Leitura de Arquivos

#include <windows.h>

#define ID_LIST 1
#define ID_TEXT 2

#define MAXREAD 8192

#define DIRATTR (DDL_READWRITE | DDL_READONLY | DDL_HIDDEN | DDL_SYSTEM | DDL_DIRECTORY | DDL_ARCHIVE | DDL_DRIVES)

#define DTFLAGS (DT_WORDBREAK | DT_EXPANDTABS | DT_NOCLIP | DT_NOPREFIX)

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK ListProc(HWND, UINT, WPARAM, LPARAM);

WNDPROC OldList;

int WINAPI WinMain(HINSTANCE hI, HINSTANCE hPI, PSTR szCL, int iCS) {
    static TCHAR szAppName[] = TEXT("Leitura");
    HWND     hwnd;
    MSG      msg;
    WNDCLASS wndclass;

    wndclass.style         = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc   = WndProc;
    wndclass.cbClsExtra    = 0;
    wndclass.cbWndExtra    = 0;
    wndclass.hInstance     = hI;
    wndclass.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH) (COLOR_BTNFACE+1);
    wndclass.lpszMenuName  = NULL;
    wndclass.lpszClassName = szAppName;

    if(!RegisterClass(&wndclass)) {
        MessageBox(NULL, TEXT("Windows NT"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName, TEXT("Leitura"),
                        WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        NULL, NULL, hI, NULL);

    ShowWindow(hwnd, iCS);
    UpdateWindow(hwnd);

    while(GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
    static BOOL bValidFile;
    static BYTE buffer[MAXREAD];
    static hwndList, hwndText;
    static RECT rect;
    static TCHAR szFile[MAX_PATH+1];
    HANDLE hFile;
    HDC    hdc;
    int    i, cxChar, cyChar;
    PAINTSTRUCT ps;
    TCHAR  szBuffer[MAX_PATH+1];

    switch(msg) {
        case WM_CREATE:
            cxChar = LOWORD(GetDialogBaseUnits());
            cyChar = HIWORD(GetDialogBaseUnits());

            rect.left = 20*cxChar;
            rect.top = 3*cyChar;

            hwndList = CreateWindow(TEXT("listbox"), NULL,
                                    WS_CHILDWINDOW | WS_VISIBLE | LBS_STANDARD,
                                    cxChar, cyChar*3,
                                    cxChar*13+GetSystemMetrics(SM_CXVSCROLL),
                                    cyChar*10,
                                    hwnd, (HMENU) ID_LIST,
                                    (HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE),
                                    NULL);

            GetCurrentDirectory(MAX_PATH+1, szBuffer);

            hwndText = CreateWindow(TEXT("static"), szBuffer,
                                    WS_CHILDWINDOW | WS_VISIBLE | SS_LEFT,
                                    cxChar, cyChar, cxChar*MAX_PATH, cyChar,
                                    hwnd, (HMENU) ID_TEXT,
                                    (HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE),
                                    NULL);

            OldList = (WNDPROC) SetWindowLong(hwndList, GWL_WNDPROC, (LPARAM) ListProc);

            SendMessage(hwndList, LB_DIR, DIRATTR, (LPARAM) TEXT("*.*"));
            return 0;
        case WM_SIZE:
            rect.right = LOWORD(lp);
            rect.bottom = HIWORD(lp);
            return 0;
        case WM_SETFOCUS:
            SetFocus(hwndList);
            return 0;
        case WM_COMMAND:
            if(LOWORD(wp)==ID_LIST && HIWORD(wp)==LBN_DBLCLK) {
                if(LB_ERR==(i=SendMessage(hwndList,LB_GETCURSEL,0,0)))
                    break;
                SendMessage(hwndList, LB_GETTEXT, i, (LPARAM) szBuffer);
                if(INVALID_HANDLE_VALUE != (hFile=CreateFile(szBuffer,
                                                             GENERIC_READ,
                                                             FILE_SHARE_READ,
                                                             NULL,
                                                             OPEN_EXISTING,
                                                             0, NULL))) {
                    CloseHandle(hFile);
                    bValidFile = TRUE;
                    lstrcpy(szFile, szBuffer);
                    GetCurrentDirectory(MAX_PATH+1, szBuffer);

                    if(szBuffer[lstrlen(szBuffer) - 1] != '\\')
                        lstrcat(szBuffer, TEXT("\\"));
                    SetWindowText(hwndText, lstrcat(szBuffer, szFile));
                }
                else {
                    bValidFile = FALSE;
                    szBuffer[lstrlen(szBuffer) - 1] = '\0';

                    if(!SetCurrentDirectory(szBuffer + 1)) {
                        szBuffer[3] = ':';
                        szBuffer[4] = '\0';
                        SetCurrentDirectory(szBuffer + 2);
                    }
                    GetCurrentDirectory(MAX_PATH + 1, szBuffer);
                    SetWindowText(hwndText, szBuffer);
                    SendMessage(hwndList, LB_RESETCONTENT, 0, 0);
                    SendMessage(hwndList, LB_DIR, DIRATTR, (LPARAM) TEXT("*.*"));
                }
                InvalidateRect(hwnd, NULL, TRUE);
            }
            return 0;
        case WM_PAINT:
            if(!bValidFile)
                break;
            if(INVALID_HANDLE_VALUE==(hFile=CreateFile(szFile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL))) {
                bValidFile = FALSE;
                break;
            }
            ReadFile(hFile, buffer, MAXREAD, &i, NULL);
            CloseHandle(hFile);

            hdc = BeginPaint(hwnd, &ps);
            (HGDIOBJ) /*SelectObject*/(hdc, (HGDIOBJ)/*GetStockObject*/(SYSTEM_FIXED_FONT));
            (HBRUSH) /*SetTextColor*/(hdc, GetSysColor(COLOR_BTNTEXT));
            (HBRUSH) /*SetBkColor*/  (hdc, GetSysColor(COLOR_BTNFACE));

            DrawTextA(hdc, buffer, i, &rect, DTFLAGS);

            EndPaint(hwnd, &ps);
            return 0;
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc(hwnd, msg, wp, lp);
}

LRESULT CALLBACK ListProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
    if(msg==WM_KEYDOWN && wp==VK_RETURN)
        SendMessage(GetParent(hwnd), WM_COMMAND, MAKELONG(1, LBN_DBLCLK), (LPARAM) hwnd);
    return CallWindowProc(OldList, hwnd, msg, wp, lp);
}