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FastSerial: avoid buffer re-allocation on re-open if possible 

we commonly re-open serial ports a lot in the AUTO GPS driver
This commit is contained in:
Andrew Tridgell 2012-06-09 07:43:06 +10:00
parent aeaebb21d5
commit 9c1ce9e1c5
1 changed files with 16 additions and 6 deletions
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10
libraries/FastSerial/FastSerial.cpp
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@ -82,6 +82,7 @@ void FastSerial::begin(long baud, unsigned int rxSpace, unsigned int txSpace)
{ {
uint16_t ubrr; uint16_t ubrr;
bool use_u2x = true; bool use_u2x = true;
bool need_allocate = true;
// if we are currently open... // if we are currently open...
if (_open) { if (_open) {
@ -92,15 +93,24 @@ void FastSerial::begin(long baud, unsigned int rxSpace, unsigned int txSpace)
if (0 == txSpace) if (0 == txSpace)
txSpace = _txBuffer->mask + 1; txSpace = _txBuffer->mask + 1;
if (rxSpace == (_rxBuffer->mask + 1) &&
txSpace == (_txBuffer->mask + 1)) {
// avoid re-allocating the buffers if possible
need_allocate = false;
*_ucsrb &= ~(_portEnableBits | _portTxBits);
} else {
// close the port in its current configuration, clears _open // close the port in its current configuration, clears _open
end(); end();
} }
}
if (need_allocate) {
// allocate buffers // allocate buffers
if (!_allocBuffer(_rxBuffer, rxSpace ? : _default_rx_buffer_size) || !_allocBuffer(_txBuffer, txSpace ? : _default_tx_buffer_size)) { if (!_allocBuffer(_rxBuffer, rxSpace ? : _default_rx_buffer_size) || !_allocBuffer(_txBuffer, txSpace ? : _default_tx_buffer_size)) {
end(); end();
return; // couldn't allocate buffers - fatal return; // couldn't allocate buffers - fatal
} }
}
// reset buffer pointers // reset buffer pointers
_txBuffer->head = _txBuffer->tail = 0; _txBuffer->head = _txBuffer->tail = 0;