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

[Abhina Sree via llvm-commits]

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+//===-- CharSet.cpp - Characters sets conversion class ------------*- 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.
+///
+//===----------------------------------------------------------------------===//
+
+// UNICODE LICENSE V3
+//
+// COPYRIGHT AND PERMISSION NOTICE
+//
+// Copyright © 2016-2024 Unicode, Inc.
+//
+// NOTICE TO USER: Carefully read the following legal agreement. BY
+// DOWNLOADING, INSTALLING, COPYING OR OTHERWISE USING DATA FILES, AND/OR
+// SOFTWARE, YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THE
+// TERMS AND CONDITIONS OF THIS AGREEMENT. IF YOU DO NOT AGREE, DO NOT
+// DOWNLOAD, INSTALL, COPY, DISTRIBUTE OR USE THE DATA FILES OR SOFTWARE.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
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+// software and any associated documentation (the "Software") to deal in the
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+// Data Files or Software are furnished to do so, provided that either (a)
+// this copyright and permission notice appear with all copies of the Data
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+//
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+// KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
+// THIRD PARTY RIGHTS.
+//
+// IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE
+// BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES,
+// OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+// WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
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+
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+// not be used in advertising or otherwise to promote the sale, use or other
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+// authorization of the copyright holder.
+
+#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.
+static void normalizeCharSetName(StringRef CSName,
+                                 SmallVectorImpl<char> &Normalized) {
+  bool PrevDigit = false;
+  for (auto Ch : CSName) {
+    if (isAlnum(Ch)) {
+      Ch = toLower(Ch);
+      if (Ch != '0' || PrevDigit) {
+        PrevDigit = isDigit(Ch);
+        Normalized.push_back(Ch);
+      }
+    }
+  }
+}
+
+// Maps the charset name to enum constant if possible.
+std::optional<text_encoding::id> getKnownCharSet(StringRef CSName) {
+  SmallString<16> Normalized;
+  normalizeCharSetName(CSName, Normalized);
+  if (Normalized.equals("utf8"))
+    return text_encoding::id::UTF8;
+  if (Normalized.equals("ibm1047"))
+    return text_encoding::id::IBM1047;
+  return std::nullopt;
+}
+
+void HandleOverflow(size_t &Capacity, char *&Output, size_t &OutputLength,
----------------
abhina-sree wrote:

Thanks, I've made this static

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