err_t qbuffer_pop_back(qbuffer_t* buf)
{
qbytes_t* bytes;
int64_t skip;
int64_t len;
qbuffer_iter_t chunk;
if ( qbuffer_num_parts(buf) == 0 ) return EINVAL;
chunk = qbuffer_end(buf);
qbuffer_iter_prev_part(buf, &chunk);
qbuffer_iter_get(chunk, qbuffer_end(buf), &bytes, &skip, &len);
deque_pop_back(sizeof(qbuffer_part_t), &buf->deque);
buf->offset_end -= len;
return 0;
}
qioerr qbuffer_pop_back(qbuffer_t* buf)
{
qbytes_t* bytes;
int64_t skip;
int64_t len;
qbuffer_iter_t chunk;
if ( qbuffer_num_parts(buf) == 0 ) QIO_RETURN_CONSTANT_ERROR(EINVAL, "cannot pop from empty buffer");
chunk = qbuffer_end(buf);
qbuffer_iter_prev_part(buf, &chunk);
qbuffer_iter_get(chunk, qbuffer_end(buf), &bytes, &skip, &len);
deque_pop_back(sizeof(qbuffer_part_t), &buf->deque);
buf->offset_end -= len;
return 0;
}
/* Advances an iterator using linear search.
*/
void qbuffer_iter_advance(qbuffer_t* buf, qbuffer_iter_t* iter, int64_t amt)
{
deque_iterator_t d_begin = deque_begin( & buf->deque );
deque_iterator_t d_end = deque_end( & buf->deque );
if( amt >= 0 ) {
// forward search.
iter->offset += amt;
while( ! deque_it_equals(iter->iter, d_end) ) {
qbuffer_part_t* qbp = (qbuffer_part_t*) deque_it_get_cur_ptr(sizeof(qbuffer_part_t), iter->iter);
if( iter->offset < qbp->end_offset ) {
// it's in this one.
return;
}
deque_it_forward_one(sizeof(qbuffer_part_t), & iter->iter);
}
// If we get here, we didn't find it. Return the buffer end.
*iter = qbuffer_end(buf);
} else {
// backward search.
iter->offset += amt; // amt is negative
if( ! deque_it_equals( iter->iter, d_end ) ) {
// is it within the current buffer?
qbuffer_part_t* qbp = (qbuffer_part_t*) deque_it_get_cur_ptr(sizeof(qbuffer_part_t), iter->iter);
if( iter->offset >= qbp->end_offset - qbp->len_bytes ) {
// it's in this one.
return;
}
}
// now we have a valid deque element.
do {
qbuffer_part_t* qbp;
deque_it_back_one(sizeof(qbuffer_part_t), & iter->iter);
qbp = (qbuffer_part_t*) deque_it_get_cur_ptr(sizeof(qbuffer_part_t), iter->iter);
if( iter->offset >= qbp->end_offset - qbp->len_bytes ) {
// it's in this one.
return;
}
} while( ! deque_it_equals(iter->iter, d_begin) );
// If we get here, we didn't find it. Return the buffer start.
*iter = qbuffer_begin(buf);
}
}
err_t qbuffer_pop_front(qbuffer_t* buf)
{
qbytes_t* bytes;
int64_t skip;
int64_t len;
qbuffer_iter_t chunk;
if ( qbuffer_num_parts(buf) == 0 ) return EINVAL;
chunk = qbuffer_begin(buf);
qbuffer_iter_get(chunk, qbuffer_end(buf), &bytes, &skip, &len);
deque_pop_front(sizeof(qbuffer_part_t), &buf->deque);
buf->offset_start += len;
return 0;
}
// find buffer iterator part in logarithmic time
// finds an offset in the window [offset_start,offset_end]
// (in other words, offset might not start at 0)
qbuffer_iter_t qbuffer_iter_at(qbuffer_t* buf, int64_t offset)
{
qbuffer_iter_t ret;
deque_iterator_t first = deque_begin(& buf->deque);
deque_iterator_t last = deque_end(& buf->deque);
deque_iterator_t middle;
qbuffer_part_t* qbp;
ssize_t num_parts = deque_it_difference(sizeof(qbuffer_part_t), last, first);
ssize_t half;
while( num_parts > 0 ) {
half = num_parts >> 1;
middle = first;
deque_it_forward_n(sizeof(qbuffer_part_t), &middle, half);
qbp = (qbuffer_part_t*) deque_it_get_cur_ptr(sizeof(qbuffer_part_t), middle);
if( offset < qbp->end_offset ) {
num_parts = half;
} else {
first = middle;
deque_it_forward_one(sizeof(qbuffer_part_t), &first);
num_parts = num_parts - half - 1;
}
}
if( deque_it_equals(first, last) ) {
ret = qbuffer_end(buf);
} else {
qbp = (qbuffer_part_t*) deque_it_get_cur_ptr(sizeof(qbuffer_part_t), first);
if( offset < qbp->end_offset - qbp->len_bytes ) {
ret = qbuffer_begin(buf);
} else {
ret.offset = offset;
ret.iter = first;
}
}
return ret;
}
