libc/src/__support/threads/callonce.h

   1 //===-- Types related to the callonce function ----------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_THREADS_CALLONCE_H
  10 #define LLVM_LIBC_SRC___SUPPORT_THREADS_CALLONCE_H
  11
  12 #include "src/__support/macros/config.h"
  13 #include "src/__support/macros/optimization.h" // LIBC_LIKELY
  14
  15 // Plaform specific routines, provides:
  16 // - OnceFlag definition
  17 // - callonce_impl::callonce_fastpath for fast path check
  18 // - callonce_impl::callonce_slowpath for slow path execution
  19 #ifdef __linux__
  20 #include "src/__support/threads/linux/callonce.h"
  21 #else
  22 #error "callonce is not supported on this platform"
  23 #endif
  24
  25 namespace LIBC_NAMESPACE_DECL {
  26
  27 // Common definitions
  28 using CallOnceCallback = void(void);
  29 namespace callonce_impl {
  30 int callonce_slowpath(CallOnceFlag *flag, CallOnceCallback *callback);
  31 } // namespace callonce_impl
  32
  33 LIBC_INLINE int callonce(CallOnceFlag *flag, CallOnceCallback *callback) {
  34   if (LIBC_LIKELY(callonce_impl::callonce_fastpath(flag)))
  35     return 0;
  36
  37   return callonce_impl::callonce_slowpath(flag, callback);
  38 }
  39 } // namespace LIBC_NAMESPACE_DECL
  40
  41 #endif // LLVM_LIBC_SRC___SUPPORT_THREADS_CALLONCE_H