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midi buffer handling: fix some logic errors in dealing with MidiRingBuffer reads

This commit is contained in:
Paul Davis 2021-09-06 13:55:26 -06:00
parent 7932c9bde1
commit 50b01732fd
1 changed files with 14 additions and 5 deletions
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19
libs/ardour/midi_ring_buffer.cc
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@ -58,16 +58,21 @@ MidiRingBuffer<T>::read (MidiBuffer& dst, samplepos_t start, samplepos_t end, sa
uint8_t peekbuf[prefix_size];
/* this cannot fail, because we've already verified that there
is prefix_space to read
*/
* is prefix_space to read
*/
this->peek (peekbuf, prefix_size);
ev_time = *(reinterpret_cast<T*>((uintptr_t)peekbuf));
ev_type = *(reinterpret_cast<Evoral::EventType*>((uintptr_t)(peekbuf + sizeof(T))));
ev_size = *(reinterpret_cast<uint32_t*>((uintptr_t)(peekbuf + sizeof(T) + sizeof (Evoral::EventType))));
if (this->read_space() < ev_size) {
break;;
/* check that we have both the prefix and the full event
* present in the buffer before continuing. If not, we can't do
* anything (and since we have only peek'ed at the buffer, it
* remains in the same state for the next read() call.
*/
if (this->read_space() < prefix_size + ev_size) {
break;
}
if (ev_time >= end) {
@ -96,12 +101,16 @@ MidiRingBuffer<T>::read (MidiBuffer& dst, samplepos_t start, samplepos_t end, sa
*/
uint8_t* write_loc = dst.reserve (ev_time, ev_type, ev_size);
if (write_loc == 0) {
/* nowhere to write to; we've already consumed the
* prefix for this event (and cannot backup). Consume the
* rest of the event (advances read pointer to next event)
*/
this->increment_read_ptr (ev_size);
if (stop_on_overflow_in_dst) {
DEBUG_TRACE (DEBUG::MidiRingBuffer, string_compose ("MidiRingBuffer: overflow in destination MIDI buffer, stopped after %1 events\n", count));
break;
}
error << "MRB: Unable to reserve space in buffer, event skipped" << endmsg;
this->increment_read_ptr (ev_size); // Advance read pointer to next event
continue;
}