From 815cd254e275f0cdaa7c73ed87a5f8a39ce7d010 Mon Sep 17 00:00:00 2001
From: Tomasz Grabiec <tgrabiec@scylladb.com>
Date: Thu, 21 Dec 2017 22:28:28 +0100
Subject: [PATCH] streamed_mutation: Introduce peek()

Will be used in assertions to merge consecutive range tombstones.
---
 streamed_mutation.hh | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/streamed_mutation.hh b/streamed_mutation.hh
index 731d3d5068..f206c2a699 100644
--- a/streamed_mutation.hh
+++ b/streamed_mutation.hh
@@ -670,6 +670,21 @@ public:
         return _impl->operator()();
     }
 
+    // Resolves with a pointer to the next fragment in the stream without consuming it from the stream,
+    // or nullptr if there are no more fragments.
+    // The returned pointer is invalidated by any other call to this object.
+    future<mutation_fragment*> peek() {
+        if (!is_buffer_empty()) {
+            return make_ready_future<mutation_fragment*>(&_impl->_buffer.front());
+        }
+        if (is_end_of_stream()) {
+            return make_ready_future<mutation_fragment*>(nullptr);
+        }
+        return fill_buffer().then([this] {
+            return peek();
+        });
+    }
+
     void set_max_buffer_size(size_t size) {
         _impl->max_buffer_size_in_bytes = size;
     }