Re: [PHP] unpacking an array of structs...

I'm actually moving from a string-encoded transport to binary for 
compactness.  The array can potentially get pretty large.  I'm shooting 
for the smallest possible representation of the data, which is 1 char 
and 1 short per data point.






On February 23, 2010, Rene Veerman <[email protected]> wrote:

> have you considered using json as transport?
> http://json.org/ has code you can re-use.
> 
> On Tue, Feb 23, 2010 at 7:29 AM, [email protected] 
> <[email protected]> wrote:
>> 
>> I have a desktop app that has a data structure that looks like this:
>> 
>> typedef struct MANGOpie
>> {
>>   unsigned char   mango;
>>   unsigned short  pie;
>> }
>> MANGOpie;
>> 
>> 
>> 
>> I manage a C array of these things in memory:
>> 
>> MANGOpie * pies = (MANGOpie *)malloc(count*sizeof(MANGOpie));
>> 
>> 
>> 
>> 
>> I pass these to a PHP script on my webserver who needs to unpack the array
>> of structs.
>> 
>> The unpack() PHP function appears to be what I need, but it doesn't 
>> like the
>> formatting I'm using to describe an array of these structs:
>> 
>> "(Cmango/npie)*"
>> 
>> What it doesn't like are the parentheses.  I've tried brackets and curlies
>> too, but nothing works.  I have to have the parentheses to tell the parser
>> to repeat the entire struct:
>> 
>> mango
>> pie
>> mango
>> pie
>> mango
>> pie
>> ...
>> 
>> 
>> 
>> Formatting without the parentheses -- "Cmango/npie*" -- is:
>> 
>> mango
>> pie
>> pie
>> pie
>> pie
>> pie
>> ...
>> 
>> 
>> 
>> One workaround is to drop the struct and just manage two separate parallel
>> arrays of each data type in the desktop app:
>> 
>> unsigned char *   mangos = (unsigned char  *)malloc(count*sizeof(unsigned
>> char));
>> unsigned short *  pies   = (unsigned short *)malloc(count*sizeof(unsigned
>> short));
>> 
>> With PHP unpack() format strings:
>> 
>> "Cmango*"
>> "npie*"
>> 
>> But, I'd rather keep the struct for the sake of code clarity and neatness.
>> 
>> 
>> 
>> Another would be to iterate thru the binary data, unpacking one struct at a
>> time, but that would be slower, presumably.
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Anyone know the trick to this?
>> 
>> Thanks.
>> 
>> 
>> 
>> 
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