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Implement non-blocking I/O on Windows.

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This commit is contained in:
Martin Ling 2013-11-25 11:47:19 +00:00
parent aac4d7f292
commit a3cb91f5e1
1 changed files with 87 additions and 3 deletions
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90
serialport.c
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@ -63,6 +63,9 @@ struct sp_port {
int nonblocking;
#ifdef _WIN32
HANDLE hdl;
OVERLAPPED write_ovl;
BYTE *write_buf;
BOOL writing;
#else
int fd;
#endif
@ -583,6 +586,7 @@ enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
#ifdef _WIN32
DWORD desired_access = 0, flags_and_attributes = 0;
COMMTIMEOUTS timeouts;
char *escaped_port_name;
/* Prefix port name with '\\.\' to work with ports above COM9. */
@ -606,6 +610,31 @@ enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
if (port->hdl == INVALID_HANDLE_VALUE)
RETURN_FAIL("CreateFile() failed");
/* All timeouts disabled. */
timeouts.ReadIntervalTimeout = 0;
timeouts.ReadTotalTimeoutMultiplier = 0;
timeouts.ReadTotalTimeoutConstant = 0;
timeouts.WriteTotalTimeoutMultiplier = 0;
timeouts.WriteTotalTimeoutConstant = 0;
if (port->nonblocking) {
/* Set read timeout such that all reads return immediately. */
timeouts.ReadIntervalTimeout = MAXDWORD;
/* Prepare OVERLAPPED structure for non-blocking writes. */
memset(&port->write_ovl, 0, sizeof(port->write_ovl));
if (!(port->write_ovl.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL))) {
sp_close(port);
RETURN_FAIL("CreateEvent() failed");
}
port->write_buf = NULL;
port->writing = FALSE;
}
if (SetCommTimeouts(port->hdl, &timeouts) == 0) {
sp_close(port);
RETURN_FAIL("SetCommTimeouts() failed");
}
#else
int flags_local = 0;
struct port_data data;
@ -668,6 +697,14 @@ enum sp_return sp_close(struct sp_port *port)
if (CloseHandle(port->hdl) == 0)
RETURN_FAIL("CloseHandle() failed");
port->hdl = INVALID_HANDLE_VALUE;
if (port->nonblocking) {
if (port->writing)
/* Write should have been stopped by closing the port, so safe to free buffer. */
free(port->write_buf);
/* Close event handle created for overlapped writes. */
if (CloseHandle(port->write_ovl.hEvent) == 0)
RETURN_FAIL("CloseHandle() failed");
}
#else
/* Returns 0 upon success, -1 upon failure. */
if (close(port->fd) == -1)
@ -749,12 +786,59 @@ enum sp_return sp_write(struct sp_port *port, const void *buf, size_t count)
DEBUG("Writing up to %d bytes to port %s", count, port->name);
if (count == 0)
RETURN_VALUE("0", 0);
#ifdef _WIN32
DWORD written = 0;
/* Returns non-zero upon success, 0 upon failure. */
if (WriteFile(port->hdl, buf, count, &written, NULL) == 0)
RETURN_FAIL("WriteFile() failed");
if (port->nonblocking) {
/* Non-blocking write. */
/* Check whether previous write is complete. */
if (port->writing) {
if (HasOverlappedIoCompleted(&port->write_ovl)) {
DEBUG("Previous write completed");
port->writing = 0;
free(port->write_buf);
port->write_buf = NULL;
} else {
DEBUG("Previous write not complete");
/* Can't take a new write until the previous one finishes. */
RETURN_VALUE("0", 0);
}
}
/* Copy user buffer. */
if (!(port->write_buf = malloc(count)))
RETURN_ERROR(SP_ERR_MEM, "buffer copy malloc failed");
memcpy(port->write_buf, buf, count);
/* Start asynchronous write. */
if (WriteFile(port->hdl, buf, count, NULL, &port->write_ovl) == 0) {
if (GetLastError() == ERROR_IO_PENDING) {
DEBUG("Asynchronous write started");
port->writing = 1;
RETURN_VALUE("%d", count);
} else {
free(port->write_buf);
port->write_buf = NULL;
/* Actual failure of some kind. */
RETURN_FAIL("WriteFile() failed");
}
} else {
DEBUG("Write completed immediately");
free(port->write_buf);
port->write_buf = NULL;
RETURN_VALUE("%d", count);
}
} else {
/* Blocking write. */
if (WriteFile(port->hdl, buf, count, &written, NULL) == 0) {
RETURN_FAIL("WriteFile() failed");
}
}
RETURN_VALUE("%d", written);
#else
/* Returns the number of bytes written, or -1 upon failure. */