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#include "stdafx.h"
#include "IOCondition.h"
#include <limits>
#ifdef POSIX
// NOTE: This does not exist on all POSIX systems (eg. MacOS)
#include <sys/eventfd.h>
#endif
namespace os {
#ifdef WINDOWS
IOCondition::IOCondition() : signaled(0) {
sema = CreateSemaphore(NULL, 0, 1, NULL);
}
IOCondition::~IOCondition() {
CloseHandle(sema);
}
void IOCondition::signal() {
// If we're the first one to signal, alter the semaphore.
if (atomicCAS(signaled, 0, 1) == 0)
ReleaseSemaphore(sema, 1, NULL);
}
void IOCondition::wait() {
// Wait for someone to signal, and then reset the signaled state for next time.
WaitForSingleObject(sema, INFINITE);
atomicCAS(signaled, 1, 0);
}
void IOCondition::wait(IOHandle &io) {
HANDLE ioHandle = io.v();
HANDLE handles[2] = { sema, ioHandle };
DWORD r = WaitForMultipleObjects(ioHandle ? 2 : 1, handles, FALSE, INFINITE);
atomicCAS(signaled, 1, 0);
}
bool IOCondition::wait(nat msTimeout) {
DWORD result = WaitForSingleObject(sema, msTimeout);
if (result == WAIT_OBJECT_0) {
atomicCAS(signaled, 1, 0);
return true;
} else {
return false;
}
}
bool IOCondition::wait(IOHandle &io, nat msTimeout) {
HANDLE ioHandle = io.v();
HANDLE handles[2] = { sema, ioHandle };
DWORD result = WaitForMultipleObjects(ioHandle ? 2 : 1, handles, FALSE, msTimeout);
if (result == WAIT_OBJECT_0 || result == WAIT_OBJECT_0+1) {
atomicCAS(signaled, 1, 0);
return true;
} else {
return false;
}
}
#endif
#ifdef POSIX
IOCondition::IOCondition() : signaled(0), fd(-1) {
fd = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
}
IOCondition::~IOCondition() {
close(fd);
}
void IOCondition::signal() {
if (atomicCAS(signaled, 0, 1) == 0) {
uint64_t val = 1;
while (true) {
ssize_t r = write(fd, &val, 8);
if (r >= 0)
break;
if (errno == EAGAIN || errno == EINTR)
continue;
perror("Failed to signal eventfd");
}
}
}
bool IOCondition::doWait(struct pollfd *fds, size_t fdCount, int timeout) {
fds[0].fd = fd;
fds[0].events = POLLIN;
fds[0].revents = 0;
int result = -1;
while (result < 0) {
result = poll(fds, fdCount, timeout);
if (result < 0) {
if (errno == EINTR) {
// TODO: We could make a better estimation.
if (timeout > 0)
timeout = 0;
continue;
}
perror("poll");
assert(false);
}
}
if (result) {
// Some entry is done. If it is entry #0, we want to read it so that it is not signaled anymore.
if (fds[0].revents != 0) {
uint64_t v = 0;
ssize_t r = read(fd, &v, 8);
if (r <= 0)
perror("Failed to read from eventfd");
}
}
// Now that we're done messing with the eventfd, we need to tell the world that they need to
// signal the eventfd if they try to wake us again.
atomicWrite(signaled, 0);
// 'result == 0' => timeout, otherwise something interesting happened.
return result != 0;
}
void IOCondition::wait() {
struct pollfd wait;
doWait(&wait, 1, -1);
}
void IOCondition::wait(IOHandle &io) {
IOHandle::Desc desc = io.desc();
doWait(desc.fds, desc.count, -1);
}
bool IOCondition::wait(nat msTimeout) {
msTimeout = min(msTimeout, nat(std::numeric_limits<int>::max()));
struct pollfd wait;
return doWait(&wait, 1, msTimeout);
}
bool IOCondition::wait(IOHandle &io, nat msTimeout) {
IOHandle::Desc desc = io.desc();
return doWait(desc.fds, desc.count, msTimeout);
}
#endif
}
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