Convert Windows Error code to error message

Document directory

• Implementation

After calling an API function, if the function fails, you can call another API function "getlasterror" to return an error code. The following class can be defined based on the error code of windows, find the error message in text:

00001: #ifndef _YHB_SYSERROR_INCLUDED_
00002: #define _YHB_SYSERROR_INCLUDED_
00003: 
00004: #include <stdexcept>
00005: #include <string>
00006: 
00007: namespace yhb {
00008: 
00009: class SysError
00010:     : public std::runtime_error
00011: {
00012: public:
00013:     SysError(int err=0)
00014:         : runtime_error(makeMsgFromErrorNum(err))
00015:     {}
00016:     SysError(const char *customMsg, int err = 0)
00017:         : runtime_error(makeMsgFromErrorNum(customMsg, err))
00018:     {}
00019:     static std::string makeMsgFromErrorNum(unsigned err = 0);
00020:     static std::string makeMsgFromErrorNum(const char *customMsg, unsigned err = 0);
00021: };
00022: 
00023: } // end of namespace
00024: 
00025: #endif

Syserror is derived from STD: runtime_error. Therefore, it can be thrown and captured as a STD: exception.

If you do not want to use exceptions, you can use two static methods to return error messages.

Implementation

00001: # include "stdafx. H"
00002: # include "./syserror. H"
00003: # include <sstream>
00004: # include <lmerr. h>
00005:
00006: # define win32_lean_and_mean
00007: # include <windows. h>
00008:
00009: Using namespace STD;
00010:
00011: namespace yhb {
00012:
00013:/****************************************** ******************************
00014:Manage the module handles loaded with loadlibrary ()
00015:**************************************** ********************************/
00016: class module {
00017: public:
00018: explicit module (hmodule handle = 0)
00019: handle _ (handle)
00020 :{}
00021 :~ Module (){
00022: Free ();
00023 :}
00024: module & operator = (hmodule handle ){
00025: Free ();
00026: handle _ = handle;
00027: return * this;
00028 :}
00029: bool isvalid () const {return 0! = Handle _;}
00030: Operator hmodule () const {return handle _;}
00031: Private:
00032: module (const module &);
00033: module & operator = (const module &);
00034: void free (){
00035: If (0! = Handle _){
00036: freelibrary (handle _);
00037: handle _ = 0;
00038 :}
00039 :}
00040: hmodule handle _;
00041 :};
00042:
00043:/****************************************** ******************************
00044:Syserror
00045:**************************************** ********************************/
00046: String syserror: makemsgfromerrornum (unsigned err/*= 0*/){
00047: If (0 = ERR ){
00048: Err = getlasterror ();
00049: If (noerror = ERR)
00050: Return "no error! ";
00051 :}
00052: module;
00053: DWORD flag = format_message_ignore_inserts | format_message_from_system;
00054: If (ERR> = nerr_base & err <= max_nerr ){
00055: module = loadlibraryexa ("netmsg. dll", 0, load_library_as_datafile );
00056. If (module. isvalid ())
00057: Flag | = format_message_from_hmodule;
00058 :}
00059: Char Buf [1024];
00060: If (formatmessagea (flag, static_cast 00061: Err, makelangid (lang_neutral, sublang_default ),
00062: Buf, sizeof (BUF), 0 ))
00063 :{
00064: Return Buf;
00065:} else {
00066: ostringstream OS;
00067: OS <"Unknown error:" <err <"(0x" 00068: Return OS. STR ();
00069 :}
00070 :}
00071:
00072: String syserror: makemsgfromerrornum (const char * custommsg, unsigned err/*= 0*/){
00073: String result (custommsg );
00074: Result + = '';
00075: Result + = makemsgfromerrornum (ERR );
00076: return result;
00077 :}
00078:
00079 :}//End of namespace 

A common method in C ++ is to encapsulate resources into a class and release the resource during the analysis. For example, the module above calls freelibrary during the analysis.