libcubescript/src/cs_util.hh

#ifndef LIBCUBESCRIPT_CS_UTIL_HH
#define LIBCUBESCRIPT_CS_UTIL_HH

#include <type_traits>
#include <unordered_map>
#include <vector>

#include <ostd/string.hh>

namespace cscript {

template<typename K, typename V>
using cs_map = std::unordered_map<K, V>;

template<typename T>
using cs_vector = std::vector<T>;

using cs_string = std::string;

cs_int cs_parse_int(
    ostd::string_range input, ostd::string_range *end = nullptr
);

cs_float cs_parse_float(
    ostd::string_range input, ostd::string_range *end = nullptr
);

template<typename F>
struct CsScopeExit {
    template<typename FF>
    CsScopeExit(FF &&f): func(std::forward<FF>(f)) {}
    ~CsScopeExit() {
        func();
    }
    std::decay_t<F> func;
};

template<typename F1, typename F2>
inline void cs_do_and_cleanup(F1 &&dof, F2 &&clf) {
    CsScopeExit<F2> cleanup(std::forward<F2>(clf));
    dof();
}

struct cs_strman;

struct cs_shared_state {
    cs_map<ostd::string_range, cs_ident *> idents;
    cs_vector<cs_ident *> identmap;
    cs_alloc_cb allocf;
    cs_vprint_cb varprintf;
    cs_strman *strman;
    void *aptr;

    void *alloc(void *ptr, size_t os, size_t ns) {
        return allocf(aptr, ptr, os, ns);
    }

    template<typename T, typename ...A>
    T *create(A &&...args) {
        T *ret = static_cast<T *>(alloc(nullptr, 0, sizeof(T)));
        new (ret) T(std::forward<A>(args)...);
        return ret;
    }

    template<typename T>
    T *create_array(size_t len) {
        T *ret = static_cast<T *>(alloc(nullptr, 0, len * sizeof(T)));
        for (size_t i = 0; i < len; ++i) {
            new (&ret[i]) T();
        }
        return ret;
    }

    template<typename T>
    void destroy(T *v) noexcept {
        v->~T();
        alloc(v, sizeof(T), 0);
    }

    template<typename T>
    void destroy_array(T *v, size_t len) noexcept {
        v->~T();
        alloc(v, len * sizeof(T), 0);
    }
};

inline cs_shared_state *cs_get_sstate(cs_state &cs) {
    return cs.p_state;
}

inline cs_strref cs_make_strref(char const *p, cs_shared_state &cs) {
    return cs_strref{p, cs};
}

/* string manager
 *
 * the purpose of this is to handle interning of strings; each string within
 * a libcs state is represented (and allocated) exactly once, and reference
 * counted; that both helps save resources, and potentially provide a means
 * to reliably represent returned strings in places that is compatible with
 * multiple threads and eliminate the chance of dangling pointers
 *
 * strings are allocated in a manner where the refcount and length are stored
 * as a part of the string's memory, so it can be easily accessed using just
 * the pointer to the string, but also this is transparent for usage
 *
 * this is not thread-safe yet, and later on it should be made that,
 * for now we don't bother...
 */

struct cs_strref_state {
    size_t length;
    size_t refcount;
};

struct cs_strman {
    cs_strman() = delete;
    cs_strman(cs_shared_state *cs): cstate{cs} {}
    ~cs_strman() {}

    cs_strman(cs_strman const &) = delete;
    cs_strman(cs_strman &&) = delete;

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

    /* adds a string into the manager using any source, and returns a managed
     * version; this is "slow" as it has to hash the string and potentially
     * allocate fresh memory for it, but is perfectly safe at any time
     */
    char const *add(ostd::string_range str);

    /* this simply increments the reference count of an existing managed
     * string, this is only safe when you know the pointer you are passing
     * is already managed the system
     */
    char const *ref(char const *ptr);

    /* this will use the provided memory, assuming it is a fresh string that
     * is yet to be added; the memory must be allocated with alloc_buf()
     */
    char const *steal(char *ptr);

    /* decrements the reference count and removes it from the system if
     * that reaches zero; likewise, only safe with pointers that are managed
     */
    void unref(char const *ptr);

    /* just finds a managed pointer with the same contents
     * as the input, if not found then a null pointer is returned
     */
    char const *find(ostd::string_range str) const;

    /* a quick helper to make a proper ostd string range out of a ptr */
    ostd::string_range get(char const *ptr) const;

    /* this will allocate a buffer of the given length (plus one for
     * terminating zero) so you can fill it; use steal() to write it
     */
    char *alloc_buf(std::size_t len) const;

    cs_shared_state *cstate;
    /* FIXME: use main allocator */
    std::unordered_map<ostd::string_range, cs_strref_state *> counts{};
};

} /* namespace cscript */

#endif /* LIBCUBESCRIPT_CS_UTIL_HH */