Function GetWinLongPath

Libraries/unrar/pathfn.cpp:908–972

We should return 'true' even if resulting path is shorter than MAX_PATH, because we can also use this function to open files with non-standard characters, even if their path length is normal.

// because we can also use this function to open files with non-standard
// characters, even if their path length is normal.
bool GetWinLongPath(const wchar *Src,wchar *Dest,size_t MaxSize)
{
  if (*Src==0)
    return false;
  const wchar *Prefix=L"\\\\?\\";
  const size_t PrefixLength=4;
  bool FullPath=IsDriveLetter(Src) && IsPathDiv(Src[2]);
  size_t SrcLength=wcslen(Src);
  if (IsFullPath(Src)) // Paths in d:\path\name format.
  {
    if (IsDriveLetter(Src))
    {
      if (MaxSize<=PrefixLength+SrcLength)
        return false;
      wcsncpyz(Dest,Prefix,MaxSize);
      wcsncatz(Dest,Src,MaxSize); // "\\?\D:\very long path".
      return true;
    }
    else
      if (Src[0]=='\\' && Src[1]=='\\')
      {
        if (MaxSize<=PrefixLength+SrcLength+2)
          return false;
        wcsncpyz(Dest,Prefix,MaxSize);
        wcsncatz(Dest,L"UNC",MaxSize);
        wcsncatz(Dest,Src+1,MaxSize); // "\\?\UNC\server\share".
        return true;
      }
    // We may be here only if we modify IsFullPath in the future.
    return false;
  }
  else
  {
    wchar CurDir[NM];
    DWORD DirCode=GetCurrentDirectory(ASIZE(CurDir)-1,CurDir);
    if (DirCode==0 || DirCode>ASIZE(CurDir)-1)
      return false;

    if (IsPathDiv(Src[0])) // Paths in \path\name format.
    {
      if (MaxSize<=PrefixLength+SrcLength+2)
        return false;
      wcsncpyz(Dest,Prefix,MaxSize);
      CurDir[2]=0;
      wcsncatz(Dest,CurDir,MaxSize); // Copy drive letter 'd:'.
      wcsncatz(Dest,Src,MaxSize);
      return true;
    }
    else  // Paths in path\name format.
    {
      AddEndSlash(CurDir,ASIZE(CurDir));
      if (MaxSize<=PrefixLength+wcslen(CurDir)+SrcLength)
        return false;
      wcsncpyz(Dest,Prefix,MaxSize);
      wcsncatz(Dest,CurDir,MaxSize);

      if (Src[0]=='.' && IsPathDiv(Src[1])) // Remove leading .\ in pathname.
        Src+=2;