diff --git a/dbms/src/IO/ReadBufferFromIStream.cpp b/dbms/src/IO/ReadBufferFromIStream.cpp
new file mode 100644
index 00000000000..a65946e5170
--- /dev/null
+++ b/dbms/src/IO/ReadBufferFromIStream.cpp
@@ -0,0 +1,36 @@
+#include <IO/ReadBufferFromIStream.h>
+#include <Common/Exception.h>
+
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int CANNOT_READ_FROM_ISTREAM;
+}
+
+bool ReadBufferFromIStream::nextImpl()
+{
+    istr.read(internal_buffer.begin(), internal_buffer.size());
+    size_t gcount = istr.gcount();
+
+    if (!gcount)
+    {
+        if (istr.eof())
+            return false;
+        else
+            throw Exception("Cannot read from istream", ErrorCodes::CANNOT_READ_FROM_ISTREAM);
+    }
+    else
+        working_buffer.resize(gcount);
+
+    return true;
+}
+
+ReadBufferFromIStream::ReadBufferFromIStream(std::istream & istr_, size_t size)
+    : BufferWithOwnMemory<ReadBuffer>(size), istr(istr_)
+{
+}
+
+}
diff --git a/dbms/src/IO/ReadBufferFromIStream.h b/dbms/src/IO/ReadBufferFromIStream.h
index 203200b0cac..7f804783ba2 100644
--- a/dbms/src/IO/ReadBufferFromIStream.h
+++ b/dbms/src/IO/ReadBufferFromIStream.h
@@ -2,8 +2,6 @@
 
 #include <iostream>
 
-#include <Common/Exception.h>
-
 #include <IO/ReadBuffer.h>
 #include <IO/BufferWithOwnMemory.h>
 
@@ -11,38 +9,15 @@
 namespace DB
 {
 
-namespace ErrorCodes
-{
-    extern const int CANNOT_READ_FROM_ISTREAM;
-}
-
-
 class ReadBufferFromIStream : public BufferWithOwnMemory<ReadBuffer>
 {
 private:
     std::istream & istr;
 
-    bool nextImpl() override
-    {
-        istr.read(internal_buffer.begin(), internal_buffer.size());
-        size_t gcount = istr.gcount();
-
-        if (!gcount)
-        {
-            if (istr.eof())
-                return false;
-            else
-                throw Exception("Cannot read from istream", ErrorCodes::CANNOT_READ_FROM_ISTREAM);
-        }
-        else
-            working_buffer.resize(gcount);
-
-        return true;
-    }
+    bool nextImpl() override;
 
 public:
-    ReadBufferFromIStream(std::istream & istr_, size_t size = DBMS_DEFAULT_BUFFER_SIZE)
-        : BufferWithOwnMemory<ReadBuffer>(size), istr(istr_) {}
+    ReadBufferFromIStream(std::istream & istr_, size_t size = DBMS_DEFAULT_BUFFER_SIZE);
 };
 
 }
diff --git a/dbms/src/IO/WriteBufferFromOStream.cpp b/dbms/src/IO/WriteBufferFromOStream.cpp
new file mode 100644
index 00000000000..c0225f77075
--- /dev/null
+++ b/dbms/src/IO/WriteBufferFromOStream.cpp
@@ -0,0 +1,54 @@
+#include <IO/WriteBufferFromOStream.h>
+#include <Common/Exception.h>
+
+
+namespace DB
+{
+
+namespace ErrorCodes
+{
+    extern const int CANNOT_WRITE_TO_OSTREAM;
+}
+
+void WriteBufferFromOStream::nextImpl()
+{
+    if (!offset())
+        return;
+
+    ostr->write(working_buffer.begin(), offset());
+    ostr->flush();
+
+    if (!ostr->good())
+        throw Exception("Cannot write to ostream", ErrorCodes::CANNOT_WRITE_TO_OSTREAM);
+}
+
+WriteBufferFromOStream::WriteBufferFromOStream(
+    size_t size,
+    char * existing_memory,
+    size_t alignment)
+    : BufferWithOwnMemory<WriteBuffer>(size, existing_memory, alignment)
+{
+}
+
+WriteBufferFromOStream::WriteBufferFromOStream(
+    std::ostream & ostr_,
+    size_t size,
+    char * existing_memory,
+    size_t alignment)
+    : BufferWithOwnMemory<WriteBuffer>(size, existing_memory, alignment), ostr(&ostr_)
+{
+}
+
+WriteBufferFromOStream::~WriteBufferFromOStream()
+{
+    try
+    {
+        next();
+    }
+    catch (...)
+    {
+        tryLogCurrentException(__PRETTY_FUNCTION__);
+    }
+}
+
+}
diff --git a/dbms/src/IO/WriteBufferFromOStream.h b/dbms/src/IO/WriteBufferFromOStream.h
index 355e4fb7e46..6a323be34d7 100644
--- a/dbms/src/IO/WriteBufferFromOStream.h
+++ b/dbms/src/IO/WriteBufferFromOStream.h
@@ -2,8 +2,6 @@
 
 #include <iostream>
 
-#include <Common/Exception.h>
-
 #include <IO/WriteBuffer.h>
 #include <IO/BufferWithOwnMemory.h>
 
@@ -11,53 +9,23 @@
 namespace DB
 {
 
-namespace ErrorCodes
-{
-    extern const int CANNOT_WRITE_TO_OSTREAM;
-}
-
 class WriteBufferFromOStream : public BufferWithOwnMemory<WriteBuffer>
 {
 protected:
     std::ostream * ostr;
 
-    void nextImpl() override
-    {
-        if (!offset())
-            return;
-
-        ostr->write(working_buffer.begin(), offset());
-        ostr->flush();
-
-        if (!ostr->good())
-            throw Exception("Cannot write to ostream", ErrorCodes::CANNOT_WRITE_TO_OSTREAM);
-    }
-
-    WriteBufferFromOStream(size_t size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0)
-        : BufferWithOwnMemory<WriteBuffer>(size, existing_memory, alignment)
-    {
-    }
+    void nextImpl() override;
 
+    WriteBufferFromOStream(size_t size = DBMS_DEFAULT_BUFFER_SIZE, char * existing_memory = nullptr, size_t alignment = 0);
 
 public:
     WriteBufferFromOStream(
         std::ostream & ostr_,
         size_t size = DBMS_DEFAULT_BUFFER_SIZE,
         char * existing_memory = nullptr,
-        size_t alignment = 0)
-        : BufferWithOwnMemory<WriteBuffer>(size, existing_memory, alignment), ostr(&ostr_) {}
+        size_t alignment = 0);
 
-    ~WriteBufferFromOStream() override
-    {
-        try
-        {
-            next();
-        }
-        catch (...)
-        {
-            tryLogCurrentException(__PRETTY_FUNCTION__);
-        }
-    }
+    ~WriteBufferFromOStream() override;
 };
 
 }