reading post request data in C module in apache http server

This question is related to C module in apache HTTP server.

The need is to read post request data in apache HTTP server & modify it, before request reaches to WebLogic application server.

We first considered to have perl filter (using mod_perl2) which will do this but we discarded perl because of reasons like it's slower etc. So we are now building same kind of filter in C language.

I am able to invoke C module (.so module) for a particular URL. It reads get request parameters also. The code is as follows:

#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"
#include "http_core.h"

/* The sample content handler */
static int hello_handler(request_rec *r)
{
    const char* user_agent;
    r->content_type="text/html";
    if(r->header_only) return OK;
    ap_rputs("<HTML><HEAD><TITLE>Greetings from Vishva</TITLE></HEAD><BODY>\n",r);
    if(r->path_info && strlen(r->path_info) > 0)
    ap_rprintf(r,"Path Info from new hello=%s\n",r->path_info);
    if(r->args && strlen(r->args)>0)
    ap_rprintf(r,"\n query is awesome from new hello=%s",r->args);    
    ap_rputs("</BODY></HTML>",r);
    return OK;
}

static void hello_register_hooks(apr_pool_t *p)
{
    ap_hook_handler(hello_handler, NULL, NULL, APR_HOOK_LAST);
}

/* Dispatch list for API hooks */
module AP_MODULE_DECLARE_DATA hello_module = {
    STANDARD20_MODULE_STUFF, 
    NULL,                  /* create per-dir    config structures */
    NULL,                  /* merge  per-dir    config structures */
    NULL,                  /* create per-server config structures */
    NULL,                  /* merge  per-server config structures */
    NULL,                  /* table of config file commands       */
    hello_register_hooks  /* register hooks                      */
};

However I didn't find any code sample which reads post request.
Can someone help?

Thanks.