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Add early-return possibility for the base read method.

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Mike Purvis 2013-10-10 15:26:33 -04:00
parent 88b628ba98
commit b992bce88f
1 changed files with 13 additions and 0 deletions
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13
src/impl/unix.cc
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@ -412,7 +412,20 @@ Serial::SerialImpl::read (uint8_t *buf, size_t size)
struct timespec timeout_endtime(timespec_now() + struct timespec timeout_endtime(timespec_now() +
read_timeout_constant_ + (read_timeout_multiplier_ * size)); read_timeout_constant_ + (read_timeout_multiplier_ * size));
// If there are already some bytes waiting to read, put those in the return
// buffer before setting up the first select call. This is important for
// performance reasons, as select/pselect can relinquish the thread even
// with data waiting.
size_t bytes_read = 0; size_t bytes_read = 0;
if (available() > 0) {
ssize_t bytes_read_now = ::read (fd_, buf, size);
if (bytes_read_now < 1) {
throw SerialException ("device reports readiness to read but "
"returned no data (device disconnected?)");
}
bytes_read += static_cast<size_t> (bytes_read_now);
}
while (bytes_read < size) { while (bytes_read < size) {
// Must determine whether the time remaining before endtime (total read // Must determine whether the time remaining before endtime (total read
// timeout) or the inter-byte timeout is sooner, and use that one as the // timeout) or the inter-byte timeout is sooner, and use that one as the