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

[Muhammad Bassiouni via libc-commits]

================
@@ -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) {
----------------
bassiounix wrote:

The intent here (if I understand correctly) is to hide the internal symbol and make it not collide with other translation units outside libc, yes even with this long namespace (you never know what could be the edge case).
If the default behavior is to hide everything and only expose the public symbols (which I don't know yet), then yes `static` here has no effect.

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