libc/src/stdlib/qsort_util.h

//===-- Implementation header for qsort utilities ---------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIBC_SRC_STDLIB_QSORT_UTIL_H
#define LLVM_LIBC_SRC_STDLIB_QSORT_UTIL_H

#include "src/stdlib/heap_sort.h"
#include "src/stdlib/quick_sort.h"

#define LIBC_QSORT_QUICK_SORT 1
#define LIBC_QSORT_HEAP_SORT 2

#ifndef LIBC_QSORT_IMPL
#define LIBC_QSORT_IMPL LIBC_QSORT_QUICK_SORT
#endif // LIBC_QSORT_IMPL

#if (LIBC_QSORT_IMPL != LIBC_QSORT_QUICK_SORT &&                               \
     LIBC_QSORT_IMPL != LIBC_QSORT_HEAP_SORT)
#error "LIBC_QSORT_IMPL is not recognized."
#endif

namespace LIBC_NAMESPACE_DECL {
namespace internal {

template <bool USE_QUICKSORT, typename F>
LIBC_INLINE void unstable_sort_impl(void *array, size_t array_len,
                                    size_t elem_size, const F &is_less) {
  if (array == nullptr || array_len == 0 || elem_size == 0)
    return;

  if constexpr (USE_QUICKSORT) {
    switch (elem_size) {
    case 4: {
      auto arr_fixed_size = internal::ArrayFixedSize<4>(array, array_len);
      quick_sort(arr_fixed_size, is_less);
      return;
    }
    case 8: {
      auto arr_fixed_size = internal::ArrayFixedSize<8>(array, array_len);
      quick_sort(arr_fixed_size, is_less);
      return;
    }
    case 16: {
      auto arr_fixed_size = internal::ArrayFixedSize<16>(array, array_len);
      quick_sort(arr_fixed_size, is_less);
      return;
    }
    default:
      auto arr_generic_size =
          internal::ArrayGenericSize(array, array_len, elem_size);
      quick_sort(arr_generic_size, is_less);
      return;
    }
  } else {
    auto arr_generic_size =
        internal::ArrayGenericSize(array, array_len, elem_size);
    heap_sort(arr_generic_size, is_less);
  }
}

template <typename F>
LIBC_INLINE void unstable_sort_dispatch(void *array, size_t array_len,
                                        size_t elem_size, F is_less) {
  constexpr bool USE_QUICK_SORT = (LIBC_QSORT_IMPL == LIBC_QSORT_QUICK_SORT);
  unstable_sort_impl<USE_QUICK_SORT>(array, array_len, elem_size, is_less);
}

template <typename CmpFn>
LIBC_INLINE void unstable_sort(void *array, size_t array_len, size_t elem_size,
                               CmpFn compare) {
  const auto is_less = [compare](const void *a, const void *b) -> bool {
    return compare(a, b) < 0;
  };
  unstable_sort_dispatch(array, array_len, elem_size, is_less);
}

template <typename CmpFn>
LIBC_INLINE void unstable_sort(void *array, size_t array_len, size_t elem_size,
                               CmpFn compare, void *context) {
  const auto is_less = [compare, context](const void *a,
                                          const void *b) -> bool {
    return compare(a, b, context) < 0;
  };
  unstable_sort_dispatch(array, array_len, elem_size, is_less);
}

} // namespace internal
} // namespace LIBC_NAMESPACE_DECL

#endif // LLVM_LIBC_SRC_STDLIB_QSORT_UTIL_H