getbits2, getbits3: rewrite to avoid left shift of negative integers #261
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Extended this PR to update more of the getbit* and setbit* functions, just avoiding undefined behaviour, checking the argument ranges, and handling edge cases. This has not detected or addressed any current issues with their usage. |
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Change the bit position and lengths to be unsigned values. This avoids having to check if they are negative, and makes it clear that these functions are only intended to be used with non-negative bit positions and lengths. Check and report bit lengths that are out of range. Better handle some edge cases, such as lengths being zero. Avoid left shits of unsigned integers which is 'undefined behaviour'.
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Left shifts of negative integers is 'undefined behaviour'. Also there was an edge case that was not handled correctly, when l1 was zero, and probably never encountered. Rewrite these function to use the same approach as getbits(), form the combined unsigned bits first and then convert to a negative number if necessary.