- RAND_add(&length, sizeof(length), 0);
- RAND_add(buf, length, 0);
+ /* Read Performance Statistics from NT/2000 registry
+ * The size of the performance data can vary from call
+ * to call so we must guess the size of the buffer to use
+ * and increase its size if we get an ERROR_MORE_DATA
+ * return instead of ERROR_SUCCESS.
+ */
+ LONG rc=ERROR_MORE_DATA;
+ char * buf=NULL;
+ DWORD bufsz=0;
+ DWORD length;
+
+ while (rc == ERROR_MORE_DATA)
+ {
+ buf = realloc(buf,bufsz+8192);
+ if (!buf)
+ break;
+ bufsz += 8192;
+
+ length = bufsz;
+ rc = RegQueryValueEx(HKEY_PERFORMANCE_DATA, TEXT("Global"),
+ NULL, NULL, buf, &length);
+ }
+ if (rc == ERROR_SUCCESS)
+ {
+ /* For entropy count assume only least significant
+ * byte of each DWORD is random.
+ */
+ RAND_add(&length, sizeof(length), 0);
+ RAND_add(buf, length, length / 4.0);
+
+ /* Close the Registry Key to allow Windows to cleanup/close
+ * the open handle
+ * Note: The 'HKEY_PERFORMANCE_DATA' key is implicitly opened
+ * when the RegQueryValueEx above is done. However, if
+ * it is not explicitly closed, it can cause disk
+ * partition manipulation problems.
+ */
+ RegCloseKey(HKEY_PERFORMANCE_DATA);
+ }
+ if (buf)
+ free(buf);