my_registry_query.h

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/* Copyright (c) 2024, Oracle and/or its affiliates.
 
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#ifndef MY_REGISTRY_QUERY_H
#define MY_REGISTRY_QUERY_H
 
#include <mysql/components/my_service.h>
#include <mysql/components/service.h>
#include <mysql/components/services/registry.h>
#include <cstring>
#include <string>
#include <unordered_set>
#include "scope_guard.h"
 
/**
  A registry query convenience class
 
  Uses the registry query service to produce an unique set of service names
  that match the pattern supplied.
 
  Typical use is:
 
  @code
    My_registry_query_string string_list("foo", h_registry);
    if (string_list.init()) error_out();
    for (auto name : string_list) {
       <do stuff with names>
    }
  @endcode
 
  @sa @ref My_registry_query_and_acquire
*/
class My_registry_query_string : public std::unordered_set<std::string> {
  const std::string m_service_name;
  SERVICE_TYPE(registry) * m_registry;
  SERVICE_TYPE(registry_query) * m_registry_query;
  my_h_service m_reg_query_handle{nullptr};
 
 public:
  bool init() {
    this->erase(this->begin(), this->end());
    SERVICE_TYPE(registry_query) *svc = m_registry_query;
    if (svc == nullptr) {
      my_service<SERVICE_TYPE(registry_query)> msvc("registry_query",
                                                    m_registry);
      if (!msvc.is_valid()) return true;
      svc = msvc.untie();
    }
    auto x = create_scope_guard([&] {
      if (svc != m_registry_query)
        m_registry->release(reinterpret_cast<my_h_service>(
            const_cast<SERVICE_TYPE_NO_CONST(registry_query) *>(svc)));
    });
 
    my_h_service_iterator iter;
    if (!svc->create(m_service_name.c_str(), &iter)) {
      while (!svc->is_valid(iter)) {
        const char *name{nullptr};
        if (svc->get(iter, &name)) return true;
        if (name == nullptr) return true;
        size_t name_len = strlen(name);
        if (strncmp(name, m_service_name.c_str(), m_service_name.length()) ||
            name_len < m_service_name.length() ||
            (name[m_service_name.length()] != '.' &&
             name[m_service_name.length()] != 0))
          break;
        this->emplace(name);
        if (svc->next(iter)) break;
      }
      svc->release(iter);
    }
    return false;
  }
 
  My_registry_query_string(const char *service_name,
                           SERVICE_TYPE(registry) * reg,
                           SERVICE_TYPE(registry_query) *reg_query = nullptr)
      : m_service_name(service_name),
        m_registry(reg),
        m_registry_query(reg_query) {
    if (m_registry_query == nullptr) {
      if (!reg->acquire("registry_query", &m_reg_query_handle)) {
        m_registry_query = reinterpret_cast<SERVICE_TYPE(registry_query) *>(
            m_reg_query_handle);
      }
    }
  }
 
  My_registry_query_string(const My_registry_query_string &other) = delete;
  My_registry_query_string(My_registry_query_string &&other) = delete;
  ~My_registry_query_string() {
    if (m_reg_query_handle) m_registry->release(m_reg_query_handle);
  }
};
 
/**
  A service acquiring registry query convenience class
 
  Uses the @ref My_registry_query_string class to get a list of
  service names matching the pattern, acquires references for these
  and keeps them until the instance's destruction.
 
  Typical use pattern is:
  @code
  My_registry_query_and_acquire<SERVICE_TYPE(foo)> qry("foo", registry_ref);
  if (qry->init()) error_out();
  for (SERVICE_TYPE(foo) *x : qry) {
    x->method();
  }
  @endcode
 
  @sa @ref My_registry_query_string
*/
 
template <class ServiceType>
class My_registry_query_and_acquire : public std::unordered_set<ServiceType *> {
  const std::string m_service_name;
  SERVICE_TYPE(registry) * m_registry;
  My_registry_query_string m_string_list;
 
 public:
  My_registry_query_and_acquire(
      const char *service_name, SERVICE_TYPE(registry) * reg,
      SERVICE_TYPE(registry_query) *reg_query = nullptr)
      : m_service_name(service_name),
        m_registry(reg),
        m_string_list(service_name, reg, reg_query) {}
 
  My_registry_query_and_acquire(const My_registry_query_and_acquire &other) =
      delete;
  My_registry_query_and_acquire(My_registry_query_and_acquire &&other) = delete;
 
  ~My_registry_query_and_acquire() { reset(); }
 
  /**
    @brief Call this method to populate the data into the class
 
    @retval true failure
    @retval false success
  */
  bool init() {
    if (m_string_list.init()) return true;
    for (auto name : m_string_list) {
      my_h_service hsvc;
      if (m_registry->acquire(name.c_str(), &hsvc)) return true;
      auto res = this->insert(reinterpret_cast<ServiceType *>(hsvc));
      if (!res.second) m_registry->release(hsvc);
    }
    m_string_list.clear();
    return false;
  }
 
  /**
    @brief Properly releases and disposes of all the references
 
    Called by the destructor too
  */
  void reset() {
    for (auto svc : *this) {
      m_registry->release(reinterpret_cast<my_h_service>(
          const_cast<void *>(reinterpret_cast<const void *>(svc))));
    }
    this->erase(this->begin(), this->end());
  }
};
#endif /* MY_REGISTRY_QUERY_H */