Re: C sizes trouble - reading longs from a file

[Lionel Pinkhard <lionelp@worldonline.co.za>]

Hmm... Well, I think I'll use the fread() method, but I'll use 4 instead of
sizeof(long), would this be correct? Since no matter what the operating
system, the data in the file will STILL be 4 bytes long! :-) I think it
would even be easier to rewrite the piece of code, than to change the
entire data file structure :-).

Thanks for the help,

Ciao,

Lionel

----------
From: slick willy <bporter@flashcom.net>
To: gameprogrammer@gameprogrammer.com
Subject: Re: C sizes trouble - reading longs from a file
Date: Monday, August 28, 2000 8:15 PM

shouldn't this:

offset = (buffer[0] << 24) + (buffer[1] << 16) + (buffer[2] << 8) +
buffer[0];

be this?:

offset = (buffer[0] << 24) + (buffer[1] << 16) + (buffer[2] << 8) +
buffer[3];

also, as someone said earlier, you should make your code more portable by
checking the sizeof(long) since on many machines a long is in fact not 4
bytes.

--Bill
  ----- Original Message ----- 
  From: Lionel Pinkhard 
  To: gameprogrammer@gameprogrammer.com 
  Sent: Thursday, January 03, 1980 3:07 PM
  Subject: C sizes trouble - reading longs from a file


  Hey guys,

  I'm having some trouble here, I have a data file which contains an offset
  to another location in the file. The offset is a long (4 bytes). I need
to
  read in the offset from a location in the file, and then move the file
  pointer to the location specified by that long. I have tried using the
  following code:

  for (index = 0; index < 4; index++) {
      buffer[index] = fgetc(data_p);
  }
  offset = (buffer[0] << 24) + (buffer[1] << 16) + (buffer[2] << 8) +
  buffer[0];
  fseek(data_p, offset, 0);

  But this doesn't seem to set me at the right location. And if I try
  printing out the data pointed to by the offset, I just get EOFs.

  What am I doing wrong? Is there a simpler way of doing this?

  I really hope somebody can help me out here!

  Ciao,

  Lionel
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