[llvm] Create a CharSetConverter class with both iconv and icu support (PR #74516)

[via llvm-commits]

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@@ -0,0 +1,160 @@
+//===-- CharSet.h - Utility class to convert between char sets ----*- 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file provides a utility class to convert between different character
+/// set encodings.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_CHARSET_H
+#define LLVM_SUPPORT_CHARSET_H
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Config/config.h"
+#include "llvm/Support/ErrorOr.h"
+
+#include <functional>
+#include <string>
+#include <system_error>
+
+namespace llvm {
+
+template <typename T> class SmallVectorImpl;
+
+namespace details {
+class CharSetConverterImplBase {
+public:
+  virtual ~CharSetConverterImplBase() = default;
+
+  /// Converts a string.
+  /// \param[in] Source source string
+  /// \param[in,out] Result container for converted string
+  /// \param[in] ShouldAutoFlush Append shift-back sequence after conversion
+  /// for multi-byte encodings iff true.
----------------
cor3ntin wrote:

```suggestion
  /// for stateful encodings if true.
```

https://github.com/llvm/llvm-project/pull/74516