93 lines
3.0 KiB
C++
93 lines
3.0 KiB
C++
#ifndef LIBCUBESCRIPT_STRMAN_HH
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#define LIBCUBESCRIPT_STRMAN_HH
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#include <cubescript/cubescript.hh>
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#include <unordered_map>
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#include <string_view>
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#include "cs_std.hh"
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#include "cs_state.hh"
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namespace cscript {
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struct cs_strref_state;
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/* string manager
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*
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* the purpose of this is to handle interning of strings; each string within
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* a libcs state is represented (and allocated) exactly once, and reference
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* counted; that both helps save resources, and potentially provide a means
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* to reliably represent returned strings in places that is compatible with
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* multiple threads and eliminate the chance of dangling pointers
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*
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* strings are allocated in a manner where the refcount and length are stored
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* as a part of the string's memory, so it can be easily accessed using just
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* the pointer to the string, but also this is transparent for usage
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*
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* this is not thread-safe yet, and later on it should be made that,
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* for now we don't bother...
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*/
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struct cs_strman {
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using allocator_type = cs_allocator<
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std::pair<std::string_view const, cs_strref_state *>
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>;
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cs_strman() = delete;
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cs_strman(cs_shared_state *cs): cstate{cs}, counts{allocator_type{cs}} {}
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~cs_strman() {}
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cs_strman(cs_strman const &) = delete;
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cs_strman(cs_strman &&) = delete;
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cs_strman &operator=(cs_strman const &) = delete;
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cs_strman &operator=(cs_strman &&) = delete;
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/* adds a string into the manager using any source, and returns a managed
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* version; this is "slow" as it has to hash the string and potentially
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* allocate fresh memory for it, but is perfectly safe at any time
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*/
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char const *add(std::string_view str);
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/* this simply increments the reference count of an existing managed
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* string, this is only safe when you know the pointer you are passing
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* is already managed the system
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*/
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char const *ref(char const *ptr);
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/* this will use the provided memory, assuming it is a fresh string that
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* is yet to be added; the memory must be allocated with alloc_buf()
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*/
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char const *steal(char *ptr);
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/* decrements the reference count and removes it from the system if
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* that reaches zero; likewise, only safe with pointers that are managed
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*/
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void unref(char const *ptr);
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/* just finds a managed pointer with the same contents
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* as the input, if not found then a null pointer is returned
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*/
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char const *find(std::string_view str) const;
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/* a quick helper to make a proper string view out of a ptr */
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std::string_view get(char const *ptr) const;
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/* this will allocate a buffer of the given length (plus one for
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* terminating zero) so you can fill it; use steal() to write it
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*/
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char *alloc_buf(std::size_t len) const;
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cs_shared_state *cstate;
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std::unordered_map<
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std::string_view, cs_strref_state *,
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std::hash<std::string_view>,
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std::equal_to<std::string_view>,
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allocator_type
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> counts;
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};
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} /* namespace cscript */
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#endif
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