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make serial.available, peek, read atomic #3848

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make serial.available, peek, read atomic #3848

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69a8bfa
make serial.available, peek, read atomic
robert-rozee Sep 23, 2015
91d817a
Update HardwareSerial.cpp
robert-rozee Sep 24, 2015
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49 changes: 42 additions & 7 deletions hardware/arduino/avr/cores/arduino/HardwareSerial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -151,26 +151,61 @@ void HardwareSerial::end()

int HardwareSerial::available(void)
{
return ((unsigned int)(SERIAL_RX_BUFFER_SIZE + _rx_buffer_head - _rx_buffer_tail)) % SERIAL_RX_BUFFER_SIZE;
#if (SERIAL_RX_BUFFER_SIZE>256)
uint8_t oldSREG = SREG; // save interrupt flag
cli(); // disable interrupts
#endif
rx_buffer_index_t head = _rx_buffer_head; // retrieve Rx head index
rx_buffer_index_t tail = _rx_buffer_tail; // retrieve Rx tail index
#if (SERIAL_RX_BUFFER_SIZE>256)
SREG = oldSREG; // restore the interrupt flag
#endif
return ((unsigned int)(SERIAL_RX_BUFFER_SIZE + head - tail)) % SERIAL_RX_BUFFER_SIZE;
}

int HardwareSerial::peek(void)
{
if (_rx_buffer_head == _rx_buffer_tail) {
#if (SERIAL_RX_BUFFER_SIZE>256)
uint8_t oldSREG = SREG; // save interrupt flag
cli(); // disable interrupts
#endif
rx_buffer_index_t head = _rx_buffer_head; // retrieve Rx head index
rx_buffer_index_t tail = _rx_buffer_tail; // retrieve Rx tail index
#if (SERIAL_RX_BUFFER_SIZE>256)
SREG = oldSREG; // restore the interrupt flag
#endif
if (head == tail) {
return -1;
} else {
return _rx_buffer[_rx_buffer_tail];
return _rx_buffer[tail];
}
}

int HardwareSerial::read(void)
{
// if the head isn't ahead of the tail, we don't have any characters
if (_rx_buffer_head == _rx_buffer_tail) {
#if (SERIAL_RX_BUFFER_SIZE>256)
uint8_t oldSREG = SREG; // save interrupt flag
cli(); // disable interrupts
#endif
rx_buffer_index_t head = _rx_buffer_head; // retrieve Rx head index
rx_buffer_index_t tail = _rx_buffer_tail; // retrieve Rx tail index
#if (SERIAL_RX_BUFFER_SIZE>256)
SREG = oldSREG; // restore the interrupt flag
#endif

if (head == tail) {
return -1;
} else {
unsigned char c = _rx_buffer[_rx_buffer_tail];
_rx_buffer_tail = (rx_buffer_index_t)(_rx_buffer_tail + 1) % SERIAL_RX_BUFFER_SIZE;
unsigned char c = _rx_buffer[tail];

#if (SERIAL_RX_BUFFER_SIZE>256)
uint8_t oldSREG = SREG; // save interrupt flag
cli(); // disable interrupts
#endif
_rx_buffer_tail = (tail + 1) % SERIAL_RX_BUFFER_SIZE;
#if (SERIAL_RX_BUFFER_SIZE>256)
SREG = oldSREG; // restore the interrupt flag
#endif
return c;
}
}
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