Document handling different types and encodings

README.md

@@ -52,10 +52,8 @@ This example shows how to read and write tag fields in a format-independent way:
 #include <tagparser/mediafileinfo.h>
 #include <tagparser/diagnostics.h>
 
-using namespace TagParser;
-
 // create a MediaFileInfo for high-level access to overall functionality of the library
-MediaFileInfo fileInfo;
+TagParser::MediaFileInfo fileInfo;
 // create container for errors, warnings, etc.
 Diagnostics diag;
 
@@ -63,45 +61,47 @@ Diagnostics diag;
 fileInfo.setPath("/path/to/some/file");
 fileInfo.open();
 // parse tags
-// (might throw exception derived from Failure for fatal parsing error or ios_base::failure for IO errors)
+// (might throw exception derived from TagParser::Failure for fatal parsing error or ios_base::failure for IO errors)
 fileInfo.parseTags(diag);
 
 // get first tag as an object derived from the Tag class
 auto tag = fileInfo.tags().at(0);
 // extract title and convert it to UTF-8 std::string
 // (toString() might throw ConversionException)
-auto title = tag->value(KnownField::Title).toString(TagTextEncoding::Utf8);
+auto title = tag->value(TagParser::KnownField::Title).toString(TagParser::TagTextEncoding::Utf8);
 
 // change album using an encoding suitable for the tag format
-tag->setValue(KnownField::Album, TagValue("some UTF-8 string", TagTextEncoding::Utf8, tag->proposedTextEncoding()));
+tag->setValue(TagParser::KnownField::Album, TagParser::TagValue("some UTF-8 string", TagParser::TagTextEncoding::Utf8, tag->proposedTextEncoding()));
 
 // create progress
-AbortableProgressFeedback progress([callback for status update], [callback for percentage-only updates]);
+TagParser::AbortableProgressFeedback progress([callback for status update], [callback for percentage-only updates]);
 
 // apply changes to the file on disk
-// (might throw exception derived from Failure for fatal processing error or ios_base::failure for IO errors)
+// (might throw exception derived from TagParser::Failure for fatal processing error or ios_base::failure for IO errors)
 fileInfo.applyChanges(diag, progress);
 ```
 
 ### Summary
-
-* So the most important class is `MediaFileInfo` providing access to everything else.
+* The most important class is `TagParser::MediaFileInfo` providing access to everything else.
 * IO errors are propagated via standard `std::ios_base::failure`.
-* Fatal processing errors are propagated by throwing a class derived from Failure.
-* All operations which might generate warnings, non-fatal errors, ... take a `Diagnostics` object to store
+* Fatal processing errors are propagated by throwing a class derived from `TagParser::Failure`.
+* All operations which might generate warnings, non-fatal errors, ... take a `TagParser::Diagnostics` object to store
   those messages.
-* All operations which can be aborted or provide progress feedback take a `AbortableProgressFeedback` object
+* All operations which can be aborted or provide progress feedback take a `TagParser::AbortableProgressFeedback` object
   for callbacks and aborting.
-* Field values are stored using `TagValue` objects. Those objects erase the actual type similar to `QVariant`
-  from the Qt framework.
+* Field values are stored using `TagParser::TagValue` objects. Those objects erase the actual type similar to `QVariant`
+  from the Qt framework. The documentation of `TagParser::TagValue` covers how different types and encodings are
+  handled.
 
 ### Further documentation
 For more examples check out the command line interface of [Tag Editor](https://github.com/Martchus/tageditor).
 API documentation can be generated using Doxygen with `make tagparser_apidoc`.
 
 ## Bugs, stability
+Bugs can be reported on GitHub.
+
 It is recommend to create backups before editing because I can not test whether the library
-works with all kinds of files (when forcing rewrite a backup is always created).
+works with all kinds of files. (When forcing rewrite a backup is always created.)
 
 ## Build instructions
 The tagparser library depends on [c++utilities](https://github.com/Martchus/cpp-utilities) and is built

tagvalue.cpp

@@ -69,6 +69,23 @@ pair<const char *, float> encodingParameter(TagTextEncoding tagTextEncoding)
  * \brief The TagValue class wraps values of different types. It is meant to be assigned to a tag field.
  *
  * For a list of supported types see TagParser::TagDataType.
+ *
+ * When constructing a TagValue choose the type which suites the value you want to store best. If the
+ * tag format uses a different type the serializer will take care of the neccassary conversion (eg. convert
+ * an integer to a string).
+ *
+ * When consuming a TagValue read from a tag one should not expect that a particular type is used. The
+ * type depends on what the particular tag format uses. However, the conversion functions provided by the
+ * TagValue class take care of neccassary conversions, eg. TagValue::toInteger() will attempt to convert a
+ * string to a number (an possibly throw a ConversionException on failure).
+ *
+ * Values of the type TagDataType::Text can be differently encoded. See TagParser::TagTextEncoding for a
+ * list of supported encodings. Be sure to use an encoding which is supported by the tag implementation.
+ * To ensure that the functions Tag::canEncodingBeUsed(), Tag::proposedTextEncoding() and
+ * Tag::ensureTextValuesAreProperlyEncoded() can be used.
+ *
+ * Values of the type TagDataType::Text are not supposed to contain Byte-Order-Marks. Before assigning text
+ * which might be prepended by a Byte-Order-Mark the helper function TagValue::stripBom() can be used.
  */
 
 /*!