/* * Copyright (C) 1996-2023 The Squid Software Foundation and contributors * * Squid software is distributed under GPLv2+ license and includes * contributions from numerous individuals and organizations. * Please see the COPYING and CONTRIBUTORS files for details. */ #ifndef SQUID_SRC_BASE_INSTANCEID_H #define SQUID_SRC_BASE_INSTANCEID_H #include /// Represents an InstanceId value independent from its owner class C. These /// "detached" IDs can be stored by and exchanged among C-unaware users at the /// price of storing a short scope c-string (that InstanceIds hard-code instead) /// and, in some cases, using more bits/space than InstanceId::value uses. class ScopedId { public: ScopedId(): scope(nullptr), value(0) {} explicit ScopedId(const char *s): scope(s), value(0) {} // when the values is zero/unknown, use other constructors ScopedId(const char *s, uint64_t v): scope(s), value(v) { /* assert(value) */ } /// either the prefix() of the InstanceId object that we were detached from /// or, for 0 values, some other description (with endless lifetime) or nil const char *scope; /// either the value of the InstanceId object that we were detached from /// or, if our creator did not know the exact value, zero uint64_t value; }; std::ostream &operator <<(std::ostream &os, const ScopedId &id); typedef unsigned int InstanceIdDefaultValueType; /** Identifier for class instances * - unique IDs for a large number of concurrent instances, but may wrap; * - useful for debugging and insecure request/response matching; * - sequential IDs within a class except when wrapping; * - always positive IDs. * TODO: add creation/destruction debugging? */ template class InstanceId { public: typedef ValueType Value; ///< id storage type InstanceId() {change();} InstanceId(InstanceId &&) = delete; // no copying/moving of any kind operator Value() const { return value; } bool operator ==(const InstanceId &o) const { return value == o.value; } bool operator !=(const InstanceId &o) const { return !(*this == o); } void change(); /// writes a compact text representation of the ID std::ostream &print(std::ostream &) const; // TODO: Refactor into static Scope(). /// \returns Class-specific nickname (with endless lifetime) const char * prefix() const; /// \returns a copy of the ID usable outside our Class context ScopedId detach() const { return ScopedId(prefix(), value); } public: Value value = Value(); ///< instance identifier }; /// An InstanceIdDefinitions() helper. Avoid direct use. #define InstanceIdDefinitions3(Class, pfx, ValueType, ...) \ template<> const char * \ InstanceId::prefix() const { \ return pfx; \ } \ template<> std::ostream & \ InstanceId::print(std::ostream &os) const { \ return os << pfx << value; \ } \ template<> void \ InstanceId::change() { \ static auto Last = Value(); \ value = ++Last ? Last : ++Last; \ } /// convenience macro to instantiate Class-specific stuff in .cc files #define InstanceIdDefinitions(...) InstanceIdDefinitions3(__VA_ARGS__, InstanceIdDefaultValueType) /// print the id template inline std::ostream &operator <<(std::ostream &os, const InstanceId &id) { return id.print(os); } #endif /* SQUID_SRC_BASE_INSTANCEID_H */