Write method for returning the number of bytes transferred

[fabik111]

The current writeValue method, used for writing the value of a characteristic, returns an integer value.
This value is used as a Boolean to indicate the success or the failure of the writing operation, without giving any indication about the amount of bytes actually transferred (in case of subscription) or "loaded" into the characteristic (in case of a readable characteristic).
Considering that the MTU, the amount of transferable data, is decided by the central and varies device by device, it is impossible for the user to determinate how many bytes are transferred and upon that to take an action.
In this PR a write method is added for the generic BLECharacteristic returning the number of bytes transferred.

It works both when the device is in peripheral and central mode.

[github-actions]

Memory usage change @ 166debb

Board	flash	%	RAM for global variables	%
arduino:mbed_nano:nano33ble	🔺 +72 - +136	+0.01 - +0.01	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	🔺 +46 - +46	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:megaavr:uno2018:mode=on	🔺 +140 - +140	+0.29 - +0.29	0 - 0	0.0 - 0.0
arduino:renesas_uno:unor4wifi	🔺 +72 - +88	+0.03 - +0.03	0 - 0	0.0 - 0.0
arduino:samd:mkrwifi1010	🔺 +48 - +48	+0.02 - +0.02	0 - 0	0.0 - 0.0
arduino:samd:nano_33_iot	🔺 +48 - +48	+0.02 - +0.02	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/Central/LedControl flash	%	examples/Central/LedControl RAM for global variables	%	examples/Central/PeripheralExplorer flash	%	examples/Central/PeripheralExplorer RAM for global variables	%	examples/Central/Scan flash	%	examples/Central/Scan RAM for global variables	%	examples/Central/ScanCallback flash	%	examples/Central/ScanCallback RAM for global variables	%	examples/Central/SensorTagButton flash	%	examples/Central/SensorTagButton RAM for global variables	%	examples/Peripheral/Advertising/EnhancedAdvertising flash	%	examples/Peripheral/Advertising/EnhancedAdvertising RAM for global variables	%	examples/Peripheral/Advertising/RawDataAdvertising flash	%	examples/Peripheral/Advertising/RawDataAdvertising RAM for global variables	%	examples/Peripheral/BatteryMonitor flash	%	examples/Peripheral/BatteryMonitor RAM for global variables	%	examples/Peripheral/ButtonLED flash	%	examples/Peripheral/ButtonLED RAM for global variables	%	examples/Peripheral/CallbackLED flash	%	examples/Peripheral/CallbackLED RAM for global variables	%	examples/Peripheral/EncryptedBatteryMonitor flash	%	examples/Peripheral/EncryptedBatteryMonitor RAM for global variables	%	examples/Peripheral/LED flash	%	examples/Peripheral/LED RAM for global variables	%
arduino:mbed_nano:nano33ble	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	136	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0	72	0.01	0	0.0
arduino:mbed_nano:nanorp2040connect	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0	46	0.0	0	0.0
arduino:megaavr:uno2018:mode=on	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0	140	0.29	0	0.0
arduino:renesas_uno:unor4wifi	88	0.03	0	0.0	72	0.03	0	0.0	72	0.03	0	0.0	72	0.03	0	0.0	88	0.03	0	0.0	88	0.03	0	0.0	72	0.03	0	0.0	72	0.03	0	0.0	88	0.03	0	0.0	72	0.03	0	0.0	72	0.03	0	0.0	88	0.03	0	0.0
arduino:samd:mkrwifi1010	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0
arduino:samd:nano_33_iot	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0	48	0.02	0	0.0

Click for full report CSV

Board,examples/Central/LedControl<br>flash,%,examples/Central/LedControl<br>RAM for global variables,%,examples/Central/PeripheralExplorer<br>flash,%,examples/Central/PeripheralExplorer<br>RAM for global variables,%,examples/Central/Scan<br>flash,%,examples/Central/Scan<br>RAM for global variables,%,examples/Central/ScanCallback<br>flash,%,examples/Central/ScanCallback<br>RAM for global variables,%,examples/Central/SensorTagButton<br>flash,%,examples/Central/SensorTagButton<br>RAM for global variables,%,examples/Peripheral/Advertising/EnhancedAdvertising<br>flash,%,examples/Peripheral/Advertising/EnhancedAdvertising<br>RAM for global variables,%,examples/Peripheral/Advertising/RawDataAdvertising<br>flash,%,examples/Peripheral/Advertising/RawDataAdvertising<br>RAM for global variables,%,examples/Peripheral/BatteryMonitor<br>flash,%,examples/Peripheral/BatteryMonitor<br>RAM for global variables,%,examples/Peripheral/ButtonLED<br>flash,%,examples/Peripheral/ButtonLED<br>RAM for global variables,%,examples/Peripheral/CallbackLED<br>flash,%,examples/Peripheral/CallbackLED<br>RAM for global variables,%,examples/Peripheral/EncryptedBatteryMonitor<br>flash,%,examples/Peripheral/EncryptedBatteryMonitor<br>RAM for global variables,%,examples/Peripheral/LED<br>flash,%,examples/Peripheral/LED<br>RAM for global variables,%
arduino:mbed_nano:nano33ble,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,136,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0,72,0.01,0,0.0
arduino:mbed_nano:nanorp2040connect,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0,46,0.0,0,0.0
arduino:megaavr:uno2018:mode=on,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0,140,0.29,0,0.0
arduino:renesas_uno:unor4wifi,88,0.03,0,0.0,72,0.03,0,0.0,72,0.03,0,0.0,72,0.03,0,0.0,88,0.03,0,0.0,88,0.03,0,0.0,72,0.03,0,0.0,72,0.03,0,0.0,88,0.03,0,0.0,72,0.03,0,0.0,72,0.03,0,0.0,88,0.03,0,0.0
arduino:samd:mkrwifi1010,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0
arduino:samd:nano_33_iot,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0,48,0.02,0,0.0

[andreagilardoni]

I would like to open a discussion about changing the behaviour of the function writeValue instead of writing a new one I would still use the same and return the length instead of 1 or 0.
The reason is if there is an error we can return 0 and there is no breaking change in that, if there is no error we return the length which can be evaluated to true in a boolean expression. The only case where this could not work is if someone is directly comparing the result of write with 1, in which the expected behaviour is not preserved.

I would also like to open the same discussion for handleInd and handleInd which can be changed to the definition I put below. The behaviour is changed in the sense that the length is returned (which cannot be higher than a 16 bit, if I recall correctly). For the same reasons I described above I don't see a reason why this cannot work in the same way.

virtual bool handleNotify(uint16_t handle, const uint8_t* value, int length);
virtual bool handleInd(uint16_t handle, const uint8_t* value, int length);

virtual uint16_t handleNotify(uint16_t handle, const uint8_t* value, uint16_t length);
virtual uint16_t handleInd(uint16_t handle, const uint8_t* value, uint16_t length);

This will help us shrink the code size and avoid repeating the definition of functions that are performing the same operation but slightly different.

[pennam]

handleNotify and handleInd are returning a bool value that is not strictly related to the length, respectively

return (numNotifications > 0); and return (numIndications > 0);

returning the length would change how the function is working

[andreagilardoni]

@pennam Then we can exclude these functions from the discussion