1 files changed, 95 insertions, 0 deletions
diff --git a/internal/strs/strings_unsafe.go b/internal/strs/strings_unsafe.go
new file mode 100644
index 00000000..56a8a4ed
--- /dev/null
+++ b/internal/strs/strings_unsafe.go
@@ -0,0 +1,95 @@
+// 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.
+
+//go:build !purego && !appengine
+// +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:])
+}