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_PyLong_AsByteArray: simplify the logic for dealing with the most-

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significant digits sign bits.  Again no change in semantics.
This commit is contained in:
Tim Peters 2001-06-14 08:53:38 +00:00
parent ce9de2f79a
commit ede0509111
1 changed files with 13 additions and 11 deletions
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24
Objects/longobject.c
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@ -388,7 +388,6 @@ _PyLong_AsByteArray(PyLongObject* v,
accumbits = 0;
carry = do_twos_comp ? 1 : 0;
for (i = 0; i < ndigits; ++i) {
unsigned int numnewbits = SHIFT;
twodigits thisdigit = v->ob_digit[i];
if (do_twos_comp) {
thisdigit = (thisdigit ^ MASK) + carry;
@ -399,22 +398,25 @@ _PyLong_AsByteArray(PyLongObject* v,
significant than what's already in accum, so needs to be
prepended to accum. */
accum |= thisdigit << accumbits;
accumbits += SHIFT;
/* How many new bits did we add? The most-significant digit
may be (probably is) at least partly empty. */
/* The most-significant digit may be (probably is) at least
partly empty. */
if (i == ndigits - 1) {
twodigits bitmask = 1 << (SHIFT - 1);
twodigits signbit = do_twos_comp << (SHIFT - 1);
/* Count # of sign bits -- they needn't be stored,
* although for signed conversion we need later to
* make sure at least one sign bit gets stored.
* First shift conceptual sign bit to real sign bit.
*/
stwodigits s = (stwodigits)(thisdigit <<
(8*sizeof(stwodigits) - SHIFT));
unsigned int nsignbits = 0;
while ((thisdigit & bitmask) == signbit && bitmask) {
while ((s < 0) == do_twos_comp && nsignbits < SHIFT) {
++nsignbits;
bitmask >>= 1;
signbit >>= 1;
s <<= 1;
}
assert(nsignbits <= SHIFT);
numnewbits -= nsignbits;
accumbits -= nsignbits;
}
accumbits += numnewbits;
/* Store as many bytes as possible. */
while (accumbits >= 8) {