intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 48 insertions, 0 deletions

diff --git a/util/stream/zerocopy_output_ut.cpp b/util/stream/zerocopy_output_ut.cpp
new file mode 100644
index 00000000000..e81f7fb056c
--- /dev/null
+++ b/util/stream/zerocopy_output_ut.cpp
@@ -0,0 +1,48 @@
+#include "zerocopy_output.h"
+
+#include <library/cpp/testing/unittest/registar.h>
+
+#include <util/generic/string.h>
+
+// This version of string output stream is written here only
+// for testing IZeroCopyOutput implementation of DoWrite.
+class TSimpleStringOutput: public IZeroCopyOutput {
+public:
+    TSimpleStringOutput(TString& s) noexcept
+        : S_(s)
+    {
+    }
+
+private:
+    size_t DoNext(void** ptr) override {
+        if (S_.size() == S_.capacity()) {
+            S_.reserve(FastClp2(S_.capacity() + 1));
+        }
+        size_t previousSize = S_.size();
+        S_.resize(S_.capacity());
+        *ptr = S_.begin() + previousSize;
+        return S_.size() - previousSize;
+    }
+
+    void DoUndo(size_t len) override {
+        Y_ENSURE(len <= S_.size());
+        S_.resize(S_.size() - len);
+    }
+
+    TString& S_;
+};
+
+Y_UNIT_TEST_SUITE(TestZerocopyOutput) {
+    Y_UNIT_TEST(Write) {
+        TString str;
+        TSimpleStringOutput output(str);
+        TString result;
+
+        for (size_t i = 0; i < 1000; ++i) {
+            result.push_back('a' + (i % 20));
+        }
+
+        output.Write(result.begin(), result.size());
+        UNIT_ASSERT_STRINGS_EQUAL(str, result);
+    }
+}