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bpo-40286: Makes simpler the relation between randbytes() and getrandbits() (GH-19574)

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Serhiy Storchaka 2020-04-17 23:51:28 +03:00 • committed by GitHub
parent 5b1d9184bb
commit 223221b290
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2 changed files with 26 additions and 16 deletions
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18
Modules/_randommodule.c
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@ -534,31 +534,25 @@ _random_Random_randbytes_impl(RandomObject *self, Py_ssize_t n)
return NULL;
}
if (n == 0) {
/* Don't consume any entropy */
return PyBytes_FromStringAndSize(NULL, 0);
}
PyObject *bytes = PyBytes_FromStringAndSize(NULL, n);
if (bytes == NULL) {
return NULL;
}
uint8_t *ptr = (uint8_t *)PyBytes_AS_STRING(bytes);
do {
for (; n; ptr += 4, n -= 4) {
uint32_t word = genrand_uint32(self);
#if PY_LITTLE_ENDIAN
/* Convert to big endian */
#if PY_BIG_ENDIAN
/* Convert to little endian */
word = _Py_bswap32(word);
#endif
if (n < 4) {
memcpy(ptr, &word, n);
/* Drop least significant bits */
memcpy(ptr, (uint8_t *)&word + (4 - n), n);
break;
}
memcpy(ptr, &word, 4);
ptr += 4;
n -= 4;
} while (n);
}
return bytes;
}