Templatize class to minimize code size. #36
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The MicroOLED class is now three different classes for the SPI, I2C, and Parallel communication modes, with the functionality in a templatized common base class. This avoids always building in the I2C, SPI, and Parallel comm code even though only one will likely be used. When using SPI mode, this resulted in a hex file using 1092 bytes less, not insignificant.
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Nice work Patrik (@lutorm ) - thank you, |
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Hmm yeah, good point, it does break backwards-compatibility although in a pretty trivial way. I think it would be pretty easy to add another class with the old name which preserves the old runtime-choice of comms, though. Let me update. |
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It got pretty convoluted with having to share the comm implementations between the "new" and a backwards compatible class, so I guess it's not worth it. |
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Thanks Patrik, |
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This is kind of a large change, but it saves 1100 bytes of program space when only using SPI. which is significant. I assume the savings are similar if you use the other comms protocols.
Because the library used a runtime variable to determine which comm method to use, the compiler could not easily eliminate code that we know will not be used since the constructor sets the comms mode.
If we instead of using a runtime variable keep this information in a template, it is obvious to the compiler at compile time which methods won't be used and it can eliminate that code. The MicroOLED class is now three different classes for the SPI, I2C, and Parallel communication modes, with the functionality in a templatized common base class. This avoids always building in the I2C, SPI, and Parallel comm code even though only one will likely be used.
The drawback is that cases that DO use more than one comms mode will now use more space. If this is a use case that people care about, it could be accommodated most simply by adding another derived class.