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package sixel
import (
"fmt"
"io"
"strings"
)
// ErrInvalidRaster is returned when Raster Attributes are invalid.
var ErrInvalidRaster = fmt.Errorf("invalid raster attributes")
// WriteRaster writes Raster attributes to a writer. If ph and pv are 0, they
// are omitted.
func WriteRaster(w io.Writer, pan, pad, ph, pv int) (n int, err error) {
if pad == 0 {
return WriteRaster(w, 1, 1, ph, pv)
}
if ph <= 0 && pv <= 0 {
return fmt.Fprintf(w, "%c%d;%d", RasterAttribute, pan, pad) //nolint:wrapcheck
}
return fmt.Fprintf(w, "%c%d;%d;%d;%d", RasterAttribute, pan, pad, ph, pv) //nolint:wrapcheck
}
// Raster represents Sixel raster attributes.
type Raster struct {
Pan, Pad, Ph, Pv int
}
// WriteTo writes Raster attributes to a writer.
func (r Raster) WriteTo(w io.Writer) (int64, error) {
n, err := WriteRaster(w, r.Pan, r.Pad, r.Ph, r.Pv)
return int64(n), err
}
// String returns the Raster as a string.
func (r Raster) String() string {
var b strings.Builder
r.WriteTo(&b) //nolint:errcheck,gosec
return b.String()
}
// DecodeRaster decodes a Raster from a byte slice. It returns the Raster and
// the number of bytes read.
func DecodeRaster(data []byte) (r Raster, n int) {
if len(data) == 0 || data[0] != RasterAttribute {
return r, n
}
ptr := &r.Pan
for n = 1; n < len(data); n++ {
if data[n] == ';' { //nolint:nestif
if ptr == &r.Pan {
ptr = &r.Pad
} else if ptr == &r.Pad {
ptr = &r.Ph
} else if ptr == &r.Ph {
ptr = &r.Pv
} else {
n++
break
}
} else if data[n] >= '0' && data[n] <= '9' {
*ptr = (*ptr)*10 + int(data[n]-'0')
} else {
break
}
}
return r, n
}
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