Problem reading an Integer in java that was written using python’s struct.pack method

Question

First I write the integer using python:
out.write( struct.pack(">i", int(i)) );

I then read the integer using DataInputStream.readInt() in Java.
I works but when it tries to read the number 10, and probably some other numbers too, it starts to read garbage.
Reading the numbers:
0, 4, 5, 0, 5, 13, 10, 1, 5, 6
Java reads:
0, 4, 5, 0, 5, 13, 167772160, 16777216, 83886080

What am I doing wrong?

RichieHindle · Accepted Answer · 2009-08-11 00:02:48Z

7

Psychic debugging: You're writing the output in text mode on Windows using code like this:

f = open("output.dat", "w")
f.write(my_data)

and that's making your 13 (which is a newline) become carriage return / newline (10, 13).

You need to write your output in binary mode:

f = open("output.dat", "wb")
f.write(my_data)

answered Aug 11, 2009 at 0:02

RichieHindle

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1 Comment

cmann Over a year ago

Of course! You have to write in binary mode to write binary data. That didn't even cross my mind. Thanks.

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