[erlang-questions] Linked-in drivers: output and outputv callbacks
Thu Dec 13 22:30:34 CET 2007
You misunderstood my question. It's not _what_ outputv does but how is
it possible that efile_drv.c sets up both outputv and output callbacks
and both seem to be called somehow.
At least I assume that they are both being called since the set of
functions that the driver performs is split over the two callbacks.
The read/write functions are in outputv and a whole bunch of others
like mkdir are in output.
On Dec 13, 2007, at 8:28 PM, Tony Rogvall wrote:
> There is actually quite some descent docs to read here:
> void outputv(ErlDrvData drv_data, ErlIOVec *ev)
> This function is called whenever the port is written to. If it is
> NULL, the output function is called instead. This function is faster
> than output, because it takes an ErlIOVec directly, which requires
> no copying of the data. The port should be in binary mode, see
> The ErlIOVec contains both a SysIOVec, suitable for writev, and one
> or more binaries. If these binaries should be retained, when the
> driver returns from outputv, they can be queued (using
> driver_enq_bin for instance), or if they are kept in a static or
> global variable, the reference counter can be incremented.
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