src/dawn/native/Blob.h

// Copyright 2022 The Dawn & Tint Authors
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#ifndef SRC_DAWN_NATIVE_BLOB_H_
#define SRC_DAWN_NATIVE_BLOB_H_

#include <cstdint>
#include <functional>
#include <span>
#include <type_traits>
#include <utility>
#include <vector>

#include "partition_alloc/pointers/raw_ptr.h"

namespace dawn::native {

// Blob represents a block of bytes. It may be constructed from
// various other container types and uses type erasure to take
// ownership of the container and release its memory on destruction.
class Blob {
  public:
    // Creates a blob of the given size.
    static Blob Create(size_t size);

    // Takes ownership of the original blob, creating a new one with subspan of the original using
    // `offset` and optionally `extent`.
    static Blob Create(Blob&& original, size_t offset, size_t extent = std::dynamic_extent);

    template <typename T>
    static Blob Create(std::vector<T> vec)
        requires(std::is_fundamental_v<T> || std::is_same_v<T, std::byte>)
    {
        // Move the vector into a new allocation so we can destruct it in the deleter.
        auto* wrapped_vec = new std::vector<T>(std::move(vec));

        uint8_t* data = reinterpret_cast<uint8_t*>(wrapped_vec->data());
        size_t size = wrapped_vec->size() * sizeof(T);

        return Blob::UnsafeCreateWithDeleter(data, size, [wrapped_vec] { delete wrapped_vec; });
    }

    // This function is used to create Blob with actual data.
    // Make sure the creation and deleter handles the data ownership and lifetime correctly.
    static Blob UnsafeCreateWithDeleter(uint8_t* data, size_t size, std::function<void()> deleter);

    Blob();
    ~Blob();

    Blob(const Blob&) = delete;
    Blob& operator=(const Blob&) = delete;

    Blob(Blob&&);
    Blob& operator=(Blob&&);

    bool Empty() const;
    std::span<const std::byte> Data() const;
    std::span<std::byte> Data();
    const std::byte* DataPtr() const;
    std::byte* DataPtr();
    size_t Size() const;

    bool operator==(const Blob& other) const;

  private:
    // The constructor should be responsible to take ownership of |data| and releases ownership by
    // calling |deleter|. The deleter function is called at ~Blob() and during std::move.
    Blob(std::span<std::byte> data, std::function<void()> deleter);

    std::span<std::byte> mData;
    std::function<void()> mDeleter;
};

}  // namespace dawn::native

#endif  // SRC_DAWN_NATIVE_BLOB_H_