Count big bits in u64 instead of usize #143
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A 32-bit target _could_ create a giant `BigUint` over 2²⁹ bytes = 512MB, not that this would be computationally useful, but that value would have more than `usize::MAX` bits. To avoid that possibility of overflow, we can better represent bit counts in `u64`. For 64-bit targets, a `BigUint` over 2⁶¹ bytes is not realistic. This changes the public API in the return values of `bits()` and `trailing_zeros()`, as well as the `bit_size` parameter of `RandBigInt` and `RandomBits`. Trying to randomize an absurd size will naturally cause a capacity overflow, just as if you'd made a huge `Vec`.
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I'm not certain this is a good idea -- I'll think on it for a bit before merging. Feedback welcome! |
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Ah, let's do it. If this makes it to 0.3 and folks complain, there's always 0.4 and beyond... bors r+ |
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A 32-bit target could create a giant
BigUintover 2²⁹ bytes = 512MB,not that this would be computationally useful, but that value would have
more than
usize::MAXbits. To avoid that possibility of overflow, wecan better represent bit counts in
u64.For 64-bit targets, a
BigUintover 2⁶¹ bytes is not realistic.This changes the public API in the return values of
bits()andtrailing_zeros(), as well as thebit_sizeparameter ofRandBigIntand
RandomBits. Trying to randomize an absurd size will naturallycause a capacity overflow, just as if you'd made a huge
Vec.