intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 76 insertions, 0 deletions

diff --git a/library/cpp/containers/bitseq/readonly_bitvector.h b/library/cpp/containers/bitseq/readonly_bitvector.h
new file mode 100644
index 00000000000..8612739c3f7
--- /dev/null
+++ b/library/cpp/containers/bitseq/readonly_bitvector.h
@@ -0,0 +1,76 @@
+#pragma once
+
+#include "bitvector.h"
+#include "traits.h"
+
+#include <util/memory/blob.h>
+
+#include <cstring>
+
+template <typename T>
+class TReadonlyBitVector {
+public:
+    using TWord = T;
+    using TTraits = TBitSeqTraits<TWord>;
+
+    TReadonlyBitVector()
+        : Size_()
+        , Data_()
+    {
+    }
+
+    explicit TReadonlyBitVector(const TBitVector<T>& vector)
+        : Size_(vector.Size_)
+        , Data_(vector.Data_.data())
+    {
+    }
+
+    bool Test(ui64 pos) const {
+        return TTraits::Test(Data_, pos, Size_);
+    }
+
+    TWord Get(ui64 pos, ui8 width, TWord mask) const {
+        return TTraits::Get(Data_, pos, width, mask, Size_);
+    }
+
+    TWord Get(ui64 pos, ui8 width) const {
+        return Get(pos, width, TTraits::ElemMask(width));
+    }
+
+    ui64 Size() const {
+        return Size_;
+    }
+
+    const T* Data() const {
+        return Data_;
+    }
+
+    static void SaveForReadonlyAccess(IOutputStream* out, const TBitVector<T>& bv) {
+        ::Save(out, bv.Size_);
+        ::Save(out, static_cast<ui64>(bv.Data_.size()));
+        ::SavePodArray(out, bv.Data_.data(), bv.Data_.size());
+    }
+
+    virtual TBlob LoadFromBlob(const TBlob& blob) {
+        size_t read = 0;
+        auto cursor = [&]() { return blob.AsUnsignedCharPtr() + read; };
+        auto readToPtr = [&](auto* ptr) {
+            memcpy(ptr, cursor(), sizeof(*ptr));
+            read += sizeof(*ptr);
+        };
+
+        readToPtr(&Size_);
+
+        ui64 wordCount{};
+        readToPtr(&wordCount);
+
+        Data_ = reinterpret_cast<const T*>(cursor());
+        read += wordCount * sizeof(T);
+
+        return blob.SubBlob(read, blob.Size());
+    }
+
+private:
+    ui64 Size_;
+    const T* Data_;
+};