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/enum.go

@@ -0,0 +1,52 @@
+package ipp
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	log "github.com/sirupsen/logrus"
+)
+
+type enum struct {
+	name  string
+	value int32
+}
+
+func NewEnum(name string, value int32) *enum {
+	e := new(enum)
+	e.name = name
+	e.value = value
+	return e
+}
+
+func (e enum) String() string {
+	return e.name + ":" + fmt.Sprint(e.value)
+}
+func (e *enum) valueTag() tag {
+	return enumValueTag
+}
+
+func (e *enum) unmarshal(byteStream io.Reader) {
+	log.Warn("Unmarshal of enum is not implemented yet")
+}
+
+func (e *enum) marshal() []byte {
+	l := 3 + len(e.name) + 6
+	b := make([]byte, 0, l)
+	buf := bytes.NewBuffer(b)
+	buf.WriteByte(byte(enumValueTag))
+	binary.Write(buf, binary.BigEndian, uint16(len(e.name)))
+	buf.WriteString(e.name)
+	binary.Write(buf, binary.BigEndian, uint16(4))
+	binary.Write(buf, binary.BigEndian, e.value)
+	return buf.Bytes()
+}
+
+func (e *enum) size() int {
+	l := 1 + 4 // The attribute tag + 2 lengths
+	l += len(e.name)
+	l += 4
+	return l
+}