CODEWITHSUNDEEP
pythonarrays
user138988
user138988

Reputation: 41

Working with bytes in Python 2.7

I'm trying to assemble a byte array in Python for a signature that resembles the following:

String A + B are utf-8 which I converted to utf-8 using unicode(string, 'utf-8')

I've tried converting each item to a byte array and joining them using the plus symbol e.g.

bytearray(len(a)) + bytearray(a, "utf-8")...

I've also stried using struct.pack e.g.

struct.pack("i", len(a)) + bytearray(access_token, "utf-8")...

But nothing seems to generate a valid signature. Is this the right way to make the above byte array in Python?

Upvotes: 2

Views: 1703

Answers (1)

Serge Ballesta
Serge Ballesta

Reputation: 148965

The last question is about endianness of the 4 byte lengths, but you can easily control it with the struct module.

I would use

def dopack(A, B, LongA):
    fmt='!'  # for network order, use < for little endian, > for big endian, = for native
    fmt += 'i'

    buf = pack(fmt, len(A))
    buf += A
    buf += pack(fmt, len(B))
    buf += B
    b = bytes(LongA)
    buf += pack(fmt, len(b))
    buf += B

In this way, the LongA value is coded in ASCII, but it is easier, and you can just do int(b) do convert it back to a long.

Upvotes: 2

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