gin/render/render.go

// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package render

import (
	"net/http"
	"sync"
)

// RenderType Names
const (
	JSONRenderType         = iota // JSON Render Type
	IntendedJSONRenderType        // IntendedJSON Render Type
	PureJSONRenderType            // PureJSON Render Type
	AsciiJSONRenderType           // AsciiJSON Render Type
	JsonpJSONRenderType           // JsonpJSON Render Type
	SecureJSONRenderType          // SecureJSON Type
	XMLRenderType                 // XML Render Type
	YAMLRenderType                // YAML Render Type
	MsgPackRenderType             // MsgPack Render Type
	ProtoBufRenderType            // ProtoBuf Render Type
	EmptyRenderType               // Empty Render Type
)

var (
	renderPool = &RenderPool{renderPools: make(map[int]sync.Pool)}
)

// Render interface is to be implemented by JSON, XML, HTML, YAML and so on.
type Render interface {
	// Render writes data with custom ContentType.
	Render(http.ResponseWriter) error
	// WriteContentType writes custom ContentType.
	WriteContentType(w http.ResponseWriter)
}

// RenderRecycler interface is to be implemented by JSON, XML, HTML, YAML and so on.
type RenderRecycler interface {
	Render
	// Setup set data and opts
	Setup(data interface{}, opts ...interface{})
	// Reset clean data and opts
	Reset()
}

// RenderFactory interface is to be implemented by other Render.
type RenderFactory interface {
	// Instance a new RenderRecycler instance
	Instance() RenderRecycler
}

// RenderPool contains Render instance
type RenderPool struct {
	mu          sync.RWMutex
	renderPools map[int]sync.Pool
}

func (p *RenderPool) get(name int) RenderRecycler {
	p.mu.RLock()
	defer p.mu.RUnlock()

	var render RenderRecycler
	if pool, ok := p.renderPools[name]; ok {
		render, _ = pool.Get().(RenderRecycler)
	} else {
		pool, _ = p.renderPools[EmptyRenderType]
		render, _ = pool.Get().(RenderRecycler)
	}
	if render == nil {
		render = &EmptyRender{}
	}
	return render
}

func (p *RenderPool) put(name int, render RenderRecycler) {
	p.mu.RLock()
	defer p.mu.RUnlock()

	if pool, ok := p.renderPools[name]; ok {
		render.Reset()
		pool.Put(render)
	}
}

func (p *RenderPool) register(name int, factory RenderFactory) {
	p.mu.Lock()
	defer p.mu.Unlock()

	if factory == nil {
		panic("gin: Register RenderFactory is nil")
	}
	if _, dup := p.renderPools[name]; dup {
		panic("gin: Register called twice for RenderFactory")
	}

	p.renderPools[name] = sync.Pool{
		New: func() interface{} {
			return factory.Instance()
		},
	}
}

// Register makes a binding available by the provided name.
// If Register is called twice with the same name or if binding is nil,
// it panics.
func Register(name int, factory RenderFactory) {
	renderPool.register(name, factory)
}

// Default returns the appropriate Render instance based on the render type.
func Default(name int) RenderRecycler {
	return renderPool.get(name)
}

// Recycle put render to sync.Pool
func Recycle(name int, render RenderRecycler) {
	renderPool.put(name, render)
}

var (
	_ RenderRecycler = &JSON{}
	_ RenderRecycler = &IndentedJSON{}
	_ RenderRecycler = &SecureJSON{}
	_ RenderRecycler = &JsonpJSON{}
	_ RenderRecycler = &XML{}
	_ Render         = String{}
	_ Render         = Redirect{}
	_ Render         = Data{}
	_ Render         = HTML{}
	_ HTMLRender     = HTMLDebug{}
	_ HTMLRender     = HTMLProduction{}
	_ RenderRecycler = &YAML{}
	_ RenderRecycler = &MsgPack{}
	_ Render         = Reader{}
	_ RenderRecycler = &AsciiJSON{}
	_ RenderRecycler = &ProtoBuf{}
)

func writeContentType(w http.ResponseWriter, value []string) {
	header := w.Header()
	if val := header["Content-Type"]; len(val) == 0 {
		header["Content-Type"] = value
	}
}