[PHP] Binary Data File reading

[Chris Mattmann]

Hi there-

Does anyone have any clue as to what may be causing this problem.  I am

trying to read from a binary data value that has temperature values stored in it

in short integer format.  So basically, for every 2 bytes of binary data, that value

in short integer is the temperature value.  I have written a simple C program to read

in the values from the out.bin binary data file I have, and echo them back to the 
console:

It prints out the correct values, here is the C program that I used:

#include

  void main(void)

   {

 FILE *fin;

 short buffer[1];

  int num_read;

fin = fopen("out.bin","r");

 num_read=1;
while(num_read>0) {
   num_read = fread(buffer, sizeof(short), 1, fin);
   printf("%d,",buffer[0]);
}

fclose(fin);
return(1);

  }

I am trying to write a php file to do the exact same thing, except instead of printing

out the values, I'm going to store them in an array.  Anyways, the php script I've 
written

looks like this:



The output I get from the php script is complete garble(a whole bunch of 0's, some 
1's, some random

int values, etc.  I know that PHP doesn't exactly have a short int type, i know that

their integers are actually stored in the C LONG_INT type, which are 8 byte integers.  
Do

you think that this may be affecting my script, and if it is, does anyone know of any

workarounds?  Your help would be greatly appreciated.

Thanks in advance.

-------
Chris Mattmann
Science Data Management and Archiving
[EMAIL PROTECTED]
NASA-JPLPasadena, CA  91109-8099
Office: 300-324C
Phone:  818-354-8810

[PHP] php unpack function

[Chris Mattmann]

Hi there-

  I am using the PHP unpack function to take a binary formatted file with 10's of 
thousands

of signed short integers stored in it, to take the file (which is in PHP STRING form)

and extract the short integer values from it.  The problem I am having is when reading

all the documentation for the pack/unpack function, I have been unable to figure out a 
way

to only take a small subset of the data.  For instance, my file is basically just

thousands of temperature values, taken 4 times a day, over a period of 20 years.  Let's

say I wanted to get a year's worth of temperatures, from the 10th year into the file

(so I would need the 4x365x10) th temperature value from the file.  How would I use the

unpack function to just select the (4x365x10)th through the (4x365x10)+(4x365)th value

(basically year 10's entire temperature range).  I see in the documentation I can

specify how many shorts to extract STARTING from the first one, how would I specify,

or is it even possible to specify a different starting location to begin extraction

from.  I cannot write the string to a file, and then use fseek while reading the file

back in to skip to a postion and unpack from there.  The way that the application is

structured, I have to begin my extraction at the point where I already have the file

in terms of a binary encoded string.  So if anyone has any suggestions, I would greatly

appreciate it.

Please reply back to my account here at work if you are posting a reply on the forum:

Thanks for your time.

---
Chris Mattmann
Science Data Management and Archiving
[EMAIL PROTECTED]
NASA-JPLPasadena, CA  91109-8099
Office: 300-324C
Phone:  818-354-8810