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objint: Implement int.from_bytes() class method and .to_bytes() method. 

These two are apprerently the most concise and efficient way to convert
int to/from bytes in Python. The alternatives are struct and array modules,
but methods using them are more verbose in Python code and less efficient
in memory/cycles.
This commit is contained in:
Paul Sokolovsky 2014-04-09 00:40:58 +03:00
parent 3aa8ee7c9e
commit a985b4593d
3 changed files with 46 additions and 0 deletions
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38
py/objint.c
View File

@ -261,6 +261,43 @@ mp_obj_t mp_obj_int_binary_op_extra_cases(int op, mp_obj_t lhs_in, mp_obj_t rhs_
return MP_OBJ_NULL;
}
STATIC mp_obj_t int_from_bytes(uint n_args, const mp_obj_t *args) {
buffer_info_t bufinfo;
mp_get_buffer_raise(args[0], &bufinfo);
assert(bufinfo.len >= sizeof(machine_int_t));
// TODO: Support long ints
// TODO: Support byteorder param
// TODO: Support signed param
return mp_obj_new_int_from_uint(*(machine_uint_t*)bufinfo.buf);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(int_from_bytes_obj, 1, 3, int_from_bytes);
STATIC mp_obj_t int_to_bytes(uint n_args, const mp_obj_t *args) {
machine_int_t val = mp_obj_int_get_checked(args[0]);
uint len = MP_OBJ_SMALL_INT_VALUE(args[1]);
byte *data;
// TODO: Support long ints
// TODO: Support byteorder param
// TODO: Support signed param
mp_obj_t o = mp_obj_str_builder_start(&mp_type_bytes, len, &data);
memset(data, 0, len);
memcpy(data, &val, len < sizeof(machine_int_t) ? len : sizeof(machine_int_t));
return mp_obj_str_builder_end(o);
}
STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(int_to_bytes_obj, 2, 4, int_to_bytes);
STATIC const mp_map_elem_t int_locals_dict_table[] = {
{ MP_OBJ_NEW_QSTR(MP_QSTR_from_bytes), (mp_obj_t)&int_from_bytes_obj },
{ MP_OBJ_NEW_QSTR(MP_QSTR_to_bytes), (mp_obj_t)&int_to_bytes_obj },
};
STATIC MP_DEFINE_CONST_DICT(int_locals_dict, int_locals_dict_table);
const mp_obj_type_t mp_type_int = {
{ &mp_type_type },
.name = MP_QSTR_int,
@ -268,4 +305,5 @@ const mp_obj_type_t mp_type_int = {
.make_new = mp_obj_int_make_new,
.unary_op = mp_obj_int_unary_op,
.binary_op = mp_obj_int_binary_op,
.locals_dict = (mp_obj_t)&int_locals_dict,
};

2
py/qstrdefs.h
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@ -96,6 +96,7 @@ Q(eval)
Q(exec)
Q(filter)
Q(float)
Q(from_bytes)
Q(getattr)
Q(globals)
Q(hash)
@ -127,6 +128,7 @@ Q(sum)
Q(super)
Q(str)
Q(sys)
Q(to_bytes)
Q(tuple)
Q(type)
Q(value)

6
tests/basics/int-bytes.py Normal file
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@ -0,0 +1,6 @@
print((10).to_bytes(1, "little"))
print((111111).to_bytes(4, "little"))
print((100).to_bytes(10, "little"))
print(int.from_bytes(b"\x00\x01\0\0\0\0\0\0", "little"))
print(int.from_bytes(b"\x01\0\0\0\0\0\0\0", "little"))
print(int.from_bytes(b"\x00\x01\0\0\0\0\0\0", "little"))