Old 04-05-2017, 03:51 AM   #1
ceanganb
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Default Can't get MIDI metadata C++

Hi. I'm using the following code in C++ to get the sysex messages:

Code:
	auto mehwnd = MIDIEditor_GetActive();
	auto mit = MIDIEditor_GetTake(mehwnd);
	int numOfNotes;
	int numOfCCs;
	int numOfSysex;

	MIDI_CountEvts(mit, &numOfNotes, &numOfCCs, &numOfSysex);
	for (int i = 0; i < numOfSysex; ++i)
	{
		bool selectedOutOptional;
		bool mutedOutOptional;
		double ppqposOutOptional;
		int typeOutOptional;
		char msgOptional[1024];
		int msgOptional_sz;

		int retval = MIDI_GetTextSysexEvt(mit, i,
			&selectedOutOptional, &mutedOutOptional, &ppqposOutOptional,
			&typeOutOptional, msgOptional, &msgOptional_sz);
		ShowConsoleMsg(msgOptional);
I tried char* msgOptional, many different array values, nothing works. All the other data are retrived fine. What am I doing wrong, guys?

Thanks.
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Last edited by ceanganb; 04-05-2017 at 03:52 AM. Reason: improve title
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Old 04-06-2017, 03:34 AM   #2
Xenakios
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Maybe msgOptional_sz needs to initially have the size of your char buffer.
Code:
char msgOptional[1024];
int msgOptional_sz=sizeof(msgOptional);
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Old 04-06-2017, 08:01 AM   #3
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I've been stumbling over this _sz also:

http://forum.cockos.com/showthread.php?t=190148
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Old 04-06-2017, 09:16 AM   #4
ceanganb
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@Xenakios: That was it, the * in the msgOptional_sz field led me to thinking I was getting a value instead of setting, like the rest of them. Thanks again for saving me.

@nofish: Yes, I'm also struggling with the older standard C-style idioms, I'm new to C++ and virtually bypassed the char* stuff, back to school again.
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Old 04-06-2017, 09:39 AM   #5
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Quote:
Originally Posted by ceanganb View Post
@Xenakios: That was it, the * in the msgOptional_sz field led me to thinking I was getting a value instead of setting
In C there isn't really much else to do for "optional" variables than to use a pointer. So you might be able to use a null pointer in this case too...But the pointer to the size variable may also be used to return how much of the buffer Reaper ended up using, so it's probably safer/more useful to give it the address of the integer size variable.
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Old 04-06-2017, 09:58 AM   #6
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Quote:
Originally Posted by Xenakios View Post
But the pointer to the size variable may also be used to return how much of the buffer Reaper ended up using, so it's probably safer/more useful to give it the address of the integer size variable.
That's what I though, the pointer made me think that it was a value returned from the function, based on other functions' signature, like GetTrackName(MediaTrack* track, char* buf, int buf_sz), where it's clear that the size must be provided. And why "optional", my poor mind can't see what is optional in a sysex message. If it was the case of an empty sysex, but then sizeof would reveal that.

P.S.: In Reaper, an empty sysex can't even exist.
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Old 04-07-2017, 06:09 AM   #7
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Quote:
Originally Posted by ceanganb View Post
And why "optional", my poor mind can't see what is optional in a sysex message
It's probably optional for the purposes of ReaScript, the C API is just using a similar function signature although the stuff isn't really optional when used from C. (In ReaScript the function can do the needed buffer allocation itself but in C it's typical the allocation and passing in the available size is the responsibility of the calling code.)
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