rippled/include/xrpl/basics/Buffer.h

#ifndef XRPL_BASICS_BUFFER_H_INCLUDED
#define XRPL_BASICS_BUFFER_H_INCLUDED

#include <xrpl/basics/Slice.h>
#include <xrpl/beast/utility/instrumentation.h>

#include <cstdint>
#include <cstring>
#include <memory>

namespace xrpl {

/** Like std::vector<char> but better.
    Meets the requirements of BufferFactory.
*/
class Buffer
{
private:
    std::unique_ptr<std::uint8_t[]> p_;
    std::size_t size_ = 0;

public:
    using const_iterator = std::uint8_t const*;

    Buffer() = default;

    /** Create an uninitialized buffer with the given size. */
    explicit Buffer(std::size_t size)
        : p_(size ? new std::uint8_t[size] : nullptr), size_(size)
    {
    }

    /** Create a buffer as a copy of existing memory.

        @param data a pointer to the existing memory. If
                    size is non-zero, it must not be null.
        @param size size of the existing memory block.
    */
    Buffer(void const* data, std::size_t size) : Buffer(size)
    {
        if (size)
            std::memcpy(p_.get(), data, size);
    }

    /** Copy-construct */
    Buffer(Buffer const& other) : Buffer(other.p_.get(), other.size_)
    {
    }

    /** Copy assign */
    Buffer&
    operator=(Buffer const& other)
    {
        if (this != &other)
        {
            if (auto p = alloc(other.size_))
                std::memcpy(p, other.p_.get(), size_);
        }
        return *this;
    }

    /** Move-construct.
        The other buffer is reset.
    */
    Buffer(Buffer&& other) noexcept
        : p_(std::move(other.p_)), size_(other.size_)
    {
        other.size_ = 0;
    }

    /** Move-assign.
        The other buffer is reset.
    */
    Buffer&
    operator=(Buffer&& other) noexcept
    {
        if (this != &other)
        {
            p_ = std::move(other.p_);
            size_ = other.size_;
            other.size_ = 0;
        }
        return *this;
    }

    /** Construct from a slice */
    explicit Buffer(Slice s) : Buffer(s.data(), s.size())
    {
    }

    /** Assign from slice */
    Buffer&
    operator=(Slice s)
    {
        // Ensure the slice isn't a subset of the buffer.
        XRPL_ASSERT(
            s.size() == 0 || size_ == 0 || s.data() < p_.get() ||
                s.data() >= p_.get() + size_,
            "xrpl::Buffer::operator=(Slice) : input not a subset");

        if (auto p = alloc(s.size()))
            std::memcpy(p, s.data(), s.size());
        return *this;
    }

    /** Returns the number of bytes in the buffer. */
    std::size_t
    size() const noexcept
    {
        return size_;
    }

    bool
    empty() const noexcept
    {
        return 0 == size_;
    }

    operator Slice() const noexcept
    {
        if (!size_)
            return Slice{};
        return Slice{p_.get(), size_};
    }

    /** Return a pointer to beginning of the storage.
        @note The return type is guaranteed to be a pointer
              to a single byte, to facilitate pointer arithmetic.
    */
    /** @{ */
    std::uint8_t const*
    data() const noexcept
    {
        return p_.get();
    }

    std::uint8_t*
    data() noexcept
    {
        return p_.get();
    }
    /** @} */

    /** Reset the buffer.
        All memory is deallocated. The resulting size is 0.
    */
    void
    clear() noexcept
    {
        p_.reset();
        size_ = 0;
    }

    /** Reallocate the storage.
        Existing data, if any, is discarded.
    */
    std::uint8_t*
    alloc(std::size_t n)
    {
        if (n != size_)
        {
            p_.reset(n ? new std::uint8_t[n] : nullptr);
            size_ = n;
        }
        return p_.get();
    }

    // Meet the requirements of BufferFactory
    void*
    operator()(std::size_t n)
    {
        return alloc(n);
    }

    const_iterator
    begin() const noexcept
    {
        return p_.get();
    }

    const_iterator
    cbegin() const noexcept
    {
        return p_.get();
    }

    const_iterator
    end() const noexcept
    {
        return p_.get() + size_;
    }

    const_iterator
    cend() const noexcept
    {
        return p_.get() + size_;
    }
};

inline bool
operator==(Buffer const& lhs, Buffer const& rhs) noexcept
{
    if (lhs.size() != rhs.size())
        return false;

    if (lhs.size() == 0)
        return true;

    return std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
}

inline bool
operator!=(Buffer const& lhs, Buffer const& rhs) noexcept
{
    return !(lhs == rhs);
}

}  // namespace xrpl

#endif