Code example for how to decode c structs

decode_c_structs.py

# See also
# https://docs.python.org/3/library/struct.html#format-strings
# https://stackoverflow.com/questions/17244488/reading-struct-in-python-from-created-struct-in-c
'''
// Create c struct
#include <stdio.h>
typedef struct { char c; double v; int t;} save_type;
int main() {
    // 1 + 8 + 4 = 13 bytes
    // 1+7 + 8 + 4+4 = 24 bytes since we are on a 64-bit machine
    save_type s = { 's', 12.1f, 17};  
    FILE *f = fopen("output", "w");
    fwrite(&s, sizeof(save_type), 1, f);
    fclose(f);
    return 0;
'''
import struct

fmt_str = 'c7x d i4x'
s = struct.Struct(fmt_str)
print(f'Format string: {s.format}. It uses: {s.size} bytes')

with open('output', 'rb') as f:
    chunk = f.read(s.size)
    while len(chunk) > 0 :
        unpacked = s.unpack(chunk)
        print(f'Unpacked Values: {unpacked}')
        chunk = f.read(s.size)