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What is the asterisk on a data type in a Windows API declaration?

开发者 https://www.devze.com 2023-03-05 00:21 出处:网络
I know what (for example) a DWORD is, it\'s a four-byte unsigned long integer. But what does DWORD * with an asterisk before the parameter name mean, as seen here:

I know what (for example) a DWORD is, it's a four-byte unsigned long integer.

But what does DWORD * with an asterisk before the parameter name mean, as seen here:

HRESULT UrlUnescape(
  __inout      PTSTR pszURL,
  __out_opt    PTSTR pszUnescaped,
  __inout_opt开发者_如何转开发  DWORD *pcchUnescaped,
  DWORD dwFlags
);

UPDATE

It occurs to me I had a few additional hints that it was a pointer. The first is that the parameter name starts with a p. The other is that it is an in/out parameter, and the only way the callee could alter the value of the caller's variable is if a pointer is passed rather than a value. Of course, the strings are pointers too, and they don't use the asterisk, but that's because a string can't be passed by value so it would be redundant, while an integer certainly can be passed by value (and often/usually is).


It means that pcchUnescaped is pointer to an object of type DWORD. That's normal C, nothing specifically related to the Windows API.


It means a pointer to a DWORD in the memory.


From MSDN:

A DWORD is a 32-bit unsigned integer (range: 0 through 4294967295 decimal). Because a DWORD is unsigned, its first bit (Most Significant Bit (MSB)) is not reserved for signing.

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