On 2008-05-29, Andrew Lunn <[EMAIL PROTECTED]> wrote:
> On Thu, May 29, 2008 at 06:27:30PM +0000, Grant Edwards wrote:
>> I find myself in need of a "pipe" like object in an eCos
>> application (one that doesn't have file I/O and Posix support
>> enabled). All I need is a simple circular buffer in RAM with
>> blocking and non-blocking read/write methods. Am I correct in
>> my conclusion that eCos doesn't have something like that as
>> part of it's core functionality?
>>
>> I haven't found anything like that in the docs, but I thought
>> I'd double-check before I go off and write something...
>
> There was a pipe implementation contributed. I spent some time
> cleaning it up a few years ago. Try the attachment.
>
> Andrew
>
> [begin attachment: pipe.tgz]
The following code looks odd:
287 //
--------------------------------------------------------------------------
288 // Implement Flush/Drain controls
289
290 static Cyg_ErrNo
291 pipe_get_config(cyg_io_handle_t handle,
292 cyg_uint32 key, void *buf, cyg_uint32 * len)
293 {
294 cyg_devtab_entry_t *devtab = (cyg_devtab_entry_t *) handle;
295 PIPE_INFO_S *pipeInfo = (PIPE_INFO_S *) devtab->priv;
296 Cyg_ErrNo retVal = ENOERR;
297
298 switch (key) {
299 // clear the buffer and signal any threads waiting.
300 case CYG_IO_GET_CONFIG_SERIAL_INPUT_FLUSH:
301 case CYG_IO_GET_CONFIG_SERIAL_OUTPUT_FLUSH:
302 case CYG_IO_GET_CONFIG_SERIAL_OUTPUT_DRAIN:
303 cyg_drv_mutex_lock(&pipeInfo->lock);
304 pipeInfo->writeIndex = 0;
305 pipeInfo->readIndex = 0;
306 pipeInfo->dataLength = 0;
307 cyg_drv_cond_broadcast(&pipeInfo->wait);
308 #ifdef CYG_IO_PIPE_SELECT_SUPPORT
309 cyg_selwakeup(&pipeInfo->selinfoTx);
310 #endif
311 cyg_drv_mutex_unlock(&pipeInfo->lock);
312 retVal = ENOERR;
313 break;
314
315 default:
316 retVal = -EINVAL;
317 break;
318 }
319
320 return (retVal);
321 }
It looks like all three of those flush/drain operations do the
same thing: discard all of the data. I can see why both flush
operations might discard the data, since it's not a
directionless interface, but shouldn't the drain operation just
block until the buffer is empty instead of discarding data?
--
Grant Edwards grante Yow! PARDON me, am I
at speaking ENGLISH?
visi.com
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