filedesc.Message, err error) {
+func (r descsByName) initMessagesDeclarations(mds []*descriptorpb.DescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (ms []filedesc.Message, err error) {
 	ms = make([]filedesc.Message, len(mds)) // allocate up-front to ensure stable pointers
 	for i, md := range mds {
 		m := &ms[i]
 		m.L2 = new(filedesc.MessageL2)
-		if m.L0, err = r.makeBase(m, parent, md.GetName(), i); err != nil {
+		if m.L0, err = r.makeBase(m, parent, md.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := md.GetOptions(); opts != nil {
@@ -93,30 +94,30 @@ func (r descsByName) initMessagesDeclarations(mds []*descriptorpb.DescriptorProt
 			}
 			m.L2.ExtensionRangeOptions = append(m.L2.ExtensionRangeOptions, optsFunc)
 		}
-		if m.L2.Fields.List, err = r.initFieldsFromDescriptorProto(md.GetField(), m); err != nil {
+		if m.L2.Fields.List, err = r.initFieldsFromDescriptorProto(md.GetField(), m, sb); err != nil {
 			return nil, err
 		}
-		if m.L2.Oneofs.List, err = r.initOneofsFromDescriptorProto(md.GetOneofDecl(), m); err != nil {
+		if m.L2.Oneofs.List, err = r.initOneofsFromDescriptorProto(md.GetOneofDecl(), m, sb); err != nil {
 			return nil, err
 		}
-		if m.L1.Enums.List, err = r.initEnumDeclarations(md.GetEnumType(), m); err != nil {
+		if m.L1.Enums.List, err = r.initEnumDeclarations(md.GetEnumType(), m, sb); err != nil {
 			return nil, err
 		}
-		if m.L1.Messages.List, err = r.initMessagesDeclarations(md.GetNestedType(), m); err != nil {
+		if m.L1.Messages.List, err = r.initMessagesDeclarations(md.GetNestedType(), m, sb); err != nil {
 			return nil, err
 		}
-		if m.L1.Extensions.List, err = r.initExtensionDeclarations(md.GetExtension(), m); err != nil {
+		if m.L1.Extensions.List, err = r.initExtensionDeclarations(md.GetExtension(), m, sb); err != nil {
 			return nil, err
 		}
 	}
 	return ms, nil
 }
 
-func (r descsByName) initFieldsFromDescriptorProto(fds []*descriptorpb.FieldDescriptorProto, parent protoreflect.Descriptor) (fs []filedesc.Field, err error) {
+func (r descsByName) initFieldsFromDescriptorProto(fds []*descriptorpb.FieldDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (fs []filedesc.Field, err error) {
 	fs = make([]filedesc.Field, len(fds)) // allocate up-front to ensure stable pointers
 	for i, fd := range fds {
 		f := &fs[i]
-		if f.L0, err = r.makeBase(f, parent, fd.GetName(), i); err != nil {
+		if f.L0, err = r.makeBase(f, parent, fd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := fd.GetOptions(); opts != nil {
@@ -138,11 +139,11 @@ func (r descsByName) initFieldsFromDescriptorProto(fds []*descriptorpb.FieldDesc
 	return fs, nil
 }
 
-func (r descsByName) initOneofsFromDescriptorProto(ods []*descriptorpb.OneofDescriptorProto, parent protoreflect.Descriptor) (os []filedesc.Oneof, err error) {
+func (r descsByName) initOneofsFromDescriptorProto(ods []*descriptorpb.OneofDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (os []filedesc.Oneof, err error) {
 	os = make([]filedesc.Oneof, len(ods)) // allocate up-front to ensure stable pointers
 	for i, od := range ods {
 		o := &os[i]
-		if o.L0, err = r.makeBase(o, parent, od.GetName(), i); err != nil {
+		if o.L0, err = r.makeBase(o, parent, od.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := od.GetOptions(); opts != nil {
@@ -153,12 +154,12 @@ func (r descsByName) initOneofsFromDescriptorProto(ods []*descriptorpb.OneofDesc
 	return os, nil
 }
 
-func (r descsByName) initExtensionDeclarations(xds []*descriptorpb.FieldDescriptorProto, parent protoreflect.Descriptor) (xs []filedesc.Extension, err error) {
+func (r descsByName) initExtensionDeclarations(xds []*descriptorpb.FieldDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (xs []filedesc.Extension, err error) {
 	xs = make([]filedesc.Extension, len(xds)) // allocate up-front to ensure stable pointers
 	for i, xd := range xds {
 		x := &xs[i]
 		x.L2 = new(filedesc.ExtensionL2)
-		if x.L0, err = r.makeBase(x, parent, xd.GetName(), i); err != nil {
+		if x.L0, err = r.makeBase(x, parent, xd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := xd.GetOptions(); opts != nil {
@@ -178,30 +179,30 @@ func (r descsByName) initExtensionDeclarations(xds []*descriptorpb.FieldDescript
 	return xs, nil
 }
 
-func (r descsByName) initServiceDeclarations(sds []*descriptorpb.ServiceDescriptorProto, parent protoreflect.Descriptor) (ss []filedesc.Service, err error) {
+func (r descsByName) initServiceDeclarations(sds []*descriptorpb.ServiceDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (ss []filedesc.Service, err error) {
 	ss = make([]filedesc.Service, len(sds)) // allocate up-front to ensure stable pointers
 	for i, sd := range sds {
 		s := &ss[i]
 		s.L2 = new(filedesc.ServiceL2)
-		if s.L0, err = r.makeBase(s, parent, sd.GetName(), i); err != nil {
+		if s.L0, err = r.makeBase(s, parent, sd.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := sd.GetOptions(); opts != nil {
 			opts = clone(opts).(*descriptorpb.ServiceOptions)
 			s.L2.Options = func() protoreflect.ProtoMessage { return opts }
 		}
-		if s.L2.Methods.List, err = r.initMethodsFromDescriptorProto(sd.GetMethod(), s); err != nil {
+		if s.L2.Methods.List, err = r.initMethodsFromDescriptorProto(sd.GetMethod(), s, sb); err != nil {
 			return nil, err
 		}
 	}
 	return ss, nil
 }
 
-func (r descsByName) initMethodsFromDescriptorProto(mds []*descriptorpb.MethodDescriptorProto, parent protoreflect.Descriptor) (ms []filedesc.Method, err error) {
+func (r descsByName) initMethodsFromDescriptorProto(mds []*descriptorpb.MethodDescriptorProto, parent protoreflect.Descriptor, sb *strs.Builder) (ms []filedesc.Method, err error) {
 	ms = make([]filedesc.Method, len(mds)) // allocate up-front to ensure stable pointers
 	for i, md := range mds {
 		m := &ms[i]
-		if m.L0, err = r.makeBase(m, parent, md.GetName(), i); err != nil {
+		if m.L0, err = r.makeBase(m, parent, md.GetName(), i, sb); err != nil {
 			return nil, err
 		}
 		if opts := md.GetOptions(); opts != nil {
@@ -214,7 +215,7 @@ func (r descsByName) initMethodsFromDescriptorProto(mds []*descriptorpb.MethodDe
 	return ms, nil
 }
 
-func (r descsByName) makeBase(child, parent protoreflect.Descriptor, name string, idx int) (filedesc.BaseL0, error) {
+func (r descsByName) makeBase(child, parent protoreflect.Descriptor, name string, idx int, sb *strs.Builder) (filedesc.BaseL0, error) {
 	if !protoreflect.Name(name).IsValid() {
 		return filedesc.BaseL0{}, errors.New("descriptor %q has an invalid nested name: %q", parent.FullName(), name)
 	}
@@ -223,9 +224,9 @@ func (r descsByName) makeBase(child, parent protoreflect.Descriptor, name string
 	// Note that enum values are a sibling to the enum parent in the namespace.
 	var fullName protoreflect.FullName
 	if _, ok := parent.(protoreflect.EnumDescriptor); ok {
-		fullName = parent.FullName().Parent().Append(protoreflect.Name(name))
+		fullName = sb.AppendFullName(parent.FullName().Parent(), protoreflect.Name(name))
 	} else {
-		fullName = parent.FullName().Append(protoreflect.Name(name))
+		fullName = sb.AppendFullName(parent.FullName(), protoreflect.Name(name))
 	}
 	if _, ok := r[fullName]; ok {
 		return filedesc.BaseL0{}, errors.New("descriptor %q already declared", fullName)

reflect/protodesc/desc_validate.go

@@ -11,6 +11,7 @@ import (
 	"google.golang.org/protobuf/internal/encoding/wire"
 	"google.golang.org/protobuf/internal/errors"
 	"google.golang.org/protobuf/internal/filedesc"
+	"google.golang.org/protobuf/internal/strs"
 	"google.golang.org/protobuf/reflect/protoreflect"
 
 	"google.golang.org/protobuf/types/descriptorpb"
@@ -53,7 +54,7 @@ func validateEnumDeclarations(es []filedesc.Enum, eds []*descriptorpb.EnumDescri
 			prefix := strings.Replace(strings.ToLower(string(e.Name())), "_", "", -1)
 			for i := 0; i < e.Values().Len(); i++ {
 				v1 := e.Values().Get(i)
-				s := enumValueName(trimEnumPrefix(v1.Name(), prefix))
+				s := strs.EnumValueName(strs.TrimEnumPrefix(string(v1.Name()), prefix))
 				if v2, ok := names[s]; ok && v1.Number() != v2.Number() {
 					return errors.New("enum %q using proto3 semantics has conflict: %q with %q", e.FullName(), v1.Name(), v2.Name())
 				}
@@ -209,7 +210,7 @@ func validateExtensionDeclarations(xs []filedesc.Extension, xds []*descriptorpb.
 			return errors.New("extension field %q has an invalid cardinality: %d", x.FullName(), x.Cardinality())
 		}
 		if xd.JsonName != nil {
-			if xd.GetJsonName() != jsonName(x.Name()) {
+			if xd.GetJsonName() != strs.JSONCamelCase(string(x.Name())) {
 				return errors.New("extension field %q may not have an explicitly set JSON name: %q", x.FullName(), xd.GetJsonName())
 			}
 		}
@@ -305,7 +306,7 @@ func checkValidMap(fd protoreflect.FieldDescriptor) error {
 		return nil
 	case fd.FullName().Parent() != md.FullName().Parent():
 		return errors.New("message and field must be declared in the same scope")
-	case md.Name() != mapEntryName(fd.Name()):
+	case md.Name() != protoreflect.Name(strs.MapEntryName(string(fd.Name()))):
 		return errors.New("incorrect implicit map entry name")
 	case fd.Cardinality() != protoreflect.Repeated:
 		return errors.New("field must be repeated")
@@ -339,87 +340,3 @@ func checkValidMap(fd protoreflect.FieldDescriptor) error {
 	}
 	return nil
 }
-
-// mapEntryName derives the name of the map entry message given the field name.
-// See protoc v3.8.0: src/google/protobuf/descriptor.cc:254-276,6057
-func mapEntryName(s protoreflect.Name) protoreflect.Name {
-	var b []byte
-	upperNext := true
-	for _, c := range s {
-		switch {
-		case c == '_':
-			upperNext = true
-		case upperNext:
-			b = append(b, byte(unicode.ToUpper(c)))
-			upperNext = false
-		default:
-			b = append(b, byte(c))
-		}
-	}
-	b = append(b, "Entry"...)
-	return protoreflect.Name(b)
-}
-
-// enumValueName derives the camel-cased enum value name.
-// See protoc v3.8.0: src/google/protobuf/descriptor.cc:297-313
-func enumValueName(s protoreflect.Name) string {
-	var b []byte
-	upperNext := true
-	for _, c := range s {
-		switch {
-		case c == '_':
-			upperNext = true
-		case upperNext:
-			b = append(b, byte(unicode.ToUpper(c)))
-			upperNext = false
-		default:
-			b = append(b, byte(unicode.ToLower(c)))
-			upperNext = false
-		}
-	}
-	return string(b)
-}
-
-// trimEnumPrefix trims the enum name prefix from an enum value name,
-// where the prefix is all lowercase without underscores.
-// See protoc v3.8.0: src/google/protobuf/descriptor.cc:330-375
-func trimEnumPrefix(s protoreflect.Name, prefix string) protoreflect.Name {
-	s0 := s // original input
-	for len(s) > 0 && len(prefix) > 0 {
-		if s[0] == '_' {
-			s = s[1:]
-			continue
-		}
-		if unicode.ToLower(rune(s[0])) != rune(prefix[0]) {
-			return s0 // no prefix match
-		}
-		s, prefix = s[1:], prefix[1:]
-	}
-	if len(prefix) > 0 {
-		return s0 // no prefix match
-	}
-	s = protoreflect.Name(strings.TrimLeft(string(s), "_"))
-	if len(s) == 0 {
-		return s0 // avoid returning empty string
-	}
-	return s
-}
-
-// jsonName creates a JSON name from the protobuf short name.
-// See protoc v3.8.0: src/google/protobuf/descriptor.cc:278-295
-func jsonName(s protoreflect.Name) string {
-	var b []byte
-	var wasUnderscore bool
-	for i := 0; i < len(s); i++ { // proto identifiers are always ASCII
-		c := s[i]
-		if c != '_' {
-			isLower := 'a' <= c && c <= 'z'
-			if wasUnderscore && isLower {
-				c -= 'a' - 'A'
-			}
-			b = append(b, c)
-		}
-		wasUnderscore = c == '_'
-	}
-	return string(b)
-}

reflect/protodesc/file_test.go

@@ -11,7 +11,6 @@ import (
 
 	"google.golang.org/protobuf/encoding/prototext"
 	"google.golang.org/protobuf/proto"
-	"google.golang.org/protobuf/reflect/protoreflect"
 	"google.golang.org/protobuf/reflect/protoregistry"
 
 	"google.golang.org/protobuf/types/descriptorpb"
@@ -883,57 +882,3 @@ func TestNewFile(t *testing.T) {
 		})
 	}
 }
-
-func TestName(t *testing.T) {
-	tests := []struct {
-		in            protoreflect.Name
-		enumPrefix    string
-		wantMapEntry  protoreflect.Name
-		wantEnumValue string
-		wantTrimValue protoreflect.Name
-		wantJSON      string
-	}{{
-		in:            "abc",
-		enumPrefix:    "",
-		wantMapEntry:  "AbcEntry",
-		wantEnumValue: "Abc",
-		wantTrimValue: "abc",
-		wantJSON:      "abc",
-	}, {
-		in:            "foo_baR_",
-		enumPrefix:    "foo_bar",
-		wantMapEntry:  "FooBaREntry",
-		wantEnumValue: "FooBar",
-		wantTrimValue: "foo_baR_",
-		wantJSON:      "fooBaR",
-	}, {
-		in:            "snake_caseCamelCase",
-		enumPrefix:    "snakecasecamel",
-		wantMapEntry:  "SnakeCaseCamelCaseEntry",
-		wantEnumValue: "SnakeCasecamelcase",
-		wantTrimValue: "Case",
-		wantJSON:      "snakeCaseCamelCase",
-	}, {
-		in:            "FiZz_BuZz",
-		enumPrefix:    "fizz",
-		wantMapEntry:  "FiZzBuZzEntry",
-		wantEnumValue: "FizzBuzz",
-		wantTrimValue: "BuZz",
-		wantJSON:      "FiZzBuZz",
-	}}
-
-	for _, tt := range tests {
-		if got := mapEntryName(tt.in); got != tt.wantMapEntry {
-			t.Errorf("mapEntryName(%q) = %q, want %q", tt.in, got, tt.wantMapEntry)
-		}
-		if got := enumValueName(tt.in); got != tt.wantEnumValue {
-			t.Errorf("enumValueName(%q) = %q, want %q", tt.in, got, tt.wantEnumValue)
-		}
-		if got := trimEnumPrefix(tt.in, tt.enumPrefix); got != tt.wantTrimValue {
-			t.Errorf("trimEnumPrefix(%q, %q) = %q, want %q", tt.in, tt.enumPrefix, got, tt.wantTrimValue)
-		}
-		if got := jsonName(tt.in); got != tt.wantJSON {
-			t.Errorf("jsonName(%q) = %q, want %q", tt.in, got, tt.wantJSON)
-		}
-	}
-}