1 files changed, 52 insertions, 0 deletions
diff --git a/src/util/asyncMemo.ts b/src/util/asyncMemo.ts
new file mode 100644
index 000000000..8b7b1c9bb
--- /dev/null
+++ b/src/util/asyncMemo.ts
@@ -0,0 +1,52 @@
+/*
+ This file is part of GNU Taler
+ (C) 2019 GNUnet e.V.
+
+ GNU Taler is free software; you can redistribute it and/or modify it under the
+ terms of the GNU General Public License as published by the Free Software
+ Foundation; either version 3, or (at your option) any later version.
+
+ GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+ */
+
+export interface MemoEntry<T> {
+  p: Promise<T>;
+  t: number;
+  n: number;
+}
+
+export class AsyncOpMemo<T> {
+  n = 0;
+  memo: { [k: string]: MemoEntry<T> } = {};
+  put(key: string, p: Promise<T>): Promise<T> {
+    const n = this.n++;
+    this.memo[key] = {
+      p,
+      n,
+      t: new Date().getTime(),
+    };
+    p.finally(() => {
+      const r = this.memo[key];
+      if (r && r.n === n) {
+        delete this.memo[key];
+      }
+    });
+    return p;
+  }
+  find(key: string): Promise<T> | undefined {
+    const res = this.memo[key];
+    const tNow = new Date().getTime();
+    if (res && res.t < tNow - 10 * 1000) {
+      delete this.memo[key];
+      return;
+    } else if (res) {
+      return res.p;
+    }
+    return;
+  }
+}
+\ No newline at end of file