[libcxx-commits] [libcxx] [libc++] Optimize std::getline (PR #121346)

[Louis Dionne via libcxx-commits]

================
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 TEST_SUPPORT_STREAM_TYPE_H
+#define TEST_SUPPORT_STREAM_TYPE_H
+
+#include <streambuf>
+#include <string>
+#include <utility>
+
+template <class CharT>
+class non_buffering_streambuf : public std::basic_streambuf<CharT> {
+  using char_type   = CharT;
+  using traits_type = std::char_traits<CharT>;
+  using int_type    = typename traits_type::int_type;
+
+public:
+  non_buffering_streambuf(std::basic_string<char_type> underlying_data)
+      : underlying_data_(std::move(underlying_data)), index_(0) {}
+
+protected:
+  int_type underflow() override {
+    if (index_ != underlying_data_.size())
+      return underlying_data_[index_];
+    return traits_type::eof();
+  }
+
+  int_type uflow() override {
+    if (index_ != underlying_data_.size())
+      return underlying_data_[index_++];
+    return traits_type::eof();
+  }
+
+private:
+  std::basic_string<char_type> underlying_data_;
+  size_t index_;
+};
+
+#endif // TEST_SUPPORT_STREAM_TYPE_H
----------------
ldionne wrote:

```suggestion
#endif // TEST_SUPPORT_STREAM_TYPES_H
```

https://github.com/llvm/llvm-project/pull/121346