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py/mpz: Do sign extension in mpz_as_bytes for negative values.

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Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2020-11-05 22:35:02 +11:00
parent 7789cd5f16
commit 1fef5662ab
3 changed files with 17 additions and 2 deletions
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10
py/mpz.c
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@ -1609,7 +1609,6 @@ bool mpz_as_uint_checked(const mpz_t *i, mp_uint_t *value) {
return true;
}
// writes at most len bytes to buf (so buf should be zeroed before calling)
void mpz_as_bytes(const mpz_t *z, bool big_endian, size_t len, byte *buf) {
byte *b = buf;
if (big_endian) {
@ -1641,6 +1640,15 @@ void mpz_as_bytes(const mpz_t *z, bool big_endian, size_t len, byte *buf) {
}
}
}
// fill remainder of buf with zero/sign extension of the integer
if (big_endian) {
len = b - buf;
} else {
len = buf + len - b;
buf = b;
}
memset(buf, z->neg ? 0xff : 0x00, len);
}
#if MICROPY_PY_BUILTINS_FLOAT

1
py/objint_mpz.c
View File

@ -116,7 +116,6 @@ mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf
void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf) {
assert(mp_obj_is_type(self_in, &mp_type_int));
mp_obj_int_t *self = MP_OBJ_TO_PTR(self_in);
memset(buf, 0, len);
mpz_as_bytes(&self->mpz, big_endian, len, buf);
}

8
tests/basics/struct1_intbig.py
View File

@ -36,3 +36,11 @@ print(struct.unpack("<Q", b"\xff\xff\xff\xff\xff\xff\xff\xff"))
# check small int overflow
print(struct.unpack("<i", b'\xff\xff\xff\x7f'))
print(struct.unpack("<q", b'\xff\xff\xff\xff\xff\xff\xff\x7f'))
# test with negative big integers that are actually small in magnitude
bigzero = (1 << 70) - (1 << 70)
for endian in "<>":
for type_ in "bhiq":
fmt = endian + type_
b = struct.pack(fmt, -2 + bigzero)
print(fmt, b, struct.unpack(fmt, b))