#pragma once
#include <cstddef>
#include <cstdint>
#include <cstring>

class span_writer {
    uint8_t *m_data;
    size_t m_capacity;
    size_t m_size = 0;

public:
    span_writer(uint8_t *data, size_t capacity) : m_data(data), m_capacity(capacity) {}

    void push_back(uint8_t v) {
        if (m_size < m_capacity) m_data[m_size++] = v;
    }

    template <class It>
    void insert(uint8_t *, It first, It last) {
        while (first != last && m_size < m_capacity)
            m_data[m_size++] = *first++;
    }

    size_t size() const { return m_size; }
    size_t capacity() const { return m_capacity; }
    bool full() const { return m_size >= m_capacity; }

    uint8_t *data() { return m_data; }
    const uint8_t *data() const { return m_data; }

    uint8_t *begin() { return m_data; }
    uint8_t *end() { return m_data + m_size; }
    const uint8_t *begin() const { return m_data; }
    const uint8_t *end() const { return m_data + m_size; }
};