Rewrite: Prevent overflow from public functions #30
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Move delay loop into internal functions . Refactor the assembly loop into its own function, to allow easier reuse in the below functions. . Add internal delay functions calling the assembly loop function. One function uses a 32 bit counter, and the other uses a 48 bit counter. These functions will be used to reactor delay_ms and delay_us to prevent overflow. . Refactor delay to use the internal delay functions.
Refactor delay_ms and delay_us to prevent overflow . Change delay_ms and delay_us to call the internal delay function with a 48 bit counter. This prevents delay_ms and delay_us from overflowing when passed a large argument. . Move the internal delay functions to their own module. Remove the unused internal delay_loop_3_cycles function.
Calculating the number of cycles to delay for in delay_ms and delay_us requires multiplying by a constant and dividing by another constant. Divide both constants by their GCD at compile time, to allow the compiler to better optimize the multiplication and division. This reduces the overhead in the case where the compiler does not know the length of the delay at compile time, or otherwise fails to inline the function.
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This is the rewrite discussed in #17. Its main purpose is to ensure that public functions cannot overflow, by having them delegate to private functions that accept larger parameters. Some work was also put in to mitigating the effects of the delays not being inlined at compile time.