Remove tracking of whether write() was called.

alltheblinkythings · alltheblinkythings · commit bc9493e690c5 · 2015-12-29T12:46:25.000-05:00
Tracking _written was required on AVR devices to work around a hardware
limitation when implementing flush().  The ESP8266 doesn't have the same
issue, so we can remove the tracking and make write() more lightweight.

The cost is a minor increase in work done in flush() when write() was not
previously called, but this should be much rarer than individual character
writes.
diff --git a/cores/esp8266/HardwareSerial.cpp b/cores/esp8266/HardwareSerial.cpp
@@ -485,7 +485,7 @@ int uart_get_debug() {
 // ####################################################################################################
 
 HardwareSerial::HardwareSerial(int uart_nr) :
-        _uart_nr(uart_nr), _uart(0), _tx_buffer(0), _rx_buffer(0), _written(false) {
+        _uart_nr(uart_nr), _uart(0), _tx_buffer(0), _rx_buffer(0) {
 }
 
 void HardwareSerial::begin(unsigned long baud, byte config, byte mode) {
@@ -519,7 +519,6 @@ void HardwareSerial::begin(unsigned long baud, byte config, byte mode) {
             _uart->txEnabled = false;
         }
     }
-    _written = false;
     delay(1);
 
     uart_finish_init(_uart);
@@ -626,8 +625,6 @@ void HardwareSerial::flush() {
         return;
     if(!_uart->txEnabled)
         return;
-    if(!_written)
-        return;
 
     const int uart_nr = _uart->uart_nr;
     while(true) {
@@ -643,13 +640,11 @@ void HardwareSerial::flush() {
         }
         yield();
     }
-    _written = false;
 }
 
 size_t HardwareSerial::write(uint8_t c) {
     if(_uart == 0 || !_uart->txEnabled)
         return 0;
-    _written = true;
 
     bool tx_now = false;
     const int uart_nr = _uart->uart_nr;
diff --git a/cores/esp8266/HardwareSerial.h b/cores/esp8266/HardwareSerial.h
@@ -117,7 +117,6 @@ class HardwareSerial: public Stream {
         uart_t* _uart;
         cbuf* _tx_buffer;
         cbuf* _rx_buffer;
-        bool _written;
 };
 
 extern HardwareSerial Serial;

Original file line number	Diff line number	Diff line change
`@@ -485,7 +485,7 @@ int uart_get_debug() {`
`485`	`485`	`// ####################################################################################################`
`486`	`486`
`487`	`487`	`HardwareSerial::HardwareSerial(int uart_nr) :`
`488`		`- _uart_nr(uart_nr), _uart(0), _tx_buffer(0), _rx_buffer(0), _written(false) {`
	`488`	`+ _uart_nr(uart_nr), _uart(0), _tx_buffer(0), _rx_buffer(0) {`
`489`	`489`	`}`
`490`	`490`
`491`	`491`	`void HardwareSerial::begin(unsigned long baud, byte config, byte mode) {`
`@@ -519,7 +519,6 @@ void HardwareSerial::begin(unsigned long baud, byte config, byte mode) {`
`519`	`519`	`_uart->txEnabled = false;`
`520`	`520`	`}`
`521`	`521`	`}`
`522`		`- _written = false;`
`523`	`522`	`delay(1);`
`524`	`523`
`525`	`524`	`uart_finish_init(_uart);`
`@@ -626,8 +625,6 @@ void HardwareSerial::flush() {`
`626`	`625`	`return;`
`627`	`626`	`if(!_uart->txEnabled)`
`628`	`627`	`return;`
`629`		`- if(!_written)`
`630`		`- return;`
`631`	`628`
`632`	`629`	`const int uart_nr = _uart->uart_nr;`
`633`	`630`	`while(true) {`
`@@ -643,13 +640,11 @@ void HardwareSerial::flush() {`
`643`	`640`	`}`
`644`	`641`	`yield();`
`645`	`642`	`}`
`646`		`- _written = false;`
`647`	`643`	`}`
`648`	`644`
`649`	`645`	`size_t HardwareSerial::write(uint8_t c) {`
`650`	`646`	`if(_uart == 0 \|\| !_uart->txEnabled)`
`651`	`647`	`return 0;`
`652`		`- _written = true;`
`653`	`648`
`654`	`649`	`bool tx_now = false;`
`655`	`650`	`const int uart_nr = _uart->uart_nr;`