nimbus-eth1/premix/js_tracer.nim

const postStateTracer* = """{
	postState: {},

	// lookupAccount injects the specified account into the postState object.
	lookupAccount: function(addr, db){
		var acc = toHex(addr);
		if (this.postState[acc] === undefined) {
			this.postState[acc] = {
				code:    toHex(db.getCode(addr)),
				storage: {}
			};
		}
	},

	// lookupStorage injects the specified storage entry of the given account into
	// the postState object.
	lookupStorage: function(addr, key, db){
		var acc = toHex(addr);
		var idx = toHex(key);
    this.lookupAccount(addr, db);
		if (this.postState[acc].storage[idx] === undefined) {
      this.postState[acc].storage[idx] = "";
		}
	},

	// result is invoked when all the opcodes have been iterated over and returns
	// the final result of the tracing.
	result: function(ctx, db) {
		this.lookupAccount(ctx.from, db);
    this.lookupAccount(ctx.to, db);

		// Return the assembled allocations (postState)
		return this.postState;
	},

	// step is invoked for every opcode that the VM executes.
	step: function(log, db) {
		// Add the current account if we just started tracing
		if (this.postState === null){
			this.postState = {};
			// Balance will potentially be wrong here, since this will include the value
			// sent along with the message. We fix that in 'result()'.
			this.lookupAccount(log.contract.getAddress(), db);
		}
		// Whenever new state is accessed, add it to the postState
		switch (log.op.toString()) {
			case "EXTCODECOPY": case "EXTCODESIZE": case "BALANCE":
				this.lookupAccount(toAddress(log.stack.peek(0).toString(16)), db);
				break;
			case "CREATE":
				var from = log.contract.getAddress();
				this.lookupAccount(toContract(from, db.getNonce(from)), db);
				break;
			case "CALL": case "CALLCODE": case "DELEGATECALL": case "STATICCALL":
				this.lookupAccount(toAddress(log.stack.peek(1).toString(16)), db);
				break;
			case 'SSTORE':case 'SLOAD':
				this.lookupStorage(log.contract.getAddress(), toWord(log.stack.peek(0).toString(16)), db);
				break;
		}
	},

	// fault is invoked when the actual execution of an opcode fails.
	fault: function(log, db) {}
}
"""