add: rb_discard function

2 files changed, 56 insertions, 0 deletions

diff --git a/include/rb.h b/include/rb.h
index 4e00305..aa17de8 100644
--- a/include/rb.h
+++ b/include/rb.h
@@ -36,6 +36,7 @@ long rb_send(struct rb *, const void *, size_t, unsigned long);
 int rb_clear(struct rb *, int);
 int rb_destroy(struct rb *);
 int rb_stop(struct rb *);
+size_t rb_discard(struct rb *, size_t);
 const char *rb_version(char *, char *, char *);
 size_t rb_count(const struct rb *);
 size_t rb_space(const struct rb *);
diff --git a/rb/rb.c b/rb/rb.c
index 9e32a92..e3efd24 100644
--- a/rb/rb.c
+++ b/rb/rb.c
@@ -988,6 +988,61 @@ int rb_stop
 
 
 /* ==========================================================================
+    Function that discards data from tail of buffer.  This works  just  like
+    rb_reads function, but is way faster as there  is  no  copying  involved
+   ========================================================================== */
+
+
+size_t rb_discard
+(
+    struct rb  *rb,       /* rb object */
+    size_t      count     /* number of elements to discard */
+)
+{
+    size_t      rbcount;  /* number of elements in rb */
+    size_t      cnte;     /* number of elements in rb until overlap */
+    /*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/
+
+
+    VALID(EINVAL, rb);
+    VALID(EINVAL, rb->buffer);
+
+#if ENABLE_THREADS
+    if ((rb->flags & O_NONBLOCK) == 0)
+    {
+        pthread_mutex_lock(&rb->lock);
+    }
+#endif
+
+    cnte = rb_count_end(rb);
+    rbcount = rb_count(rb);
+
+    if (count > rbcount)
+    {
+        count = rbcount;
+    }
+
+    if (count > cnte)
+    {
+        rb->tail = count - cnte;
+    }
+    else
+    {
+        rb->tail += count;
+        rb->tail &= rb->count -1;
+    }
+
+#if ENABLE_THREADS
+    if ((rb->flags & O_NONBLOCK) == 0)
+    {
+        pthread_mutex_unlock(&rb->lock);
+    }
+#endif
+
+}
+
+
+/* ==========================================================================
     Returns version of the library
    ========================================================================== */