制作一个指向两个字节的指针

发布于 2024-08-02 11:29:47 字数 669 浏览 6 评论 0原文

除了呼吸之外，我在所有事情上都是一个完全的新手，如果我不清楚的话，很抱歉，但是这里是：

我在 C 中有一个函数，它通过 I2C 总线将字节写入电路，在头文件中它看起来像这样：

BOOL WINAPI JidaI2CWrite(HJIDA hJida, DWORD dwType, BYTE bAddr, LPBYTE pBytes, DWORD dwLen);

hJida：板句柄。
dwType：I2C 从零开始的编号公共汽车。
bAddr：设备的地址 I2C 总线，完整的 8 位写入总线。
pBytes：指向该位置的指针包含字节。
dwLen：要写入的字节数。

如果我只想向地址为 0x98 的电路写入一个字节，我会这样做：

unsigned char writing[1];
writing[0]=0x10;

unsigned char *pointer;
pointer = &writing[0];


JidaI2CWrite(hJida,0,0x98,pointer,1);

这似乎可行，但如果我想写入两个字节，例如 0x10FF，则不行。那么如何制作一个指向两个字节而不是仅一个字节的指针呢？

谢谢

原文

I'm a complete novice in everything except maybe breathing, so sorry if I'm not being clear, but here goes:

I have a function in C which writes bytes to a circuit via an I2C bus, and in the header file it looks like this:

BOOL WINAPI JidaI2CWrite(HJIDA hJida, DWORD dwType, BYTE bAddr, LPBYTE pBytes, DWORD dwLen);

hJida: Board handle.
dwType: Zero-based number of the I2C
bus.
bAddr: Address of the device on the
I2C bus, the full 8 bits as it is
written to the bus.
pBytes: Pointer to location that
contains the bytes.
dwLen: Number of bytes to write.

If I wanted to write just one byte to a circuit with the address 0x98, I would do something like this:

unsigned char writing[1];
writing[0]=0x10;

unsigned char *pointer;
pointer = &writing[0];


JidaI2CWrite(hJida,0,0x98,pointer,1);

which seems to work, but if I wanted to write two bytes, say 0x10FF, it doesn't. So how do I make a pointer that points to two bytes instead of just one?

Thanks

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ゃ懵逼小萝莉 2024-08-09 11:29:47

您想要这样的东西：

unsigned char writing[2];
writing[0] = 0x01;
writing[1] = 0x02;

JidaI2CWrite(hJida, 0, 0x98, writing, 2);

请注意，C 中的数组通常可以像指针一样使用。变量 writing 可以被认为是一个指向内存块的指针，在本例中内存块的大小为 2 个字节。创建另一个指针来指向该位置是多余的（在本例中）。

请注意，您可以使其指向任意数量的字节：

unsigned char writing[12];

//fill the array with data

JidaI2CWrite(hJida, 0, 0x98, writing, 12);

You want something like this:

unsigned char writing[2];
writing[0] = 0x01;
writing[1] = 0x02;

JidaI2CWrite(hJida, 0, 0x98, writing, 2);

Notice that an array in C can be usually be used just like a pointer. The variable writing can be thought of as just a pointer to a chunk of memory that in this case has a size of 2 bytes. Creating another pointer to point to that location is redundant (in this case).

Note you could make it point to any number of bytes:

unsigned char writing[12];

//fill the array with data

JidaI2CWrite(hJida, 0, 0x98, writing, 12);

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等你爱我 2024-08-09 11:29:47

试试这个...

//A buffer containing the bytes to be written
unsigned char writeBuffer[] = {0x10, 0xFF}; 

//writeBuffer itself points to the start of the write buffer
//you dont need an extra pointer variable
//Indicate the size of the buffer in the call to the function
//pointers do not carry array size information with them (in C/C++)
JidaI2CWrite(hJida,0,0x98,writeBuffer,2);

或者更好

unsigned char writeBuffer[] = {0x10, 0xFF};

JidaI2CWrite(hJida,0,0x98,writeBuffer
              ,sizeof(writeBuffer)/sizeof(unsigned char));

注意：sizeof(writeBuffer)/sizeof(writeBuffer[0]) 会自动为您计算数组的大小（以字节为单位）

Try this...

//A buffer containing the bytes to be written
unsigned char writeBuffer[] = {0x10, 0xFF}; 

//writeBuffer itself points to the start of the write buffer
//you dont need an extra pointer variable
//Indicate the size of the buffer in the call to the function
//pointers do not carry array size information with them (in C/C++)
JidaI2CWrite(hJida,0,0x98,writeBuffer,2);

or better yet

unsigned char writeBuffer[] = {0x10, 0xFF};

JidaI2CWrite(hJida,0,0x98,writeBuffer
              ,sizeof(writeBuffer)/sizeof(unsigned char));

Note: sizeof(writeBuffer)/sizeof(writeBuffer[0]) automatically calculates the size of the array in bytes for you

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简美 2024-08-09 11:29:47

看起来好像dwLen 参数是要写入的字节数。因此：

unsigned char writing[2];
writing[0] = 0x10;
writing[1] = 0xff;
JidaI2CWrite(hJida, 0, 0x98, writing, 2);

请注意，您使用指向 writing[1] 的 pointer 可能不应该按书面方式工作，因为这会将 pointer 设置为指向您真正想要写入的字节之后的字节。我怀疑这是一个拼写错误，但如果不是，您可能希望在继续之前检查现有代码。

It appears as though the dwLen parameter is the number of bytes to write. So:

unsigned char writing[2];
writing[0] = 0x10;
writing[1] = 0xff;
JidaI2CWrite(hJida, 0, 0x98, writing, 2);

Note that your use of pointer pointing to writing[1] probably shouldn't work as written, because that sets pointer to point to the byte after the byte you really want to write. I'm suspecting this is a typo, but if not you may wish to review your existing code before proceeding.

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