chap5.lst

The Art of C++一书的配套源代码

  bool reload = false; 
 
  if(argc==2 && !strcmp(argv[1], "reload")) 
      reload = true; 
 
  cout << "Beginning download.\n"; 
 
  try { 
    if(Download::download(url, reload, showprogress)) 
      cout << "Download Complete\n"; 
  } catch(DLExc exc) { 
    cout << exc.geterr() << endl; 
    cout << "Download Interrupted\n"; 
  }    
 
  return 0; 
}

listing 4
// WinDL: A GUI-based file download utility. 
 
#include <windows.h> 
#include <commctrl.h> 
#include <cstring> 
#include <cstdio> 
#include "windl.h" 
#include <process.h> 
#include "dl.h" 
 
const int URL_BUF_SIZE = 1024; 
 
LRESULT CALLBACK WindowFunc(HWND, UINT, WPARAM, LPARAM); 
BOOL CALLBACK DialogFunc(HWND, UINT, WPARAM, LPARAM); 
 
void showprogress(unsigned long total, 
                  unsigned long part); 
void resetprogress(); 
unsigned __stdcall dlstart(void * reload); 
 
char szWinName[] = "Download"; // name of window class  
 
HINSTANCE hInst; // instance handle 
HWND hwnd;       // handle of main window 
HWND hProgWnd;   // handle of progress bar 
 
HANDLE hThrd = 0;  // thread handle 
unsigned long Tid; // thread ID 
 
// Progress counters. 
int percentdone = 0; 
int oldpercentdone = 0; 
 
// A small struct for passing info to dlstart(). 
struct ThrdInfo { 
  char *url;     // pointer to URL string 
  int reload;    // reload flag 
  HWND hPBStart; // handle of Start button 
}; 
 
int WINAPI WinMain(HINSTANCE hThisInst, HINSTANCE hPrevInst,  
                   LPSTR lpszArgs, int nWinMode) 
{ 
  MSG msg; 
  WNDCLASSEX wcl; 
  INITCOMMONCONTROLSEX cc; 
 
  // Define a window class.  
  wcl.cbSize = sizeof(WNDCLASSEX);  
 
  wcl.hInstance = hThisInst;     // handle to this instance  
  wcl.lpszClassName = szWinName; // window class name  
  wcl.lpfnWndProc = WindowFunc;  // window function  
  wcl.style = 0;                 // default style  
 
  wcl.hIcon = LoadIcon(NULL, IDI_APPLICATION); // large icon  
  wcl.hIconSm = NULL; // use small version of large icon 
  wcl.hCursor = LoadCursor(NULL, IDC_ARROW);  // cursor style 
 
  wcl.lpszMenuName = NULL; // no menu  
 
  wcl.cbClsExtra = 0; // no extras 
  wcl.cbWndExtra = 0;  
 
  wcl.hbrBackground = NULL; // not used 
 
  // Register the window class.  
  if(!RegisterClassEx(&wcl)) return 0; 
 
  // Create a main window that won't be visible. 
  hwnd = CreateWindow( 
    szWinName,  // name of window class  
    "File Downloader", // title 
    0,          // no style needed 
    0, 0, 0, 0, // no dimensions    
    NULL,       // no parent window  
    NULL,       // no menu 
    hThisInst,  // instance handle 
    NULL        // no additional arguments  
  ); 
 
  hInst = hThisInst; // save the current instance handle  
 
  // Initialize the common controls. This is 
  // needed because of the progress bar. 
  cc.dwSize = sizeof(INITCOMMONCONTROLSEX); 
  cc.dwICC = ICC_PROGRESS_CLASS;  
  InitCommonControlsEx(&cc);  
 
  // Show the window minimized. 
  ShowWindow(hwnd, SW_SHOWMINIMIZED); 
 
  // Create the download dialog box. 
  DialogBox(hInst, "DLDB", hwnd, (DLGPROC) DialogFunc); 
 
  // Create the message loop.  
  while(GetMessage(&msg, NULL, 0, 0)) 
  { 
    TranslateMessage(&msg); // translate keyboard messages 
    DispatchMessage(&msg); // return control to Windows 
  } 
 
  return msg.wParam; 
} 
 
// Window function. 
LRESULT CALLBACK WindowFunc(HWND hwnd, UINT message, 
                            WPARAM wParam, LPARAM lParam) 
{ 
  switch(message) { 
    case WM_DESTROY: 
      PostQuitMessage(0); // terminate the program 
      break; 
    default: 
      return DefWindowProc(hwnd, message, wParam, lParam); 
  } 
  return 0; 
} 
 
// Downloader Dialog function. 
BOOL CALLBACK DialogFunc(HWND hdwnd, UINT message, 
                         WPARAM wParam, LPARAM lParam) 
{ 
  // Here, url is initialized with a sample url for 
  // demonstration purposes only. 
  static char url[URL_BUF_SIZE] = 
    "http://www.osborne.com/products/0072226803/0072226803_code.zip"; 
 
  static ThrdInfo ti; 
 
  switch(message) { 
    case WM_INITDIALOG: 
      // Initialize edit box with URL. 
      SetDlgItemText(hdwnd, IDD_EB1, url); 
 
      // Create progress bar. 
      hProgWnd = CreateWindow(PROGRESS_CLASS, 
                   "", 
                   WS_CHILD | WS_VISIBLE | WS_BORDER, 
                   4, 64, 320, 12, 
                   hdwnd, NULL, hInst, NULL); 
 
      // Set step increment to 1. 
      SendMessage(hProgWnd, PBM_SETSTEP, 1, 0); 
 
      return 1; 
    case WM_COMMAND: 
      switch(LOWORD(wParam)) { 
        case IDCANCEL: 
          EndDialog(hdwnd, 0); 
          PostQuitMessage(0); 
 
          return 1; 
 
        case IDD_START: // start download 
          // Set position to zero. 
          SendMessage(hProgWnd, PBM_SETPOS, 0, 0); 
 
          // Get URL from edit box. 
          GetDlgItemText(hdwnd, IDD_EB1, url, URL_BUF_SIZE); 
          ti.url = url; 
 
          // Get reload status. 
          ti.reload = SendDlgItemMessage(hdwnd, IDD_CB1, 
                       BM_GETCHECK, 0, 0); 
 
          // Get handle to Start button. 
          ti.hPBStart = GetDlgItem(hdwnd, IDD_START); 
 
          // Reset progress counters. 
          resetprogress(); 
 
          // Start download thread. 
          if(!hThrd)  
            hThrd = (HANDLE) _beginthreadex(NULL, 0, dlstart, 
                    (void *) &ti, 0, (unsigned *) &Tid);   
   
          return 1; 
      } 
  } 
 
  return 0; 
} 
 
// Show progress in the progress bar.  This is called 
// by the download() function. 
void showprogress(unsigned long total, 
                  unsigned long part) { 
 
  percentdone = (part*100)/total; 
 
  if(percentdone > oldpercentdone) { 
    for(int i= oldpercentdone; i < percentdone; i++) { 
      // Advance the progress bar. 
      SendMessage(hProgWnd, PBM_STEPIT, 0, 0); 
    } 
    oldpercentdone = percentdone; 
  } 
} 
 
// Reset the progress counters. 
void resetprogress() { 
  percentdone = 0; 
  oldpercentdone = 0; 
} 
 
// Thread entry function that begins downloading. 
unsigned __stdcall dlstart(void * param) { 
  ThrdInfo *tip = (ThrdInfo *) param; 
 
  // Disable Start button. 
  EnableWindow(tip->hPBStart, 0); 
 
  try { 
    if(tip->reload == BST_CHECKED) 
      Download::download(tip->url, true, showprogress); 
    else 
      Download::download(tip->url, false, showprogress); 
  } catch(DLExc exc) { 
      MessageBox(hwnd, exc.geterr(), 
                 "Download Error", MB_OK); 
  } 
 
  // Enable Start button. 
  EnableWindow(tip->hPBStart, 1); 
 
  CloseHandle(hThrd); // close the thread handle 
  hThrd = 0; // set thread handle to inactive 
 
  return 0; 
}


listing 5
// Resources for file downloader. 
#include <windows.h> 
#include "windl.h" 
 
DLDB DIALOGEX 18, 18, 164, 100 
CAPTION "Download a File" 
STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTION | 
      WS_SYSMENU | WS_VISIBLE 
{ 
  PUSHBUTTON "Start", IDD_START, 42, 80, 30, 14 
  PUSHBUTTON "Cancel", IDCANCEL, 90, 80, 30, 14 
 
  CTEXT "Download Progress", IDD_TEXT2, 2, 40, 160, 12 
 
  CTEXT "Enter URL", IDD_TEXT1, 2, 16, 160, 12 
  EDITTEXT IDD_EB1, 2, 1, 160, 12, ES_LEFT | WS_CHILD | 
           WS_VISIBLE | WS_BORDER | ES_AUTOHSCROLL 
 
  AUTOCHECKBOX "Reload", IDD_CB1, 62, 56, 36, 14 
}

listing 6
#define IDD_START    100 
 
#define IDD_CB1      200 
 
#define IDD_EB1      300 
 
#define IDD_TEXT1    401 
#define IDD_TEXT2    402