分手LPARAM可变的放大器;看着比特组 [英] Breaking up a LPARAM variable & looking at groups of bits

问题描述

我知道一个LPARAM变量设置（里面）的某些位标识信息，如长按键presses＆安培;等等。当我收到一个WM_KEYDOWN事件。

所以我想分手LPARAM可变的放大器;看个人位值放的群体;位和放大器组;该值（如看16日至24日比特及从该值）。

我的问题：我不知道如何来看待各个位和放大器;比特组？我如何分手的LPARAM变量和放大器;看位值（打印出来以二进制，十六进制和放大器;十进制）。

我有这到目前为止，但在比特级工作混淆了我很多，所以我不能确定，如果我真的很期待在24日，25日和放大器;十进制和放大器16位值;等等。

  LRESULT CALLBACK的WndProc（HWND HWND，UINT MSG，WPARAM wParam参数，LPARAM lParam的）
{    开关（MSG）
    {
        案例WM_KEYDOWN：
        {
            //我知道一个LPARAM变量是一个32位（或者是字节？）长变量。我将如何看
            // 16位的值？我怎么会看，从16日至24日位的价值？
            的printf（A：％D，％D，％d个\\ N，lParam的＆GT;＆GT; 24，lParam的＆GT;＆GT; 25，lParam的＆GT;＆GT; 16）;
        }
        打破;
 

解决方案

在一般情况下，您使用按位与检查，如果某个位设置：

  unsigned int类型的标志; //一些标志如果（旗＆安培; 0×01）{} // 0位
如果（标志＆放大器; 0×02）{} //位1被置
如果（旗＆安培; 0×04）{} // 2位中
...
如果（标志及（1U＆所述;＆所述; n））的{} //位n被设置
 

不过，不依赖于物理位值。相反，API定义描述该标志的含义USEFUL_CONSTANTS：

  LPARAM标志= ApiFunction（）;
如果（标志＆放大器; USEFUL_CONSTANT）{} //检查是否设置了标志
 

检查相关信息的API文档，找出这些定义的值。

更新：我看到你的情况，你可能会真正想要的值的，而不仅仅是标志。因此，要获得最低的16位的值，你只要按位与具有相应的位掩码值： unsigned int类型REPEAT_COUNT =标志和放大器; 0xFFFF的; 注意0xFFFF的是二进制1111111111111111

I know that a LPARAM variable has certain bits set(inside it) that identify information such as long key presses & etc. when I receive a WM_KEYDOWN event.

So I am trying to break up a LPARAM variable & look at groups of individual bit values & groups of bits & that value(for eg looking at the 16th to the 24th bit & the value from that).

My Problem: I dont know how to look at individual bits & groups of bits? How do I break up the LPARAM variable & look at bit values (printing it out in binary, hex & decimal).

I have this so far, but working at the bit level confuses me alot, so I am unsure if I am really looking at the 24th, 25th & 16th bit value in decimal & etc.

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{

    switch(msg)
    {
        case WM_KEYDOWN:
        {
            // I know that a LPARAM variable is a 32 bit(or is it byte?) long variable. How would I look at the
            // 16th bit value? How would I look that the value from the 16th to the 24th bit?
            printf("A: %d, %d, %d\n", lParam >> 24, lParam >> 25, lParam >> 16 );
        }
        break;

解决方案

In general, you use bitwise-AND to check if a certain bit is set:

unsigned int flags;  // some flags

if (flags & 0x01) { } // bit 0 is set
if (flags & 0x02) { } // bit 1 is set
if (flags & 0x04) { } // bit 2 is set
...
if (flags & (1U << n)) { } // bit n is set

However, don't rely on the physical bit values. Instead, the API defines USEFUL_CONSTANTS that describe the meaning of the flags:

LPARAM flags = ApiFunction();
if (flags & USEFUL_CONSTANT) { } // check if the flag is set

Check the API documentation of the relevant message to find out which values are defined.

Update: I see that in your case you might actually want values rather than just flags. So, to get the value of the lowest 16 bits, you just bitwise-AND the value with the corresponding bitmask: unsigned int repeat_count = flags & 0xFFFF; Note that 0xFFFF is 1111111111111111 in binary.

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