Ecore Connection Buffering

As Ecore_Con works on an event driven design, as data arrives, events will be produced containing the data that arrived.

As Ecore_Con works on an event driven design, as data arrives, events will be produced containing the data that arrived.

It is up to the user of Ecore_Con to either parse as they go, append to a file to later parse the whole file in one go, or append to memory to parse or handle later.

To help with this Eina has some handy API's. The Eina_Binbuf and Eina_Strbuf APIs, abstract dynamic buffer management and make it trivial to handle buffers at runtime, without having to manage them. Eina_Binbuf makes it possible to create, expand, reset and slice a blob of memory - all via API. No system calls, no pointer manipulations and no size calculation.

Additional functions include adding content at specified byte positions in the buffer, escaping the inputs, find and replace strings. This provides extreme flexibility to play around, with a dynamic blob of memory.

It is good to free it (using eina_binbuf_free()) after using it.

Eina_Binbuf compliments Ecore_Con use cases, where dynamic sizes of data arrive from the network (think http download in chunks). Using Eina_Binbuf provides enough flexibility to handle data as it arrives and to defer its processing until desired, without having to think about where to store the temporary data and how to manage its size.

An example of how to use these with Ecore_Con follows.

#include <Eina.h>
#include <Ecore.h>
#include <Ecore_Con.h>
 
static Eina_Bool
data_callback(void *data, int type, void *event)
{
   Ecore_Con_Event_Url_Data *url_data = event;
   if ( url_data->size > 0)
     {
        // append data as it arrives - don't worry where or how it gets stored.
        // Also don't worry about size, expanding, reallocing etc.
        // just keep appending - size is automatically handled.
 
        eina_binbuf_append_length(data, url_data->data, url_data->size);
 
        fprintf(stderr, "Appended %d \n", url_data->size);
     }
   return EINA_TRUE;
}
 
 
 
static Eina_Bool
completion_callback(void *data, int type, void *event)
{
   Ecore_Con_Event_Url_Complete *url_complete = event;
   printf("download completed with status code: %d\n", url_complete->status);
 
   // get the data back from Eina_Binbuf
   char *ptr = eina_binbuf_string_get(data);
   size_t size = eina_binbuf_length_get(data);
 
   // process data as required (write to file)
   fprintf(stderr, "Size of data = %d bytes\n", size);
   int fd = open("./elm.png", O_CREAT);
   write(fd, ptr, size);
   close(fd);
 
   // free it when done.
   eina_binbuf_free(data);
 
   ecore_main_loop_quit();
 
   return EINA_TRUE;
}
 
 
int
main(int argc, char **argv)
{
 
   const char *url = "http://www.enlightenment.org/p/index/d/logo.png";
 
   ecore_init();
   ecore_con_init();
   ecore_con_url_init();
 
 
   // This is single additional line to manage dynamic network data.
   Eina_Binbuf *data = eina_binbuf_new();
   Ecore_Con_Url *url_con = ecore_con_url_new(url);
 
   ecore_event_handler_add(ECORE_CON_EVENT_URL_COMPLETE,
                                                      completion_callback,
                                                      data);
   ecore_event_handler_add(ECORE_CON_EVENT_URL_DATA,
                                                      data_callback,
                                                      data);
   ecore_con_url_get(url_con);
 
   ecore_main_loop_begin();
   return 0;
}