From 9f3faaf3c4825f13da91f985502d8625ce3ea848 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Tue, 15 Nov 2022 00:55:39 +0100
Subject: [PATCH] lib/icu/Transliterator: wrapper for UTransliterator

---
 src/lib/icu/Transliterator.cxx | 64 ++++++++++++++++++++++++++++++++++
 src/lib/icu/Transliterator.hxx | 64 ++++++++++++++++++++++++++++++++++
 src/lib/icu/meson.build        |  1 +
 3 files changed, 129 insertions(+)
 create mode 100644 src/lib/icu/Transliterator.cxx
 create mode 100644 src/lib/icu/Transliterator.hxx

diff --git a/src/lib/icu/Transliterator.cxx b/src/lib/icu/Transliterator.cxx
new file mode 100644
index 000000000..b1470d609
--- /dev/null
+++ b/src/lib/icu/Transliterator.cxx
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2003-2022 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "Transliterator.hxx"
+#include "util/AllocatedArray.hxx"
+
+#include <algorithm> // for std::copy()
+#include <stdexcept>
+
+static UTransliterator *
+OpenTransliterator(const UChar *id, const UChar *rules)
+{
+	UErrorCode error_code = U_ZERO_ERROR;
+
+	UTransliterator *t = utrans_openU(id, -1, UTRANS_FORWARD,
+					  rules, -1,
+					  nullptr, &error_code);
+	if (t == nullptr)
+	       throw std::runtime_error(u_errorName(error_code));
+
+	return t;
+}
+
+IcuTransliterator::IcuTransliterator(const UChar *id, const UChar *rules)
+	:transliterator(OpenTransliterator(id, rules))
+{
+}
+
+AllocatedArray<UChar>
+IcuTransliterator::Transliterate(std::basic_string_view<UChar> src) noexcept
+{
+	AllocatedArray<UChar> dest(src.size() * 2U);
+	std::copy(src.begin(), src.end(), dest.begin());
+
+	int32_t length = src.size();
+	int32_t limit = length;
+
+	UErrorCode status = U_ZERO_ERROR;
+	utrans_transUChars(transliterator,
+			   dest.data(), &length, dest.size(),
+			   0, &limit,
+			   &status);
+	if (U_FAILURE(status))
+		return nullptr;
+
+	dest.SetSize(length);
+	return dest;
+}
diff --git a/src/lib/icu/Transliterator.hxx b/src/lib/icu/Transliterator.hxx
new file mode 100644
index 000000000..38ab86e9d
--- /dev/null
+++ b/src/lib/icu/Transliterator.hxx
@@ -0,0 +1,64 @@
+/*
+ * Copyright 2003-2022 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#pragma once
+
+#include <unicode/utrans.h>
+
+#include <utility> // for std::exchange()
+
+template<class T> class AllocatedArray;
+
+/**
+ * Wrapper for an ICU #UTransliterator instance.
+ */
+class IcuTransliterator {
+	UTransliterator *transliterator = nullptr;
+
+	IcuTransliterator(UTransliterator *_transliterator) noexcept
+		:transliterator(_transliterator) {}
+
+public:
+	IcuTransliterator() noexcept = default;
+
+	/**
+	 * Throws on error.
+	 */
+	IcuTransliterator(const UChar *id, const UChar *rules);
+
+	~IcuTransliterator() noexcept {
+		if (transliterator != nullptr)
+			    utrans_close(transliterator);
+	}
+
+	IcuTransliterator(IcuTransliterator &&src) noexcept
+		:transliterator(std::exchange(src.transliterator, nullptr)) {}
+
+	IcuTransliterator &operator=(IcuTransliterator &&src) noexcept {
+		using std::swap;
+		swap(transliterator, src.transliterator);
+		return *this;
+	}
+
+	/**
+	 * @return the transliterated string (or nullptr on error)
+	 */
+	[[gnu::pure]]
+	AllocatedArray<UChar> Transliterate(std::basic_string_view<UChar> src) noexcept;
+};
diff --git a/src/lib/icu/meson.build b/src/lib/icu/meson.build
index 57b816946..65d90b199 100644
--- a/src/lib/icu/meson.build
+++ b/src/lib/icu/meson.build
@@ -19,6 +19,7 @@ if icu_dep.found()
     'Util.cxx',
     'FoldCase.cxx',
     'Normalize.cxx',
+    'Transliterator.cxx',
   ]
 else
   if meson.version().version_compare('>= 0.60')