Problem - Kevin Tafuro

creates a modal dialog. A modal dialog can be used for capturing mouse messages
instead of the modeless dialog that was required for gathering keyboard entropy in
Recipe 11.20, because normal dialog processing doesn’t eat mouse messages the way
it eats keyboard messages.
Once the dialog is successfully created, the message handling procedure handles WM_
MOUSEMOVE messages, which will be received whenever the mouse pointer moves over
the dialog or its controls. The position of the mouse pointer is extracted from the
message, converted to screen coordinates, combined with a timestamp, and fed into
the hash object. If the current pointer position is the same as the previous pointer
position, it is not counted as entropy but is added into the hash anyway. As mouse
movements are collected, the progress bar is updated, and when the requested
amount of entropy has been obtained, the OK button is enabled.
When the OK button is clicked, the dialog is destroyed, terminating the message
loop. The output from the hash function is copied into the output buffer from the
caller, and internal data is cleaned up before returning to the caller.
#include
#include
#include
#define SPC_ENTROPY_PER_SAMPLE 0.5
#define SPC_MOUSE_DLGID 102
#define SPC_PROGRESS_BARID 1000
#define SPC_MOUSE_COLLECTID 1003
#define SPC_MOUSE_STATIC 1002
typedef struct {
double dEntropy;
DWORD cbRequested;
POINT ptLastPos;
DWORD dwLastTime;
HCRYPTHASH hHash;
} SPC_DIALOGDATA;
typedef struct {
POINT ptMousePos;
DWORD dwTickCount;
} SPC_MOUSEPOS;
static BOOL CALLBACK MouseEntropyProc(HWND hwndDlg, UINT uMsg, WPARAM wParam,
LPARAM lParam) {
SPC_MOUSEPOS MousePos;
SPC_DIALOGDATA *pDlgData;
switch (uMsg) {
case WM_INITDIALOG:
pDlgData = (SPC_DIALOGDATA *)lParam;
SetWindowLong(hwndDlg, DWL_USER, lParam);
SendDlgItemMessage(hwndDlg, SPC_PROGRESS_BARID, PBM_SETRANGE32, 0,
640 | Chapter 11: Random Numbers
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