new way to define Else statements

ebpfcat/ebpf.py

@@ -273,6 +273,20 @@ def comparison(uposop, unegop, sposop, snegop):
     return ret
 
 
+class Elser:
+    def __init__(self, comp):
+        self.comp = comp
+
+    def __enter__(self):
+        return self.comp.Else()
+
+    def __exit__(self, exc_type, exc, tb):
+        self.comp.__exit__(exc_type, exc, tb)
+
+    def Else(self):
+        return self.comp.Else()
+
+
 class Comparison(ABC):
     """Base class for all logical operations"""
 
@@ -283,7 +297,7 @@ class Comparison(ABC):
     def __enter__(self):
         if self.else_origin is None:
             self.compare(True)
-        return self
+        return Elser(self)
 
     def __exit__(self, exc_type, exc, tb):
         if self.else_origin is None:

ebpfcat/ebpf_test.py

@@ -391,6 +391,31 @@ class Tests(TestCase):
              Instruction(opcode=O.JMP, dst=0, src=0, off=1, imm=0),
              Instruction(opcode=O.MOV+O.LONG, dst=7, src=0, off=0, imm=8)])
 
+    def test_with_new(self):
+        e = EBPF()
+        e.owners = set(range(11))
+        with e.r2 > 3 as Else:
+            e.r2 = 5
+        with Else:
+            e.r6 = 7
+        with e.r2:
+            e.r3 = 2
+        with e.r4 > 3 as Else:
+            e.r5 = 7
+        with Else:
+            e.r7 = 8
+        self.assertEqual(e.opcodes,
+            [Instruction(opcode=0xb5, dst=2, src=0, off=2, imm=3),
+             Instruction(opcode=0xb7, dst=2, src=0, off=0, imm=5),
+             Instruction(opcode=0x5, dst=0, src=0, off=1, imm=0),
+             Instruction(opcode=O.MOV+O.LONG, dst=6, src=0, off=0, imm=7),
+             Instruction(opcode=O.JEQ, dst=2, src=0, off=1, imm=0),
+             Instruction(opcode=O.MOV+O.LONG, dst=3, src=0, off=0, imm=2),
+             Instruction(opcode=O.JLE, dst=4, src=0, off=2, imm=3),
+             Instruction(opcode=O.MOV+O.LONG, dst=5, src=0, off=0, imm=7),
+             Instruction(opcode=O.JMP, dst=0, src=0, off=1, imm=0),
+             Instruction(opcode=O.MOV+O.LONG, dst=7, src=0, off=0, imm=8)])
+
     def test_with_inversion(self):
         e = EBPF()
         with e.r1 & 1 as cond: