See comments below.
On Mar 19, 2008, at 8:07 AM, Thomas Börkel wrote:
HI!
I am trying to call a function, that takes a buffer as parameter.
This buffer could be anything, but is today a specific struct.
The function can be called with buffer length 0 to determine the
needed buffer size. Then you call it again with the correct
allocated buffer.
There are plenty of Win32 function that work like this.
But how do I later convert the buffer to the Structure? I only know
a way to convert a Pointer to a Structure (with useMemory()).
This is the function:
BOOL WINAPI QueryServiceStatusEx(
__in SC_HANDLE hService,
__in SC_STATUS_TYPE InfoLevel,
__out_opt LPBYTE lpBuffer,
__in DWORD cbBufSize,
__out LPDWORD pcbBytesNeeded
);
When I declare lpBuffer as type of the Structure and call the
function first with cbBufSize = 0 and then with cbBufSize =
pcbBytesNeeded, it works. But that's only for the current
implementation.
For this, I have declared the function like this:
public boolean QueryServiceStatusEx(Pointer hService, int InfoLevel,
SERVICE_STATUS_PROCESS lpBuffer, int cbBufSize, IntByReference
pcbBytesNeeded);
But I'd like it more like this, to make it more future proof:
Not sure what you mean by future-proof. I would think declaring a
specific structure preferable to a generic buffer. If the parameter
accepts different types you can always declare a different method for
each acceptable type.
public boolean QueryServiceStatusEx(Pointer hService, int InfoLevel,
byte[] lpBuffer, int cbBufSize, IntByReference pcbBytesNeeded);
But then how to convert lpBuffer to the Structure?
The following should do the trick (or something similar; I'm not
looking at the javadoc right now):
MyStructure s ...;
s.getPointer().write(0, lpBuffer, 0, lpBuffer.length);
s.read();
You could also use a direct byte buffer, then call
Structure.useMemory() with Native.getDirectBufferPointer().
3 messages in net.java.dev.jna.usersRe: [jna-users] Buffer to Structure
