Implement build() for a few attributes

Implement build() for AS4PathAttribute, ASPathAttribute
and OriginAttribute.

3 files changed, 82 insertions, 7 deletions

diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
index 796fbea..cd52173 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/AS4PathAttribute.java
@@ -1,5 +1,6 @@
 package com.lumaserv.bgp.protocol.attribute;
 
+import lombok.NoArgsConstructor;
 import lombok.Getter;
 import lombok.Setter;
 
@@ -7,6 +8,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 @Getter
+@NoArgsConstructor
 @Setter
 public class AS4PathAttribute implements PathAttribute {
 
@@ -34,7 +36,27 @@ public class AS4PathAttribute implements PathAttribute {
     }
 
     public byte[] build() {
-        return new byte[0];
+        byte length = 0;
+        for (Segment seg: segments) {
+            length += 2 + seg.asns.size() * 4;
+        }
+        int offset = 0;
+        byte[] data = new byte[length];
+
+        for (Segment seg: segments) {
+            data[offset] = seg.type;
+            data[offset + 1] = (byte)seg.asns.size();
+            for (int i=0; i<seg.asns.size(); i++) {
+                int asn = seg.asns.get(i);
+                data[offset + 2 + (i * 4)] = (byte)((asn >> 24) & 0xFF);
+                data[offset + 3 + (i * 4)] = (byte)((asn >> 16) & 0xFF);
+                data[offset + 4 + (i * 4)] = (byte)((asn >> 8) & 0xFF);
+                data[offset + 5 + (i * 4)] = (byte)(asn & 0xFF);
+            }
+            offset += 2 + seg.asns.size() * 4;
+        }
+
+        return data;
     }
 
     @Getter
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
index ed95b2a..44deb8f 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/ASPathAttribute.java
@@ -7,21 +7,26 @@ import lombok.Getter;
 import lombok.Setter;
 
 import java.util.ArrayList;
+import java.util.EnumSet;
 import java.util.List;
 
 @Getter
-@NoArgsConstructor
 @Setter
 public class ASPathAttribute implements PathAttribute {
 
+    final private boolean isAS4;
     List<Segment> segments = new ArrayList<>();
 
+    public ASPathAttribute(BGPSession session) {
+        isAS4 = session.isAS4Capability();
+    }
+
     public ASPathAttribute(BGPSession session, byte typeCode, byte[] data) {
-        final boolean isAS4 = session.isAS4Capability();
+        this(session);
         final int asnLen = isAS4 ? 4 : 2;
         int offset = 0;
         while (offset < data.length) {
-            Segment segment = new Segment().setType(data[offset]);
+            Segment segment = new Segment().setType(Segment.Type.fromByte(data[offset]));
             byte length = data[offset + 1];
             for(int i=0; i<length; i++) {
                 int asn;
@@ -46,13 +51,59 @@ public class ASPathAttribute implements PathAttribute {
     }
 
     public byte[] build() {
-        return new byte[0];
+        final int asnLen = isAS4 ? 4 : 2;
+        byte length = 0;
+        for (Segment seg: segments) {
+            length += 2 + seg.asns.size() * asnLen;
+        }
+        int offset = 0;
+        byte[] data = new byte[length];
+
+        for (Segment seg: segments) {
+            data[offset] = seg.type.code;
+            data[offset + 1] = (byte)seg.asns.size();
+            for (int i=0; i<seg.asns.size(); i++) {
+                int asn = seg.asns.get(i);
+                if (isAS4) {
+                    data[offset + 2 + (i * 4)] = (byte)((asn >> 24) & 0xFF);
+                    data[offset + 3 + (i * 4)] = (byte)((asn >> 16) & 0xFF);
+                    data[offset + 4 + (i * 4)] = (byte)((asn >> 8) & 0xFF);
+                    data[offset + 5 + (i * 4)] = (byte)(asn & 0xFF);
+                } else {
+                    data[offset + 2 + (i * 2)] = (byte)((asn >> 8) & 0xFF);
+                    data[offset + 3 + (i * 2)] = (byte)(asn & 0xFF);
+                }
+            }
+            offset += 2 + seg.asns.size() * asnLen;
+        }
+
+        return data;
     }
 
     @Getter
     @Setter
     public static class Segment {
-        byte type;
+        @Getter
+        public enum Type {
+            SET(1),
+            SEQUENCE(2);
+
+            byte code;
+
+            Type(int code) {
+                this.code = (byte)code;
+            }
+
+            public static Type fromByte(byte code) {
+                return EnumSet.allOf(Type.class)
+                    .stream()
+                .filter(e -> e.getCode() == code)
+                    .findAny()
+                    .orElseThrow(() -> new IllegalArgumentException("unknown path segment type: " + code));
+            }
+        }
+
+        Type type;
         List<Integer> asns = new ArrayList<>();
 
         public String toString() {
diff --git a/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java b/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
index dcb17fb..575b848 100644
--- a/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
+++ b/src/main/java/com/lumaserv/bgp/protocol/attribute/OriginAttribute.java
@@ -43,7 +43,9 @@ public class OriginAttribute implements PathAttribute {
     }
 
     public byte[] build() {
-        return new byte[0];
+        byte[] data = new byte[1];
+        data[0] = origin.code;
+        return data;
     }
 
     public String toString() {