Add a cache for gallery thumbnails (#496)

pkg/api/cache_thumbs.go

@@ -0,0 +1,72 @@
+package api
+
+import (
+	"github.com/stashapp/stash/pkg/logger"
+	"github.com/stashapp/stash/pkg/manager/paths"
+	"github.com/stashapp/stash/pkg/models"
+	"github.com/stashapp/stash/pkg/utils"
+	"io/ioutil"
+)
+
+type thumbBuffer struct {
+	path string
+	dir  string
+	data []byte
+}
+
+func newCacheThumb(dir string, path string, data []byte) *thumbBuffer {
+	t := thumbBuffer{dir: dir, path: path, data: data}
+	return &t
+}
+
+var writeChan chan *thumbBuffer
+var touchChan chan *string
+
+func startThumbCache() { // TODO add extra wait, close chan code if/when stash gets a stop mode
+
+	writeChan = make(chan *thumbBuffer, 20)
+	go thumbnailCacheWriter()
+}
+
+//serialize file writes to avoid race conditions
+func thumbnailCacheWriter() {
+
+	for thumb := range writeChan {
+		exists, _ := utils.FileExists(thumb.path)
+		if !exists {
+			err := utils.WriteFile(thumb.path, thumb.data)
+			if err != nil {
+				logger.Errorf("Write error for thumbnail %s: %s ", thumb.path, err)
+			}
+		}
+	}
+
+}
+
+// get thumbnail from cache, otherwise create it and store to cache
+func cacheGthumb(gallery *models.Gallery, index int, width int) []byte {
+	thumbPath := paths.GetGthumbPath(gallery.Checksum, index, width)
+	exists, _ := utils.FileExists(thumbPath)
+	if exists { // if thumbnail exists in cache return that
+		content, err := ioutil.ReadFile(thumbPath)
+		if err == nil {
+			return content
+		} else {
+			logger.Errorf("Read Error for file %s : %s", thumbPath, err)
+		}
+
+	}
+	data := gallery.GetThumbnail(index, width)
+	thumbDir := paths.GetGthumbDir(gallery.Checksum)
+	t := newCacheThumb(thumbDir, thumbPath, data)
+	writeChan <- t // write the file to cache
+	return data
+}
+
+// create all thumbs for a given gallery
+func CreateGthumbs(gallery *models.Gallery) {
+	count := gallery.ImageCount()
+	for i := 0; i < count; i++ {
+		cacheGthumb(gallery, i, models.DefaultGthumbWidth)
+	}
+}