Initial Release

env/Utils.go

@@ -0,0 +1,84 @@
+package env
+
+import (
+	"runtime"
+	"sync"
+	"sync/atomic"
+)
+
+type ImageType string
+
+const (
+	IMAGE_OTHER ImageType = "UNKNOWN"
+	IMAGE_WEBP  ImageType = "WEBP"
+	IMAGE_JPEG  ImageType = "JPG"
+	IMAGE_PNG   ImageType = "PNG"
+	IMAGE_GIF   ImageType = "GIF"
+)
+
+// Classify the contents of a file based on it's starting bytes
+// https://en.wikipedia.org/wiki/Magic_number_(programming)#Magic_numbers_in_files)
+func ImageSniffType(d []byte) ImageType {
+	switch {
+	case len(d) > 3 && // JPEG
+		d[0] == 0xFF && d[1] == 0xD8 && d[2] == 0xFF:
+		return IMAGE_JPEG
+
+	case len(d) > 8 && // PNG
+		d[0] == 0x89 && d[1] == 0x50 && d[2] == 0x4E && d[3] == 0x47 &&
+		d[4] == 0x0D && d[5] == 0x0A && d[6] == 0x1A && d[7] == 0x0A:
+		return IMAGE_PNG
+
+	case len(d) > 4 && // GIF
+		d[0] == 0x47 && d[1] == 0x49 && d[2] == 0x46 && d[3] == 0x38:
+		return IMAGE_GIF
+
+	case len(d) > 12 && // WEBP
+		d[0] == 0x52 && d[1] == 0x49 && d[2] == 0x46 && d[3] == 0x46 &&
+		d[8] == 0x57 && d[9] == 0x45 && d[10] == 0x42 && d[11] == 0x50:
+		return IMAGE_WEBP
+
+	default:
+		return IMAGE_OTHER
+	}
+}
+
+// Easily spread a workload across all available threads, returning the error if any
+func Multithread(jobCount int, handler func(i int) error) error {
+	threads := runtime.NumCPU()
+	channel := make(chan int, jobCount)
+	var wait sync.WaitGroup
+	var fail atomic.Value
+
+	// Startup Goroutines
+	for workerId := 0; workerId < threads; workerId++ {
+		wait.Add(1)
+		go func() {
+			defer wait.Done()
+			for i := range channel {
+				// Exit early if an error has ocurred
+				if fail.Load() != nil {
+					return
+				}
+				// Run Handler and store it's error (if any)
+				if err := handler(i); err != nil {
+					fail.Store(err)
+					return
+				}
+			}
+		}()
+	}
+
+	// Queue and Complete Work Across all Threads
+	for i := 0; i < jobCount; i++ {
+		channel <- i
+	}
+	close(channel) // close or wait forever
+	wait.Wait()
+
+	// Return Error (if any)
+	if v := fail.Load(); v != nil {
+		return v.(error)
+	}
+	return nil
+}