From a4c8ac016deecb625370dc0bf042ba690b15a15d Mon Sep 17 00:00:00 2001
From: Xavek <theofficalgautam200@gmail.com>
Date: Fri, 26 Jul 2024 22:24:10 +0545
Subject: [PATCH] implement opcode fromaltstack

---
 src/compiler.cairo        | 1 +
 src/opcodes/opcodes.cairo | 9 ++++++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/compiler.cairo b/src/compiler.cairo
index 6444ac72..8453ad29 100644
--- a/src/compiler.cairo
+++ b/src/compiler.cairo
@@ -40,6 +40,7 @@ pub impl CompilerTraitImpl of CompilerTrait {
         opcodes.insert('OP_1ADD', Opcode::OP_1ADD);
         opcodes.insert('OP_ADD', Opcode::OP_ADD);
         opcodes.insert('OP_MAX', Opcode::OP_MAX);
+        opcodes.insert('OP_FROMALTSTACK', Opcode::OP_FROMALTSTACK);
         Compiler { opcodes }
     }
 
diff --git a/src/opcodes/opcodes.cairo b/src/opcodes/opcodes.cairo
index 6354b3e1..df54fca9 100644
--- a/src/opcodes/opcodes.cairo
+++ b/src/opcodes/opcodes.cairo
@@ -21,6 +21,7 @@ pub mod Opcode {
     pub const OP_1ADD: u8 = 139;
     pub const OP_ADD: u8 = 147;
     pub const OP_MAX: u8 = 164;
+    pub const OP_FROMALTSTACK: u8 = 108;
 
     use shinigami::engine::Engine;
     use shinigami::stack::ScriptStackTrait;
@@ -134,7 +135,7 @@ pub mod Opcode {
             105 => not_implemented(ref engine),
             106 => not_implemented(ref engine),
             107 => not_implemented(ref engine),
-            108 => not_implemented(ref engine),
+            108 => opcode_fromaltstack(ref engine),
             109 => not_implemented(ref engine),
             110 => not_implemented(ref engine),
             111 => not_implemented(ref engine),
@@ -234,4 +235,10 @@ pub mod Opcode {
             b
         });
     }
+
+    fn opcode_fromaltstack(ref engine: Engine) {
+        //TODO: Error handling
+        let a = engine.astack.pop_byte_array();
+        engine.dstack.push_byte_array(a);
+    }
 }