Splitting Bytes in C

[sde]

I am working on midi events.

There is one byte in the event which I need to take apart.

B0 (hex value)

B is refers to the event being a control change, and 0 refers to the midi channel.

in C, how can i put each of these in their own variable?

[Blood Night]

i think it's similar to the operation that the decimal does.

for instance

how will you split the 21 into two variables?
21%10=1
21/10=2

just a referrence

[Valmont]

How are the two bytes stored and to what (in what datatype) do you wish to store the single byte.
In case you were looking for what Blood Night meant, then here is a play thingy:

#include <iostream.h>

const unsigned short currentbyte = 0xB3;

int main()
{
	//unsigned short = max 2 bytes; e.g. 0xFF;
	unsigned short value, remain;
	
	//A bit of toying: 0x10 = 16 Decimal!

	value = currentbyte / 0x10;
	//Convert to hex
	cout<<hex<<value<<endl; //b
	cout<<value<<endl;	//b
	//convert to decimal
	cout<<dec<<value<<endl;	//11
	cout<<value<<endl;	//11
	
	remain = currentbyte % 0x10;
	cout<<hex<<remain<<endl;	//3
	cout<<remain<<endl;		//3
	cout<<dec<<remain<<endl;	//3
	cout<<remain<<endl;		//3

	return 0;
}

[joe_bruin]

unsigned char v, control, channel;

v = 0xB0;
control = (v >> 4);
channel = (v & 0xf);

[sde]

the original type is DWORD.

when i do this, i have problems casting DWORD to unsigned char:

v = (dwParam1>>0);

after a little bit of fussing around with it, this works out good.

unsigned char cc,channel,value;
cc = (dwParam1>>8);
channel = (dwParam1>>0)%16;
value = (dwParam1>>16);

i am suprised that i'm not getting some sort of type casting errors that second way.

thanks again!

[joe_bruin]

alright, let's see if we understand this correctly.

what is the dword's value? is it 0x000000b0 ?
and you want the 'b' and the last '0' (ie, two nibbles from the last byte)?

[sde]

the DWORD is representing a short MIDI Event message.

Normal MIDI Events can be up to 4 bytes: status byte, data1, data2, data3

this is how i understand it anyway.

the control change and channel information is in the first byte (status byte), the value of that is in the second byte(data1). in this message, the third and forth bytes are not used.

http://harmony-central.com/MIDI/Doc/table1.html

That is sorta what is going on here. It's not a great example, but you might get a more clear picture of the MIDI event.

[sde]

when i open a midi port, i can designate a callback function. this function is triggered whenever a midi event is sent to the midi input.

if you really want to understand what i'm doing, here is some of the callback function:

void CALLBACK midiCallback(HMIDIIN handle, UINT uMsg, DWORD dwInstance, DWORD dwParam1, DWORD dwParam2)
{
  LPMIDIHDR lpMIDIHeader;
  unsigned char *ptr;
  TCHAR buffer[80];
  unsigned char bytes;
  
  switch (uMsg)
  {
    // Received some regular MIDI message
    case MIM_DATA:
    {    
      // ignore active sensing
      if( dwParam1 != 0xF8 ){
            
        unsigned char cc,channel,value;
        cc = (dwParam1>>8);
        channel = (dwParam1>>0)%16;
        value = (dwParam1>>16);
        
        sprintf(&buffer[0], "cc: %d ch: %d v: %d \r\n", cc, 
                                                        channel, 
                                                        value);
        _cputs(&buffer[0]);
      }
      
      break;
    }
  }
}