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Given a C header file with a lot structures defined and a raw hex string, I would like to parse the string into corresponding C structure.

I've looked into struct.unpack() to accomplish this, but I wasn't able to come up with a way to derive the format string automatically (which is desirable, since this header file is often updated).

Is finding a way to generate the format string for struct.unpack() the right approach? Or is there an easier way to parse hex strings into C structures? 

import struct

'''
Example structure:

typedef struct {
  struct {
    uint8_t   a_flag:1;
    uint8_t   b_flag:1;
    uint8_t   c_flag:1; 
    uint8_t   d_flag:1;
    uint8_t   unused:3;  
    uint8_t   e_flag:1; 
  } PACKED flag_byte_0;

  struct {
    uint8_t   unused:6;
    uint8_t   f_flag:1; 
    uint8_t   g_flag:1; 
  } PACKED flag_byte_1;

 struct {
    uint8_t   unused:5;
    uint8_t   h_flag:1; 
    uint8_t   i_flag:1;
    uint8_t   j_flag:1; 
 } PACKED flag_byte_2;

 struct {
    uint8_t   unused:2;
    uint8_t   k_flag;
    uint8_t   l_flag:1;
    uint8_t   unused_2:4;
 } PACKED flag_byte_3;

  uint16_t    field_a;
  uint16_t    field_b; 
  uint32_t    field_c:24;
  uint32_t    field_d:8; 
} PACKED struct_example; 
'''

if __name__ == '__main__':
    hex_string = '\x10\x08\x00\x00\x3d\x00\x08\xd7\x90\x00\x00\x0a'
    format_string = 'BBBBHHI'
    struct.unpack(format_string, hex_string)
    # returns (16, 8, 0, 0, 61, 55048, 167772304)
    # really want:
    #   a_flag:1
    #   g_flag:1
    #   ...
    #   field_a: 0x3d00
    #   etc...
4

1 回答 1

0

使用cffi：

from cffi import FFI

ffi = FFI()
ffi.cdef('''
typedef struct {
  struct {
    uint8_t   a_flag:1;
    uint8_t   b_flag:1;
    uint8_t   c_flag:1;
    uint8_t   d_flag:1;
    uint8_t   unused:3;
    uint8_t   e_flag:1;
  } flag_byte_0;

  struct {
    uint8_t   unused:6;
    uint8_t   f_flag:1;
    uint8_t   g_flag:1;
  } flag_byte_1;

  struct {
    uint8_t   unused:5;
    uint8_t   h_flag:1;
    uint8_t   i_flag:1;
    uint8_t   j_flag:1;
  } flag_byte_2;

  struct {
    uint8_t   unused:2;
    uint8_t   k_flag:1;
    uint8_t   l_flag:1;
    uint8_t   unused_2:4;
  } flag_byte_3;

  uint16_t    field_a;
  uint16_t    field_b;
  uint32_t    field_c:24;
  uint32_t    field_d:8;
} struct_example;
''')


data = '\x10\x08\x00\x00\x3d\x00\x08\xd7\x90\x00\x00\x0a'
buf = ffi.new('char[]', data)
st = ffi.cast('struct_example*', buf)

print st.flag_byte_0.a_flag
print st.flag_byte_1.g_flag
print st.flag_byte_2.h_flag
print st.flag_byte_2.i_flag
print st.flag_byte_2.j_flag
print st.flag_byte_3.k_flag
print st.flag_byte_3.l_flag
print st.field_a
print st.field_b
print st.field_c
print st.field_d
于 2013-07-09T18:19:59.863 回答