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