Convert int to BitArray[Resolved]

[GlenW]

I want to convert an int to binary and put the binary number's bits into a BitArray.
Anyone know how to do this?

[jmcilhinney]

Dim myInteger As Integer                                        'Store integer value here.
        Dim myBinaryString As String = Convert.ToString(myInteger, 2)   'Convert integer to biary string.
        Dim myBitArray As New BitArray(myBinaryString.Length)           'Initialise bit array.
 
        'Store True for every "1" and False for every "0".
        For i As Integer = 0 To myBitArray.Length - 1 Step 1
            myBitArray(i) = (myBinaryString.Chars(i) = "1"c)
        Next i

[jmcilhinney]

Oops. Let's try that again in C#:

int myInteger; // Store integer value here.
string myBinaryString = Convert.ToString(myInteger, 2); // Convert integer to binary string.
BitArray myBitArray = new BitArray(myBinaryString.Length); // Initialise bit array.

// Store True for every "1" and False for every "0".
for(int i = 0; i < myBitArray.Length; i++)
{
    myBitArray[i] = (myBinaryString.Chars[i] == '1')
}

I just typed this rather than pasting from the IDE but I believe it's sound.

[NoteMe]

It is nearly too tempting to post this now..

To do it in pure IL

// TestILAssembler.il
// 11.28.04 Jeff Louie
.assembly extern mscorlib {}
.assembly TestILAssembler {.ver 1:0:1:0}

.method private static void  Main(string[] args) cil managed
{
	.entrypoint
	.custom instance void [mscorlib]System.STAThreadAttribute::.ctor() = 
		( 01 00 00 00 ) 
	.maxstack  4
	.locals init ([0] int32 n_counter,[1] int32 n_input)
	 .try  // get user input
	{
			ldstr "Enter number: "
			call void [mscorlib]System.Console::Write(string)
			call string [mscorlib]System.Console::ReadLine()
			call int32 [mscorlib]System.Int32::Parse(string)
			// parse may throw exception
			stloc.1  // place valid user input into n_input
      			leave.s   got_value  // leave don't branch from try
	}  // end .try
	catch [mscorlib]System.Object 
	{
		pop  	// remove exception from stack
		ldstr    "Invalid Number."
		call     void [mscorlib]System.Console::WriteLine(string)
		leave    exit  // invalid input so exit program
	}  // end handler

 	got_value:	ldloc.1  // push value n_input onto stack
			dup
			call void [mscorlib]System.Console::Write(int32)
			ldstr " [Input value] "
			call void [mscorlib]System.Console::WriteLine(string)
			// **** (for int i=0; i<32; i++)  ****
	load_counter:	ldc.i4 0  // initialize n_counter 0
			stloc.0  // store in local variable n_count
	begin_loop:	ldloc.0  // get current counter value
			ldc.i4 32
			bge end_loop  // break loop if counter is >=32
			dup
  			ldc.i4 0x80000000  
			// bit mask 10000000000000000000000000000000
  			and  // clear all bits except most significant
			ldc.i4 0x80000000 
			ceq  // push 1 if most sig bit is true, else 0
  			call void [mscorlib]System.Console::Write(int32)
			ldc.i4 1  // push 1
  			shl  // *** shift left 1, zero least sig bit ****
			ldloc.0  // get n_counter
			ldc.i4 1
			add  // add 1 to n_counter, postfix increment
			stloc.0 // store new n_counter value
			br begin_loop  // branch to loop again
			// **** end for loop ****
	end_loop:	pop  // remove input value should be all zeros
			ldstr " [32 bit value] "
	end_algo:	call void [mscorlib]System.Console::WriteLine(string)
	exit:		ldstr "JAL 11.25.04"
			call void [mscorlib]System.Console::WriteLine(string)
			ret
} // end of method Main

Input/output

Enter number: 10
10 [Input value]
00000000000000000000000000001010 [32 bit value]

[GlenW]

I think this is the best way

BitArray larrBits = new BitArray(System.BitConverter.GetBytes(123));

[jmcilhinney]

I think this is the best way

BitArray larrBits = new BitArray(System.BitConverter.GetBytes(123));

I think you may be right. Way to ask a question and then make me look silly by giving a better answer yourself. I've learned something new so it was worthwhile.

[GlenW]

Only problem is the BitArray returned is little endian, actually this is better for me because I'm using it to save mutliple bool values in one integer in a database. Just looping through the CheckBoxes in a CheckBoxList and adding bit values to an integer. Then when you read the integer back you loop through the approriate index of the BitArray to set the CheckBoxes again. In the past I've converted integers into bit strings and used them.

Also BitArrays don't support the reverse method so if you want a big endian BitArray you'll have to reverse it long-hand, not exactly rocket-science.