ex_httpgetvar.c

Assume that the page "status.cgi" needs to display the serial number of the HTTP Web server device. The page "status.cgi" being served by the HTTP Server contains the following HTML line:

Serial Number=%S01

The 'S' is the Variable Group and the '01' is the VarValue in uppercase hex. During processing of this file, the HTTP Server encounters the ‘%S01’ string. After parsing it, the HTTP Server makes a callback to HTTPGetVar(httpInfo, val). The httpInfo->var.get.varRef will have the value HTTP_START_OF_VAR. The main user application implements HTTPGetVar as follows:

#include "projdefs.h"
#include "net\http.h"

ROM char SerialNumberStr[] = "123456SER";

WORD HTTPGetVar(HTTP_INFO* httpInfo, BYTE* val)
{
    BYTE varValue, varGroup, ref;

    varValue = httpInfo->var.get.tagVal;        //Variable Value of requested variable
    varGroup = httpInfo->var.get.tagGroup;      //Variable Group of requested variable
    ref      = httpInfo->var.get.varRef;        //Current callback reference with respect
                                                // to 'var' variable.
    

    //In case requested var not found, set it to NULL character and return HTTP_END_OF_VAR
    *val = '\0';    
    
    //Identify variable group
    if (varGroup == 'S')
    {
        // Identify variable value.
        if ( varValue == 0x01 )
        {
            // Serial Number is a NULL terminated string.
            // First of all determine, if this is very first call.
            if ( ref == HTTP_START_OF_VAR )
            {
                // This is the first call. Initialize index to SerialNumber
                // string. We are using ref as our index.
                ref = (BYTE)0;
            }
            
            // Now access byte at current index and save it in buffer.
            *val = SerialNumberStr[(BYTE)ref];
            
            // Did we reach end of string?
            if ( *val == ‘\0’ )
            {
                // Yes, we are done transferring the string.
                // Return with HTTP_END_OF_VAR to notify HTTP server that we
                // are finished transferring the value.
                return HTTP_END_OF_VAR;
            } 
            // Or else, increment array index and return it to HTTP server.
            (BYTE)ref++;
            // Since value of ref is not HTTP_END_OF_VAR, HTTP server will call
            // us again for rest of the value.
            return ref;
        }
        else {
            // Check for other variables values...
        }
    }
}