1 files changed, 67 insertions, 0 deletions
diff --git a/libc/src/pthread/pthread_rwlock_init.cpp b/libc/src/pthread/pthread_rwlock_init.cpp
new file mode 100644
index 000000000000..b1b58aac6c6f
--- /dev/null
+++ b/libc/src/pthread/pthread_rwlock_init.cpp
@@ -0,0 +1,67 @@
+//===-- Linux implementation of the pthread_rwlock_init function ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/pthread/pthread_rwlock_init.h"
+
+#include "src/__support/CPP/new.h"
+#include "src/__support/common.h"
+#include "src/__support/libc_assert.h"
+#include "src/__support/threads/linux/rwlock.h"
+
+#include <errno.h>
+#include <pthread.h>
+
+namespace LIBC_NAMESPACE {
+
+static_assert(
+    sizeof(RwLock) == sizeof(pthread_rwlock_t) &&
+        alignof(RwLock) == alignof(pthread_rwlock_t),
+    "The public pthread_rwlock_t type must be of the same size and alignment "
+    "as the internal rwlock type.");
+
+LLVM_LIBC_FUNCTION(int, pthread_rwlock_init,
+                   (pthread_rwlock_t * rwlock,
+                    const pthread_rwlockattr_t *__restrict attr)) {
+  pthread_rwlockattr_t rwlockattr{
+      /*pshared=*/PTHREAD_PROCESS_PRIVATE,
+      /*pref*/ PTHREAD_RWLOCK_PREFER_READER_NP,
+  };
+  // POSIX does not specify this check, so we add an assertion to catch it.
+  LIBC_ASSERT(rwlock && "rwlock is null");
+  if (attr)
+    rwlockattr = *attr;
+
+  // PTHREAD_RWLOCK_PREFER_WRITER_NP is not supported.
+  rwlock::Role preference;
+  switch (rwlockattr.pref) {
+  case PTHREAD_RWLOCK_PREFER_READER_NP:
+    preference = rwlock::Role::Reader;
+    break;
+  case PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP:
+    preference = rwlock::Role::Writer;
+    break;
+  default:
+    return EINVAL;
+  }
+  bool is_pshared;
+  switch (rwlockattr.pshared) {
+  case PTHREAD_PROCESS_PRIVATE:
+    is_pshared = false;
+    break;
+  case PTHREAD_PROCESS_SHARED:
+    is_pshared = true;
+    break;
+  default:
+    return EINVAL;
+  }
+
+  new (rwlock) RwLock(preference, is_pshared);
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE