[libc-commits] [libc] [libc][wctype] Upstream zip utility from PtrHash-cc prototype to LLVM libc (PR #174759)

[Marcell Leleszi via libc-commits]

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@@ -0,0 +1,78 @@
+//===-- Internal utils for wctype conversion code - zip ---------*- 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
+//
+//===----------------------------------------------------------------------===//
+// Helper iterator for zipping two containers together. `__support` code can not
+// have dependencies, so we implement a minimal zip here used internally.
+
+#ifndef LLVM_LIBC_SRC___SUPPORT_WCTYPE_CONVERSION_UTILS_ZIP_H
+#define LLVM_LIBC_SRC___SUPPORT_WCTYPE_CONVERSION_UTILS_ZIP_H
+
+#include "src/__support/CPP/tuple.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace wctype_internal {
+
+namespace conversion_utils {
+
+namespace {
+
+template <typename It1, typename It2> class ZipIterator {
+public:
+  using value_type = cpp::tuple<It1, It2>;
+
+  LIBC_INLINE constexpr ZipIterator(It1 it1, It2 it2) : it1(it1), it2(it2) {}
+
+  LIBC_INLINE constexpr const ZipIterator &operator++() const {
+    ++it1;
+    ++it2;
+    return *this;
+  }
+
+  LIBC_INLINE constexpr bool operator!=(const ZipIterator &other) const {
+    return it1 != other.it1 && it2 != other.it2;
+  }
+
+  LIBC_INLINE constexpr auto operator*() const { return cpp::tie(*it1, *it2); }
+
+private:
+  mutable It1 it1;
+  mutable It2 it2;
+};
+
+template <typename Container1, typename Container2> class ZipWrapper {
+public:
+  LIBC_INLINE constexpr ZipWrapper(Container1 &c1, Container2 &c2)
+      : c1(c1), c2(c2) {}
+
+  LIBC_INLINE constexpr auto begin() const {
+    return ZipIterator(c1.begin(), c2.begin());
+  }
+  LIBC_INLINE constexpr auto end() const {
+    return ZipIterator(c1.end(), c2.end());
+  }
+
+private:
+  Container1 &c1;
+  Container2 &c2;
+};
+
+} // namespace
+
+// Helper `zip` function
+template <typename C1, typename C2>
+LIBC_INLINE static constexpr ZipWrapper<C1, C2> zip(C1 &c1, C2 &c2) {
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mleleszi wrote:

static has no effect here and could be removed

https://github.com/llvm/llvm-project/pull/174759