The :cpp:class:`String` class is probably the most used class in Arduino and Sming.
Unfortunately it gets the blame for one of the most indidious problems in the embedded world, heap fragmentation.
To alleviate this problem, Sming uses a technique known as Small String Optimisation, which uses the available space inside the String object itself to avoid using the heap for small allocations of 10 characters or fewer.
This was lifted from the Arduino Esp8266 core. Superb work - thank you!
.. envvar:: STRING_OBJECT_SIZE
minimum: 12 bytes (default)
maximum: 128 bytes
Must be an integer multiple of 4 bytes.
This is an experimental feature which lets you increase the size of a String object to
reduce heap allocations further. The effect of this will vary depending on your application,
but you can see some example figures in :pull-request:`1951`.
Benefits of increasing :envvar:`STRING_OBJECT_SIZE`:
- Increase code speed
- Fewer heap allocations
Drawbacks:
- Increased static memory usage for global/static String objects or embedded within global/static class instances.
- A String can use SSO *or* the heap, but not both together, so in heap mode any additional SSO space will remain unused.
Allows the size of a String object to be changed to increase the string length available before the heap is used.
.. note::
The current implementation uses one byte for a NUL terminator, and another to store the length,
so the maximum SSO string length is (STRING_OBJECT_SIZE - 2) characters.
However, the implementation may change so if you need to check the maximum SSO string size
in your code, please use ``String::SSO_CAPACITY``.
.. doxygenclass:: String :members: