Vorbis dev - Jun 2003 - Trouble decoding number of codebooks

I'm having trouble decoding the number of codebooks out of an ogg file,
and was wondering if anyone here could lend a hand?

I read in the sync pattern, and I think the codebook dimensions properly,
but when I try and read in the number of codebook entries, I get a number
larger than the number of bytes in the file, which I have to assume is
wrong :)

Anyway this is how I read in the numbers :

void readCodeBooks(ifstream *file, int codebookCount)
{
  //read in the 24 bit sync pattern
  unsigned char *c = readBytes(file, 3);

  //read the codebook dimensions
  unsigned char *dimensions = readBytes(file,2);
  int codebookDimensions = (int)convertArray2(dimensions, 2);

  //read codebook entries
  unsigned char *entries = readBytes(file,3);
  long codebookEntries = convertArray2(entries,3);
}

long convertArray2(unsigned char *array, int size)
{
  //reverse the array
  unsigned char revArray[size];
  for(int i = size - 1; i >= 0; i--)
    revArray[(size-1) - i] = array[i];

  //return a pointer to a long
  long *result = (long *)revArray;
  return *result;
}

The results that I get from the code are :

 Sync Pattern (starting byte #269) : 42 43 56   (outputed as integers)
 Codebook dimensions (starting byte #272) : 256
 Codebook entries (starting byte #274) : 4194304

Cheers for the help,

Oliver Sneyd
ots1@cs.waikato.ac.nz

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On Saturday, June 14, 2003, at 12:36 am, <ots1@cs.waikato.ac.nz> wrote:
> I read in the sync pattern, and I think the codebook dimensions 
> properly,
> but when I try and read in the number of codebook entries, I get a 
> number
> larger than the number of bytes in the file, which I have to assume is
> wrong :)
The code you've written isn't at all portable, but assuming you're 
trying to convert from vorbis little-endian to native integers on a 
big-endian host, your problem is convertArray2().

Assuming 'readBytes()' reads in a byte at a time, you start with 
entries = byte0,byte1,byte2,unknown,.... convertArray2 swaps this to 
byte2,byte1,byte0,unknown, and then casts to a long. The actual value 
is 0,byte2,byte1,byte0, so your result is multiplied by 256 + a random 
value. The dimensions read is wrong too.

Hope that helps,
  -r

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I can see why that would completely mangle the results that i'm getting,
but I can't see why my code is doing this. When I display whats going on
in the for loop, it seems to work  on the right number of bytes. If Print
out each iteration I get

array[(size - i) - 1] :  64          revArray[(size-1) - 1] : 0
array[(size - i) - 1] :   0          revArray[(size-1) - 1] : 0
array[(size - i) - 1] :   0          revArray[(size-1) - 1] : 64

o I can see that in  the file i'm working on, there are going to be 64
codebooks. Is the problem i'm having to do with  the casting of the long ?

readBytes does read in a single byte at a time.

Cheers,

Oliver Sneyd
(ots1@cs.waikato.ac.nz)

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