X-Git-Url: https://sigrok.org/gitweb/?p=libserialport.git;a=blobdiff_plain;f=serialport.c;h=e6097eeda975f914ec7b960f72c9e2df546e8281;hp=9671731b58fdaf56a7e3ced53d7870584424ae30;hb=HEAD;hpb=5a8810e2b2e0ccd2567306469f7fc668337af415

diff --git a/serialport.c b/serialport.c
index 9671731..1b5a95e 100644
--- a/serialport.c
+++ b/serialport.c
@@ -2,8 +2,8 @@
  * This file is part of the libserialport project.
  *
  * Copyright (C) 2010-2012 Bert Vermeulen <bert@biot.com>
- * Copyright (C) 2010-2012 Uwe Hermann <uwe@hermann-uwe.de>
- * Copyright (C) 2013 Martin Ling <martin-libserialport@earth.li>
+ * Copyright (C) 2010-2015 Uwe Hermann <uwe@hermann-uwe.de>
+ * Copyright (C) 2013-2015 Martin Ling <martin-libserialport@earth.li>
  * Copyright (C) 2013 Matthias Heidbrink <m-sigrok@heidbrink.biz>
  * Copyright (C) 2014 Aurelien Jacobs <aurel@gnuage.org>
  *
@@ -21,10 +21,9 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "libserialport.h"
 #include "libserialport_internal.h"
 
-const struct std_baudrate std_baudrates[] = {
+static const struct std_baudrate std_baudrates[] = {
 #ifdef _WIN32
 	/*
 	 * The baudrates 50/75/134/150/200/1800/230400/460800 do not seem to
@@ -44,6 +43,8 @@ const struct std_baudrate std_baudrates[] = {
 #endif
 };
 
+#define NUM_STD_BAUDRATES ARRAY_SIZE(std_baudrates)
+
 void (*sp_debug_handler)(const char *format, ...) = sp_default_debug_handler;
 
 static enum sp_return get_config(struct sp_port *port, struct port_data *data,
@@ -58,7 +59,7 @@ SP_API enum sp_return sp_get_port_by_name(const char *portname, struct sp_port *
 #ifndef NO_PORT_METADATA
 	enum sp_return ret;
 #endif
-	int len;
+	size_t len;
 
 	TRACE("%s, %p", portname, port_ptr);
 
@@ -70,7 +71,21 @@ SP_API enum sp_return sp_get_port_by_name(const char *portname, struct sp_port *
 	if (!portname)
 		RETURN_ERROR(SP_ERR_ARG, "Null port name");
 
-	DEBUG("Building structure for port %s", portname);
+	DEBUG_FMT("Building structure for port %s", portname);
+
+#if !defined(_WIN32) && defined(HAVE_REALPATH)
+	/*
+	 * get_port_details() below tries to be too smart and figure out
+	 * some transport properties from the port name which breaks with
+	 * symlinks. Therefore we canonicalize the portname first.
+	 */
+	char pathbuf[PATH_MAX + 1];
+	char *res = realpath(portname, pathbuf);
+	if (!res)
+		RETURN_ERROR(SP_ERR_ARG, "Could not retrieve realpath behind port name");
+
+	portname = pathbuf;
+#endif
 
 	if (!(port = malloc(sizeof(struct sp_port))))
 		RETURN_ERROR(SP_ERR_MEM, "Port structure malloc failed");
@@ -85,7 +100,10 @@ SP_API enum sp_return sp_get_port_by_name(const char *portname, struct sp_port *
 	memcpy(port->name, portname, len);
 
 #ifdef _WIN32
+	port->usb_path = NULL;
 	port->hdl = INVALID_HANDLE_VALUE;
+	port->write_buf = NULL;
+	port->write_buf_size = 0;
 #else
 	port->fd = -1;
 #endif
@@ -120,27 +138,24 @@ SP_API char *sp_get_port_name(const struct sp_port *port)
 	if (!port)
 		return NULL;
 
-	RETURN_VALUE("%s", port->name);
+	RETURN_STRING(port->name);
 }
 
-SP_API char *sp_get_port_description(struct sp_port *port)
+SP_API char *sp_get_port_description(const struct sp_port *port)
 {
 	TRACE("%p", port);
 
 	if (!port || !port->description)
 		return NULL;
 
-	RETURN_VALUE("%s", port->description);
+	RETURN_STRING(port->description);
 }
 
-SP_API enum sp_transport sp_get_port_transport(struct sp_port *port)
+SP_API enum sp_transport sp_get_port_transport(const struct sp_port *port)
 {
 	TRACE("%p", port);
 
-	if (!port)
-		RETURN_ERROR(SP_ERR_ARG, "Null port");
-
-	RETURN_VALUE("%d", port->transport);
+	RETURN_INT(port ? port->transport : SP_TRANSPORT_NATIVE);
 }
 
 SP_API enum sp_return sp_get_port_usb_bus_address(const struct sp_port *port,
@@ -155,8 +170,10 @@ SP_API enum sp_return sp_get_port_usb_bus_address(const struct sp_port *port,
 	if (port->usb_bus < 0 || port->usb_address < 0)
 		RETURN_ERROR(SP_ERR_SUPP, "Bus and address values are not available");
 
-	if (usb_bus)      *usb_bus     = port->usb_bus;
-	if (usb_address)  *usb_address = port->usb_address;
+	if (usb_bus)
+		*usb_bus = port->usb_bus;
+	if (usb_address)
+		*usb_address = port->usb_address;
 
 	RETURN_OK();
 }
@@ -173,8 +190,10 @@ SP_API enum sp_return sp_get_port_usb_vid_pid(const struct sp_port *port,
 	if (port->usb_vid < 0 || port->usb_pid < 0)
 		RETURN_ERROR(SP_ERR_SUPP, "VID:PID values are not available");
 
-	if (usb_vid)  *usb_vid = port->usb_vid;
-	if (usb_pid)  *usb_pid = port->usb_pid;
+	if (usb_vid)
+		*usb_vid = port->usb_vid;
+	if (usb_pid)
+		*usb_pid = port->usb_pid;
 
 	RETURN_OK();
 }
@@ -186,7 +205,7 @@ SP_API char *sp_get_port_usb_manufacturer(const struct sp_port *port)
 	if (!port || port->transport != SP_TRANSPORT_USB || !port->usb_manufacturer)
 		return NULL;
 
-	RETURN_VALUE("%s", port->usb_manufacturer);
+	RETURN_STRING(port->usb_manufacturer);
 }
 
 SP_API char *sp_get_port_usb_product(const struct sp_port *port)
@@ -196,7 +215,7 @@ SP_API char *sp_get_port_usb_product(const struct sp_port *port)
 	if (!port || port->transport != SP_TRANSPORT_USB || !port->usb_product)
 		return NULL;
 
-	RETURN_VALUE("%s", port->usb_product);
+	RETURN_STRING(port->usb_product);
 }
 
 SP_API char *sp_get_port_usb_serial(const struct sp_port *port)
@@ -206,7 +225,7 @@ SP_API char *sp_get_port_usb_serial(const struct sp_port *port)
 	if (!port || port->transport != SP_TRANSPORT_USB || !port->usb_serial)
 		return NULL;
 
-	RETURN_VALUE("%s", port->usb_serial);
+	RETURN_STRING(port->usb_serial);
 }
 
 SP_API char *sp_get_port_bluetooth_address(const struct sp_port *port)
@@ -217,7 +236,7 @@ SP_API char *sp_get_port_bluetooth_address(const struct sp_port *port)
 	    || !port->bluetooth_address)
 		return NULL;
 
-	RETURN_VALUE("%s", port->bluetooth_address);
+	RETURN_STRING(port->bluetooth_address);
 }
 
 SP_API enum sp_return sp_get_port_handle(const struct sp_port *port,
@@ -227,6 +246,8 @@ SP_API enum sp_return sp_get_port_handle(const struct sp_port *port,
 
 	if (!port)
 		RETURN_ERROR(SP_ERR_ARG, "Null port");
+	if (!result_ptr)
+		RETURN_ERROR(SP_ERR_ARG, "Null result pointer");
 
 #ifdef _WIN32
 	HANDLE *handle_ptr = result_ptr;
@@ -257,7 +278,7 @@ SP_API enum sp_return sp_copy_port(const struct sp_port *port,
 
 	DEBUG("Copying port structure");
 
-	RETURN_VALUE("%p", sp_get_port_by_name(port->name, copy_ptr));
+	RETURN_INT(sp_get_port_by_name(port->name, copy_ptr));
 }
 
 SP_API void sp_free_port(struct sp_port *port)
@@ -286,6 +307,8 @@ SP_API void sp_free_port(struct sp_port *port)
 #ifdef _WIN32
 	if (port->usb_path)
 		free(port->usb_path);
+	if (port->write_buf)
+		free(port->write_buf);
 #endif
 
 	free(port);
@@ -297,9 +320,10 @@ SP_PRIV struct sp_port **list_append(struct sp_port **list,
                                      const char *portname)
 {
 	void *tmp;
-	unsigned int count;
+	size_t count;
 
-	for (count = 0; list[count]; count++);
+	for (count = 0; list[count]; count++)
+		;
 	if (!(tmp = realloc(list, sizeof(struct sp_port *) * (count + 2))))
 		goto fail;
 	list = tmp;
@@ -315,39 +339,39 @@ fail:
 
 SP_API enum sp_return sp_list_ports(struct sp_port ***list_ptr)
 {
+#ifndef NO_ENUMERATION
 	struct sp_port **list;
 	int ret;
+#endif
 
 	TRACE("%p", list_ptr);
 
 	if (!list_ptr)
 		RETURN_ERROR(SP_ERR_ARG, "Null result pointer");
 
+	*list_ptr = NULL;
+
+#ifdef NO_ENUMERATION
+	RETURN_ERROR(SP_ERR_SUPP, "Enumeration not supported on this platform");
+#else
 	DEBUG("Enumerating ports");
 
-	if (!(list = malloc(sizeof(struct sp_port **))))
+	if (!(list = malloc(sizeof(struct sp_port *))))
 		RETURN_ERROR(SP_ERR_MEM, "Port list malloc failed");
 
 	list[0] = NULL;
 
-#ifdef NO_ENUMERATION
-	ret = SP_ERR_SUPP;
-#else
 	ret = list_ports(&list);
-#endif
 
-	switch (ret) {
-	case SP_OK:
+	if (ret == SP_OK) {
 		*list_ptr = list;
-		RETURN_OK();
-	case SP_ERR_SUPP:
-		DEBUG_ERROR(SP_ERR_SUPP, "Enumeration not supported on this platform");
-	default:
-		if (list)
-			sp_free_port_list(list);
+	} else {
+		sp_free_port_list(list);
 		*list_ptr = NULL;
-		return ret;
 	}
+
+	RETURN_CODEVAL(ret);
+#endif
 }
 
 SP_API void sp_free_port_list(struct sp_port **list)
@@ -371,20 +395,20 @@ SP_API void sp_free_port_list(struct sp_port **list)
 }
 
 #define CHECK_PORT() do { \
-	if (port == NULL) \
+	if (!port) \
 		RETURN_ERROR(SP_ERR_ARG, "Null port"); \
-	if (port->name == NULL) \
+	if (!port->name) \
 		RETURN_ERROR(SP_ERR_ARG, "Null port name"); \
 } while (0)
 #ifdef _WIN32
 #define CHECK_PORT_HANDLE() do { \
 	if (port->hdl == INVALID_HANDLE_VALUE) \
-		RETURN_ERROR(SP_ERR_ARG, "Invalid port handle"); \
+		RETURN_ERROR(SP_ERR_ARG, "Port not open"); \
 } while (0)
 #else
 #define CHECK_PORT_HANDLE() do { \
 	if (port->fd < 0) \
-		RETURN_ERROR(SP_ERR_ARG, "Invalid port fd"); \
+		RETURN_ERROR(SP_ERR_ARG, "Port not open"); \
 } while (0)
 #endif
 #define CHECK_OPEN_PORT() do { \
@@ -392,6 +416,43 @@ SP_API void sp_free_port_list(struct sp_port **list)
 	CHECK_PORT_HANDLE(); \
 } while (0)
 
+#ifdef WIN32
+/** To be called after port receive buffer is emptied. */
+static enum sp_return restart_wait(struct sp_port *port)
+{
+	DWORD wait_result;
+
+	if (port->wait_running) {
+		/* Check status of running wait operation. */
+		if (GetOverlappedResult(port->hdl, &port->wait_ovl,
+				&wait_result, FALSE)) {
+			DEBUG("Previous wait completed");
+			port->wait_running = FALSE;
+		} else if (GetLastError() == ERROR_IO_INCOMPLETE) {
+			DEBUG("Previous wait still running");
+			RETURN_OK();
+		} else {
+			RETURN_FAIL("GetOverlappedResult() failed");
+		}
+	}
+
+	if (!port->wait_running) {
+		/* Start new wait operation. */
+		if (WaitCommEvent(port->hdl, &port->events,
+				&port->wait_ovl)) {
+			DEBUG("New wait returned, events already pending");
+		} else if (GetLastError() == ERROR_IO_PENDING) {
+			DEBUG("New wait running in background");
+			port->wait_running = TRUE;
+		} else {
+			RETURN_FAIL("WaitCommEvent() failed");
+		}
+	}
+
+	RETURN_OK();
+}
+#endif
+
 SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 {
 	struct port_data data;
@@ -402,10 +463,10 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 
 	CHECK_PORT();
 
-	if (flags > (SP_MODE_READ | SP_MODE_WRITE))
+	if (flags > SP_MODE_READ_WRITE)
 		RETURN_ERROR(SP_ERR_ARG, "Invalid flags");
 
-	DEBUG("Opening port %s", port->name);
+	DEBUG_FMT("Opening port %s", port->name);
 
 #ifdef _WIN32
 	DWORD desired_access = 0, flags_and_attributes = 0, errors;
@@ -424,13 +485,13 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 	if (flags & SP_MODE_WRITE)
 		desired_access |= GENERIC_WRITE;
 
-	port->hdl = CreateFile(escaped_port_name, desired_access, 0, 0,
+	port->hdl = CreateFileA(escaped_port_name, desired_access, 0, 0,
 			 OPEN_EXISTING, flags_and_attributes, 0);
 
 	free(escaped_port_name);
 
 	if (port->hdl == INVALID_HANDLE_VALUE)
-		RETURN_FAIL("port CreateFile() failed");
+		RETURN_FAIL("Port CreateFile() failed");
 
 	/* All timeouts initially disabled. */
 	port->timeouts.ReadIntervalTimeout = 0;
@@ -465,21 +526,20 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 		RETURN_FAIL("SetCommMask() failed");
 	}
 
-	/* Start background operation for RX and error events. */
-	if (WaitCommEvent(port->hdl, &port->events, &port->wait_ovl) == 0) {
-		if (GetLastError() != ERROR_IO_PENDING) {
-			sp_close(port);
-			RETURN_FAIL("WaitCommEvent() failed");
-		}
-	}
-
 	port->writing = FALSE;
+	port->wait_running = FALSE;
 
+	ret = restart_wait(port);
+
+	if (ret < 0) {
+		sp_close(port);
+		RETURN_CODEVAL(ret);
+	}
 #else
-	int flags_local = O_NONBLOCK | O_NOCTTY;
+	int flags_local = O_NONBLOCK | O_NOCTTY | O_CLOEXEC;
 
 	/* Map 'flags' to the OS-specific settings. */
-	if (flags & (SP_MODE_READ | SP_MODE_WRITE))
+	if ((flags & SP_MODE_READ_WRITE) == SP_MODE_READ_WRITE)
 		flags_local |= O_RDWR;
 	else if (flags & SP_MODE_READ)
 		flags_local |= O_RDONLY;
@@ -488,6 +548,39 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 
 	if ((port->fd = open(port->name, flags_local)) < 0)
 		RETURN_FAIL("open() failed");
+
+	/*
+	 * On POSIX in the default case the file descriptor of a serial port
+	 * is not opened exclusively. Therefore the settings of a port are
+	 * overwritten if the serial port is opened a second time. Windows
+	 * opens all serial ports exclusively.
+	 * So the idea is to open the serial ports alike in the exclusive mode.
+	 *
+	 * ioctl(*, TIOCEXCL) defines the file descriptor as exclusive. So all
+	 * further open calls on the serial port will fail.
+	 *
+	 * There is a race condition if two processes open the same serial
+	 * port. None of the processes will notice the exclusive ownership of
+	 * the other process because ioctl() doesn't return an error code if
+	 * the file descriptor is already marked as exclusive.
+	 * This can be solved with flock(). It returns an error if the file
+	 * descriptor is already locked by another process.
+	 */
+#ifdef HAVE_FLOCK
+	if (flock(port->fd, LOCK_EX | LOCK_NB) < 0)
+		RETURN_FAIL("flock() failed");
+#endif
+
+#ifdef TIOCEXCL
+	/*
+	 * Before Linux 3.8 ioctl(*, TIOCEXCL) was not implemented and could
+	 * lead to EINVAL or ENOTTY.
+	 * These errors aren't fatal and can be ignored.
+	 */
+	if (ioctl(port->fd, TIOCEXCL) < 0 && errno != EINVAL && errno != ENOTTY)
+		RETURN_FAIL("ioctl() failed");
+#endif
+
 #endif
 
 	ret = get_config(port, &data, &config);
@@ -497,13 +590,22 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 		RETURN_CODEVAL(ret);
 	}
 
+	/*
+	 * Assume a default baudrate if the OS does not provide one.
+	 * Cannot assign -1 here since Windows holds the baudrate in
+	 * the DCB and does not configure the rate individually.
+	 */
+	if (config.baudrate == 0) {
+		config.baudrate = 9600;
+	}
+
 	/* Set sane port settings. */
 #ifdef _WIN32
 	data.dcb.fBinary = TRUE;
 	data.dcb.fDsrSensitivity = FALSE;
 	data.dcb.fErrorChar = FALSE;
 	data.dcb.fNull = FALSE;
-	data.dcb.fAbortOnError = TRUE;
+	data.dcb.fAbortOnError = FALSE;
 #else
 	/* Turn off all fancy termios tricks, give us a raw channel. */
 	data.term.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IMAXBEL);
@@ -540,7 +642,8 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum sp_mode flags)
 	data.term.c_cc[VTIME] = 0;
 
 	/* Ignore modem status lines; enable receiver; leave control lines alone on close. */
-	data.term.c_cflag |= (CLOCAL | CREAD | HUPCL);
+	data.term.c_cflag |= (CLOCAL | CREAD);
+	data.term.c_cflag &= ~(HUPCL);
 #endif
 
 #ifdef _WIN32
@@ -564,12 +667,12 @@ SP_API enum sp_return sp_close(struct sp_port *port)
 
 	CHECK_OPEN_PORT();
 
-	DEBUG("Closing port %s", port->name);
+	DEBUG_FMT("Closing port %s", port->name);
 
 #ifdef _WIN32
 	/* Returns non-zero upon success, 0 upon failure. */
 	if (CloseHandle(port->hdl) == 0)
-		RETURN_FAIL("port CloseHandle() failed");
+		RETURN_FAIL("Port CloseHandle() failed");
 	port->hdl = INVALID_HANDLE_VALUE;
 
 	/* Close event handles for overlapped structures. */
@@ -582,6 +685,10 @@ SP_API enum sp_return sp_close(struct sp_port *port)
 	CLOSE_OVERLAPPED(write_ovl);
 	CLOSE_OVERLAPPED(wait_ovl);
 
+	if (port->write_buf) {
+		free(port->write_buf);
+		port->write_buf = NULL;
+	}
 #else
 	/* Returns 0 upon success, -1 upon failure. */
 	if (close(port->fd) == -1)
@@ -603,7 +710,8 @@ SP_API enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers)
 
 	const char *buffer_names[] = {"no", "input", "output", "both"};
 
-	DEBUG("Flushing %s buffers on port %s", buffer_names[buffers], port->name);
+	DEBUG_FMT("Flushing %s buffers on port %s",
+		buffer_names[buffers], port->name);
 
 #ifdef _WIN32
 	DWORD flags = 0;
@@ -615,13 +723,16 @@ SP_API enum sp_return sp_flush(struct sp_port *port, enum sp_buffer buffers)
 	/* Returns non-zero upon success, 0 upon failure. */
 	if (PurgeComm(port->hdl, flags) == 0)
 		RETURN_FAIL("PurgeComm() failed");
+
+	if (buffers & SP_BUF_INPUT)
+		TRY(restart_wait(port));
 #else
 	int flags = 0;
-	if (buffers & SP_BUF_BOTH)
+	if (buffers == SP_BUF_BOTH)
 		flags = TCIOFLUSH;
-	else if (buffers & SP_BUF_INPUT)
+	else if (buffers == SP_BUF_INPUT)
 		flags = TCIFLUSH;
-	else if (buffers & SP_BUF_OUTPUT)
+	else if (buffers == SP_BUF_OUTPUT)
 		flags = TCOFLUSH;
 
 	/* Returns 0 upon success, -1 upon failure. */
@@ -637,7 +748,7 @@ SP_API enum sp_return sp_drain(struct sp_port *port)
 
 	CHECK_OPEN_PORT();
 
-	DEBUG("Draining port %s", port->name);
+	DEBUG_FMT("Draining port %s", port->name);
 
 #ifdef _WIN32
 	/* Returns non-zero upon success, 0 upon failure. */
@@ -647,7 +758,9 @@ SP_API enum sp_return sp_drain(struct sp_port *port)
 #else
 	int result;
 	while (1) {
-#ifdef __ANDROID__
+#if defined(__ANDROID__) && (__ANDROID_API__ < 21)
+		/* Android only has tcdrain from platform 21 onwards.
+		 * On previous API versions, use the ioctl directly. */
 		int arg = 1;
 		result = ioctl(port->fd, TCSBRK, &arg);
 #else
@@ -667,89 +780,129 @@ SP_API enum sp_return sp_drain(struct sp_port *port)
 #endif
 }
 
+#ifdef _WIN32
+static enum sp_return await_write_completion(struct sp_port *port)
+{
+	TRACE("%p", port);
+	DWORD bytes_written;
+	BOOL result;
+
+	/* Wait for previous non-blocking write to complete, if any. */
+	if (port->writing) {
+		DEBUG("Waiting for previous write to complete");
+		result = GetOverlappedResult(port->hdl, &port->write_ovl, &bytes_written, TRUE);
+		port->writing = 0;
+		if (!result)
+			RETURN_FAIL("Previous write failed to complete");
+		DEBUG("Previous write completed");
+	}
+
+	RETURN_OK();
+}
+#endif
+
 SP_API enum sp_return sp_blocking_write(struct sp_port *port, const void *buf,
-                                        size_t count, unsigned int timeout)
+                                        size_t count, unsigned int timeout_ms)
 {
-	TRACE("%p, %p, %d, %d", port, buf, count, timeout);
+	TRACE("%p, %p, %d, %d", port, buf, count, timeout_ms);
 
 	CHECK_OPEN_PORT();
 
 	if (!buf)
 		RETURN_ERROR(SP_ERR_ARG, "Null buffer");
 
-	if (timeout)
-		DEBUG("Writing %d bytes to port %s, timeout %d ms", count, port->name, timeout);
+	if (timeout_ms)
+		DEBUG_FMT("Writing %d bytes to port %s, timeout %d ms",
+			count, port->name, timeout_ms);
 	else
-		DEBUG("Writing %d bytes to port %s, no timeout", count, port->name);
+		DEBUG_FMT("Writing %d bytes to port %s, no timeout",
+			count, port->name);
 
 	if (count == 0)
-		RETURN_VALUE("0", 0);
+		RETURN_INT(0);
 
 #ifdef _WIN32
-	DWORD bytes_written = 0;
-	BOOL result;
+	DWORD remaining_ms, write_size, bytes_written;
+	size_t remaining_bytes, total_bytes_written = 0;
+	const uint8_t *write_ptr = (uint8_t *) buf;
+	bool result;
+	struct timeout timeout;
 
-	/* Wait for previous non-blocking write to complete, if any. */
-	if (port->writing) {
-		DEBUG("Waiting for previous write to complete");
-		result = GetOverlappedResult(port->hdl, &port->write_ovl, &bytes_written, TRUE);
-		port->writing = 0;
-		if (!result)
-			RETURN_FAIL("Previous write failed to complete");
-		DEBUG("Previous write completed");
-	}
+	timeout_start(&timeout, timeout_ms);
 
-	/* Set timeout. */
-	port->timeouts.WriteTotalTimeoutConstant = timeout;
-	if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-		RETURN_FAIL("SetCommTimeouts() failed");
+	TRY(await_write_completion(port));
 
-	/* Start write. */
-	if (WriteFile(port->hdl, buf, count, NULL, &port->write_ovl) == 0) {
-		if (GetLastError() == ERROR_IO_PENDING) {
+	while (total_bytes_written < count) {
+
+		if (timeout_check(&timeout))
+			break;
+
+		remaining_ms = timeout_remaining_ms(&timeout);
+
+		if (port->timeouts.WriteTotalTimeoutConstant != remaining_ms) {
+			port->timeouts.WriteTotalTimeoutConstant = remaining_ms;
+			if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+				RETURN_FAIL("SetCommTimeouts() failed");
+		}
+
+		/* Reduce write size if it exceeds the WriteFile limit. */
+		remaining_bytes = count - total_bytes_written;
+		if (remaining_bytes > WRITEFILE_MAX_SIZE)
+			write_size = WRITEFILE_MAX_SIZE;
+		else
+			write_size = (DWORD) remaining_bytes;
+
+		/* Start write. */
+
+		result = WriteFile(port->hdl, write_ptr, write_size, NULL, &port->write_ovl);
+
+		timeout_update(&timeout);
+
+		if (result) {
+			DEBUG("Write completed immediately");
+			bytes_written = write_size;
+		} else if (GetLastError() == ERROR_IO_PENDING) {
 			DEBUG("Waiting for write to complete");
-			GetOverlappedResult(port->hdl, &port->write_ovl, &bytes_written, TRUE);
-			DEBUG("Write completed, %d/%d bytes written", bytes_written, count);
-			RETURN_VALUE("%d", bytes_written);
+			if (GetOverlappedResult(port->hdl, &port->write_ovl, &bytes_written, TRUE) == 0) {
+				if (GetLastError() == ERROR_SEM_TIMEOUT) {
+					DEBUG("Write timed out");
+					break;
+				} else {
+					RETURN_FAIL("GetOverlappedResult() failed");
+				}
+			}
+			DEBUG_FMT("Write completed, %d/%d bytes written", bytes_written, write_size);
 		} else {
 			RETURN_FAIL("WriteFile() failed");
 		}
-	} else {
-		DEBUG("Write completed immediately");
-		RETURN_VALUE("%d", count);
+
+		write_ptr += bytes_written;
+		total_bytes_written += bytes_written;
 	}
+
+	RETURN_INT((int) total_bytes_written);
 #else
 	size_t bytes_written = 0;
 	unsigned char *ptr = (unsigned char *) buf;
-	struct timeval start, delta, now, end = {0, 0};
+	struct timeout timeout;
 	fd_set fds;
-	int result;
+	ssize_t result;
 
-	if (timeout) {
-		/* Get time at start of operation. */
-		gettimeofday(&start, NULL);
-		/* Define duration of timeout. */
-		delta.tv_sec = timeout / 1000;
-		delta.tv_usec = (timeout % 1000) * 1000;
-		/* Calculate time at which we should give up. */
-		timeradd(&start, &delta, &end);
-	}
+	timeout_start(&timeout, timeout_ms);
+
+	FD_ZERO(&fds);
+	FD_SET(port->fd, &fds);
 
 	/* Loop until we have written the requested number of bytes. */
-	while (bytes_written < count)
-	{
-		/* Wait until space is available. */
-		FD_ZERO(&fds);
-		FD_SET(port->fd, &fds);
-		if (timeout) {
-			gettimeofday(&now, NULL);
-			if (timercmp(&now, &end, >)) {
-				DEBUG("write timed out");
-				RETURN_VALUE("%d", bytes_written);
-			}
-			timersub(&end, &now, &delta);
-		}
-		result = select(port->fd + 1, NULL, &fds, NULL, timeout ? &delta : NULL);
+	while (bytes_written < count) {
+
+		if (timeout_check(&timeout))
+			break;
+
+		result = select(port->fd + 1, NULL, &fds, NULL, timeout_timeval(&timeout));
+
+		timeout_update(&timeout);
+
 		if (result < 0) {
 			if (errno == EINTR) {
 				DEBUG("select() call was interrupted, repeating");
@@ -758,8 +911,8 @@ SP_API enum sp_return sp_blocking_write(struct sp_port *port, const void *buf,
 				RETURN_FAIL("select() failed");
 			}
 		} else if (result == 0) {
-			DEBUG("write timed out");
-			RETURN_VALUE("%d", bytes_written);
+			/* Timeout has expired. */
+			break;
 		}
 
 		/* Do write. */
@@ -778,7 +931,10 @@ SP_API enum sp_return sp_blocking_write(struct sp_port *port, const void *buf,
 		ptr += result;
 	}
 
-	RETURN_VALUE("%d", bytes_written);
+	if (bytes_written < count)
+		DEBUG("Write timed out");
+
+	RETURN_INT(bytes_written);
 #endif
 }
 
@@ -792,14 +948,13 @@ SP_API enum sp_return sp_nonblocking_write(struct sp_port *port,
 	if (!buf)
 		RETURN_ERROR(SP_ERR_ARG, "Null buffer");
 
-	DEBUG("Writing up to %d bytes to port %s", count, port->name);
+	DEBUG_FMT("Writing up to %d bytes to port %s", count, port->name);
 
 	if (count == 0)
-		RETURN_VALUE("0", 0);
+		RETURN_INT(0);
 
 #ifdef _WIN32
-	DWORD written = 0;
-	BYTE *ptr = (BYTE *) buf;
+	size_t buf_bytes;
 
 	/* Check whether previous write is complete. */
 	if (port->writing) {
@@ -809,139 +964,151 @@ SP_API enum sp_return sp_nonblocking_write(struct sp_port *port,
 		} else {
 			DEBUG("Previous write not complete");
 			/* Can't take a new write until the previous one finishes. */
-			RETURN_VALUE("0", 0);
+			RETURN_INT(0);
 		}
 	}
 
 	/* 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 for it.
-	 * At that point we know the buffer is full. */
-	while (written < count)
-	{
-		/* Copy first byte of user buffer. */
-		port->pending_byte = *ptr++;
-
-		/* Start asynchronous write. */
-		if (WriteFile(port->hdl, &port->pending_byte, 1, NULL, &port->write_ovl) == 0) {
-			if (GetLastError() == ERROR_IO_PENDING) {
-				if (HasOverlappedIoCompleted(&port->write_ovl)) {
-					DEBUG("Asynchronous write completed immediately");
-					port->writing = 0;
-					written++;
-					continue;
-				} else {
-					DEBUG("Asynchronous write running");
-					port->writing = 1;
-					RETURN_VALUE("%d", ++written);
-				}
-			} else {
-				/* Actual failure of some kind. */
-				RETURN_FAIL("WriteFile() failed");
-			}
+	/* Reduce count if it exceeds the WriteFile limit. */
+	if (count > WRITEFILE_MAX_SIZE)
+		count = WRITEFILE_MAX_SIZE;
+
+	/* Copy data to our write buffer. */
+	buf_bytes = min(port->write_buf_size, count);
+	memcpy(port->write_buf, buf, buf_bytes);
+
+	/* Start asynchronous write. */
+	if (WriteFile(port->hdl, port->write_buf, (DWORD) buf_bytes, NULL, &port->write_ovl) == 0) {
+		if (GetLastError() == ERROR_IO_PENDING) {
+			if ((port->writing = !HasOverlappedIoCompleted(&port->write_ovl)))
+				DEBUG("Asynchronous write completed immediately");
+			else
+				DEBUG("Asynchronous write running");
 		} else {
-			DEBUG("Single byte written immediately");
-			written++;
+			/* Actual failure of some kind. */
+			RETURN_FAIL("WriteFile() failed");
 		}
 	}
 
 	DEBUG("All bytes written immediately");
 
-	RETURN_VALUE("%d", written);
+	RETURN_INT((int) buf_bytes);
 #else
 	/* Returns the number of bytes written, or -1 upon failure. */
 	ssize_t written = write(port->fd, buf, count);
 
-	if (written < 0)
-		RETURN_FAIL("write() failed");
-	else
-		RETURN_VALUE("%d", written);
+	if (written < 0) {
+		if (errno == EAGAIN)
+			// Buffer is full, no bytes written.
+			RETURN_INT(0);
+		else
+			RETURN_FAIL("write() failed");
+	} else {
+		RETURN_INT(written);
+	}
 #endif
 }
 
+#ifdef _WIN32
+/* Restart wait operation if buffer was emptied. */
+static enum sp_return restart_wait_if_needed(struct sp_port *port, unsigned int bytes_read)
+{
+	DWORD errors;
+	COMSTAT comstat;
+
+	if (bytes_read == 0)
+		RETURN_OK();
+
+	if (ClearCommError(port->hdl, &errors, &comstat) == 0)
+		RETURN_FAIL("ClearCommError() failed");
+
+	if (comstat.cbInQue == 0)
+		TRY(restart_wait(port));
+
+	RETURN_OK();
+}
+#endif
+
 SP_API enum sp_return sp_blocking_read(struct sp_port *port, void *buf,
-                                       size_t count, unsigned int timeout)
+                                       size_t count, unsigned int timeout_ms)
 {
-	TRACE("%p, %p, %d, %d", port, buf, count, timeout);
+	TRACE("%p, %p, %d, %d", port, buf, count, timeout_ms);
 
 	CHECK_OPEN_PORT();
 
 	if (!buf)
 		RETURN_ERROR(SP_ERR_ARG, "Null buffer");
 
-	if (timeout)
-		DEBUG("Reading %d bytes from port %s, timeout %d ms", count, port->name, timeout);
+	if (timeout_ms)
+		DEBUG_FMT("Reading %d bytes from port %s, timeout %d ms",
+			count, port->name, timeout_ms);
 	else
-		DEBUG("Reading %d bytes from port %s, no timeout", count, port->name);
+		DEBUG_FMT("Reading %d bytes from port %s, no timeout",
+			count, port->name);
 
 	if (count == 0)
-		RETURN_VALUE("0", 0);
+		RETURN_INT(0);
 
 #ifdef _WIN32
-	DWORD bytes_read = 0;
+	DWORD bytes_read;
 
 	/* Set timeout. */
-	port->timeouts.ReadIntervalTimeout = 0;
-	port->timeouts.ReadTotalTimeoutConstant = timeout;
-	if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
-		RETURN_FAIL("SetCommTimeouts() failed");
+	if (port->timeouts.ReadIntervalTimeout != 0 ||
+			port->timeouts.ReadTotalTimeoutMultiplier != 0 ||
+			port->timeouts.ReadTotalTimeoutConstant != timeout_ms) {
+		port->timeouts.ReadIntervalTimeout = 0;
+		port->timeouts.ReadTotalTimeoutMultiplier = 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) {
-		if (GetLastError() == ERROR_IO_PENDING) {
-			DEBUG("Waiting for read to complete");
-			GetOverlappedResult(port->hdl, &port->read_ovl, &bytes_read, TRUE);
-			DEBUG("Read completed, %d/%d bytes read", bytes_read, count);
-		} else {
-			RETURN_FAIL("ReadFile() failed");
-		}
-	} else {
+	if (ReadFile(port->hdl, buf, (DWORD) count, NULL, &port->read_ovl)) {
 		DEBUG("Read completed immediately");
-		bytes_read = count;
+		bytes_read = (DWORD) count;
+	} else if (GetLastError() == ERROR_IO_PENDING) {
+		DEBUG("Waiting for read to complete");
+		if (GetOverlappedResult(port->hdl, &port->read_ovl, &bytes_read, TRUE) == 0)
+			RETURN_FAIL("GetOverlappedResult() failed");
+		DEBUG_FMT("Read completed, %d/%d bytes read", bytes_read, count);
+	} else {
+		RETURN_FAIL("ReadFile() failed");
 	}
 
-	/* Start background operation for subsequent events. */
-	if (WaitCommEvent(port->hdl, &port->events, &port->wait_ovl) == 0) {
-		if (GetLastError() != ERROR_IO_PENDING)
-			RETURN_FAIL("WaitCommEvent() failed");
-	}
+	TRY(restart_wait_if_needed(port, bytes_read));
 
-	RETURN_VALUE("%d", bytes_read);
+	RETURN_INT((int) bytes_read);
 
 #else
 	size_t bytes_read = 0;
 	unsigned char *ptr = (unsigned char *) buf;
-	struct timeval start, delta, now, end = {0, 0};
+	struct timeout timeout;
 	fd_set fds;
-	int result;
+	ssize_t result;
 
-	if (timeout) {
-		/* Get time at start of operation. */
-		gettimeofday(&start, NULL);
-		/* Define duration of timeout. */
-		delta.tv_sec = timeout / 1000;
-		delta.tv_usec = (timeout % 1000) * 1000;
-		/* Calculate time at which we should give up. */
-		timeradd(&start, &delta, &end);
-	}
+	timeout_start(&timeout, timeout_ms);
+
+	FD_ZERO(&fds);
+	FD_SET(port->fd, &fds);
 
 	/* Loop until we have the requested number of bytes. */
-	while (bytes_read < count)
-	{
-		/* Wait until data is available. */
-		FD_ZERO(&fds);
-		FD_SET(port->fd, &fds);
-		if (timeout) {
-			gettimeofday(&now, NULL);
-			if (timercmp(&now, &end, >))
-				/* Timeout has expired. */
-				RETURN_VALUE("%d", bytes_read);
-			timersub(&end, &now, &delta);
-		}
-		result = select(port->fd + 1, &fds, NULL, NULL, timeout ? &delta : NULL);
+	while (bytes_read < count) {
+
+		if (timeout_check(&timeout))
+			/* Timeout has expired. */
+			break;
+
+		result = select(port->fd + 1, &fds, NULL, NULL, timeout_timeval(&timeout));
+
+		timeout_update(&timeout);
+
 		if (result < 0) {
 			if (errno == EINTR) {
 				DEBUG("select() call was interrupted, repeating");
@@ -950,8 +1117,8 @@ SP_API enum sp_return sp_blocking_read(struct sp_port *port, void *buf,
 				RETURN_FAIL("select() failed");
 			}
 		} else if (result == 0) {
-			DEBUG("read timed out");
-			RETURN_VALUE("%d", bytes_read);
+			/* Timeout has expired. */
+			break;
 		}
 
 		/* Do read. */
@@ -959,7 +1126,10 @@ SP_API enum sp_return sp_blocking_read(struct sp_port *port, void *buf,
 
 		if (result < 0) {
 			if (errno == EAGAIN)
-				/* This shouldn't happen because we did a select() first, but handle anyway. */
+				/*
+				 * This shouldn't happen because we did a
+				 * select() first, but handle anyway.
+				 */
 				continue;
 			else
 				/* This is an actual failure. */
@@ -970,7 +1140,129 @@ SP_API enum sp_return sp_blocking_read(struct sp_port *port, void *buf,
 		ptr += result;
 	}
 
-	RETURN_VALUE("%d", bytes_read);
+	if (bytes_read < count)
+		DEBUG("Read timed out");
+
+	RETURN_INT(bytes_read);
+#endif
+}
+
+SP_API enum sp_return sp_blocking_read_next(struct sp_port *port, void *buf,
+                                            size_t count, unsigned int timeout_ms)
+{
+	TRACE("%p, %p, %d, %d", port, buf, count, timeout_ms);
+
+	CHECK_OPEN_PORT();
+
+	if (!buf)
+		RETURN_ERROR(SP_ERR_ARG, "Null buffer");
+
+	if (count == 0)
+		RETURN_ERROR(SP_ERR_ARG, "Zero count");
+
+	if (timeout_ms)
+		DEBUG_FMT("Reading next max %d bytes from port %s, timeout %d ms",
+			count, port->name, timeout_ms);
+	else
+		DEBUG_FMT("Reading next max %d bytes from port %s, no timeout",
+			count, port->name);
+
+#ifdef _WIN32
+	DWORD bytes_read = 0;
+
+	/* If timeout_ms == 0, set maximum timeout. */
+	DWORD timeout_val = (timeout_ms == 0 ? MAXDWORD - 1 : timeout_ms);
+
+	/* Set timeout. */
+	if (port->timeouts.ReadIntervalTimeout != MAXDWORD ||
+			port->timeouts.ReadTotalTimeoutMultiplier != MAXDWORD ||
+			port->timeouts.ReadTotalTimeoutConstant != timeout_val) {
+		port->timeouts.ReadIntervalTimeout = MAXDWORD;
+		port->timeouts.ReadTotalTimeoutMultiplier = MAXDWORD;
+		port->timeouts.ReadTotalTimeoutConstant = timeout_val;
+		if (SetCommTimeouts(port->hdl, &port->timeouts) == 0)
+			RETURN_FAIL("SetCommTimeouts() failed");
+	}
+
+	/* Loop until we have at least one byte, or timeout is reached. */
+	while (bytes_read == 0) {
+		/* Start read. */
+		if (ReadFile(port->hdl, buf, (DWORD) count, &bytes_read, &port->read_ovl)) {
+			DEBUG("Read completed immediately");
+		} else if (GetLastError() == ERROR_IO_PENDING) {
+			DEBUG("Waiting for read to complete");
+			if (GetOverlappedResult(port->hdl, &port->read_ovl, &bytes_read, TRUE) == 0)
+				RETURN_FAIL("GetOverlappedResult() failed");
+			if (bytes_read > 0) {
+				DEBUG("Read completed");
+			} else if (timeout_ms > 0) {
+				DEBUG("Read timed out");
+				break;
+			} else {
+				DEBUG("Restarting read");
+			}
+		} else {
+			RETURN_FAIL("ReadFile() failed");
+		}
+	}
+
+	TRY(restart_wait_if_needed(port, bytes_read));
+
+	RETURN_INT(bytes_read);
+
+#else
+	size_t bytes_read = 0;
+	struct timeout timeout;
+	fd_set fds;
+	ssize_t result;
+
+	timeout_start(&timeout, timeout_ms);
+
+	FD_ZERO(&fds);
+	FD_SET(port->fd, &fds);
+
+	/* Loop until we have at least one byte, or timeout is reached. */
+	while (bytes_read == 0) {
+
+		if (timeout_check(&timeout))
+			/* Timeout has expired. */
+			break;
+
+		result = select(port->fd + 1, &fds, NULL, NULL, timeout_timeval(&timeout));
+
+		timeout_update(&timeout);
+
+		if (result < 0) {
+			if (errno == EINTR) {
+				DEBUG("select() call was interrupted, repeating");
+				continue;
+			} else {
+				RETURN_FAIL("select() failed");
+			}
+		} else if (result == 0) {
+			/* Timeout has expired. */
+			break;
+		}
+
+		/* Do read. */
+		result = read(port->fd, buf, count);
+
+		if (result < 0) {
+			if (errno == EAGAIN)
+				/* This shouldn't happen because we did a select() first, but handle anyway. */
+				continue;
+			else
+				/* This is an actual failure. */
+				RETURN_FAIL("read() failed");
+		}
+
+		bytes_read = result;
+	}
+
+	if (bytes_read == 0)
+		DEBUG("Read timed out");
+
+	RETURN_INT(bytes_read);
 #endif
 }
 
@@ -984,34 +1276,34 @@ SP_API enum sp_return sp_nonblocking_read(struct sp_port *port, void *buf,
 	if (!buf)
 		RETURN_ERROR(SP_ERR_ARG, "Null buffer");
 
-	DEBUG("Reading up to %d bytes from port %s", count, port->name);
+	DEBUG_FMT("Reading up to %d bytes from port %s", count, port->name);
 
 #ifdef _WIN32
 	DWORD bytes_read;
 
 	/* 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.ReadTotalTimeoutMultiplier != 0 ||
+			port->timeouts.ReadTotalTimeoutConstant != 0) {
+		port->timeouts.ReadIntervalTimeout = MAXDWORD;
+		port->timeouts.ReadTotalTimeoutMultiplier = 0;
+		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)
-		RETURN_FAIL("ReadFile() failed");
+	if (ReadFile(port->hdl, buf, (DWORD) count, NULL, &port->read_ovl) == 0)
+		if (GetLastError() != ERROR_IO_PENDING)
+			RETURN_FAIL("ReadFile() failed");
 
 	/* Get number of bytes read. */
-	if (GetOverlappedResult(port->hdl, &port->read_ovl, &bytes_read, TRUE) == 0)
+	if (GetOverlappedResult(port->hdl, &port->read_ovl, &bytes_read, FALSE) == 0)
 		RETURN_FAIL("GetOverlappedResult() failed");
 
-	if (bytes_read > 0) {
-		/* Start background operation for subsequent events. */
-		if (WaitCommEvent(port->hdl, &port->events, &port->wait_ovl) == 0) {
-			if (GetLastError() != ERROR_IO_PENDING)
-				RETURN_FAIL("WaitCommEvent() failed");
-		}
-	}
+	TRY(restart_wait_if_needed(port, bytes_read));
 
-	RETURN_VALUE("%d", bytes_read);
+	RETURN_INT(bytes_read);
 #else
 	ssize_t bytes_read;
 
@@ -1024,7 +1316,7 @@ SP_API enum sp_return sp_nonblocking_read(struct sp_port *port, void *buf,
 			/* This is an actual failure. */
 			RETURN_FAIL("read() failed");
 	}
-	RETURN_VALUE("%d", bytes_read);
+	RETURN_INT(bytes_read);
 #endif
 }
 
@@ -1034,7 +1326,7 @@ SP_API enum sp_return sp_input_waiting(struct sp_port *port)
 
 	CHECK_OPEN_PORT();
 
-	DEBUG("Checking input bytes waiting on port %s", port->name);
+	DEBUG_FMT("Checking input bytes waiting on port %s", port->name);
 
 #ifdef _WIN32
 	DWORD errors;
@@ -1042,12 +1334,12 @@ SP_API enum sp_return sp_input_waiting(struct sp_port *port)
 
 	if (ClearCommError(port->hdl, &errors, &comstat) == 0)
 		RETURN_FAIL("ClearCommError() failed");
-	RETURN_VALUE("%d", comstat.cbInQue);
+	RETURN_INT(comstat.cbInQue);
 #else
 	int bytes_waiting;
 	if (ioctl(port->fd, TIOCINQ, &bytes_waiting) < 0)
 		RETURN_FAIL("TIOCINQ ioctl failed");
-	RETURN_VALUE("%d", bytes_waiting);
+	RETURN_INT(bytes_waiting);
 #endif
 }
 
@@ -1055,9 +1347,14 @@ SP_API enum sp_return sp_output_waiting(struct sp_port *port)
 {
 	TRACE("%p", port);
 
+#ifdef __CYGWIN__
+	/* TIOCOUTQ is not defined in Cygwin headers */
+	RETURN_ERROR(SP_ERR_SUPP,
+			"Getting output bytes waiting is not supported on Cygwin");
+#else
 	CHECK_OPEN_PORT();
 
-	DEBUG("Checking output bytes waiting on port %s", port->name);
+	DEBUG_FMT("Checking output bytes waiting on port %s", port->name);
 
 #ifdef _WIN32
 	DWORD errors;
@@ -1065,12 +1362,13 @@ SP_API enum sp_return sp_output_waiting(struct sp_port *port)
 
 	if (ClearCommError(port->hdl, &errors, &comstat) == 0)
 		RETURN_FAIL("ClearCommError() failed");
-	RETURN_VALUE("%d", comstat.cbOutQue);
+	RETURN_INT(comstat.cbOutQue);
 #else
 	int bytes_waiting;
 	if (ioctl(port->fd, TIOCOUTQ, &bytes_waiting) < 0)
 		RETURN_FAIL("TIOCOUTQ ioctl failed");
-	RETURN_VALUE("%d", bytes_waiting);
+	RETURN_INT(bytes_waiting);
+#endif
 #endif
 }
 
@@ -1105,13 +1403,14 @@ static enum sp_return add_handle(struct sp_event_set *event_set,
 
 	if (!(new_handles = realloc(event_set->handles,
 			sizeof(event_handle) * (event_set->count + 1))))
-		RETURN_ERROR(SP_ERR_MEM, "handle array realloc() failed");
+		RETURN_ERROR(SP_ERR_MEM, "Handle array realloc() failed");
+
+	event_set->handles = new_handles;
 
 	if (!(new_masks = realloc(event_set->masks,
 			sizeof(enum sp_event) * (event_set->count + 1))))
-		RETURN_ERROR(SP_ERR_MEM, "mask array realloc() failed");
+		RETURN_ERROR(SP_ERR_MEM, "Mask array realloc() failed");
 
-	event_set->handles = new_handles;
 	event_set->masks = new_masks;
 
 	((event_handle *) event_set->handles)[event_set->count] = handle;
@@ -1174,22 +1473,23 @@ SP_API void sp_free_event_set(struct sp_event_set *event_set)
 }
 
 SP_API enum sp_return sp_wait(struct sp_event_set *event_set,
-                              unsigned int timeout)
+                              unsigned int timeout_ms)
 {
-	TRACE("%p, %d", event_set, timeout);
+	TRACE("%p, %d", event_set, timeout_ms);
 
 	if (!event_set)
 		RETURN_ERROR(SP_ERR_ARG, "Null event set");
 
 #ifdef _WIN32
 	if (WaitForMultipleObjects(event_set->count, event_set->handles, FALSE,
-			timeout ? timeout : INFINITE) == WAIT_FAILED)
+			timeout_ms ? timeout_ms : INFINITE) == WAIT_FAILED)
 		RETURN_FAIL("WaitForMultipleObjects() failed");
 
 	RETURN_OK();
 #else
-	struct timeval start, delta, now, end = {0, 0};
-	int result, timeout_remaining;
+	struct timeout timeout;
+	int poll_timeout;
+	int result;
 	struct pollfd *pollfds;
 	unsigned int i;
 
@@ -1197,7 +1497,7 @@ SP_API enum sp_return sp_wait(struct sp_event_set *event_set,
 		RETURN_ERROR(SP_ERR_MEM, "pollfds malloc() failed");
 
 	for (i = 0; i < event_set->count; i++) {
-		pollfds[i].fd = ((int *) event_set->handles)[i];
+		pollfds[i].fd = ((int *)event_set->handles)[i];
 		pollfds[i].events = 0;
 		pollfds[i].revents = 0;
 		if (event_set->masks[i] & SP_EVENT_RX_READY)
@@ -1208,30 +1508,24 @@ SP_API enum sp_return sp_wait(struct sp_event_set *event_set,
 			pollfds[i].events |= POLLERR;
 	}
 
-	if (timeout) {
-		/* Get time at start of operation. */
-		gettimeofday(&start, NULL);
-		/* Define duration of timeout. */
-		delta.tv_sec = timeout / 1000;
-		delta.tv_usec = (timeout % 1000) * 1000;
-		/* Calculate time at which we should give up. */
-		timeradd(&start, &delta, &end);
-	}
+	timeout_start(&timeout, timeout_ms);
+	timeout_limit(&timeout, INT_MAX);
 
 	/* Loop until an event occurs. */
-	while (1)
-	{
-		if (timeout) {
-			gettimeofday(&now, NULL);
-			if (timercmp(&now, &end, >)) {
-				DEBUG("wait timed out");
-				break;
-			}
-			timersub(&end, &now, &delta);
-			timeout_remaining = delta.tv_sec * 1000 + delta.tv_usec / 1000;
+	while (1) {
+
+		if (timeout_check(&timeout)) {
+			DEBUG("Wait timed out");
+			break;
 		}
 
-		result = poll(pollfds, event_set->count, timeout ? timeout_remaining : -1);
+		poll_timeout = (int) timeout_remaining_ms(&timeout);
+		if (poll_timeout == 0)
+			poll_timeout = -1;
+
+		result = poll(pollfds, event_set->count, poll_timeout);
+
+		timeout_update(&timeout);
 
 		if (result < 0) {
 			if (errno == EINTR) {
@@ -1243,7 +1537,8 @@ SP_API enum sp_return sp_wait(struct sp_event_set *event_set,
 			}
 		} else if (result == 0) {
 			DEBUG("poll() timed out");
-			break;
+			if (!timeout.overflow)
+				break;
 		} else {
 			DEBUG("poll() completed");
 			break;
@@ -1269,7 +1564,7 @@ static enum sp_return get_baudrate(int fd, int *baudrate)
 
 	if (ioctl(fd, get_termios_get_ioctl(), data) < 0) {
 		free(data);
-		RETURN_FAIL("getting termios failed");
+		RETURN_FAIL("Getting termios failed");
 	}
 
 	*baudrate = get_termios_speed(data);
@@ -1292,7 +1587,7 @@ static enum sp_return set_baudrate(int fd, int baudrate)
 
 	if (ioctl(fd, get_termios_get_ioctl(), data) < 0) {
 		free(data);
-		RETURN_FAIL("getting termios failed");
+		RETURN_FAIL("Getting termios failed");
 	}
 
 	DEBUG("Setting baud rate");
@@ -1301,7 +1596,7 @@ static enum sp_return set_baudrate(int fd, int baudrate)
 
 	if (ioctl(fd, get_termios_set_ioctl(), data) < 0) {
 		free(data);
-		RETURN_FAIL("setting termios failed");
+		RETURN_FAIL("Setting termios failed");
 	}
 
 	free(data);
@@ -1324,7 +1619,7 @@ static enum sp_return get_flow(int fd, struct port_data *data)
 
 	if (ioctl(fd, TCGETX, termx) < 0) {
 		free(termx);
-		RETURN_FAIL("getting termiox failed");
+		RETURN_FAIL("Getting termiox failed");
 	}
 
 	get_termiox_flow(termx, &data->rts_flow, &data->cts_flow,
@@ -1348,7 +1643,7 @@ static enum sp_return set_flow(int fd, struct port_data *data)
 
 	if (ioctl(fd, TCGETX, termx) < 0) {
 		free(termx);
-		RETURN_FAIL("getting termiox failed");
+		RETURN_FAIL("Getting termiox failed");
 	}
 
 	DEBUG("Setting advanced flow control");
@@ -1358,7 +1653,7 @@ static enum sp_return set_flow(int fd, struct port_data *data)
 
 	if (ioctl(fd, TCSETX, termx) < 0) {
 		free(termx);
-		RETURN_FAIL("setting termiox failed");
+		RETURN_FAIL("Setting termiox failed");
 	}
 
 	free(termx);
@@ -1374,7 +1669,7 @@ static enum sp_return get_config(struct sp_port *port, struct port_data *data,
 
 	TRACE("%p, %p, %p", port, data, config);
 
-	DEBUG("Getting configuration for port %s", port->name);
+	DEBUG_FMT("Getting configuration for port %s", port->name);
 
 #ifdef _WIN32
 	if (!GetCommState(port->hdl, &data->dcb))
@@ -1393,28 +1688,25 @@ static enum sp_return get_config(struct sp_port *port, struct port_data *data,
 
 	config->bits = data->dcb.ByteSize;
 
-	if (data->dcb.fParity)
-		switch (data->dcb.Parity) {
-		case NOPARITY:
-			config->parity = SP_PARITY_NONE;
-			break;
-		case ODDPARITY:
-			config->parity = SP_PARITY_ODD;
-			break;
-		case EVENPARITY:
-			config->parity = SP_PARITY_EVEN;
-			break;
-		case MARKPARITY:
-			config->parity = SP_PARITY_MARK;
-			break;
-		case SPACEPARITY:
-			config->parity = SP_PARITY_SPACE;
-			break;
-		default:
-			config->parity = -1;
-		}
-	else
+	switch (data->dcb.Parity) {
+	case NOPARITY:
 		config->parity = SP_PARITY_NONE;
+		break;
+	case ODDPARITY:
+		config->parity = SP_PARITY_ODD;
+		break;
+	case EVENPARITY:
+		config->parity = SP_PARITY_EVEN;
+		break;
+	case MARKPARITY:
+		config->parity = SP_PARITY_MARK;
+		break;
+	case SPACEPARITY:
+		config->parity = SP_PARITY_SPACE;
+		break;
+	default:
+		config->parity = -1;
+	}
 
 	switch (data->dcb.StopBits) {
 	case ONESTOPBIT:
@@ -1591,9 +1883,13 @@ static enum sp_return set_config(struct sp_port *port, struct port_data *data,
 
 	TRACE("%p, %p, %p", port, data, config);
 
-	DEBUG("Setting configuration for port %s", port->name);
+	DEBUG_FMT("Setting configuration for port %s", port->name);
 
 #ifdef _WIN32
+	BYTE* new_buf;
+
+	TRY(await_write_completion(port));
+
 	if (config->baudrate >= 0) {
 		for (i = 0; i < NUM_STD_BAUDRATES; i++) {
 			if (config->baudrate == std_baudrates[i].value) {
@@ -1604,6 +1900,13 @@ static enum sp_return set_config(struct sp_port *port, struct port_data *data,
 
 		if (i == NUM_STD_BAUDRATES)
 			data->dcb.BaudRate = config->baudrate;
+
+		/* Allocate write buffer for 50ms of data at baud rate. */
+		port->write_buf_size = max(config->baudrate / (8 * 20), 1);
+		new_buf = realloc(port->write_buf, port->write_buf_size);
+		if (!new_buf)
+			RETURN_ERROR(SP_ERR_MEM, "Allocating write buffer failed");
+		port->write_buf = new_buf;
 	}
 
 	if (config->bits >= 0)
@@ -1942,8 +2245,10 @@ static enum sp_return set_config(struct sp_port *port, struct port_data *data,
 	if (baud_nonstd != B0) {
 		if (ioctl(port->fd, IOSSIOSPEED, &baud_nonstd) == -1)
 			RETURN_FAIL("IOSSIOSPEED ioctl failed");
-		/* Set baud rates in data->term to correct, but incompatible
-		 * with tcsetattr() value, same as delivered by tcgetattr(). */
+		/*
+		 * Set baud rates in data->term to correct, but incompatible
+		 * with tcsetattr() value, same as delivered by tcgetattr().
+		 */
 		if (cfsetspeed(&data->term, baud_nonstd) < 0)
 			RETURN_FAIL("cfsetspeed() failed");
 	}
@@ -1975,7 +2280,7 @@ SP_API enum sp_return sp_new_config(struct sp_port_config **config_ptr)
 	*config_ptr = NULL;
 
 	if (!(config = malloc(sizeof(struct sp_port_config))))
-		RETURN_ERROR(SP_ERR_MEM, "config malloc failed");
+		RETURN_ERROR(SP_ERR_MEM, "Config malloc failed");
 
 	config->baudrate = -1;
 	config->bits = -1;
@@ -2053,6 +2358,8 @@ SP_API enum sp_return sp_set_##x(struct sp_port *port, type x) { \
 SP_API enum sp_return sp_get_config_##x(const struct sp_port_config *config, \
                                         type *x) { \
 	TRACE("%p, %p", config, x); \
+	if (!x) \
+		RETURN_ERROR(SP_ERR_ARG, "Null result pointer"); \
 	if (!config) \
 		RETURN_ERROR(SP_ERR_ARG, "Null config"); \
 	*x = config->x; \
@@ -2141,7 +2448,7 @@ SP_API enum sp_return sp_get_signals(struct sp_port *port,
 	if (!signals)
 		RETURN_ERROR(SP_ERR_ARG, "Null result pointer");
 
-	DEBUG("Getting control signals for port %s", port->name);
+	DEBUG_FMT("Getting control signals for port %s", port->name);
 
 	*signals = 0;
 #ifdef _WIN32
@@ -2206,35 +2513,38 @@ SP_API enum sp_return sp_end_break(struct sp_port *port)
 
 SP_API int sp_last_error_code(void)
 {
-	TRACE("");
+	TRACE_VOID();
 #ifdef _WIN32
-	RETURN_VALUE("%d", GetLastError());
+	RETURN_INT(GetLastError());
 #else
-	RETURN_VALUE("%d", errno);
+	RETURN_INT(errno);
 #endif
 }
 
 SP_API char *sp_last_error_message(void)
 {
-	TRACE("");
+	TRACE_VOID();
 
 #ifdef _WIN32
-	LPVOID message;
+	char *message;
 	DWORD error = GetLastError();
 
-	FormatMessage(
+	DWORD length = FormatMessageA(
 		FORMAT_MESSAGE_ALLOCATE_BUFFER |
 		FORMAT_MESSAGE_FROM_SYSTEM |
 		FORMAT_MESSAGE_IGNORE_INSERTS,
 		NULL,
 		error,
 		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
-		(LPTSTR) &message,
+		(LPSTR) &message,
 		0, NULL );
 
-	RETURN_VALUE("%s", message);
+	if (length >= 2 && message[length - 2] == '\r')
+		message[length - 2] = '\0';
+
+	RETURN_STRING(message);
 #else
-	RETURN_VALUE("%s", strerror(errno));
+	RETURN_STRING(strerror(errno));
 #endif
 }