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tailscale/types/strbuilder/strbuilder.go

75 lines
1.8 KiB
Go

// Copyright (c) 2020 Tailscale Inc & 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 strbuilder defines a string builder type that allocates
// less than the standard library's strings.Builder by using a
// sync.Pool, so it doesn't matter if the compiler can't prove that
// the builder doesn't escape into the fmt package, etc.
package strbuilder
import (
"bytes"
"strconv"
"sync"
)
var pool = sync.Pool{
New: func() interface{} { return new(Builder) },
}
type Builder struct {
bb bytes.Buffer
scratch [20]byte // long enough for MinInt64, MaxUint64
locked bool // in pool, not for use
}
// Get returns a new or reused string Builder.
func Get() *Builder {
b := pool.Get().(*Builder)
b.bb.Reset()
b.locked = false
return b
}
// String both returns the Builder's string, and returns the builder
// to the pool.
func (b *Builder) String() string {
if b.locked {
panic("String called twiced on Builder")
}
s := b.bb.String()
b.locked = true
pool.Put(b)
return s
}
func (b *Builder) WriteByte(v byte) error {
return b.bb.WriteByte(v)
}
func (b *Builder) WriteString(s string) (int, error) {
return b.bb.WriteString(s)
}
func (b *Builder) Write(p []byte) (int, error) {
return b.bb.Write(p)
}
func (b *Builder) WriteInt(v int64) {
b.Write(strconv.AppendInt(b.scratch[:0], v, 10))
}
func (b *Builder) WriteUint(v uint64) {
b.Write(strconv.AppendUint(b.scratch[:0], v, 10))
}
// Grow grows the buffer's capacity, if necessary, to guarantee space
// for another n bytes. After Grow(n), at least n bytes can be written
// to the buffer without another allocation. If n is negative, Grow
// will panic. If the buffer can't grow it will panic with
// ErrTooLarge.
func (b *Builder) Grow(n int) {
b.bb.Grow(n)
}