mfbt/Try.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_Try_h
   8 #define mozilla_Try_h
   9
  10 #include "mozilla/Result.h"
  11
  12 /**
  13  * MOZ_TRY(expr) is the C++ equivalent of Rust's `try!(expr);`. First, it
  14  * evaluates expr, which must produce a Result value. On success, it
  15  * discards the result altogether. On error, it immediately returns an error
  16  * Result from the enclosing function.
  17  */
  18 #define MOZ_TRY(expr)                                   \
  19   do {                                                  \
  20     auto mozTryTempResult_ = ::mozilla::ToResult(expr); \
  21     if (MOZ_UNLIKELY(mozTryTempResult_.isErr())) {      \
  22       return mozTryTempResult_.propagateErr();          \
  23     }                                                   \
  24   } while (0)
  25
  26 /**
  27  * MOZ_TRY_VAR(target, expr) is the C++ equivalent of Rust's `target =
  28  * try!(expr);`. First, it evaluates expr, which must produce a Result value. On
  29  * success, the result's success value is assigned to target. On error,
  30  * immediately returns the error result. |target| must be an lvalue.
  31  */
  32 #define MOZ_TRY_VAR(target, expr)                     \
  33   do {                                                \
  34     auto mozTryVarTempResult_ = (expr);               \
  35     if (MOZ_UNLIKELY(mozTryVarTempResult_.isErr())) { \
  36       return mozTryVarTempResult_.propagateErr();     \
  37     }                                                 \
  38     (target) = mozTryVarTempResult_.unwrap();         \
  39   } while (0)
  40
  41 #endif  // mozilla_Try_h