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Reverse int to bytes buffer overflow conditionals

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Rather than jumping to a label when an overflow is known to have
occurred, return early when one is known not to have.
This commit is contained in:
Matt Wozniski 2019-05-09 22:02:13 -04:00
parent fb7bb40575
commit 1d0c61642b
1 changed files with 15 additions and 26 deletions
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37
py/objint.c
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@ -303,43 +303,32 @@ char *mp_obj_int_formatted(char **buf, size_t *buf_size, size_t *fmt_size, mp_co
void mp_obj_int_buffer_overflow_check(mp_obj_t self_in, size_t nbytes, bool is_signed)
{
if (is_signed) {
// edge = 1 << (nbytes * 8 - 1)
// self must be < 2**(bits - 1)
mp_obj_t edge = mp_binary_op(MP_BINARY_OP_INPLACE_LSHIFT,
mp_obj_new_int(1),
mp_obj_new_int(nbytes * 8 - 1));
// if self >= edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_MORE_EQUAL, self_in, edge) == mp_const_true) {
goto raise;
}
// edge = -edge
edge = mp_unary_op(MP_UNARY_OP_NEGATIVE, edge);
// if self < edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_LESS, self_in, edge) == mp_const_true) {
goto raise;
// and >= -2**(bits - 1)
edge = mp_unary_op(MP_UNARY_OP_NEGATIVE, edge);
if (mp_binary_op(MP_BINARY_OP_MORE_EQUAL, self_in, edge) == mp_const_true) {
return;
}
}
} else {
if (mp_obj_int_sign(self_in) < 0) {
// Negative numbers never fit in an unsigned value
goto raise;
}
// edge = 1 << (nbytes * 8)
// self must be >= 0
if (mp_obj_int_sign(self_in) >= 0) {
// and < 2**(bits)
mp_obj_t edge = mp_binary_op(MP_BINARY_OP_INPLACE_LSHIFT,
mp_obj_new_int(1),
mp_obj_new_int(nbytes * 8));
// if self >= edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_MORE_EQUAL, self_in, edge) == mp_const_true) {
goto raise;
}
}
if (mp_binary_op(MP_BINARY_OP_LESS, self_in, edge) == mp_const_true) {
return;
}
}
}
raise:
mp_raise_OverflowError_varg(translate("value would overflow a %d byte buffer"), nbytes);
}