upstream/emscripten/system/lib/libcxx/src/pstl/libdispatch.cpp

//===----------------------------------------------------------------------===//
//
// 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 <__algorithm/min.h>
#include <__config>
#include <__pstl/backends/libdispatch.h>
#include <dispatch/dispatch.h>

_LIBCPP_BEGIN_NAMESPACE_STD
namespace __pstl::__libdispatch {

void __dispatch_apply(size_t chunk_count, void* context, void (*func)(void* context, size_t chunk)) noexcept {
  ::dispatch_apply_f(chunk_count, DISPATCH_APPLY_AUTO, context, func);
}

__chunk_partitions __partition_chunks(ptrdiff_t element_count) noexcept {
  __chunk_partitions partitions;
  partitions.__chunk_count_      = std::max<ptrdiff_t>(1, element_count / 256);
  partitions.__chunk_size_       = element_count / partitions.__chunk_count_;
  partitions.__first_chunk_size_ = element_count - (partitions.__chunk_count_ - 1) * partitions.__chunk_size_;
  if (partitions.__chunk_count_ == 0 && element_count > 0)
    partitions.__chunk_count_ = 1;
  return partitions;
}

} // namespace __pstl::__libdispatch
_LIBCPP_END_NAMESPACE_STD