Trait gio::prelude::ConverterExtManual [−][src]
pub trait ConverterExtManual {
fn convert<IN: AsRef<[u8]>, OUT: AsMut<[u8]>>(
&self,
inbuf: IN,
outbuf: OUT,
flags: ConverterFlags
) -> Result<(ConverterResult, usize, usize), Error>;
}Required methods
This is the main operation used when converting data. It is to be called
multiple times in a loop, and each time it will do some work, i.e.
producing some output (in outbuf) or consuming some input (from inbuf) or
both. If its not possible to do any work an error is returned.
Note that a single call may not consume all input (or any input at all). Also a call may produce output even if given no input, due to state stored in the converter producing output.
If any data was either produced or consumed, and then an error happens, then only the successful conversion is reported and the error is returned on the next call.
A full conversion loop involves calling this method repeatedly, each time
giving it new input and space output space. When there is no more input
data after the data in inbuf, the flag ConverterFlags::INPUT_AT_END must be set.
The loop will be (unless some error happens) returning ConverterResult::Converted
each time until all data is consumed and all output is produced, then
ConverterResult::Finished is returned instead. Note, that ConverterResult::Finished
may be returned even if ConverterFlags::INPUT_AT_END is not set, for instance
in a decompression converter where the end of data is detectable from the
data (and there might even be other data after the end of the compressed data).
When some data has successfully been converted bytes_read and is set to
the number of bytes read from inbuf, and bytes_written is set to indicate
how many bytes was written to outbuf. If there are more data to output
or consume (i.e. unless the ConverterFlags::INPUT_AT_END is specified) then
ConverterResult::Converted is returned, and if no more data is to be output
then ConverterResult::Finished is returned.
On error ConverterResult::Error is returned and error is set accordingly.
Some errors need special handling:
IOErrorEnum::NoSpace is returned if there is not enough space
to write the resulting converted data, the application should
call the function again with a larger outbuf to continue.
IOErrorEnum::PartialInput is returned if there is not enough
input to fully determine what the conversion should produce,
and the ConverterFlags::INPUT_AT_END flag is not set. This happens for
example with an incomplete multibyte sequence when converting text,
or when a regexp matches up to the end of the input (and may match
further input). It may also happen when inbuf_size is zero and
there is no more data to produce.
When this happens the application should read more input and then
call the function again. If further input shows that there is no
more data call the function again with the same data but with
the ConverterFlags::INPUT_AT_END flag set. This may cause the conversion
to finish as e.g. in the regexp match case (or, to fail again with
IOErrorEnum::PartialInput in e.g. a charset conversion where the
input is actually partial).
After ConverterExtManual::convert() has returned ConverterResult::Finished the
converter object is in an invalid state where its not allowed
to call ConverterExtManual::convert() anymore. At this time you can only
free the object or call ConverterExt::reset() to reset it to the
initial state.
If the flag ConverterFlags::FLUSH is set then conversion is modified
to try to write out all internal state to the output. The application
has to call the function multiple times with the flag set, and when
the available input has been consumed and all internal state has
been produced then ConverterResult::Flushed (or ConverterResult::Finished if
really at the end) is returned instead of ConverterResult::Converted.
This is somewhat similar to what happens at the end of the input stream,
but done in the middle of the data.
This has different meanings for different conversions. For instance in a compression converter it would mean that we flush all the compression state into output such that if you uncompress the compressed data you get back all the input data. Doing this may make the final file larger due to padding though. Another example is a regexp conversion, where if you at the end of the flushed data have a match, but there is also a potential longer match. In the non-flushed case we would ask for more input, but when flushing we treat this as the end of input and do the match.
Flushing is not always possible (like if a charset converter flushes
at a partial multibyte sequence). Converters are supposed to try
to produce as much output as possible and then return an error
(typically IOErrorEnum::PartialInput).
inbuf
the buffer containing the data to convert.
outbuf
a buffer to write converted data in.
flags
a ConverterFlags controlling the conversion details
Returns
a ConverterResult, ConverterResult::Error on error.
bytes_read
will be set to the number of bytes read from inbuf on success
bytes_written
will be set to the number of bytes written to outbuf on success