imgproxy/bufpool.go

package main

import (
	"bytes"
	"sync"
)

type bufPool struct {
	mutex sync.Mutex
	name  string
	size  int
	top   *bufPoolEntry
}

type bufPoolEntry struct {
	buf  *bytes.Buffer
	next *bufPoolEntry
}

func newBufPool(name string, n int, size int) *bufPool {
	pool := bufPool{name: name, size: size}

	for i := 0; i < n; i++ {
		pool.grow()
	}

	return &pool
}

func (p *bufPool) grow() {
	var buf *bytes.Buffer

	buf = new(bytes.Buffer)

	if p.size > 0 {
		buf.Grow(p.size)
	}

	p.top = &bufPoolEntry{buf: buf, next: p.top}

	if prometheusEnabled {
		incrementBuffersTotal(p.name)
	}
}

func (p *bufPool) get() *bytes.Buffer {
	p.mutex.Lock()
	defer p.mutex.Unlock()

	if p.top == nil {
		p.grow()
	}

	buf := p.top.buf
	buf.Reset()

	p.top = p.top.next

	return buf
}

func (p *bufPool) put(buf *bytes.Buffer) {
	p.mutex.Lock()
	defer p.mutex.Unlock()

	p.top = &bufPoolEntry{buf: buf, next: p.top}

	if prometheusEnabled {
		observeBufferSize(p.name, buf.Cap())
	}
}