From d035454d9e96fbbf7bcfc630ee3cf735b6ed2983 Mon Sep 17 00:00:00 2001
From: Roman Zeyde <me@romanzey.de>
Date: Tue, 7 Aug 2018 11:17:05 +0300
Subject: [PATCH] Allow retrieving WriteBatch serialized size

---
 src/db.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/db.rs b/src/db.rs
index 78fd8c7..0bed62c 100644
--- a/src/db.rs
+++ b/src/db.rs
@@ -1106,6 +1106,15 @@ impl WriteBatch {
         unsafe { ffi::rocksdb_writebatch_count(self.inner) as usize }
     }
 
+    /// Return WriteBatch serialized size (in bytes).
+    pub fn size_in_bytes(&self) -> usize {
+        unsafe {
+            let mut batch_size: size_t = 0;
+            ffi::rocksdb_writebatch_data(self.inner, &mut batch_size);
+            batch_size as usize
+        }
+    }
+
     pub fn is_empty(&self) -> bool {
         self.len() == 0
     }
@@ -1403,6 +1412,14 @@ fn writebatch_works() {
             assert!(p.is_ok());
             assert!(db.get(b"k1").unwrap().is_none());
         }
+        {
+            // test size_in_bytes
+            let mut batch = WriteBatch::default();
+            let before = batch.size_in_bytes();
+            let _ = batch.put(b"k1", b"v1234567890");
+            let after = batch.size_in_bytes();
+            assert!(before + 10 <= after);
+        }
     }
     let opts = Options::default();
     assert!(DB::destroy(&opts, path).is_ok());