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//
// Copyright (c) 2019-2024 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#ifndef BOOST_MYSQL_IMPL_INTERNAL_PROTOCOL_IMPL_NULL_BITMAP_HPP
#define BOOST_MYSQL_IMPL_INTERNAL_PROTOCOL_IMPL_NULL_BITMAP_HPP
#include <boost/mysql/field_view.hpp>
#include <boost/assert.hpp>
#include <boost/config.hpp>
#include <boost/core/span.hpp>
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstring>
namespace boost {
namespace mysql {
namespace detail {
// When parsing binary rows, we need to add this offset to
// field positions to get the actual field index to use -
// the first two positions are reserved
BOOST_INLINE_CONSTEXPR std::size_t binary_row_null_bitmap_offset = 2;
// Helper to parse the null bitmap contained in binary rows
class null_bitmap_parser
{
std::size_t num_fields_;
public:
constexpr null_bitmap_parser(std::size_t num_fields) noexcept : num_fields_{num_fields} {};
constexpr std::size_t byte_count() const { return (num_fields_ + 7 + binary_row_null_bitmap_offset) / 8; }
bool is_null(const std::uint8_t* first, std::size_t field_pos) const
{
BOOST_ASSERT(field_pos < num_fields_);
std::size_t byte_pos = (field_pos + binary_row_null_bitmap_offset) / 8;
std::size_t bit_pos = (field_pos + binary_row_null_bitmap_offset) % 8;
return first[byte_pos] & (1 << bit_pos);
}
};
class null_bitmap_generator
{
span<const field_view> fields_;
std::size_t current_{0};
public:
null_bitmap_generator(span<const field_view> fields) noexcept : fields_(fields) {}
bool done() const { return current_ == fields_.size(); }
std::uint8_t next()
{
BOOST_ASSERT(current_ < fields_.size());
std::uint8_t res = 0;
// Generate
const std::size_t max_i = (std::min)(fields_.size(), current_ + 8u);
for (std::size_t i = current_; i < max_i; ++i)
{
if (fields_[i].is_null())
{
const auto bit_pos = i % 8;
res |= (1 << bit_pos);
}
}
// Update state
current_ = max_i;
// Return
return res;
}
};
} // namespace detail
} // namespace mysql
} // namespace boost
#endif /* INCLUDE_NULL_BITMAP_HPP_ */
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