On 22.04.19 09:34, Tanu Kaskinen wrote:
On Sat, 2019-04-20 at 11:38 +0200, Georg Chini wrote:
PA uses malloc() in the IO-thread, so are we doing things wrong?
I think using malloc() when a parameter changes is not interfering
with real-time operation because the filter must be reset after
a parameter change anyway.
Am I allowed to use free() from the I/O-thread? The current scheme for
updating
parameters I have in mind should work for any of the existing filters
and relies on
passing around parameter structures:
/* The following functions can be provided to set and get
parameters. The parameter
* structure is defined by the filter and should contain all
parameters that are
* configurable by the user. The library code makes no assumption
on the contents
* of the structure but only passes references. The library
implements a message
* handler which supports the following messages that use the
functions below:
* get_parameter - Retrieve a single parameter.
* set_parameter - Set a single parameter.
* get_all_parameters - Retrieve all parameters as a comma
separated list.
* set_all_parameters - Set all parameters simultaneously.
* get_parameter_description - Returns a list that describes all
parameters.
* Format of the list elements is:
* {{Identifier}{Type}{default}{min}{max}}
* The last message can be used to get information about the filter
or to implement
* a filter control GUI that is independent of the filter type. */
/* Get the value of the parameter described by identifier. The
value shall be returned
* as a string in value. The identifier may be any string that the
filter recognizes
* like a name or index, depending of the implementation of this
function. */
int (*parameter_get)(const char *identifier, char **value, void
*userdata);
/* Sets the value of the parameter described by identifier. The
value is expected as
* a string. The identifier may be any string that the filter
recognizes like a name
* or index. Returns a parameter structure filled with all current
parameter values,
* reflecting the updated parameter, so that the structure can be
passed to
* update_filter_parameter(). update_filter_parameter() will
replace the current
* parameter set with the new structure. */
void *(*parameter_set)(const char *identifier, const char *value,
void *userdata);
/* Returns a comma separated list of the values of all filter
parameters. */
char *(*parameter_get_all)(void *userdata);
/* Expects a comma separated list of all filter parameter values
and returns a parameter
* structure that can be passed to update_filter_parameters(). See
set_parameter(). */
void *(*parameter_set_all(const char *all_params, void *userdata);
/* Returns a parameter description string as described above. */
This would allocate the memory in the main thread but would require that
the I/O-thread frees the old parameter structure when it is replaced.
Alternatively
the function that replaces the old structure with the new one could return a
pointer to the old structure, so that it can be freed in the main thread.
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