The routines protect against too much data overflowing the buffersize
and allow for multiple calls. I thought that maybe if curl changed the
pointer coming in I could run into trouble but that doesnt appear to be
the case.

The two routines are below. Let me know what you think.

Thanks,
Rob

-----

Write callback:
static size_t read_memory_callback(void *ptr, size_t size, size_t
nmemb, void *stream)
{
   size_t retcode;
   long my_size;
   int thread_id;
   int i;

   thread_id = get_our_thread_id();

   if ((nmemb*size) > BIG_BUFFER_SIZE)
   {
      my_size = BIG_BUFFER_SIZE;
   }
   else
   {
      my_size = nmemb * size;
   }

   if (my_size > sizeLeft[thread_id])
   {
      my_size = sizeLeft[thread_id];
   }

   if (my_size > 0)
   {
      memcpy(ptr, stream, my_size);
      sizeLeft[thread_id] -= my_size;
   }

   retcode = my_size;

   return retcode;
}

Read callback:
static size_t write_memory_callback(void *ptr, size_t size, size_t
nmemb, void *stream)
{
   size_t retcode;
   int my_size;
   int thread_id;
   int i;

   thread_id = get_our_thread_id();

   if ((nmemb*size) > BIG_BUFFER_SIZE)
   {
      my_size = BIG_BUFFER_SIZE;
   }
   else
   {
      my_size = nmemb * size;
   }

   if (my_size > 0)
   {
      memcpy(stream, ptr, my_size);
   }

   sizeLeft[thread_id] += my_size;
   retcode = my_size;
   return retcode;
}

> ------------------------------
>
> Message: 9
> Date: Mon, 23 Aug 2004 15:42:06 -0700
> From: "Dylan Salisbury" <dylan_at_tellme.com>
> Subject: RE: Multithreaded Issues
> To: "'libcurl development'" <curl-library_at_cool.haxx.se>
> Message-ID: <20040823224206.5F7138B3_at_mail01.corp.tellme.com>
> Content-Type: text/plain; charset="US-ASCII"
>
> You might be overflowing your data buffers (local variables
> writeBuffer and
> readBuffer). Here are some questions about your callback functions:
>
> 1. What do your callback functions do if the amount of data given to
> them is
> more than BIG_BUFFER_SIZE?
>
> 2. Do they correctly deal with the response being split up between
> multiple
> calls?
>
> 3. Do they assume that the buffer will be initialized to anything in
> particular before the first time libcurl calls them? The code you
> posted
> does not initialize the buffers, so they may contain data from previous
> calls.
>
>> From the code that you posted, I would guess that your callbacks are
>> not
> robust enough, and when you test with all GETs or all PUTs you do not
> notice
> the problem because all the actions are very similar.
>
> If this reply is not helpful enough, you could post your callback
> functions
> to the list, as well as a more specific description of the undesirable
> behavior.
>
>
> Dylan
>
>
Received on 2004-08-24