error.h

// -*- mode: cpp; mode: fold -*-
// SPDX-License-Identifier: GPL-2.0+
// Description                                                          /*{{{*/
/* ######################################################################
   
   Global Error Class - Global error mechanism
 
   This class has a single global instance. When a function needs to 
   generate an error condition, such as a read error, it calls a member
   in this class to add the error to a stack of errors. 
   
   By using a stack the problem with a scheme like errno is removed and
   it allows a very detailed account of what went wrong to be transmitted
   to the UI for display. (Errno has problems because each function sets
   errno to 0 if it didn't have an error thus eraseing erno in the process
   of cleanup)
   
   Several predefined error generators are provided to handle common 
   things like errno. The general idea is that all methods return a bool.
   If the bool is true then things are OK, if it is false then things 
   should start being undone and the stack should unwind under program
   control.
   
   A Warning should not force the return of false. Things did not fail, but
   they might have had unexpected problems. Errors are stored in a FIFO
   so Pop will return the first item..
   
   I have some thoughts about extending this into a more general UI<-> 
   Engine interface, ie allowing the Engine to say 'The disk is full' in 
   a dialog that says 'Panic' and 'Retry'.. The error generator functions
   like errno, Warning and Error return false always so this is normal:
     if (open(..))
        return _error->Errno(..);
   
   This file had this historic note, but now includes further changes
   under the GPL-2.0+:
 
   This source is placed in the Public Domain, do with it what you will
   It was originally written by Jason Gunthorpe.
   
   ##################################################################### */
                                                                        /*}}}*/
#ifndef PKGLIB_ERROR_H
#define PKGLIB_ERROR_H
 
#include <apt-pkg/macros.h>
 
#include <iostream>
#include <list>
#include <string>
 
#include <cstdarg>
#include <cstddef>
 
class APT_PUBLIC GlobalError                                            /*{{{*/
{
public:                                                                 /*{{{*/
        enum MsgType {
                FATAL = 40,
                ERROR = 30,
                WARNING = 20,
                NOTICE = 10,
                AUDIT = 5,
                DEBUG = 0
        };
 
        bool FatalE(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool Errno(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool WarningE(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool NoticeE(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool AuditE(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool DebugE(const char *Function,const char *Description,...) APT_PRINTF(3) APT_COLD;
 
        bool InsertErrno(MsgType const &type, const char* Function,
                         const char* Description,...) APT_PRINTF(4) APT_COLD;
 
        bool InsertErrno(MsgType type, const char* Function,
                         const char* Description, va_list &args,
                         int const errsv, size_t &msgSize) APT_COLD;
 
        bool Fatal(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Error(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Warning(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Notice(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Audit(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Debug(const char *Description,...) APT_PRINTF(2) APT_COLD;
 
        bool Insert(MsgType const &type, const char* Description,...) APT_PRINTF(3) APT_COLD;
 
        bool Insert(MsgType type, const char* Description,
                         va_list &args, size_t &msgSize) APT_COLD;
 
        inline bool PendingError() const APT_PURE {return PendingFlag;};
 
        bool empty(MsgType const &threshold = WARNING) const APT_PURE;
 
        bool PopMessage(std::string &Text);
 
        void Discard();
 
        void DumpErrors(std::ostream &out, MsgType const &threshold = WARNING,
                        bool const &mergeStack = true);
 
        void inline DumpErrors(MsgType const &threshold) {
                DumpErrors(std::cerr, threshold);
        }
 
        // mvo: we do this instead of using a default parameter in the
        //      previous declaration to avoid a (subtle) API break for
        //      e.g. sigc++ and mem_fun0
        void inline DumpErrors() {
                DumpErrors(WARNING);
        }
 
        void PushToStack();
 
        void RevertToStack();
 
        void MergeWithStack();
 
        size_t StackCount() const APT_PURE {
                return Stacks.size();
        }
 
        GlobalError();
                                                                        /*}}}*/
private:                                                                /*{{{*/
        struct Item {
                std::string Text;
                MsgType Type;
 
                Item(char const *Text, MsgType const &Type) :
                        Text(Text), Type(Type) {};
 
                APT_HIDDEN friend std::ostream &operator<<(std::ostream &out, Item i);
        };
 
        APT_HIDDEN friend std::ostream &operator<<(std::ostream &out, Item i);
 
        std::list<Item> Messages;
        bool PendingFlag;
 
        struct MsgStack {
                std::list<Item> Messages;
                bool const PendingFlag;
 
                MsgStack(std::list<Item> const &Messages, bool const &Pending) :
                         Messages(Messages), PendingFlag(Pending) {};
        };
 
        std::list<MsgStack> Stacks;
                                                                        /*}}}*/
};
                                                                        /*}}}*/
 
// The 'extra-ansi' syntax is used to help with collisions. 
APT_PUBLIC GlobalError *_GetErrorObj();
static struct {
        inline GlobalError* operator ->() { return _GetErrorObj(); }
} _error [[maybe_unused]];
 
#endif