Python如何利用struct进行二进制文件或数据流

import struct
 
x1 = struct.pack('H', 0x1516)
x2 = struct.pack('>H', 0x1516)
print('x1:{} x2:{}'.format(x1, x2))
 
# running result:
# x1:b'\x15\x13' x2:b'\x13\x15'

import struct
 
x = struct.pack('BI', 0xaa, 0x11223344)
d1, d2 = struct.unpack('BI', x)
print('pack:{} unpack:{:#x} {:#x}'.format(x, d1, d2))
 
# running result:
# pack:b'\xaa\x00\x00\x00D3"\x11' unpack:0xaa 0x11223344

# python3.7.6
 
import struct
from ctypes import create_string_buffer
 
 
"""
Python struct example
    package a format into binary finle
    
    format define:
    31               15              0
    +--------------------------------+
    |              mark              |
    +----------------+---------------+
    |     version    |    length     |
    +----------------+---------------+
    |            checksum            |
    +--------------------------------+
    |              data...           |
    +--------------------------------+
"""
 
 
def dump(mark, version, length, data, checksum):
    print('\n---- dump ----')
    print('mark:{:#X}'.format(mark))
    print('version:{}.{}'.format(version['major'], version['minor']))
    print('data length:{}'.format(length))
    print('checksum:{}'.format(checksum))
    print('data:{}'.format(data))
    print('--------------\n')
 
 
def save_bin(binary_file='test.bin', mark=0x5A5A5A5A, version={'major':1, 'minor':0}):
    
    offset = 0
    checksum = 0
    dataLength = 0
    data = [1,2,3,4,5,6,7,8]
    
    # create buffer
    buffer_size = 4+2+2+4+len(data)*4
    buffer = create_string_buffer(buffer_size)
    print('create buffer with {}byte'.format(buffer_size))
 
    # pack mark+version+length
    fmt = 'IBBH'
    dataLength = len(data)
    struct.pack_into(fmt, buffer, offset, mark, version['major'], version['minor'], dataLength)
    offset = offset + struct.calcsize(fmt)
 
    # pack data
    fmt = 'I'
    offset = offset + 4     # skip checksum
    for x in data:
        struct.pack_into(fmt, buffer, offset, x)
        offset = offset + struct.calcsize(fmt)
 
    # pack checksum
    fmt = 'I'
    offset = 8
    for x in buffer:
        d = x[0]
        checksum = checksum + d
    struct.pack_into(fmt, buffer, offset, checksum)
 
    # write to file
    f = open(binary_file, 'wb')
    f.write(buffer)
    f.close()
 
    dump(mark, version, dataLength, data, checksum)
 
    print('{}byte write to {}'.format(len(buffer), binary_file))
 
def read_bin(binary_file='test.bin'):
 
    offset = 0
    data = []
 
    # open and read file
    fmt = 'IBBHI'
    f = open(binary_file, 'rb')
    buffer = f.read()
    mark, major, minor, length, checksum = struct.unpack_from(fmt, buffer, 0)
    version = {'major':major, 'minor':minor}
 
    offset = struct.calcsize(fmt)
    for i in range(length-1):
        offset = offset + 4
        d = struct.unpack_from('I', buffer, offset)
        data.append(d[0])
 
    dump(mark, version, length, data, checksum)
    print('read {}byte from {}'.format(len(buffer), binary_file))
 
 
save_bin()
read_bin()
 
 
"""
running result:
create buffer with 44byte
---- dump ----
mark:0X5A5A5A5A
version:1.0
data length:8
checksum:405
data:[1, 2, 3, 4, 5, 6, 7, 8]
--------------
44byte write to test.bin
---- dump ----
mark:0X5A5A5A5A
version:1.0
data length:8
checksum:405
data:[2, 3, 4, 5, 6, 7, 8]
--------------
read 44byte from test.bin
"""