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Convert text values to a supported encoding if needed on the fly 

* This makes it harder to use the library wrongly and does not lead to
  worse performance as character set conversions are only done as needed.
* That's actually already done by serializers for most tag formats. This
  change ensures serializers for Matroska and Vorbis tag fields do this as
  well.
* Update documentation accordingly.
This commit is contained in:
Martchus 2022-07-21 23:30:45 +02:00
parent 2ae83a2301
commit ccf77959b4
3 changed files with 18 additions and 6 deletions
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2
matroska/matroskatagfield.cpp
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@ -220,7 +220,7 @@ MatroskaTagFieldMaker::MatroskaTagFieldMaker(MatroskaTagField &field, Diagnostic
if (m_field.value().type() == TagDataType::Popularity) {
m_stringValue = m_field.value().toScaledPopularity(TagType::MatroskaTag).toString();
} else {
m_stringValue = m_field.value().toString();
m_stringValue = m_field.value().toString(TagTextEncoding::Utf8);
}
} catch (const ConversionException &) {
diag.emplace_back(DiagLevel::Warning,

20
tagvalue.cpp
View File

@ -87,10 +87,22 @@ pair<const char *, float> encodingParameter(TagTextEncoding tagTextEncoding)
* 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 can be differently encoded.
* - See TagParser::TagTextEncoding for a list of encodings supported by this library.
* - Tag formats usually only support a subset of these encodings. The serializers for the varoius tag
* formats provided by this library will keep the encoding if possible and otherwise convert the assigned
* text to an encoding supported by the tag format on the fly. Note that ID3v1 does not specify which
* encodings are supported (or unsupported) so the serializer will just write text data as-is.
* - The deserializers will store text data in the encoding that is used in the tag.
* - The functions Tag::canEncodingBeUsed() and Tag::proposedTextEncoding() can be used to check
* whether an encoding can be used by a certain tag format to avoid any unnecessary character set
* conversions.
* - There's also the function Tag::ensureTextValuesAreProperlyEncoded() which can be used to convert all
* text values currently assigned to a tag to the encoding which is deemed best for the current tag format.
* This function is a bit more agressive than the implict conversions, e.g. it ensures no UTF-16 encoded
* text ends up in ID3v1 tags.
* - If you want to use UTF-8 everywhere, simply always assign UTF-8 text and use
* TagValue::toString(TagTextEncoding::Utf8) when reading text.
*
* Values of the type TagDataType::Popularity might use different rating scales depending on the tag
* format.

2
vorbis/vorbiscommentfield.cpp
View File

@ -213,7 +213,7 @@ bool VorbisCommentField::make(BinaryWriter &writer, VorbisCommentFlags flags, Di
valueString = value().toScaledPopularity(TagType::VorbisComment).toString();
} else {
// make normal string value
valueString = value().toString();
valueString = value().toString(TagTextEncoding::Utf8);
}
const auto size(valueString.size() + id().size() + 1);
if (size > numeric_limits<std::uint32_t>::max()) {