add back tu_fifo_discard_n() since it may be useful in the future.

2 files changed, 13 insertions, 0 deletions

diff --git a/src/common/tusb_fifo.c b/src/common/tusb_fifo.c
index 2faf72ba8..e97b6ccce 100644
--- a/src/common/tusb_fifo.c
+++ b/src/common/tusb_fifo.c
@@ -448,6 +448,15 @@ uint16_t tu_fifo_write_n_access_mode(tu_fifo_t *f, const void *data, uint16_t n,
   return n;
 }
 
+uint16_t tu_fifo_discard_n(tu_fifo_t *f, uint16_t n) {
+  const uint16_t count = tu_min16(n, tu_fifo_count(f)); // limit to available count
+  ff_lock(f->mutex_rd);
+  f->rd_idx = advance_index(f->depth, f->rd_idx, count);
+  ff_unlock(f->mutex_rd);
+
+  return count;
+}
+
 //--------------------------------------------------------------------+
 // One API
 //--------------------------------------------------------------------+
diff --git a/src/common/tusb_fifo.h b/src/common/tusb_fifo.h
index f13c195e5..2e2a0db6f 100644
--- a/src/common/tusb_fifo.h
+++ b/src/common/tusb_fifo.h
@@ -205,6 +205,10 @@ TU_ATTR_ALWAYS_INLINE static inline uint16_t tu_fifo_read_n(tu_fifo_t *f, void *
   return tu_fifo_read_n_access_mode(f, buffer, n, TU_FIFO_INC_ADDR_RW8);
 }
 
+// discard first n items from fifo i.e advance read pointer by n with mutex
+// return number of discarded items
+uint16_t tu_fifo_discard_n(tu_fifo_t *f, uint16_t n);
+
 //--------------------------------------------------------------------+
 // Write API
 //--------------------------------------------------------------------+