alQueryValues(3dm) alQueryValues(3dm)
alQueryValues - get the set of possible values for a parameter
#include <dmedia/audio.h>
int alQueryValues(int res, int param, ALvalue *set, int setsize,
ALpv *quals, int qualsize);
res expects the audio resource (see alResources(3dm)) for which you
desire the information.
param
expects the parameter whose values you desire. Not all parameters
support alQueryValues(3dm); see alParams(3dm) for which parameters
apply.
set expects an array of ALvalues large enough to hold the results. See
alParams(3dm) and alSetParams(3dm) for more information on ALvalues.
setsize
is the number of ALvalues in set.
quals
expects an array of ALpv structs called qualifiers. These are used
to filter the results before putting them in the given set. See
alParams(3dm) and alSetParams(3dm) for more information on ALpv
structs.
qualsize
is the number of ALpv structs in quals.
alQueryValues returns the set of possible values for a given parameter on
a given resource, optionally filtering through the results to see if they
meet certain qualifiers.
alQueryValues only applies to certain parameters whose values are
resources, enumerated values, or sets. See alParams(3dm) for information
on which parameters apply.
Qualifiers only apply to parameters whose values are resources. If quals
is non-NULL and qualsize is non-zero, alQueryValues will acquire the set
of potential values for param, then filter through it, selecting only
those resources whose current values for the parameters in quals match
the corresponding values in quals.
alQueryValues will fill no more than setsize elements in set. If setsize
is 0, or set is NULL, alQueryValues will ignore set. In any case, it will
return the number of possible values which meet the given qualifiers.
Page 1
alQueryValues(3dm) alQueryValues(3dm)
#include <audio.h>
/*
* A simple function to dump information about an
* AL resource.
*/
void
dump_resources(ALvalue *x, int rv)
{
ALpv y[3];
char n[32];
int i;
for (i = 0; i < rv; i++) {
y[0].param = AL_NAME;
y[0].value.ptr = n;
y[0].sizeIn = 32;
y[1].param = AL_RATE;
y[2].param = AL_TYPE;
alGetParams(x[i].i,y,3);
printf("found resource %d [%s] -- rate %lf, type %d\n",x[i].i, n,alFixedToDouble(y[1].value.ll), y[2].value.i);
}
}
main()
{
ALvalue vals[32];
ALpv quals[16];
int rv;
/*
* alQueryValues can be used to count the number of
* potential values for a parameter. We simply leave out
* the sets. Here we ask how many different values
* AL_DEFAULT_OUTPUT can have on our machine. This returns
* the number of output devices on the system.
*/
if ((rv= alQueryValues(AL_SYSTEM,AL_DEFAULT_OUTPUT,0,0,0,0))>=0) {
printf("There are %d output devices on this system\n",rv);
}
else {
printf("alQueryValues failed: %s\n", alGetErrorString(oserror()));
exit(-1);
}
/*
* Now we find a device with a particular name. We could use
* alQueryValues for this, using AL_NAME as a qualifier, e.g.
*
* quals[0].param = AL_NAME;
* quals[0].value.ptr = "AnalogIn";
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alQueryValues(3dm) alQueryValues(3dm)
* quals[0].sizeIn = strlen(quals[0].value.ptr)+1; // add 1 to count the NULL
* if ((rv= alQueryValues(AL_SYSTEM,AL_DEVICES,vals,16,quals,1))>0) {
* printf("AnalogIn is resource %d\n",vals[0].i);
* }
*
* ... but alGetResourceByName is easier.
*/
if (rv=alGetResourceByName(AL_SYSTEM, "AnalogIn", AL_DEVICE_TYPE)) {
printf("AnalogIn is resource %d\n",rv);
}
/*
* We look up the master clocks that this device can get to,
* and find all whose types are AL_CRYSTAL_MCLK_TYPE.
* Note that the device understands AL_MASTER_CLOCK even though
* it's a clock-generator parameter -- parameters for interfaces
* and clock-generators can be sent to the devices that use them.
*/
quals[0].param = AL_TYPE;
quals[0].value.i = AL_CRYSTAL_MCLK_TYPE;
if ((rv= alQueryValues(rv,AL_MASTER_CLOCK,vals,16,quals,1))>0) {
dump_resources(vals, rv);
}
if (rv < 0) {
printf("alQueryValues failed: %s\n", alGetErrorString(oserror()));
}
}
alQueryValues always returns the number of possible values which meet the
qualifiers. If it finds no such possible values, it returns 0. If the
call fails for other reasons, it returns -1. In this case, the error
code retrieved by oserror(3C) will be one of:
AL_BAD_PVBUFFER [Toc] [Back]
quals is invalid and qualsize is nonzero.
AL_BAD_BUFFERLENGTH [Toc] [Back]
qualsize or setsize is patently wrong (e.g. negative).
AL_BAD_DEVICE_ACCESS [Toc] [Back]
The audio system is inaccessible, either because it is not installed
on the system, or because it is incorrectly configured.
AL_BAD_RESOURCE [Toc] [Back]
The given resource res does not exist.
AL_BAD_PARAM [Toc] [Back]
The given parameter param is not supported by the given resource.
Page 3
alQueryValues(3dm) alQueryValues(3dm)
oserror(3C), alParams(3dm), alGetParamInfo(3dm), alGetParams(3dm)
PPPPaaaaggggeeee 4444 [ Back ]
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