Cleanup error messages

camera.go

@@ -1,7 +1,7 @@
 package vidio
 
 import (
-	"errors"
+	"fmt"
 	"io"
 	"os"
 	"os/exec"
@@ -70,11 +70,9 @@ func getDevicesWindows() ([]string, error) {
 	)
 	pipe, err := cmd.StderrPipe()
 	if err != nil {
-		pipe.Close()
 		return nil, err
 	}
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return nil, err
 	}
 	// Read list devices from Stdout.
@@ -110,12 +108,10 @@ func getCameraData(device string, camera *Camera) error {
 	// it will write the meta data to Stderr.
 	pipe, err := cmd.StderrPipe()
 	if err != nil {
-		pipe.Close()
 		return err
 	}
 	// Start the command.
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return err
 	}
 	// Read ffmpeg output from Stdout.
@@ -156,11 +152,11 @@ func NewCamera(stream int) (*Camera, error) {
 			return nil, err
 		}
 		if stream >= len(devices) {
-			return nil, errors.New("Could not find device with index: " + strconv.Itoa(stream))
+			return nil, fmt.Errorf("could not find device with index: %d", stream)
 		}
 		device = "video=" + devices[stream]
 	default:
-		return nil, errors.New("Unsupported OS: " + runtime.GOOS)
+		return nil, fmt.Errorf("unsupported OS: %s", runtime.GOOS)
 	}
 
 	camera := Camera{name: device, depth: 3}
@@ -196,13 +192,11 @@ func initCamera(camera *Camera) error {
 	camera.cmd = cmd
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
-		pipe.Close()
 		return err
 	}
 
 	camera.pipe = &pipe
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return err
 	}
 

imageio.go

@@ -1,7 +1,6 @@
 package vidio
 
 import (
-	"errors"
 	"fmt"
 	"image"
 	"os"
@@ -9,9 +8,7 @@ import (
 
 	"image/color"
 	"image/jpeg"
-	_ "image/jpeg"
 	"image/png"
-	_ "image/png"
 )
 
 // Reads an image from a file. Currently only supports png and jpeg.
@@ -33,12 +30,11 @@ func Read(filename string, buffer ...[]byte) (int, int, []byte, error) {
 	var data []byte
 	if len(buffer) > 0 {
 		if len(buffer[0]) < size {
-			errmsg := fmt.Sprintf("Buffer size (%d) is smaller than image size (%d)", len(buffer[0]), size)
-			return 0, 0, nil, errors.New(errmsg)
+			return 0, 0, nil, fmt.Errorf("buffer size (%d) is smaller than image size (%d)", len(buffer[0]), size)
 		}
 		data = buffer[0]
 	} else {
-		data = make([]byte, size, size)
+		data = make([]byte, size)
 	}
 
 	index := 0
@@ -46,12 +42,10 @@ func Read(filename string, buffer ...[]byte) (int, int, []byte, error) {
 		for w := 0; w < bounds.X; w++ {
 			r, g, b, _ := image.At(w, h).RGBA()
 			r, g, b = r/256, g/256, b/256
-			data[index] = byte(r)
-			index++
-			data[index] = byte(g)
-			index++
-			data[index] = byte(b)
-			index++
+			data[index+0] = byte(r)
+			data[index+1] = byte(g)
+			data[index+2] = byte(b)
+			index += 3
 		}
 	}
 	return bounds.X, bounds.Y, data, nil
@@ -84,6 +78,8 @@ func Write(filename string, width, height int, buffer []byte) error {
 		if err := jpeg.Encode(f, image, nil); err != nil {
 			return err
 		}
+	default:
+		return fmt.Errorf("unsupported file extension: %s", filepath.Ext(filename))
 	}
 
 	return nil

utils.go

@@ -2,6 +2,7 @@ package vidio
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"os"
 	"os/exec"
@@ -27,13 +28,12 @@ func exists(filename string) bool {
 // Checks if the given program is installed.
 func checkExists(program string) error {
 	cmd := exec.Command(program, "-version")
+	errmsg := fmt.Errorf("%s is not installed", program)
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
-		return errors.New(program + " is not installed.")
+		return errmsg
 	}
 	if err := cmd.Wait(); err != nil {
-		cmd.Process.Kill()
-		return errors.New(program + " is not installed.")
+		return errmsg
 	}
 	return nil
 }
@@ -53,12 +53,10 @@ func ffprobe(filename, stype string) (map[string]string, error) {
 
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
-		pipe.Close()
 		return nil, err
 	}
 
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return nil, err
 	}
 	// Read ffprobe output from Stdout.
@@ -73,7 +71,6 @@ func ffprobe(filename, stype string) (map[string]string, error) {
 	}
 	// Wait for ffprobe command to complete.
 	if err := cmd.Wait(); err != nil {
-		cmd.Process.Kill()
 		return nil, err
 	}
 
@@ -138,8 +135,7 @@ func parse(data string) float64 {
 
 // Returns the webcam name used for the -f option with ffmpeg.
 func webcam() (string, error) {
-	os := runtime.GOOS
-	switch os {
+	switch runtime.GOOS {
 	case "linux":
 		return "v4l2", nil
 	case "darwin":
@@ -147,7 +143,7 @@ func webcam() (string, error) {
 	case "windows":
 		return "dshow", nil // vfwcap
 	default:
-		return "", errors.New("Unsupported OS: " + os)
+		return "", fmt.Errorf("unsupported OS: %s", runtime.GOOS)
 	}
 }
 
@@ -221,7 +217,7 @@ func parseWebcamData(buffer []byte, camera *Camera) {
 	}
 	bufferstr = bufferstr[index:]
 	// Dimensions. widthxheight.
-	regex := regexp.MustCompile("\\d{2,}x\\d{2,}")
+	regex := regexp.MustCompile(`\d{2,}x\d{2,}`)
 	match := regex.FindString(bufferstr)
 	if len(match) > 0 {
 		split := strings.Split(match, "x")
@@ -229,7 +225,7 @@ func parseWebcamData(buffer []byte, camera *Camera) {
 		camera.height = int(parse(split[1]))
 	}
 	// FPS.
-	regex = regexp.MustCompile("\\d+(.\\d+)? fps")
+	regex = regexp.MustCompile(`\d+(.\d+)? fps`)
 	match = regex.FindString(bufferstr)
 	if len(match) > 0 {
 		index = strings.Index(match, " fps")
@@ -242,7 +238,7 @@ func parseWebcamData(buffer []byte, camera *Camera) {
 	regex = regexp.MustCompile("Video: .+,")
 	match = regex.FindString(bufferstr)
 	if len(match) > 0 {
-		match = match[7:]
+		match = match[len("Video: "):]
 		index = strings.Index(match, "(")
 		if index != -1 {
 			match = match[:index]

video.go

@@ -1,7 +1,7 @@
 package vidio
 
 import (
-	"errors"
+	"fmt"
 	"io"
 	"os"
 	"os/exec"
@@ -87,7 +87,7 @@ func (video *Video) SetFrameBuffer(buffer []byte) {
 // Uses ffprobe to get video information and fills in the Video struct with this data.
 func NewVideo(filename string) (*Video, error) {
 	if !exists(filename) {
-		return nil, errors.New("Video file " + filename + " does not exist")
+		return nil, fmt.Errorf("video file %s does not exist", filename)
 	}
 	// Check if ffmpeg and ffprobe are installed on the users machine.
 	if err := checkExists("ffmpeg"); err != nil {
@@ -134,12 +134,10 @@ func initVideo(video *Video) error {
 	video.cmd = cmd
 	pipe, err := cmd.StdoutPipe()
 	if err != nil {
-		pipe.Close()
 		return err
 	}
 	video.pipe = &pipe
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return err
 	}
 

videowriter.go

@@ -1,7 +1,6 @@
 package vidio
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -142,14 +141,14 @@ func NewVideoWriter(filename string, width, height int, options *Options) (*Vide
 
 	if options.Audio != "" {
 		if !exists(options.Audio) {
-			return nil, errors.New("Audio file " + options.Audio + " does not exist.")
+			return nil, fmt.Errorf("audio file %s does not exist", options.Audio)
 		}
 
 		audioData, err := ffprobe(options.Audio, "a")
 		if err != nil {
 			return nil, err
 		} else if len(audioData) == 0 {
-			return nil, errors.New("Given \"audio\" file " + options.Audio + " has no audio.")
+			return nil, fmt.Errorf("given audio file %s has no audio", options.Audio)
 		}
 
 		writer.audio = options.Audio
@@ -258,12 +257,10 @@ func initVideoWriter(writer *VideoWriter) error {
 
 	pipe, err := cmd.StdinPipe()
 	if err != nil {
-		pipe.Close()
 		return err
 	}
 	writer.pipe = &pipe
 	if err := cmd.Start(); err != nil {
-		cmd.Process.Kill()
 		return err
 	}