decoder/OpusReader: use std::string_view

src/decoder/plugins/OpusReader.hxx

@@ -20,10 +20,9 @@
 #ifndef MPD_OPUS_READER_HXX
 #define MPD_OPUS_READER_HXX
 
-#include "util/StringView.hxx"
-
 #include <algorithm>
 #include <cstdint>
+#include <string_view>
 
 #include <string.h>
 
@@ -83,14 +82,14 @@ public:
 		return ReadWord(length) && Skip(length);
 	}
 
-	constexpr StringView ReadString() noexcept {
+	constexpr std::string_view ReadString() noexcept {
 		uint32_t length;
 		if (!ReadWord(length))
-			return nullptr;
+			return {};
 
 		const char *src = (const char *)Read(length);
 		if (src == nullptr)
-			return nullptr;
+			return {};
 
 		return {src, length};
 	}

src/decoder/plugins/OpusTags.cxx

@@ -26,6 +26,7 @@
 #include "util/ASCII.hxx"
 #include "tag/ReplayGainInfo.hxx"
 #include "util/NumberParser.hxx"
+#include "util/StringSplit.hxx"
 #include "util/StringView.hxx"
 
 #include <cstdint>
@@ -104,11 +105,11 @@ ScanOpusTags(const void *data, size_t size,
 
 	while (n-- > 0) {
 		const auto s = r.ReadString();
-		if (s == nullptr)
+		if (s.data() == nullptr)
 			return false;
 
-		const auto split = s.Split('=');
+		const auto split = Split(s, '=');
-		if (split.first.empty() || split.second.IsNull())
+		if (split.first.empty() || split.second.data() == nullptr)
 			continue;
 
 		ScanOneOpusTag(split.first, split.second, rgi, handler);