dhcpv4: simplify option parsing.

option's codes and lengths were being parsed twice: once in ParseOption
and once in each option type's Parse implementation. Consolidate such
that it only happens once.

Additionally, only pass data to options that they should parse -- we
know the length before the Parse function is called, so the option only
gets to see the data it needs to see.

Also, use uio.Lexer to simplify parsing code in general. Easier to read
and reason about.

1 files changed, 3 insertions, 16 deletions

diff --git a/dhcpv4/bsdp/bsdp_option_machine_name.go b/dhcpv4/bsdp/bsdp_option_machine_name.go
index dc05378..cffba2e 100644
--- a/dhcpv4/bsdp/bsdp_option_machine_name.go
+++ b/dhcpv4/bsdp/bsdp_option_machine_name.go
@@ -1,15 +1,13 @@
 package bsdp
 
 import (
-	"fmt"
-
 	"github.com/insomniacslk/dhcp/dhcpv4"
 )
 
+// OptMachineName represents a BSDP message type.
+//
 // Implements the BSDP option machine name, which gives the Netboot server's
 // machine name.
-
-// OptMachineName represents a BSDP message type.
 type OptMachineName struct {
 	Name string
 }
@@ -17,18 +15,7 @@ type OptMachineName struct {
 // ParseOptMachineName constructs an OptMachineName struct from a sequence of
 // bytes and returns it, or an error.
 func ParseOptMachineName(data []byte) (*OptMachineName, error) {
-	if len(data) < 2 {
-		return nil, dhcpv4.ErrShortByteStream
-	}
-	code := dhcpv4.OptionCode(data[0])
-	if code != OptionMachineName {
-		return nil, fmt.Errorf("expected option %v, got %v instead", OptionMachineName, code)
-	}
-	length := int(data[1])
-	if len(data) < length+2 {
-		return nil, fmt.Errorf("expected length %d, got %d instead", length, len(data))
-	}
-	return &OptMachineName{Name: string(data[2 : length+2])}, nil
+	return &OptMachineName{Name: string(data)}, nil
 }
 
 // Code returns the option code.