95 lines
2.4 KiB
Go
95 lines
2.4 KiB
Go
|
// 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:])
|
||
|
|
}
|