diff options
Diffstat (limited to 'packages/taler-wallet-core/src/util/asyncMemo.ts')
-rw-r--r-- | packages/taler-wallet-core/src/util/asyncMemo.ts | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/packages/taler-wallet-core/src/util/asyncMemo.ts b/packages/taler-wallet-core/src/util/asyncMemo.ts new file mode 100644 index 000000000..6e88081b6 --- /dev/null +++ b/packages/taler-wallet-core/src/util/asyncMemo.ts @@ -0,0 +1,87 @@ +/* + 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/> + */ + +interface MemoEntry<T> { + p: Promise<T>; + t: number; + n: number; +} + +export class AsyncOpMemoMap<T> { + private n = 0; + private memoMap: { [k: string]: MemoEntry<T> } = {}; + + private cleanUp(key: string, n: number): void { + const r = this.memoMap[key]; + if (r && r.n === n) { + delete this.memoMap[key]; + } + } + + memo(key: string, pg: () => Promise<T>): Promise<T> { + const res = this.memoMap[key]; + if (res) { + return res.p; + } + const n = this.n++; + // Wrap the operation in case it immediately throws + const p = Promise.resolve().then(() => pg()); + this.memoMap[key] = { + p, + n, + t: new Date().getTime(), + }; + return p.finally(() => { + this.cleanUp(key, n); + }); + } + clear(): void { + this.memoMap = {}; + } +} + +export class AsyncOpMemoSingle<T> { + private n = 0; + private memoEntry: MemoEntry<T> | undefined; + + private cleanUp(n: number): void { + if (this.memoEntry && this.memoEntry.n === n) { + this.memoEntry = undefined; + } + } + + memo(pg: () => Promise<T>): Promise<T> { + const res = this.memoEntry; + if (res) { + return res.p; + } + const n = this.n++; + // Wrap the operation in case it immediately throws + const p = Promise.resolve().then(() => pg()); + p.finally(() => { + this.cleanUp(n); + }); + this.memoEntry = { + p, + n, + t: new Date().getTime(), + }; + return p; + } + clear(): void { + this.memoEntry = undefined; + } +} |