size_t cbuf_write(cbuf_t *cbuf, const void *_buf, size_t len, bool canreschedule)
{
const char *buf = (const char *)_buf;
LTRACEF("len %zd\n", len);
DEBUG_ASSERT(cbuf);
DEBUG_ASSERT(_buf);
DEBUG_ASSERT(len < valpow2(cbuf->len_pow2));
enter_critical_section();
size_t write_len;
size_t pos = 0;
while (pos < len && cbuf_space_avail(cbuf) > 0) {
if (cbuf->head >= cbuf->tail) {
write_len = MIN(valpow2(cbuf->len_pow2) - cbuf->head, len - pos);
} else {
write_len = MIN(cbuf->tail - cbuf->head - 1, len - pos);
}
// if it's full, abort and return how much we've written
if (write_len == 0) {
break;
}
memcpy(cbuf->buf + cbuf->head, buf + pos, write_len);
cbuf->head = INC_POINTER(cbuf, cbuf->head, write_len);
pos += write_len;
}
if (cbuf->head != cbuf->tail)
event_signal(&cbuf->event, canreschedule);
exit_critical_section();
return pos;
}
size_t cbuf_read(cbuf_t *cbuf, void *_buf, size_t buflen, bool block)
{
size_t ret;
char *buf = (char *)_buf;
DEBUG_ASSERT(cbuf);
DEBUG_ASSERT(_buf);
enter_critical_section();
if (block)
event_wait(&cbuf->event);
// see if there's data available
if (cbuf->tail != cbuf->head) {
size_t pos = 0;
// loop until we've read everything we need
// at most this will make two passes to deal with wraparound
while (pos < buflen && cbuf->tail != cbuf->head) {
size_t read_len;
if (cbuf->head > cbuf->tail) {
// simple case where there is no wraparound
read_len = MIN(cbuf->head - cbuf->tail, buflen - pos);
} else {
// read to the end of buffer in this pass
read_len = MIN(valpow2(cbuf->len_pow2) - cbuf->tail, buflen - pos);
}
memcpy(buf + pos, cbuf->buf + cbuf->tail, read_len);
cbuf->tail = INC_POINTER(cbuf, cbuf->tail, read_len);
pos += read_len;
}
if (cbuf->tail == cbuf->head) {
// we've emptied the buffer, unsignal the event
event_unsignal(&cbuf->event);
}
ret = pos;
} else {
DEBUG_ASSERT(!block);
ret = 0;
}
exit_critical_section();
return ret;
}
size_t cbuf_space_avail(cbuf_t *cbuf)
{
uint consumed = modpow2((uint)(cbuf->head - cbuf->tail), cbuf->len_pow2);
return valpow2(cbuf->len_pow2) - consumed - 1;
}
