1 files changed, 43 insertions, 5 deletions

diff --git a/src/dbwrapper.h b/src/dbwrapper.h
index 414df76a7c..24ef71bfbf 100644
--- a/src/dbwrapper.h
+++ b/src/dbwrapper.h
@@ -6,14 +6,13 @@
 #define BITCOIN_DBWRAPPER_H
 
 #include "clientversion.h"
+#include "fs.h"
 #include "serialize.h"
 #include "streams.h"
 #include "util.h"
 #include "utilstrencodings.h"
 #include "version.h"
 
-#include <boost/filesystem/path.hpp>
-
 #include <leveldb/db.h>
 #include <leveldb/write_batch.h>
 
@@ -56,11 +55,19 @@ private:
     CDataStream ssKey;
     CDataStream ssValue;
 
+    size_t size_estimate;
+
 public:
     /**
      * @param[in] _parent   CDBWrapper that this batch is to be submitted to
      */
-    CDBBatch(const CDBWrapper &_parent) : parent(_parent), ssKey(SER_DISK, CLIENT_VERSION), ssValue(SER_DISK, CLIENT_VERSION) { };
+    CDBBatch(const CDBWrapper &_parent) : parent(_parent), ssKey(SER_DISK, CLIENT_VERSION), ssValue(SER_DISK, CLIENT_VERSION), size_estimate(0) { };
+
+    void Clear()
+    {
+        batch.Clear();
+        size_estimate = 0;
+    }
 
     template <typename K, typename V>
     void Write(const K& key, const V& value)
@@ -75,6 +82,14 @@ public:
         leveldb::Slice slValue(ssValue.data(), ssValue.size());
 
         batch.Put(slKey, slValue);
+        // LevelDB serializes writes as:
+        // - byte: header
+        // - varint: key length (1 byte up to 127B, 2 bytes up to 16383B, ...)
+        // - byte[]: key
+        // - varint: value length
+        // - byte[]: value
+        // The formula below assumes the key and value are both less than 16k.
+        size_estimate += 3 + (slKey.size() > 127) + slKey.size() + (slValue.size() > 127) + slValue.size();
         ssKey.clear();
         ssValue.clear();
     }
@@ -87,8 +102,16 @@ public:
         leveldb::Slice slKey(ssKey.data(), ssKey.size());
 
         batch.Delete(slKey);
+        // LevelDB serializes erases as:
+        // - byte: header
+        // - varint: key length
+        // - byte[]: key
+        // The formula below assumes the key is less than 16kB.
+        size_estimate += 2 + (slKey.size() > 127) + slKey.size();
         ssKey.clear();
     }
+
+    size_t SizeEstimate() const { return size_estimate; }
 };
 
 class CDBIterator
@@ -195,7 +218,7 @@ public:
      * @param[in] obfuscate   If true, store data obfuscated via simple XOR. If false, XOR
      *                        with a zero'd byte array.
      */
-    CDBWrapper(const boost::filesystem::path& path, size_t nCacheSize, bool fMemory = false, bool fWipe = false, bool obfuscate = false);
+    CDBWrapper(const fs::path& path, size_t nCacheSize, bool fMemory = false, bool fWipe = false, bool obfuscate = false);
     ~CDBWrapper();
 
     template <typename K, typename V>
@@ -282,7 +305,22 @@ public:
      * Return true if the database managed by this class contains no entries.
      */
     bool IsEmpty();
+
+    template<typename K>
+    size_t EstimateSize(const K& key_begin, const K& key_end) const
+    {
+        CDataStream ssKey1(SER_DISK, CLIENT_VERSION), ssKey2(SER_DISK, CLIENT_VERSION);
+        ssKey1.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
+        ssKey2.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
+        ssKey1 << key_begin;
+        ssKey2 << key_end;
+        leveldb::Slice slKey1(ssKey1.data(), ssKey1.size());
+        leveldb::Slice slKey2(ssKey2.data(), ssKey2.size());
+        uint64_t size = 0;
+        leveldb::Range range(slKey1, slKey2);
+        pdb->GetApproximateSizes(&range, 1, &size);
+        return size;
+    }
 };
 
 #endif // BITCOIN_DBWRAPPER_H
-