ots/tplFuncs.go

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package main
import (
"crypto/sha512"
"encoding/base64"
"path"
"sync"
"text/template"
)
var (
sriCacheStore = newSRICache()
tplFuncs = template.FuncMap{
"list": func(args ...string) []string { return args },
"assetSRI": assetSRIHash,
}
)
func assetSRIHash(assetName string) string {
if sri, ok := sriCacheStore.Get(assetName); ok {
return sri
}
data, err := assets.ReadFile(path.Join("frontend", assetName))
if err != nil {
panic(err)
}
h := sha512.New384()
h.Write(data)
sum := h.Sum(nil)
sri := "sha384-" + base64.StdEncoding.EncodeToString(sum)
sriCacheStore.Set(assetName, sri)
return sri
}
type sriCache struct {
c map[string]string
l sync.RWMutex
}
func newSRICache() *sriCache { return &sriCache{c: map[string]string{}} }
func (s *sriCache) Get(assetName string) (string, bool) {
s.l.RLock()
defer s.l.RUnlock()
h, ok := s.c[assetName]
return h, ok
}
func (s *sriCache) Set(assetName, hash string) {
s.l.Lock()
defer s.l.Unlock()
s.c[assetName] = hash
}