interconversion between embedded types and binary

interconversion.py

import struct
import ctypes
import array

# 16bit unsigned int to binary
uint16 = 0xff00
raw = array.array("B", struct.pack("<H", uint16))   # "<" means little-endian. ">" means big-endian
print(raw)  # array('B', [0, 255])

# multible 16bit unsigned int to binary
uint16_array = array.array("H", [0xff00, 0x55aa])
fmt = "<" + str(len(uint16_array)) + "H"
raw = array.array("B", struct.pack(fmt, *uint16_array))   # "<2H" means little-endian 2 words of uint16
print(raw)  # array('B', [0, 255, 170, 85])

# single float to binary
single = 3.14
raw = array.array("B", struct.pack("<f", single))
print(raw)  # array('B', [195, 245, 72, 64])

# binary to 32bit int
raw = array.array("B", [0x01, 0x02, 0x03, 0x04])
uint32 = struct.unpack("<L", raw)   # struct.unpack() returns tupple
print(uint32[0])    # 67305985 means 0x04030201

# binary to multiple 32bit int
raw = array.array("B", [0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08])
fmt = "<" + str(int(len(raw)/ctypes.sizeof(ctypes.c_uint32))) + "L"
uint32 = array.array("L", struct.unpack(fmt, raw))
print(uint32)    # array('L', [67305985, 134678021])

# binary to double float
raw = array.array('B', [20, 174, 71, 225, 122, 20, 2, 64])
double = struct.unpack("<d", raw)   # struct.unpack() returns tupple
print(double[0])    # 2.26

''' typecode reference
b   int8    1byte
B   uint8   1byte
h   int16   2byte
H   uint16  2byte
l   int32   4byte
L   uint32  4byte
q   int64   8byte
Q   uint64  8byte
f   single float    4byte
d   double float    8byte
'''