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#include <sys/eventfd.h>
#include <poll.h>
#include <inttypes.h>
#include <errno.h>
#include <unistd.h>
/*
* Linux implementation of signals.
* Internally, eventfds are used for signalling, as they
* provide the least overhead. We don't allocate any struct
* ever, but cast the event fd+1 to dnbd3_signal_t*
* to save all the malloc() and free() calls.
*/
dnbd3_signal_t* signal_new()
{
// On error, eventfd() returns -1, so essentially we return NULL on error.
// (Yes, NULL doesn't have to be 0 everywhere, but cmon)
return (dnbd3_signal_t*)(intptr_t)( eventfd( 0, EFD_NONBLOCK ) + 1 );
}
dnbd3_signal_t* signal_newBlocking()
{
return (dnbd3_signal_t*)(intptr_t)( eventfd( 0, 0 ) + 1 );
}
int signal_call(const dnbd3_signal_t* const signal)
{
if ( signal == NULL ) return SIGNAL_ERROR;
static uint64_t one = 1;
const int signalFd = ( (int)(intptr_t)signal ) - 1;
return write( signalFd, &one, sizeof one ) == sizeof one ? SIGNAL_OK : SIGNAL_ERROR;
}
int signal_wait(const dnbd3_signal_t* const signal, int timeoutMs)
{
if ( signal == NULL ) return SIGNAL_ERROR;
const int signalFd = ( (int)(intptr_t)signal ) - 1;
struct pollfd ps = {
.fd = signalFd,
.events = POLLIN
};
int ret = poll( &ps, 1, timeoutMs );
if ( ret == 0 ) return SIGNAL_TIMEOUT;
if ( ret == -1 ) return SIGNAL_ERROR;
if ( ps.revents & ( POLLERR | POLLNVAL ) ) return SIGNAL_ERROR;
return signal_clear( signal );
}
int signal_clear(const dnbd3_signal_t* const signal)
{
if ( signal == NULL ) return SIGNAL_ERROR;
uint64_t ret;
const int signalFd = ( (int)(intptr_t)signal ) - 1;
if ( read( signalFd, &ret, sizeof ret ) != sizeof ret ) {
if ( errno == EAGAIN ) return 0;
return SIGNAL_ERROR;
}
return (int)ret;
}
void signal_close(const dnbd3_signal_t* const signal)
{
const int signalFd = ( (int)(intptr_t)signal ) - 1;
close( signalFd );
}
int signal_getWaitFd(const dnbd3_signal_t* const signal)
{
if ( signal == NULL ) return -1;
const int signalFd = ( (int)(intptr_t)signal ) - 1;
return signalFd;
}
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