golden/go/diffstore/common/common.go

package common

import (
	"fmt"
	"image"
	"image/png"
	"io"
	"os"
	"path"

	"github.com/boltdb/bolt"
	"go.skia.org/infra/go/fileutil"
	"go.skia.org/infra/go/util"
	"go.skia.org/infra/golden/go/diff"
	"go.skia.org/infra/golden/go/types"
)

const (
	// IMG_EXTENSION is the default extension of images.
	IMG_EXTENSION = "png"
)

// SaveFile writes the given file to disk.
func SaveFile(targetPath string, r io.Reader) error {
	f, err := os.Create(targetPath)
	if err != nil {
		return err
	}
	defer util.Close(f)

	_, err = io.Copy(f, r)
	return err
}

// LoadImg loads an image from disk.
func LoadImg(sourcePath string) (*image.NRGBA, error) {
	f, err := os.Open(sourcePath)
	if err != nil {
		return nil, err
	}
	defer util.Close(f)
	return DecodeImg(f)
}

// EncodeImg encodes the given image as a PNG and writes the result to the
// given writer.
func EncodeImg(w io.Writer, img *image.NRGBA) error {
	encoder := png.Encoder{CompressionLevel: png.BestSpeed}
	if err := encoder.Encode(w, img); err != nil {
		return err
	}
	return nil
}

// DecodeImg decodes an image from the given reader and returns it as a NRGBA image.
func DecodeImg(reader io.Reader) (*image.NRGBA, error) {
	im, err := png.Decode(reader)
	if err != nil {
		return nil, err
	}
	return diff.GetNRGBA(im), nil
}

// GetDigestImageFileName returns the image name based on the digest.
func GetDigestImageFileName(digest types.Digest) string {
	return fmt.Sprintf("%s.%s", digest, IMG_EXTENSION)
}

// OpenBoltDB opens a boltDB in the given given directory with the given name.
func OpenBoltDB(baseDir, name string) (*bolt.DB, error) {
	baseDir, err := fileutil.EnsureDirExists(baseDir)
	if err != nil {
		return nil, err
	}

	return bolt.Open(path.Join(baseDir, name), 0600, nil)
}

// SaveFilePath saves the given buffer in path.
func SaveFilePath(path string, r io.Reader) error {
	err := fileutil.EnsureDirPathExists(path)
	if err != nil {
		return fmt.Errorf("Unable to create path for %s: %s", path, err)
	}

	if err := SaveFile(path, r); err != nil {
		return fmt.Errorf("Unable to save file %s. Got error: %s", path, err)
	}
	return nil
}

func AsStrings(xd types.DigestSlice) []string {
	s := make([]string, 0, len(xd))
	for _, d := range xd {
		s = append(s, string(d))
	}
	return s
}