2-add-keyword-support (#6)

More development.

More types.
Fixed attribute groups in requests.
Started on client.
Saving data to file.

More types. Printing from chromeos works a little bit.

More types.

Spelling corrections.

WIP: Fix keyword handling

Move request to a separate file and add test.

Co-authored-by: Henrik Sölver <henrik.solver@gmail.com>
Reviewed-on: #6
Co-Authored-By: henrik <henrik.solver@gmail.com>
Co-Committed-By: henrik <henrik.solver@gmail.com>

packages/ipp/resolution.go

@@ -0,0 +1,63 @@
+package ipp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+type resolution struct {
+	name                string
+	crossFeedResolution int32
+	feedResolution      int32
+	units               int8
+}
+
+func NewResolution(name string, xfres int32, fres int32) *resolution {
+	r := new(resolution)
+	r.name = name
+	r.crossFeedResolution = xfres
+	r.feedResolution = fres
+	r.units = 3 // 3 seems to mean dpi (rfc3805)
+	return r
+}
+
+func (r *resolution) unmarshal(byteStream io.Reader) {
+	var length uint16
+	binary.Read(byteStream, binary.BigEndian, &length)
+	attributeName := make([]byte, length)
+	if length > 0 {
+		binary.Read(byteStream, binary.BigEndian, attributeName)
+	}
+	r.name = string(attributeName)
+	binary.Read(byteStream, binary.BigEndian, &length)
+	if length != 9 {
+		panic("Wrong length in resolution")
+	}
+	binary.Read(byteStream, binary.BigEndian, &r.crossFeedResolution)
+	binary.Read(byteStream, binary.BigEndian, &r.feedResolution)
+	binary.Read(byteStream, binary.BigEndian, &r.units)
+}
+
+func (r resolution) String() string {
+	return fmt.Sprintf("%v:%v,%v,%v", r.name, r.crossFeedResolution, r.feedResolution, r.units)
+}
+
+func (r *resolution) marshal() []byte {
+
+	b := make([]byte, 0, 14+len(r.name))
+	buf := bytes.NewBuffer(b)
+	buf.WriteByte(byte(resolutionValueTag))
+	binary.Write(buf, binary.BigEndian, uint16(len(r.name)))
+	buf.WriteString(r.name)
+	binary.Write(buf, binary.BigEndian, uint16(9))
+	binary.Write(buf, binary.BigEndian, int32(r.crossFeedResolution))
+	binary.Write(buf, binary.BigEndian, int32(r.feedResolution))
+	buf.WriteByte(byte(r.units))
+	return buf.Bytes()
+}
+
+func (r *resolution) valueTag() tag {
+	return resolutionValueTag
+}