diff --git a/packages/asm/src.ts/assembler.ts b/packages/asm/src.ts/assembler.ts
index 3033e900dd..ef98720803 100644
--- a/packages/asm/src.ts/assembler.ts
+++ b/packages/asm/src.ts/assembler.ts
@@ -591,11 +591,16 @@ export class ScopeNode extends LabelledNode {
 export type Operation = {
     opcode: Opcode;
     offset: number;
+    length: number;
     pushValue?: string;
 };
 
 export interface Bytecode extends Array<Operation> {
     getOperation(offset: number): Operation;
+    getByte(offset: number): number;
+    getBytes(offset: number, length: number): Uint8Array;
+    byteLength: number;
+    operationCount: number;
 }
 
 export function disassemble(bytecode: string): Bytecode {
@@ -616,7 +621,8 @@ export function disassemble(bytecode: string): Bytecode {
 
         const op: Operation = {
             opcode: opcode,
-            offset: i
+            offset: i,
+            length: 1
         };
         offsets[i] = op;
         ops.push(op);
@@ -628,6 +634,7 @@ export function disassemble(bytecode: string): Bytecode {
             const data = ethers.utils.hexlify(bytes.slice(i, i + push));
             if (ethers.utils.hexDataLength(data) === push) {
                 op.pushValue = data;
+                op.length += push;
                 i += push;
             } else {
                 oob = true;
@@ -636,9 +643,34 @@ export function disassemble(bytecode: string): Bytecode {
     }
 
     (<Bytecode>ops).getOperation = function(offset: number): Operation {
+        if (offset >= bytes.length) {
+            return {
+                opcode: Opcode.from("STOP"),
+                offset: offset,
+                length: 1
+            };
+        }
         return (offsets[offset] || null);
     };
 
+    (<Bytecode>ops).getByte = function(offset: number): number {
+        if (offset >= bytes.length) {
+            return 0x00;
+        }
+        return bytes[offset];
+    };
+
+    (<Bytecode>ops).getBytes = function(offset: number, length: number): Uint8Array {
+        const result = new Uint8Array(length);
+        result.fill(0);
+        if (offset < bytes.length) {
+            result.set(bytes.slice(offset));
+        }
+        return ethers.utils.arrayify(result);
+    };
+
+    (<Bytecode>ops).byteLength = bytes.length;
+
     return (<Bytecode>ops);
 }
 
diff --git a/packages/asm/src.ts/opcodes.ts b/packages/asm/src.ts/opcodes.ts
index 2fcefcb300..d5ec966267 100644
--- a/packages/asm/src.ts/opcodes.ts
+++ b/packages/asm/src.ts/opcodes.ts
@@ -145,6 +145,8 @@ const _Opcodes: { [ name: string ]: _Opcode } = {
     number:         { value: 0x43, delta: 0, alpha: 1, doc: "blockNumber = number" },
     difficulty:     { value: 0x44, delta: 0, alpha: 1, doc: "diff = difficulty" },
     gaslimit:       { value: 0x45, delta: 0, alpha: 1, doc: "gas = gaslimit" },
+    chainid:        { value: 0x46, delta: 0, alpha: 1, doc: "chainid = chainid" },
+    selfbalance:    { value: 0x47, delta: 0, alpha: 1, doc: "bal = selfbalance" },
 
     // Stack, Memory, Storage and Flow Operations
     pop:            { value: 0x50, delta: 1, alpha: 0, doc: "stackTopValue = pop" },