libc/src/pthread/pthread_rwlock_init.cpp

   1 //===-- Linux implementation of the pthread_rwlock_init 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 #include "src/pthread/pthread_rwlock_init.h"
  10
  11 #include "src/__support/CPP/new.h"
  12 #include "src/__support/common.h"
  13 #include "src/__support/libc_assert.h"
  14 #include "src/__support/macros/config.h"
  15 #include "src/__support/threads/linux/rwlock.h"
  16
  17 #include <pthread.h>
  18
  19 namespace LIBC_NAMESPACE_DECL {
  20
  21 static_assert(
  22     sizeof(RwLock) == sizeof(pthread_rwlock_t) &&
  23         alignof(RwLock) == alignof(pthread_rwlock_t),
  24     "The public pthread_rwlock_t type must be of the same size and alignment "
  25     "as the internal rwlock type.");
  26
  27 LLVM_LIBC_FUNCTION(int, pthread_rwlock_init,
  28                    (pthread_rwlock_t * rwlock,
  29                     const pthread_rwlockattr_t *__restrict attr)) {
  30   pthread_rwlockattr_t rwlockattr{
  31       /*pshared=*/PTHREAD_PROCESS_PRIVATE,
  32       /*pref*/ PTHREAD_RWLOCK_PREFER_READER_NP,
  33   };
  34   // POSIX does not specify this check, so we add an assertion to catch it.
  35   LIBC_ASSERT(rwlock && "rwlock is null");
  36   if (attr)
  37     rwlockattr = *attr;
  38
  39   // PTHREAD_RWLOCK_PREFER_WRITER_NP is not supported.
  40   rwlock::Role preference;
  41   switch (rwlockattr.pref) {
  42   case PTHREAD_RWLOCK_PREFER_READER_NP:
  43     preference = rwlock::Role::Reader;
  44     break;
  45   case PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP:
  46     preference = rwlock::Role::Writer;
  47     break;
  48   default:
  49     return EINVAL;
  50   }
  51   bool is_pshared;
  52   switch (rwlockattr.pshared) {
  53   case PTHREAD_PROCESS_PRIVATE:
  54     is_pshared = false;
  55     break;
  56   case PTHREAD_PROCESS_SHARED:
  57     is_pshared = true;
  58     break;
  59   default:
  60     return EINVAL;
  61   }
  62
  63   new (rwlock) RwLock(preference, is_pshared);
  64   return 0;
  65 }
  66
  67 } // namespace LIBC_NAMESPACE_DECL