devapp/cache.go

// Copyright 2016 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.

package main

import (
	"bytes"
	"compress/gzip"
	"encoding/gob"
	"fmt"
	"log"
	"sync"

	"golang.org/x/build/godash"
)

// A Cache contains serialized data for dashboards.
type Cache struct {
	// Value contains a gzipped gob'd serialization of the object
	// to be cached.
	Value []byte
}

var (
	dstore   = map[string]*Cache{}
	dstoreMu sync.Mutex
)

func parseData(cache *Cache) (*godash.Data, error) {
	data := &godash.Data{Reviewers: &godash.Reviewers{}}
	return data, unpackCache(cache, &data)
}

func unpackCache(cache *Cache, data interface{}) error {
	if len(cache.Value) > 0 {
		gzr, err := gzip.NewReader(bytes.NewReader(cache.Value))
		if err != nil {
			return err
		}
		defer gzr.Close()
		if err := gob.NewDecoder(gzr).Decode(data); err != nil {
			return err
		}
	}
	return nil
}

func writeCache(name string, data interface{}) error {
	var cache Cache
	var cacheout bytes.Buffer
	cachegz := gzip.NewWriter(&cacheout)
	e := gob.NewEncoder(cachegz)
	if err := e.Encode(data); err != nil {
		return err
	}
	if err := cachegz.Close(); err != nil {
		return err
	}
	cache.Value = cacheout.Bytes()
	log.Printf("Cache %q update finished; writing %d bytes", name, cacheout.Len())
	return putCache(name, &cache)
}

func putCache(name string, c *Cache) error {
	dstoreMu.Lock()
	defer dstoreMu.Unlock()
	dstore[name] = c
	return nil
}

func getCache(name string) (*Cache, error) {
	dstoreMu.Lock()
	defer dstoreMu.Unlock()
	cache, ok := dstore[name]
	if ok {
		return cache, nil
	}
	return &Cache{}, fmt.Errorf("cache key %s not found", name)
}