CStrIntern.h

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/* Copyright (C) 2021 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#ifndef INCLUDED_CSTRINTERN
#define INCLUDED_CSTRINTERN
 
class CStrInternInternals;
 
/**
 * Interned 8-bit strings.
 * Each instance with the same string content is a pointer to the same piece of
 * memory, allowing very fast string comparisons.
 *
 * Since a CStrIntern is just a dumb pointer, copying is very fast,
 * and pass-by-value should be preferred over pass-by-reference.
 *
 * Memory allocated for strings will never be freed, so don't use this for
 * unbounded numbers of strings (e.g. text rendered by gameplay scripts) -
 * it's intended for a small number of short frequently-used strings.
 *
 * Not thread-safe - only allocate these strings from the main thread.
 */
class CStrIntern
{
public:
    CStrIntern();
    explicit CStrIntern(const char* str);
    explicit CStrIntern(const std::string& str);
 
    /**
     * Returns cached FNV1-A hash of the string.
     */
    u32 GetHash() const;
 
    /**
     * Returns null-terminated string.
     */
    const char* c_str() const;
 
    /**
     * Returns length of string in bytes.
     */
    size_t length() const;
 
    bool empty() const;
 
    /**
     * Returns as std::string.
     */
    const std::string& string() const;
 
    /**
     * String equality.
     */
    bool operator==(const CStrIntern& b) const
    {
        return m == b.m;
    }
 
    bool operator!=(const CStrIntern& b) const
    {
        return m != b.m;
    }
 
    /**
     * Compare with some arbitrary total order.
     * (In particular, this is not alphabetic order,
     * and is not consistent between runs of the game.)
     */
    bool operator<(const CStrIntern& b) const
    {
        return m < b.m;
    }
 
private:
    CStrInternInternals* m;
};
 
namespace std
{
template<>
struct hash<CStrIntern>
{
    std::size_t operator()(const CStrIntern& str) const
    {
        return str.GetHash();
    }
};
}
 
#endif // INCLUDED_CSTRINTERN