On Thu, Apr 23, 2015 at 7:14 PM, Martin Ling <martin-sig...@earth.li> wrote:
> On Thu, Apr 23, 2015 at 05:17:33PM -0400, Cody P Schafer wrote:
>>
>> Do note that the lack of posix-like blocking behavior (ie: read at
>> least 1 byte but up to N bytes) means one must either read one byte at
>> a time or wire up the sp_event_set infra to do "read until X".
>
> How and why would you use the sp_event_set infrastructure for this?
>
So in posix I'd do something like the following (buffer fullness &
error checking omitted):
int b_fd = open_and_configure_port_as_blocking();
uint8_t buf[1024];
size_t used = 0;
for (;;) {
ssize_t r = read(b_fd, buf + used, sizeof(buf) - used);
/* scan for 'X', if found break */
if (memchr(buf + used, 'X', r))
break;
used += r;
}
With libserialport to get the same behaviour I need to:
struct sp_port *p = open_and_configure_port();
uint8_t buf[1024];
size_t used = 0;
struct sp_event_set *ev;
sp_new_event_set(&ev);
sp_add_port_events(ev, p, SP_EVENT_RX_READY);
for (;;) {
sp_wait(ev, 0);
sp_nonblocking_read(p, buf + used, sizeof(buf) - used);
/* scan for 'X', if found break */
if (memchr(buf + used, 'X', r))
break;
used += r;
}
Because sp_blocking_read() doesn't return early (like posix read does).
[Both of these examples were put together directly in this email, they
are untested, and they lack handling of buffer fullness & errors, no
_not_ use them directly without fixing those weaknesses]
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