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

[via llvm-commits]

================
@@ -0,0 +1,370 @@
+//===-- CharSet.cpp - 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 utility classes to convert between different character
+/// set encoding.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/CharSet.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/ConvertEBCDIC.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <limits>
+#include <system_error>
+
+#ifdef HAVE_ICU
+#include <unicode/ucnv.h>
+#elif defined(HAVE_ICONV)
+#include <iconv.h>
+#endif
+
+using namespace llvm;
+
+// Normalize the charset name with the charset alias matching algorithm proposed
+// in https://www.unicode.org/reports/tr22/tr22-8.html#Charset_Alias_Matching.
+void normalizeCharSetName(StringRef CSName, SmallVectorImpl<char> &Normalized) {
----------------
cor3ntin wrote:

normalizeCharSetName could return a smallVector directly, slightly easier to use

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