[libc-commits] [libc] [libc][wctype] Upstream custom slice implementation from PtrHash-cc prototype to LLVM libc (PR #174779)

[Marcell Leleszi via libc-commits]

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@@ -0,0 +1,133 @@
+//===-- Internal utils for wctype conversion code - slice -------*- 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
+//
+//===----------------------------------------------------------------------===//
+// Similar to cpp::span with additional functionality
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_WCTYPE_CONVERSION_UTILS_SLICE_H
+#define LLVM_LIBC_SRC___SUPPORT_WCTYPE_CONVERSION_UTILS_SLICE_H
+
+#include "hdr/types/size_t.h"
+#include "src/__support/CPP/algorithm.h"
+#include "src/__support/CPP/expected.h"
+#include "src/__support/CPP/span.h"
+#include "src/__support/libc_assert.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace wctype_internal {
+
+namespace conversion_utils {
+
+enum class Ordering {
+  /// An ordering where a compared value is less than another.
+  Less = -1,
+  /// An ordering where a compared value is equal to another.
+  Equal = 0,
+  /// An ordering where a compared value is greater than another.
+  Greater = 1,
+};
+
+template <typename T> struct Slice : public cpp::span<T> {
+  LIBC_INLINE constexpr Slice() : cpp::span<T>() {}
+
+  LIBC_INLINE constexpr Slice(T *ptr, size_t len) : cpp::span<T>(ptr, len) {}
+  LIBC_INLINE constexpr Slice(T const *ptr, size_t len)
+      : cpp::span<T>(ptr, len) {}
+
+  template <typename U, size_t N>
+  LIBC_INLINE constexpr Slice<U>(cpp::array<U, N> &arr) : cpp::span<T>(arr) {}
+
+  LIBC_INLINE constexpr Slice(const Slice<T> &) = default;
+  LIBC_INLINE constexpr Slice(Slice<T> &&) = default;
+
+  LIBC_INLINE constexpr Slice(const cpp::span<T> &s) : cpp::span<T>(s) {}
+  LIBC_INLINE constexpr Slice(cpp::span<T> &&s) : cpp::span<T>(s) {}
+
+  LIBC_INLINE constexpr Slice &operator=(const Slice<T> &n) = default;
+  LIBC_INLINE constexpr Slice &operator=(Slice<T> &&n) = default;
+
+  LIBC_INLINE constexpr Slice &operator=(const cpp::span<T> &n) {
+    cpp::span<T>::operator=(n);
+    return *this;
+  }
+  LIBC_INLINE constexpr Slice &operator=(cpp::span<T> &&n) {
+    cpp::span<T>::operator=(n);
+    return *this;
+  }
+
+  // Binary searches this slice with a comparator function.
+  //
+  // The comparator function should return an order code that indicates whether
+  // its argument is `Less`, `Equal` or `Greater` the desired target.
+  // If the slice is not sorted or if the comparator function does not
+  // implement an order consistent with the sort order of the underlying
+  // slice, the returned result is unspecified and meaningless.
+  //
+  // If the value is found then `cpp::expected<size_t>` is returned,
+  // containing the index of the matching element. If there are multiple
+  // matches, then any one of the matches could be returned. The index is chosen
+  // deterministically.
+  // If the value is not found then `cpp::unexpected<size_t>` is returned,
+  // containing the index where a matching element could be inserted while
+  // maintaining sorted order.
+  template <typename Fn>
+  LIBC_INLINE constexpr cpp::expected<size_t, size_t>
+  binary_search_by(Fn func) const {
+    auto size = this->size();
+    if (size == 0) {
+      return cpp::unexpected<size_t>(0);
+    }
+
+    auto base = 0;
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mleleszi wrote:

base gets deduced to an int here, it should be a size_t, you'll get some implicit conversion errors

https://github.com/llvm/llvm-project/pull/174779