Translate text frame nulls to '/' (fixes polyfloyd#82)

Null bytes in text frames is an ID3v2.4 feature. A valid substitute is
to use '/' in prior versions. This was always the intended behaviour,
hence this is considered a bug fix.

src/stream/frame/content.rs

@@ -71,7 +71,10 @@ impl<W: io::Write> Encoder<W> {
 
     fn text_content(&mut self, content: &str) -> crate::Result<()> {
         self.encoding()?;
-        self.string(content)
+        match self.version {
+            Version::Id3v22 | Version::Id3v23 => self.string(&content.replace('\0', "/")),
+            Version::Id3v24 => self.string(content),
+        }
     }
 
     fn extended_text_content(&mut self, content: &ExtendedText) -> crate::Result<()> {
@@ -427,6 +430,10 @@ impl<'a> Decoder<'a> {
             },
         };
         let text = encoding.decode(self.bytes(end)?)?;
+        let text = match self.version {
+            Version::Id3v22 | Version::Id3v23 => text.replace('/', "\0"),
+            Version::Id3v24 => text,
+        };
         Ok(Content::Text(text))
     }
 
@@ -1075,40 +1082,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_null_terminated_text_v3() {
-        assert!(decode("TRCK", Version::Id3v23, &[][..]).is_err());
-        let text = "text\u{0}test\u{0}";
-        for encoding in &[
-            Encoding::Latin1,
-            Encoding::UTF8,
-            Encoding::UTF16,
-            Encoding::UTF16BE,
-        ] {
-            println!("`{}`, `{:?}`", text, encoding);
-            let mut data = Vec::new();
-            data.push(*encoding as u8);
-            data.extend(bytes_for_encoding(text, *encoding).into_iter());
-
-            assert_eq!(
-                decode("TALB", Version::Id3v23, &data[..])
-                    .unwrap()
-                    .text()
-                    .unwrap(),
-                "text"
-            );
-            let mut data_out = Vec::new();
-            encode(
-                &mut data_out,
-                &Content::Text(text.to_string()),
-                Version::Id3v23,
-                *encoding,
-            )
-            .unwrap();
-            assert_eq!(data, data_out);
-        }
-    }
-
     #[test]
     fn test_null_terminated_text_v4() {
         assert!(decode("TRCK", Version::Id3v24, &[][..]).is_err());

src/stream/tag.rs

@@ -344,6 +344,10 @@ mod tests {
         tag.set_title("Title");
         tag.set_artist("Artist");
         tag.set_genre("Genre");
+        tag.add_frame(Frame::with_content(
+            "TPE4",
+            Content::new_text_values(["artist 1", "artist 2", "artist 3"]),
+        ));
         tag.set_duration(1337);
         tag.add_frame(EncapsulatedObject {
             mime_type: "Some Object".to_string(),

src/tag.rs

@@ -495,6 +495,17 @@ mod tests {
         println!("{}", output);
     }
 
+    #[test]
+    fn github_issue_82() {
+        let mut tag = Tag::new();
+        tag.set_artist("artist 1\0artist 2\0artist 3");
+        assert_eq!(tag.artist(), Some("artist 1\0artist 2\0artist 3"));
+        let mut buf = Vec::new();
+        tag.write_to(&mut buf, Version::Id3v22).unwrap();
+        let tag = Tag::read_from(&buf[..]).unwrap();
+        assert_eq!(tag.artist(), Some("artist 1\0artist 2\0artist 3"));
+    }
+
     #[test]
     fn aiff_read_and_write() {
         // Copy