collations_internal.h

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/* Copyright (c) 2020, 2025, Oracle and/or its affiliates.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.
 
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.
 
   You should have received a copy of the GNU General Public License
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   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
#ifndef STRINGS_COLLATIONS_INTERNAL_H_
#define STRINGS_COLLATIONS_INTERNAL_H_
 
#include <functional>
#include <mutex>
#include <string>
#include <string_view>
#include <unordered_map>
#include <utility>
 
#include "mysql/strings/m_ctype.h"
 
constexpr char MY_CHARSET_INDEX[]{"Index.xml"};
 
typedef int myf;
 
namespace mysql {
 
namespace collation {
class Name;
}  // namespace collation
 
namespace collation_internals {
 
using id_hash_map = std::unordered_map<unsigned, CHARSET_INFO *>;
 
struct string_hash {
  using is_transparent = void;
  [[nodiscard]] size_t operator()(std::string_view txt) const {
    return std::hash<std::string_view>{}(txt);
  }
};
 
using sv_hash_map = std::unordered_map<std::string, CHARSET_INFO *, string_hash,
                                       std::equal_to<>>;
 
/**
  Helper class: implementation of character set/collation library
 
  @see mysql::collation_internals::entry.
*/
class Collations final {
 public:
  Collations(const Collations &) = delete;
  Collations &operator=(const Collations &) = delete;
 
  /**
    Constructor
 
    @param charset_dir  Optional "/\0"-terminated path to the directory
                        containing Index.xml
    @param loader       Optional user-specified hooks to the character
                        set/collation parser/initializer.
  */
  explicit Collations(const char *charset_dir,
                      MY_CHARSET_LOADER *loader = nullptr);
 
  ~Collations();
 
  /**
    Finds collation by its name
 
    @note Forces collation parsing/initialization if not done yet.
 
    @param name         Collation name
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns pointer to a collation object on success, nullptr if not found
  */
  CHARSET_INFO *find_by_name(const mysql::collation::Name &name, myf flags = 0,
                             MY_CHARSET_ERRMSG *errmsg = nullptr);
 
  /**
    Finds collation by its number
 
    @note Forces collation parsing/initialization if not done yet.
 
    @param id           Collation id (hardcoded in library sources or
                        specified in Index.xml)
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns pointer to a collation object on success, nullptr if not found
  */
  CHARSET_INFO *find_by_id(unsigned id, myf flags = 0,
                           MY_CHARSET_ERRMSG *errmsg = nullptr);
 
  /**
    Finds primary collation by its character set name
 
    @note Forces collation parsing/initialization if not done yet.
 
    @param cs_name      Character set name
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns pointer to a collation object on success, nullptr if not found
  */
  CHARSET_INFO *find_primary(const mysql::collation::Name &cs_name,
                             myf flags = 0,
                             MY_CHARSET_ERRMSG *errmsg = nullptr);
 
  /**
    Finds binary collation by its character set name
 
    @note Forces collation parsing/initialization if not done yet.
 
    @param cs_name      Character set name
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns pointer to a collation object on success, nullptr if not found
  */
  CHARSET_INFO *find_default_binary(const mysql::collation::Name &cs_name,
                                    myf flags = 0,
                                    MY_CHARSET_ERRMSG *errmsg = nullptr);
 
  /**
    Finds collation by its name and returns its id
 
    @param name         Collation name
 
    @returns collation id
  */
  unsigned get_collation_id(const mysql::collation::Name &name) const;
 
  /**
    Finds character set by its name and returns an id of its primary collation
 
    @param name         Collation name
 
    @returns primary collation id
  */
  unsigned get_primary_collation_id(const mysql::collation::Name &name) const;
 
  /**
    Finds character set by its name and returns an id of its default binary
    collation
 
    @param name         Collation name
 
    @returns default binary collation id
  */
  unsigned get_default_binary_collation_id(
      const mysql::collation::Name &name) const;
 
  /**
    If not done yet, force collation parsing/initialization under m_mutex lock
 
    @param cs           Pointer to collation object
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns @p cs on success, otherwise nullptr
  */
  CHARSET_INFO *safe_init_when_necessary(CHARSET_INFO *cs, myf flags = 0,
                                         MY_CHARSET_ERRMSG *errmsg = nullptr);
 
  /**
    Like find_by_name but without initialization of return value
 
    @param name         Collation name
 
    @returns Pointer to CHARSET_INFO object on success, nullptr if not found.
             The resulting value can point to a half-initialized object.
             Moreover, further initialization of that object or parsing
             of its collation XML can fail.
  */
  CHARSET_INFO *find_by_name_unsafe(const mysql::collation::Name &name);
 
  /**
    For registering compile-time collations
 
    @param cs Collation object
 
    @returns false on success, otherwise true.
  */
  bool add_internal_collation(CHARSET_INFO *cs);
 
  /**
    Iterate over all collation objects known to the library
 
    @param f    Closure to execute on each collation object known to the library
  */
  void iterate(const std::function<void(const CHARSET_INFO *)> &f) {
    for (const auto &i : m_all_by_collation_name) {
      f(i.second);
    }
  }
 
 protected:
  /**
    Internals of safe_init_when_necessary()
 
    This function is similar to safe_init_when_necessary, but, unlike
    safe_init_when_necessary(), it doesn't acquire locks.
 
    @param cs           Pointer to collation object
 
    @param flags        Optional mysys-specific flags
 
    @param [out] errmsg Optional buffer to return error message from
                        collation parser/initializer
 
    @returns @p cs on success, otherwise nullptr
  */
  CHARSET_INFO *unsafe_init(CHARSET_INFO *cs, myf flags,
                            MY_CHARSET_ERRMSG *errmsg);
 
  /**
    Optional '/'-terminated path to the directory containing Index.xml
  */
  const std::string m_charset_dir;
 
  /**
    Maps collation ids to CHARSET_INFO object pointers
  */
  id_hash_map m_all_by_id;
 
  /**
    Maps normalized strings of all known character set names, collation names,
    and their aliases to CHARSET_INFO object pointers
 
    @note see old_conv and get_old_charset_by_name() for exclusions
    @see old_conv(), get_old_charset_by_name()
  */
  sv_hash_map m_all_by_collation_name;
 
  /**
    Maps normalized strings of character set names to CHARSET_INFO object
    pointers
 
    @note In MySQL, CHARSET_INFO object of character set is also an object
    of its primary collation.
  */
  sv_hash_map m_primary_by_cs_name;
 
  /**
    Maps normalized strings of character set names to CHARSET_INFO objects
    of preferred binary collations
 
    @note utf8mb4 has two separate binary collations, so m_binary_by_cs_name
          contains a reference to utf8mb4_bin only.
  */
  sv_hash_map m_binary_by_cs_name;
 
  /**
    False if m_loader references external MY_CHARSET_LOADER, otherwise true.
  */
  const bool m_owns_loader;
 
  /**
    Shared MY_CHARSET_LOADER implementation for use in collation parser and
    initializer
 
    By default references an instance of mysql::collation_internals::Loader.
  */
  MY_CHARSET_LOADER *m_loader;
 
 private:
  /**
    Collation parser/initializer mutex
 
    The library parses collations and initializes CHARSET_INFO objects in
    depth on demand, so m_mutex is necessary to guarantee a safety of
    concurrent find_... function calls.
  */
  std::mutex m_mutex;
};
 
/**
  Global entry point to character set/collation library internals
*/
extern Collations *entry;
 
}  // namespace collation_internals
}  // namespace mysql
 
#endif  // STRINGS_COLLATIONS_INTERNAL_H_