apt-pkg/contrib/error.h

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: error.h,v 1.2 1998/07/07 04:17:11 jgg Exp $
   4 /* ######################################################################
   5
   6    Global Erorr Class - Global error mechanism
   7
   8    This class has a single global instance. When a function needs to
   9    generate an error condition, such as a read error, it calls a member
  10    in this class to add the error to a stack of errors.
  11
  12    By using a stack the problem with a scheme like errno is removed and
  13    it allows a very detailed account of what went wrong to be transmitted
  14    to the UI for display. (Errno has problems because each function sets
  15    errno to 0 if it didn't have an error thus eraseing erno in the process
  16    of cleanup)
  17
  18    Several predefined error generators are provided to handle common
  19    things like errno. The general idea is that all methods return a bool.
  20    If the bool is true then things are OK, if it is false then things
  21    should start being undone and the stack should unwind under program
  22    control.
  23
  24    A Warning should not force the return of false. Things did not fail, but
  25    they might have had unexpected problems. Errors are stored in a FIFO
  26    so Pop will return the first item..
  27
  28    I have some thoughts about extending this into a more general UI<->
  29    Engine interface, ie allowing the Engine to say 'The disk is full' in
  30    a dialog that says 'Panic' and 'Retry'.. The error generator functions
  31    like errno, Warning and Error return false always so this is normal:
  32      if (open(..))
  33         return _error->Errno(..);
  34
  35    This source is placed in the Public Domain, do with it what you will
  36    It was originally written by Jason Gunthorpe.
  37
  38    ##################################################################### */
  39                                                                         /*}}}*/
  40 // Header section: pkglib
  41 #ifndef PKGLIB_ERROR_H
  42 #define PKGLIB_ERROR_H
  43
  44 #ifdef __GNUG__
  45 #pragma interface "pkglib/error.h"
  46 #endif
  47
  48 #include <string>
  49
  50 class GlobalError
  51 {
  52    struct Item
  53    {
  54       string Text;
  55       bool Error;
  56       Item *Next;
  57    };
  58
  59    Item *List;
  60    bool PendingFlag;
  61    void Insert(Item *I);
  62
  63    public:
  64
  65    // Call to generate an error from a library call.
  66    bool Errno(const char *Function,const char *Description,...);
  67
  68    /* A warning should be considered less severe than an error, and may be
  69       ignored by the client. */
  70    bool Error(const char *Description,...);
  71    bool Warning(const char *Description,...);
  72
  73    // Simple accessors
  74    inline bool PendingError() {return PendingFlag;};
  75    inline bool empty() {return List == 0;};
  76    bool PopMessage(string &Text);
  77    void Discard();
  78
  79    // Usefull routine to dump to cerr
  80    void DumpErrors();
  81
  82    GlobalError();
  83 };
  84
  85 /* The 'extra-ansi' syntax is used to help with collisions. This is the
  86    single global instance of this class. */
  87 extern GlobalError *_error;
  88
  89 #endif