add utils for safe computer (#384)

Author: hundredark

src/client/utils/computer.ts

@@ -0,0 +1,41 @@
+import { parse } from 'uuid';
+import BigNumber from 'bignumber.js';
+import { base64RawURLEncode } from './base64';
+
+export const MAX_BASE64_SIZE = 1644;
+
+export const OperationTypeAddUser = 1;
+export const OperationTypeSystemCall = 2;
+
+export const userIdToBytes = (uid: string) => {
+  const x = BigNumber(uid);
+  const bytes = [];
+  let i = x;
+  do {
+    bytes.unshift(i.mod(256).toNumber());
+    i = i.dividedToIntegerBy(256);
+  } while (!i.isZero());
+  do {
+    bytes.unshift(0);
+  } while (bytes.length < 8);
+  return Buffer.from(bytes);
+};
+
+// bytes of Solana transaction: Buffer.from(tx.serialize())
+export const checkSystemCallSize = (txBuf: Buffer) => txBuf.toString('base64').length < MAX_BASE64_SIZE;
+
+export const buildSystemCallExtra = (uid: string, cid: string, skipPostProcess: boolean, fid?: string) => {
+  const flag = skipPostProcess ? 1 : 0;
+  const ib = userIdToBytes(uid);
+  const cb = parse(cid);
+  const data = [ib, cb, Buffer.from([flag])];
+  if (fid) data.push(parse(fid));
+  return Buffer.concat(data);
+};
+
+export const buildComputerExtra = (operation: number, extra: Buffer) => Buffer.concat([Buffer.from([operation]), extra]);
+
+export const encodeMtgExtra = (app_id: string, extra: Buffer) => {
+  const data = Buffer.concat([parse(app_id), extra]);
+  return base64RawURLEncode(data);
+};