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Check for valid pin properly (fixes #4605) 

Fix for `pinMode()`, `digitalWrite()`, `digitalRead()` (issue #4605).
Current behavior: look up pin number in `digital_pin_to_port_PGM[]` and then check if it returned `NOT_A_PIN`.  Causes undefined behavior if provided `pin` number is out of the range of `digital_pin_to_port_PGM[]`.
Proposed behavior (from issue #4605): check if `pin` is within the valid range of `digital_pin_to_port_PGM[]`, and THEN look it up.

Additionally, remove second check for `port` not being `NOT_A_PIN` (which was useful for boards where the pin numbering skips some numbers).  This can still be achieved by making `bit = digitalPinToBitMask(pin)` be 0 for invalid pins, which causes further bitwise operations such as `*reg &= ~bit;` and `*out |= bit;` to not actually modify the value of the register.  (This removal makes the operation complete a bit faster for valid pins and slower for invalid pins, which I think is a good trade; plus it saves binary size.)
This commit is contained in:
cousteau 2016-03-03 23:10:26 +01:00 committed by Martino Facchin
parent b084848f2e
commit e2016d57de
1 changed files with 10 additions and 8 deletions
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18
cores/arduino/wiring_digital.c
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@ -26,14 +26,16 @@
#include "wiring_private.h"
#include "pins_arduino.h"
#define PIN_MAX (sizeof digital_pin_to_port_PGM / sizeof *digital_pin_to_port_PGM)
void pinMode(uint8_t pin, uint8_t mode)
{
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
if (pin >= PIN_MAX) return;
uint8_t bit = digitalPinToBitMask(pin); // bit mask, or 0 for invalid pins
uint8_t port = digitalPinToPort(pin); // must be a valid port (even for invalid pins)
volatile uint8_t *reg, *out;
if (port == NOT_A_PIN) return;
// JWS: can I let the optimizer do this?
reg = portModeRegister(port);
out = portOutputRegister(port);
@ -137,13 +139,13 @@ static void turnOffPWM(uint8_t timer)
void digitalWrite(uint8_t pin, uint8_t val)
{
if (pin >= PIN_MAX) return;
uint8_t timer = digitalPinToTimer(pin);
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
volatile uint8_t *out;
if (port == NOT_A_PIN) return;
// If the pin that support PWM output, we need to turn it off
// before doing a digital write.
if (timer != NOT_ON_TIMER) turnOffPWM(timer);
@ -164,12 +166,12 @@ void digitalWrite(uint8_t pin, uint8_t val)
int digitalRead(uint8_t pin)
{
if (pin >= PIN_MAX) return LOW;
uint8_t timer = digitalPinToTimer(pin);
uint8_t bit = digitalPinToBitMask(pin);
uint8_t port = digitalPinToPort(pin);
if (port == NOT_A_PIN) return LOW;
// If the pin that support PWM output, we need to turn it off
// before getting a digital reading.
if (timer != NOT_ON_TIMER) turnOffPWM(timer);