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use AND operator to perform mod #16

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use AND operator to perform mod #16

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ff24ff2
use AND operator to perform mod
StefanoBelloni Jun 2, 2021
80fe0ae
improved static assertion
StefanoBelloni Jun 3, 2021
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11 changes: 7 additions & 4 deletions SoftwareSerial.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -387,6 +387,9 @@ inline void DebugPulse(uint8_t pin, uint8_t count)
*pport = val | digitalPinToBitMask(pin);
*pport = val;
}
#else
(void) pin;
(void) count;
#endif
}

Expand Down Expand Up @@ -478,11 +481,11 @@ void SoftwareSerial::recv()
d = ~d;

// if buffer full, set the overflow flag and return
if ((_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF != _receive_buffer_head)
if ( ( (_receive_buffer_tail + 1) & _SS_MAX_RX_BUFF_MASK ) != _receive_buffer_head)
{
// save new data in buffer: tail points to where byte goes
_receive_buffer[_receive_buffer_tail] = d; // save new byte
_receive_buffer_tail = (_receive_buffer_tail + 1) % _SS_MAX_RX_BUFF;
_receive_buffer_tail = (_receive_buffer_tail + 1) & _SS_MAX_RX_BUFF_MASK;
}
else
{
Expand Down Expand Up @@ -665,7 +668,7 @@ int SoftwareSerial::read()

// Read from "head"
uint8_t d = _receive_buffer[_receive_buffer_head]; // grab next byte
_receive_buffer_head = (_receive_buffer_head + 1) % _SS_MAX_RX_BUFF;
_receive_buffer_head = (_receive_buffer_head + 1) & _SS_MAX_RX_BUFF_MASK;
return d;
}

Expand All @@ -674,7 +677,7 @@ int SoftwareSerial::available()
if (!isListening())
return 0;

return (_receive_buffer_tail + _SS_MAX_RX_BUFF - _receive_buffer_head) % _SS_MAX_RX_BUFF;
return (_receive_buffer_tail + _SS_MAX_RX_BUFF - _receive_buffer_head) & _SS_MAX_RX_BUFF_MASK;
}

size_t SoftwareSerial::write(uint8_t b)
Expand Down
15 changes: 14 additions & 1 deletion SoftwareSerial.h
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Original file line number Diff line number Diff line change
Expand Up @@ -40,11 +40,24 @@ The latest version of this library can always be found at
* Definitions
******************************************************************************/

#define _SS_MAX_RX_BUFF 64 // RX buffer size
#ifndef GCC_VERSION
#define GCC_VERSION (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__)
#endif

const unsigned int _SS_MAX_RX_BUFF = 64u; // RX buffer size
const unsigned int _SS_MAX_RX_BUFF_MASK = _SS_MAX_RX_BUFF - 1u; // mask for buffer size

/******************************************************************************
* Compile time check that _SS_MAX_RX_BUFF is a power of 2
* https://stackoverflow.com/questions/3385515/static-assert-in-cj
******************************************************************************/

#define STATIC_ASSERT_IS_POWER_OF_2(_v_, _MSG_) \
typedef char static_assertion_##_MSG_[ \
( (_v_) && ( ( (_v_) & ( (_v_) - 1) ) == 0 ) ) ? 1 : -1 ]

STATIC_ASSERT_IS_POWER_OF_2(_SS_MAX_RX_BUFF, Max_RX_buffer_should_be_a_power_of_2);

#if defined(__MK20DX128__) || defined(__MK20DX256__) || defined(__MKL26Z64__) || defined(__MK64FX512__) || defined(__MK66FX1M0__) || defined(__IMXRT1052__) || defined(__IMXRT1062__)

class SoftwareSerial : public Stream
Expand Down