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windows: Use an adaptively sized buffer for nonblocking writes.

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This commit is contained in:
Martin Ling 2017-07-03 21:43:38 +01:00 committed by Uwe Hermann
parent 6bd6a8b520
commit 39df7833f7
2 changed files with 32 additions and 30 deletions
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3
libserialport_internal.h
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@ -107,7 +107,8 @@ struct sp_port {
OVERLAPPED read_ovl;
OVERLAPPED wait_ovl;
DWORD events;
BYTE pending_byte;
BYTE *write_buf;
DWORD write_buf_size;
BOOL writing;
BOOL wait_running;
#else

59
serialport.c
View File

@ -104,6 +104,8 @@ SP_API enum sp_return sp_get_port_by_name(const char *portname, struct sp_port *
#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
@ -310,6 +312,8 @@ 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);
@ -643,6 +647,10 @@ 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)
@ -892,8 +900,7 @@ SP_API enum sp_return sp_nonblocking_write(struct sp_port *port,
RETURN_INT(0);
#ifdef _WIN32
DWORD written = 0;
BYTE *ptr = (BYTE *) buf;
DWORD buf_bytes;
/* Check whether previous write is complete. */
if (port->writing) {
@ -914,40 +921,26 @@ SP_API enum sp_return sp_nonblocking_write(struct sp_port *port,
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++;
/* 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->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_INT(++written);
}
} else {
/* Actual failure of some kind. */
RETURN_FAIL("WriteFile() failed");
}
/* Start asynchronous write. */
if (WriteFile(port->hdl, port->write_buf, 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_INT(written);
RETURN_INT(buf_bytes);
#else
/* Returns the number of bytes written, or -1 upon failure. */
ssize_t written = write(port->fd, buf, count);
@ -1894,6 +1887,14 @@ 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);
port->write_buf = realloc(port->write_buf,
port->write_buf_size);
if (!port->write_buf)
RETURN_ERROR(SP_ERR_MEM, "Allocating write buffer failed");
}
if (config->bits >= 0)