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#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/soundcard.h>
//OSS4 soundcard.h includes below SNDCTL defines, but OSS3 does not
//However, OSS4 soundcard.h does not reside in <sys/>
//Therefore, attempt to manually define SNDCTL values if using OSS3 header
//Note that if the defines below fail to work on any specific platform, one can point soundcard.h
//above to the correct location for OSS4 (usually /usr/lib/oss/include/sys/soundcard.h)
//Failing that, one can disable OSS4 ioctl calls inside init() and remove the below defines
#ifndef SNDCTL_DSP_COOKEDMODE
#define SNDCTL_DSP_COOKEDMODE _IOW('P', 30, signed)
#endif
#ifndef SNDCTL_DSP_POLICY
#define SNDCTL_DSP_POLICY _IOW('P', 45, signed)
#endif
struct AudioOSS : Audio {
~AudioOSS() { term(); }
struct {
signed fd = -1;
signed format = AFMT_S16_LE;
signed channels = 2;
} device;
struct {
string device = "/dev/dsp";
bool synchronize = true;
unsigned frequency = 22050;
} settings;
auto cap(const string& name) -> bool {
if(name == Audio::Device) return true;
if(name == Audio::Synchronize) return true;
if(name == Audio::Frequency) return true;
return false;
}
auto get(const string& name) -> any {
if(name == Audio::Device) return settings.device;
if(name == Audio::Synchronize) return settings.synchronize;
if(name == Audio::Frequency) return settings.frequency;
return {};
}
auto set(const string& name, const any& value) -> bool {
if(name == Audio::Device && value.is<string>()) {
settings.device = value.get<string>();
if(!settings.device) settings.device = "/dev/dsp";
return true;
}
if(name == Audio::Synchronize && value.is<bool>()) {
settings.synchronize = value.get<bool>();
updateSynchronization();
return true;
}
if(name == Audio::Frequency && value.is<unsigned>()) {
settings.frequency = value.get<unsigned>();
if(device.fd >= 0) init();
return true;
}
return false;
}
auto sample(uint16_t left, uint16_t right) -> void {
uint32_t sample = left << 0 | right << 16;
auto unused = write(device.fd, &sample, 4);
}
auto clear() -> void {
}
auto init() -> bool {
device.fd = open(settings.device, O_WRONLY, O_NONBLOCK);
if(device.fd < 0) return false;
#if 1 //SOUND_VERSION >= 0x040000
//attempt to enable OSS4-specific features regardless of version
//OSS3 ioctl calls will silently fail, but sound will still work
signed cooked = 1, policy = 4; //policy should be 0 - 10, lower = less latency, more CPU usage
ioctl(device.fd, SNDCTL_DSP_COOKEDMODE, &cooked);
ioctl(device.fd, SNDCTL_DSP_POLICY, &policy);
#endif
signed freq = settings.frequency;
ioctl(device.fd, SNDCTL_DSP_CHANNELS, &device.channels);
ioctl(device.fd, SNDCTL_DSP_SETFMT, &device.format);
ioctl(device.fd, SNDCTL_DSP_SPEED, &freq);
updateSynchronization();
return true;
}
auto term() -> void {
if(device.fd >= 0) {
close(device.fd);
device.fd = -1;
}
}
private:
auto updateSynchronization() -> void {
if(device.fd < 0) return;
auto flags = fcntl(device.fd, F_GETFL);
if(flags < 0) return;
settings.synchronize ? flags &=~ O_NONBLOCK : flags |= O_NONBLOCK;
fcntl(device.fd, F_SETFL, flags);
}
};
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