do arnie

vendor/code.superseriousbusiness.org/go-jpeg-image-structure/v2/media_parser.go

@@ -0,0 +1,139 @@
+package jpegstructure
+
+import (
+	"bufio"
+	"bytes"
+	"image"
+	"io"
+	"os"
+
+	"image/jpeg"
+
+	"github.com/dsoprea/go-logging"
+	"github.com/dsoprea/go-utility/v2/image"
+)
+
+// JpegMediaParser is a `riimage.MediaParser` that knows how to parse JPEG
+// images.
+type JpegMediaParser struct {
+}
+
+// NewJpegMediaParser returns a new JpegMediaParser.
+func NewJpegMediaParser() *JpegMediaParser {
+
+	// TODO(dustin): Add test
+
+	return new(JpegMediaParser)
+}
+
+// Parse parses a JPEG uses an `io.ReadSeeker`. Even if it fails, it will return
+// the list of segments encountered prior to the failure.
+func (jmp *JpegMediaParser) Parse(rs io.ReadSeeker, size int) (ec riimage.MediaContext, err error) {
+	defer func() {
+		if state := recover(); state != nil {
+			err = log.Wrap(state.(error))
+		}
+	}()
+
+	s := bufio.NewScanner(rs)
+
+	// Since each segment can be any size, our buffer must allowed to grow as
+	// large as the file.
+	buffer := []byte{}
+	s.Buffer(buffer, size)
+
+	js := NewJpegSplitter(nil)
+	s.Split(js.Split)
+
+	for s.Scan() != false {
+	}
+
+	// Always return the segments that were parsed, at least until there was an
+	// error.
+	ec = js.Segments()
+
+	log.PanicIf(s.Err())
+
+	return ec, nil
+}
+
+// ParseFile parses a JPEG file. Even if it fails, it will return the list of
+// segments encountered prior to the failure.
+func (jmp *JpegMediaParser) ParseFile(filepath string) (ec riimage.MediaContext, err error) {
+	defer func() {
+		if state := recover(); state != nil {
+			err = log.Wrap(state.(error))
+		}
+	}()
+
+	// TODO(dustin): Add test
+
+	f, err := os.Open(filepath)
+	log.PanicIf(err)
+
+	defer f.Close()
+
+	stat, err := f.Stat()
+	log.PanicIf(err)
+
+	size := stat.Size()
+
+	sl, err := jmp.Parse(f, int(size))
+
+	// Always return the segments that were parsed, at least until there was an
+	// error.
+	ec = sl
+
+	log.PanicIf(err)
+
+	return ec, nil
+}
+
+// ParseBytes parses a JPEG byte-slice. Even if it fails, it will return the
+// list of segments encountered prior to the failure.
+func (jmp *JpegMediaParser) ParseBytes(data []byte) (ec riimage.MediaContext, err error) {
+	defer func() {
+		if state := recover(); state != nil {
+			err = log.Wrap(state.(error))
+		}
+	}()
+
+	br := bytes.NewReader(data)
+
+	sl, err := jmp.Parse(br, len(data))
+
+	// Always return the segments that were parsed, at least until there was an
+	// error.
+	ec = sl
+
+	log.PanicIf(err)
+
+	return ec, nil
+}
+
+// LooksLikeFormat indicates whether the data looks like a JPEG image.
+func (jmp *JpegMediaParser) LooksLikeFormat(data []byte) bool {
+	if len(data) < 4 {
+		return false
+	}
+
+	l := len(data)
+	if data[0] != 0xff || data[1] != MARKER_SOI || data[l-2] != 0xff || data[l-1] != MARKER_EOI {
+		return false
+	}
+
+	return true
+}
+
+// GetImage returns an image.Image-compatible struct.
+func (jmp *JpegMediaParser) GetImage(r io.Reader) (img image.Image, err error) {
+	img, err = jpeg.Decode(r)
+	log.PanicIf(err)
+
+	return img, nil
+}
+
+var (
+	// Enforce interface conformance.
+	_ riimage.MediaParser = new(JpegMediaParser)
+)