]> sigrok.org Git - libserialport.git/blobdiff - serialport.c
change type of result variables to ssize_t
[libserialport.git] / serialport.c
index 9671731b58fdaf56a7e3ced53d7870584424ae30..1b5a95e21d87fdfe48c7c10d686a47e2acac0e24 100644 (file)
@@ -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>
  *
  * 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
 }