Support snapshot max-size limitation

[lttng-tools.git] / src / common / consumer.c

diff --git a/src/common/consumer.c b/src/common/consumer.c
index bcede1ef5d8f3857515baeaf709ad9b78294a684..9b544dd112cbc58b4e339a3126b19e83116fd577 100644 (file)
--- a/src/common/consumer.c
+++ b/src/common/consumer.c
@@ -3457,3 +3457,23 @@ int consumer_send_status_channel(int sock,
 
        return lttcomm_send_unix_sock(sock, &msg, sizeof(msg));
 }
+
+/*
+ * Using a maximum stream size with the produced and consumed position of a
+ * stream, computes the new consumed position to be as close as possible to the
+ * maximum possible stream size.
+ *
+ * If maximum stream size is lower than the possible buffer size (produced -
+ * consumed), the consumed_pos given is returned untouched else the new value
+ * is returned.
+ */
+unsigned long consumer_get_consumed_maxsize(unsigned long consumed_pos,
+               unsigned long produced_pos, uint64_t max_stream_size)
+{
+       if (max_stream_size && max_stream_size < (produced_pos - consumed_pos)) {
+               /* Offset from the produced position to get the latest buffers. */
+               return produced_pos - max_stream_size;
+       }
+
+       return consumed_pos;
+}