photofinder.go

package main

import (
	"bufio"
	"fmt"
	"image"
	_ "image/jpeg"
	"os"
	"os/exec"
	"runtime"
	"sync"
)

func checkFile(path string) error {
	f, err := os.Open(path)
	if err != nil {
		return err
	}

	defer f.Close()

	cfg, _, err := image.DecodeConfig(f)

	if cfg.Width > 2500 {
		fmt.Printf("%s: %d x %d\n", path, cfg.Height, cfg.Width)
	}

	return nil
}

type photoChecker struct {
	done   chan struct{}
	wg     sync.WaitGroup
	fileCh chan string
}

func newPhotoChecker() *photoChecker {
	return &photoChecker{
		done:   make(chan struct{}),
		fileCh: make(chan string, 1),
	}
}

func (p *photoChecker) run(numRoutines int) {
	for i := 0; i < numRoutines; i++ {
		p.wg.Add(1)
		go func() {
			run := true
			for run {
				select {
				case file := <-p.fileCh: // get the next file name from the queue
					err := checkFile(file)
					if err != nil {
						fmt.Fprintln(os.Stderr, err)
					}
				case <-p.done: // will exec when the channel is closed
					run = false
				}
			}
			p.wg.Done()
		}()
	}
}

func (p *photoChecker) addFile(path string) {
	p.fileCh <- path
}

func (p *photoChecker) stopAndWait() {
	close(p.done) // reading from a closed channel immediately yields nil, forever
	p.wg.Wait()
}

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	cmd := exec.Command("find", ".", "-name", "*.jpg")
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	if err := cmd.Start(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}

	checker := newPhotoChecker()
	checker.run(runtime.NumCPU())

	scanner := bufio.NewScanner(stdout)

	for scanner.Scan() {
		checker.addFile(scanner.Text())
	}

	err = scanner.Err()
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
	}

	err = cmd.Wait()
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
	}

	checker.stopAndWait()
}