dhcpv4: nicer API for option parsing.

From:
  r := d.GetOneOption(OptionRouter).(*OptRouter).Routers
  d.UpdateOption(&OptRouter{Routers: []net.IP{net.IP{192, 168, 0, 1}}})

To:
  r := GetRouter(d.Options)
  d.UpdateOption(OptRouter(net.IP{192, 168, 0, 1}, ...))

1 files changed, 44 insertions, 0 deletions

diff --git a/iana/archtype.go b/iana/archtype.go
index 510c6fc..255687c 100644
--- a/iana/archtype.go
+++ b/iana/archtype.go
@@ -1,5 +1,12 @@
 package iana
 
+import (
+	"fmt"
+	"strings"
+
+	"github.com/u-root/u-root/pkg/uio"
+)
+
 // Arch encodes an architecture type per RFC 4578, Section 2.1.
 type Arch uint16
 
@@ -38,3 +45,40 @@ func (a Arch) String() string {
 	}
 	return "unknown"
 }
+
+// Archs represents multiple Arch values.
+type Archs []Arch
+
+// ToBytes returns the serialized option defined by RFC 4578 (DHCPv4) and RFC
+// 5970 (DHCPv6) as the Client System Architecture Option.
+func (a Archs) ToBytes() []byte {
+	buf := uio.NewBigEndianBuffer(nil)
+	for _, at := range a {
+		buf.Write16(uint16(at))
+	}
+	return buf.Data()
+}
+
+// String returns the list of archs in a human-readable manner.
+func (a Archs) String() string {
+	s := make([]string, 0, len(a))
+	for _, arch := range a {
+		s = append(s, arch.String())
+	}
+	return strings.Join(s, ", ")
+}
+
+// FromBytes parses a DHCP list of architecture types as defined by RFC 4578
+// and RFC 5970.
+func (a *Archs) FromBytes(data []byte) error {
+	buf := uio.NewBigEndianBuffer(data)
+	if buf.Len() == 0 {
+		return fmt.Errorf("must have at least one archtype if option is present")
+	}
+
+	*a = make([]Arch, 0, buf.Len()/2)
+	for buf.Has(2) {
+		*a = append(*a, Arch(buf.Read16()))
+	}
+	return buf.FinError()
+}