Accept interfaces where appropriate. (#103)

* Accept interfaces where appropriate.

`Fpdf.RawWriteBuf` only needs an `io.Reader`, it doesn't have to be a `bytes.Buffer`.

The only reason I can see not to do this is to avoid the interface "boxing" if the caller is actually using a `bytes.Buffer`;
however, since eventually this gets into `binary.Read` which takes an `io.Reader` the boxing will happen anyway (and possibly repeatedly if `readByte` gets called a number of times; I didn't bother to check).

* Also use interface for segmentRead

* Use read-only bytes.Reader instead of bytes.Buffer where appropriate.

1 files changed, 5 insertions, 5 deletions

diff --git a/font.go b/font.go
index 35f59f1..4d151c2 100644
--- a/font.go
+++ b/font.go
@@ -144,22 +144,22 @@ type segmentType struct {
 	data   []byte
 }
 
-func segmentRead(f *os.File) (s segmentType, err error) {
-	if err = binary.Read(f, binary.LittleEndian, &s.marker); err != nil {
+func segmentRead(r io.Reader) (s segmentType, err error) {
+	if err = binary.Read(r, binary.LittleEndian, &s.marker); err != nil {
 		return
 	}
 	if s.marker != 128 {
 		err = fmt.Errorf("font file is not a valid binary Type1")
 		return
 	}
-	if err = binary.Read(f, binary.LittleEndian, &s.tp); err != nil {
+	if err = binary.Read(r, binary.LittleEndian, &s.tp); err != nil {
 		return
 	}
-	if err = binary.Read(f, binary.LittleEndian, &s.size); err != nil {
+	if err = binary.Read(r, binary.LittleEndian, &s.size); err != nil {
 		return
 	}
 	s.data = make([]byte, s.size)
-	_, err = f.Read(s.data)
+	_, err = r.Read(s.data)
 	return
 }