56 lines
1.0 KiB
Go
56 lines
1.0 KiB
Go
package exif
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import "io"
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type (
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writerSkipper struct {
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io.Writer
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bytesToSkip int
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}
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)
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func NewWriterExif(w io.Writer, exif []byte) (io.Writer, error) {
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writer := &writerSkipper{
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Writer: w,
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bytesToSkip: 2,
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}
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soi := []byte{0xff, 0xd8}
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if _, err := w.Write(soi); err != nil {
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return nil, err
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}
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if exif != nil {
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app1Marker := 0xe1
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markerlen := 2 + len(exif)
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marker := []byte{0xff, uint8(app1Marker), uint8(markerlen >> 8), uint8(markerlen & 0xff)}
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if _, err := w.Write(marker); err != nil {
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return nil, err
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}
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if _, err := w.Write(exif); err != nil {
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return nil, err
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}
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}
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return writer, nil
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}
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func (w *writerSkipper) Write(data []byte) (int, error) {
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if w.bytesToSkip <= 0 {
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return w.Writer.Write(data)
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}
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if dataLen := len(data); dataLen < w.bytesToSkip {
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w.bytesToSkip -= dataLen
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return dataLen, nil
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}
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if n, err := w.Writer.Write(data[w.bytesToSkip:]); err == nil {
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n += w.bytesToSkip
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w.bytesToSkip = 0
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return n, nil
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} else {
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return n, err
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}
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}
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