diff options
Diffstat (limited to 'Objects/longobject.c')
| -rw-r--r-- | Objects/longobject.c | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/Objects/longobject.c b/Objects/longobject.c index 92f8b046a0..fac8bb648b 100644 --- a/Objects/longobject.c +++ b/Objects/longobject.c @@ -364,20 +364,33 @@ _PyLong_AsByteArray(PyLongObject* v, accumbits = 0; carry = do_twos_comp ? 1 : 0; for (i = 0; i < ndigits; ++i) { + unsigned int oldaccumbits = accumbits; twodigits thisdigit = v->ob_digit[i]; if (do_twos_comp) { thisdigit = (thisdigit ^ MASK) + carry; carry = thisdigit >> SHIFT; thisdigit &= MASK; } + if (i < ndigits - 1) + accumbits += SHIFT; + else { + /* The most-significant digit may be partly empty. */ + twodigits bitmask = 1 << (SHIFT - 1); + twodigits signbit = do_twos_comp << (SHIFT - 1); + unsigned int nsignbits = 0; + while ((thisdigit & bitmask) == signbit && bitmask) { + ++nsignbits; + bitmask >>= 1; + signbit >>= 1; + } + accumbits += SHIFT - nsignbits; + } /* Because we're going LSB to MSB, thisdigit is more significant than what's already in accum, so needs to be prepended to accum. */ - accum |= thisdigit << accumbits; - accumbits += SHIFT; + accum |= thisdigit << oldaccumbits; /* Store as many bytes as possible. */ - assert(accumbits >= 8); - do { + while (accumbits >= 8) { if (j >= n) goto Overflow; ++j; @@ -385,13 +398,13 @@ _PyLong_AsByteArray(PyLongObject* v, p += pincr; accumbits -= 8; accum >>= 8; - } while (accumbits >= 8); + } } /* Store the straggler (if any). */ assert(accumbits < 8); assert(carry == 0); /* else do_twos_comp and *every* digit was 0 */ - if (accum) { + if (accumbits > 0) { if (j >= n) goto Overflow; ++j; |