windows: Avoid unnecessary calls to SetCommTimeouts().

[libserialport.git] / serialport.c

diff --git a/serialport.c b/serialport.c
index aaa609545b20675343b7445fd2e0ccc9716d4b2b..e624f717858ee5cf88755ea50cb1dae4d78760f9 100644 (file)
--- a/serialport.c
+++ b/serialport.c
@@ -751,9 +751,11 @@ SP_API enum sp_return sp_blocking_write(struct sp_port *port, const void *buf,
        }
 
        /* Set timeout. */
-       port->timeouts.WriteTotalTimeoutConstant = timeout_ms;
-       if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-               RETURN_FAIL("SetCommTimeouts() failed");
+       if (port->timeouts.WriteTotalTimeoutConstant != timeout_ms) {
+               port->timeouts.WriteTotalTimeoutConstant = timeout_ms;
+               if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+                       RETURN_FAIL("SetCommTimeouts() failed");
+       }
 
        /* Start write. */
        if (WriteFile(port->hdl, buf, count, NULL, &port->write_ovl) == 0) {
@@ -864,9 +866,11 @@ SP_API enum sp_return sp_nonblocking_write(struct sp_port *port,
        }
 
        /* Set timeout. */
-       port->timeouts.WriteTotalTimeoutConstant = 0;
-       if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-               RETURN_FAIL("SetCommTimeouts() failed");
+       if (port->timeouts.WriteTotalTimeoutConstant != 0) {
+               port->timeouts.WriteTotalTimeoutConstant = 0;
+               if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+                       RETURN_FAIL("SetCommTimeouts() failed");
+       }
 
        /*
         * Keep writing data until the OS has to actually start an async IO
@@ -939,10 +943,13 @@ SP_API enum sp_return sp_blocking_read(struct sp_port *port, void *buf,
        int ret;
 
        /* Set timeout. */
-       port->timeouts.ReadIntervalTimeout = 0;
-       port->timeouts.ReadTotalTimeoutConstant = timeout_ms;
-       if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-               RETURN_FAIL("SetCommTimeouts() failed");
+       if (port->timeouts.ReadIntervalTimeout != 0 ||
+                       port->timeouts.ReadTotalTimeoutConstant != timeout_ms) {
+               port->timeouts.ReadIntervalTimeout = 0;
+               port->timeouts.ReadTotalTimeoutConstant = timeout_ms;
+               if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+                       RETURN_FAIL("SetCommTimeouts() failed");
+       }
 
        /* Start read. */
        if (ReadFile(port->hdl, buf, count, NULL, &port->read_ovl) == 0) {
@@ -1051,10 +1058,13 @@ SP_API enum sp_return sp_nonblocking_read(struct sp_port *port, void *buf,
        int ret;
 
        /* Set timeout. */
-       port->timeouts.ReadIntervalTimeout = MAXDWORD;
-       port->timeouts.ReadTotalTimeoutConstant = 0;
-       if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-               RETURN_FAIL("SetCommTimeouts() failed");
+       if (port->timeouts.ReadIntervalTimeout != MAXDWORD ||
+                       port->timeouts.ReadTotalTimeoutConstant != 0) {
+               port->timeouts.ReadIntervalTimeout = MAXDWORD;
+               port->timeouts.ReadTotalTimeoutConstant = 0;
+               if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+                       RETURN_FAIL("SetCommTimeouts() failed");
+       }
 
        /* Do read. */
        if (ReadFile(port->hdl, buf, count, NULL, &port->read_ovl) == 0)