py-packed-struct
An implementation of C-like packed structures in Python based on the bitstruct package
py-packed-struct allows to define C-like structures in an elegant way and to convert them into bytes objects without having to specify the format as required by struct:
# with struct
>>> from struct import *
>>> one, two, three = 1, 2, 3
>>> pack(">bhl", one, two, three)
b'\x01\x00\x02\x00\x00\x00\x03'
# with py-packed-struct
>>> from packed_struct import *
>>> s = Struct({"one": c_signed_int(8), "two": c_signed_int(16), "three": c_signed_int(32) })
>>> s.set_data(one = 1, two = 2, three = 3)
>>> serialized = s.pack(byte_endianness="big")
>>> print(serialized)
b'\x01\x00\x02\x00\x00\x00\x03'
>>>
>>> s.unpack(serialized)
>>> {'one': 1, 'two': 2, 'three': 3}Who needs to remember struct format strings? :)
In addition, py-packed-struct allows to work with bit-fields and nested structures (see examples).
Installation
pip install py-packed-structSupported features
- C-like struct
- bit-fields handling
- byte endianess
- (TODO) bit endianness
Example
This example can be found in example/mqtt. publisher.py publishes a message on a MQTT topic and subscriber.c is subscribed to that topic. The publisher publishes the following structure:
person = Struct(
{
"name": c_char(10*8),
"age": c_unsigned_int(8),
"weight": c_float(32),
"dresses": Struct(
{
"tshirt": c_char(10*8),
"shorts": c_char(10*8),
"shoes": Struct(
{
"number": c_unsigned_int(8),
"brand": c_char(10*8)
}
)
}
)
}
)
# set data values
person.set_data(name="Luca", age=29, weight=76.9)
person.dresses.set_data(tshirt="foo", shorts="boo")
person.dresses.shoes.set_data(number=42, brand="bar")The subscriber copies the incoming buffer in the following struct:
typedef struct __attribute__((packed)) {
uint8_t number;
char brand[10];
} shoes_t;
typedef struct __attribute__((packed)) {
char tshirt[10];
char shorts[10];
shoes_t shoes;
} clothes_t;
typedef struct __attribute__((packed)) {
char name[10];
uint8_t age;
float weight;
clothes_t clothes;
} person;The result is the following:
