util/IterableSplitString: cheaper variant of SplitString()

Makefile.am

@@ -415,6 +415,7 @@ libutil_a_SOURCES = \
 	src/util/WStringAPI.hxx \
 	src/util/DivideString.cxx src/util/DivideString.hxx \
 	src/util/SplitString.cxx src/util/SplitString.hxx \
+	src/util/IterableSplitString.hxx \
 	src/util/FormatString.cxx src/util/FormatString.hxx \
 	src/util/Tokenizer.cxx src/util/Tokenizer.hxx \
 	src/util/TextFile.hxx \

src/output/plugins/JackOutputPlugin.cxx

@@ -23,7 +23,7 @@
 #include "../Wrapper.hxx"
 #include "config/ConfigError.hxx"
 #include "util/ConstBuffer.hxx"
-#include "util/SplitString.hxx"
+#include "util/IterableSplitString.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
@@ -355,14 +355,14 @@ static unsigned
 parse_port_list(const char *source, std::string dest[], Error &error)
 {
 	unsigned n = 0;
-	for (auto &&i : SplitString(source, ',')) {
+	for (auto i : IterableSplitString(source, ',')) {
 		if (n >= MAX_PORTS) {
 			error.Set(config_domain,
 				  "too many port names");
 			return 0;
 		}
 
-		dest[n++] = std::move(i);
+		dest[n++] = std::string(i.data, i.size);
 	}
 
 	if (n == 0) {

src/util/IterableSplitString.hxx

+/*
+ * Copyright (C) 2013-2016 Max Kellermann <max@duempel.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
+ * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ITERABLE_SPLIT_STRING_HXX
+#define ITERABLE_SPLIT_STRING_HXX
+
+#include "StringView.hxx"
+
+#include <iterator>
+
+/**
+ * Split a string at a certain separator character into sub strings
+ * and allow iterating over the segments.
+ *
+ * Two consecutive separator characters result in an empty string.
+ *
+ * An empty input string returns one empty string.
+ */
+class IterableSplitString {
+	StringView s;
+
+	char separator;
+
+public:
+	constexpr IterableSplitString(StringView _s, char _separator)
+		:s(_s), separator(_separator) {}
+
+	class Iterator final {
+		friend class IterableSplitString;
+
+		StringView current, rest;
+
+		char separator;
+
+		Iterator(StringView _s, char _separator)
+			:rest(_s), separator(_separator) {
+			Next();
+		}
+
+		constexpr Iterator(std::nullptr_t n)
+			:current(n), rest(n), separator(0) {}
+
+		void Next() {
+			if (rest.IsNull())
+				current = nullptr;
+			else {
+				const char *i = rest.Find(separator);
+				if (i == nullptr) {
+					current = rest;
+					rest.data = nullptr;
+				} else {
+					current.data = rest.data;
+					current.size = i - current.data;
+					rest.size -= current.size + 1;
+					rest.data = i + 1;
+				}
+			}
+		}
+
+	public:
+		typedef std::forward_iterator_tag iterator_category;
+
+		Iterator &operator++() {
+			Next();
+			return *this;
+		}
+
+		constexpr bool operator==(Iterator other) const {
+			return current.data == other.current.data;
+		}
+
+		constexpr bool operator!=(Iterator other) const {
+			return !(*this == other);
+		}
+
+		constexpr StringView operator*() const {
+			return current;
+		}
+
+		constexpr const StringView *operator->() const {
+			return &current;
+		}
+	};
+
+	typedef Iterator iterator;
+	typedef Iterator const_iterator;
+
+	const_iterator begin() const {
+		return {s, separator};
+	}
+
+	constexpr const_iterator end() const {
+		return {nullptr};
+	}
+};
+
+#endif

src/util/SplitString.cxx

@@ -28,6 +28,7 @@
  */
 
 #include "SplitString.hxx"
+#include "IterableSplitString.hxx"
 #include "StringUtil.hxx"
 
 #include <string.h>
@@ -44,26 +45,16 @@ SplitString(const char *s, char separator, bool strip)
 
 	auto i = list.before_begin();
 
-	while (true) {
-		const char *next = strchr(s, separator);
-		if (next == nullptr)
-			break;
+	for (auto value : IterableSplitString(s, separator)) {
+		const char *begin = value.begin(), *end = value.end();
 
-		const char *end = next++;
-		if (strip)
-			end = StripRight(s, end);
+		if (strip) {
+			begin = StripLeft(begin, end);
+			end = StripRight(begin, end);
+		}
 
-		i = list.emplace_after(i, s, end);
-
-		s = next;
-		if (strip)
-			s = StripLeft(s);
+		i = list.emplace_after(i, begin, end);
 	}
 
-	const char *end = s + strlen(s);
-	if (strip)
-		end = StripRight(s, end);
-
-	list.emplace_after(i, s, end);
 	return list;
 }