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Changed how the memory is allocated in the read operation and changed how the timeouts function. If the timeout is -1, then it will block until it finishes the reads.

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This commit is contained in:
John Harrison 2012-01-13 11:33:55 -06:00
parent 6011f2847c
commit f81268fdf0
1 changed files with 33 additions and 17 deletions
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50
src/impl/unix.cc
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@ -215,42 +215,58 @@ Serial::SerialImpl::read (size_t size) {
throw PortNotOpenedException("Serial::read");
}
string message = "";
char buf[1024]; // TODO(ash_gti): Should this be 1024? or...?
char *buf = NULL;
// Using size+1 to leave room for a null character
if (size > 1024) {
buf = (char*)malloc((size + 1) * sizeof(*buf));
}
else {
buf = (char*)alloca((size + 1) * sizeof(*buf));
}
fd_set readfds;
memset(buf, 0, (size + 1) * sizeof(*buf));
ssize_t bytes_read = 0;
while (message.length() < size) {
FD_ZERO(&readfds);
FD_SET(fd_, &readfds);
struct timeval timeout;
timeout.tv_sec = timeout_ / 1000;
timeout.tv_usec = (int) timeout_ % 1000;
int r = select(fd_ + 1, &readfds, NULL, NULL, &timeout);
if (timeout_ == -1) {
FD_ZERO(&readfds);
FD_SET(fd_, &readfds);
struct timeval timeout;
timeout.tv_sec = timeout_ / 1000;
timeout.tv_usec = (int) timeout_ % 1000;
int r = select(fd_ + 1, &readfds, NULL, NULL, &timeout);
if (r == -1 && errno == EINTR)
continue;
if (r == -1 && errno == EINTR)
continue;
if (r == -1) {
perror("select()");
exit(EXIT_FAILURE);
if (r == -1) {
perror("select()");
exit(EXIT_FAILURE);
}
}
if (FD_ISSET(fd_, &readfds)) {
memset(buf, 0, 1024);
ssize_t bytes_read = ::read(fd_, buf, size-strlen(buf));
if (timeout_ == 1 || FD_ISSET(fd_, &readfds)) {
ssize_t newest_read = ::read(fd_,
buf + bytes_read,
size - static_cast<size_t>(bytes_read));
// read should always return some data as select reported it was
// ready to read when we get to this point.
if (bytes_read < 1) {
if (newest_read < 1) {
// Disconnected devices, at least on Linux, show the
// behavior that they are always ready to read immediately
// but reading returns nothing.
throw SerialExecption("device reports readiness to read but "
"returned no data (device disconnected?)");
}
message.append(buf, (size_t)bytes_read);
bytes_read += newest_read;
}
else {
break; // Timeout
}
}
if (bytes_read > 0)
message.append(buf, (size_t)bytes_read);
if (size > 1024)
free(buf);
return message;
}