Ciao!
Il 2020-09-30 09:03 ni...@lysator.liu.se ha scritto:
Marco Bodrato <bodr...@mail.dm.unipi.it> writes:
limb = sp[sn];
if (GMP_LIMB_BITS > CHAR_BIT || shift > 0)
limb >>= bits - shift;
else
limb = 0;
Do we really need to support bits == GMP_LIMB_BITS here? If not, the
About mpn_set_str, the manual reads "base can vary from 2 to 256".
Moreover we are fool enough to (unofficially) support "typedef unsigned
char mp_limb_t;" in mini-gmp...
above 5 lines could be simplified to just
limb = (sp[sn] >> 1) >> (bits - 1 - shift);
it should be safe in all cases.
I agree.
Anyway, there may be a problem only if we shift sp[sn] (unsigned char)
or limb (possibly the same type) by 8 bits (if bits=8 and shift=0).
An even simpler solution could be to cast to unsigned int (at least 16
bits, right?) so:
limb = (unsigned int) sp[sn] >> (bits - shift);
Maybe the cast is unnecessary, because the C standard says that the left
operand of a shift operation is always promoted to (unsigned) int if it
is smaller, correct? But it shouldn't be dangerous.
Ĝis,
m
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