Re: [PATCH] aplay: Introduce and use xwrite helper

[Takashi Iwai <tiwai@suse.de>]

On Fri, 07 Apr 2017 17:35:40 +0200,
Daniel Baluta wrote:
> 
> Write can return less then requested bytes, but we treat this as
> an error thus ending up with confusing error messages.
> 
> Fix this by introducing xwrite helper, which makes sure all bytes
> are written or an error is returned.
> 
> With this patch an usecase where disk is filled by recording will
> print:
> $ /mnt/msc/audio.wav: No space left on device
> 
> instead of random messages like:
> 
> $/mnt/msc/audio.wav: No such file or directory
> 
> Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
> ---
> This is a follow up of:
> 
> http://mailman.alsa-project.org/pipermail/alsa-devel/2017-April/119632.html
> 
> where I tried to fix the error message instead of write :).
> 
>  aplay/aplay.c | 55 +++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 37 insertions(+), 18 deletions(-)
> 
> diff --git a/aplay/aplay.c b/aplay/aplay.c
> index ee480f2..74d3d37 100644
> --- a/aplay/aplay.c
> +++ b/aplay/aplay.c
> @@ -429,6 +429,25 @@ enum {
>  	OPT_FATAL_ERRORS,
>  };
>  
> +/*
> + * make sure we write all bytes or return an error
> + */
> +static ssize_t xwrite(int fd, const void *buf, size_t count)
> +{
> +	ssize_t written;
> +	size_t offset = 0;
> +
> +	while (offset < count) {
> +		written = write(fd, buf + offset, count - offset);
> +		if (written <= 0)
> +			return written;
> +
> +		offset += written;
> +	};
> +
> +	return written;

This will return a partial written size.
Return "offset" instead.


thanks,

Takashi