JsonParser.getCurrentLocation is not updated for `DataInput` input

[fabienrenaud]

Issue

Using a JsonParser instantiated via JsonParser.createParser(DataInput) does not update JsonLocation values returned by JsonParser.getCurrentLocation (everything defaults to -1).

Switching to JsonParser.createParser(InputStream) with the same input object populates the JsonLocation data as expected.

Use case

I use JsonParser to manually extract slices of Netty byte buffers (that contain Json). To feed Netty ByteBufs to JsonParser, I have to wrap the ByteBuf in a ByteBufInputStream which extends InputStream and implements DataInput. JsonParser accepts both types so explicit casting is required.

• This works and populates JsonLocation values:

ByteBuf buf = ...;
JsonParser parser = JSON_FACTORY.createParser((InputStream) new ByteBufInputStream(buf));

• This does not populate JsonLocation values:

ByteBuf buf = ...;
JsonParser parser = JSON_FACTORY.createParser((DataInput) new ByteBufInputStream(buf));

Issue affects at least versions 2.9.8 and 2.10.2.

[cowtowncoder]

Yeah, this is missing, as there is no input pointer to use. So it's not a simple tweak.

[fabienrenaud]

I am not sure why it works for InputStream and not DataInput though. Are there any methods InputStream provides that DataInput does not (to make this work in Jackson)?

[cowtowncoder]

It's just because all reads from InputStream / Reader are buffered first and access is from those buffers; single-byte/char reads are not used. In contrast, DataInput is read byte-by-byte (leading to lower performance). There is no way to safely try bulk reads either, as far as I know. So to keep track of location, separate byte counter would need to be maintained.