问题
I have a BitArray with the length of 8, and I need a function to convert it to a byte. How to do it?
Specifically, I need a correct function of ConvertToByte:
BitArray bit = new BitArray(new bool[]
{
false, false, false, false,
false, false, false, true
});
//How to write ConvertToByte
byte myByte = ConvertToByte(bit);
var recoveredBit = new BitArray(new[] { myByte });
Assert.AreEqual(bit, recoveredBit);
回答1:
This should work:
byte ConvertToByte(BitArray bits)
{
if (bits.Count != 8)
{
throw new ArgumentException("bits");
}
byte[] bytes = new byte[1];
bits.CopyTo(bytes, 0);
return bytes[0];
}
回答2:
A bit late post, but this works for me:
public static byte[] BitArrayToByteArray(BitArray bits)
{
byte[] ret = new byte[(bits.Length - 1) / 8 + 1];
bits.CopyTo(ret, 0);
return ret;
}
Works with:
string text = "Test";
byte[] bytes = System.Text.Encoding.ASCII.GetBytes(text);
BitArray bits = new BitArray(bytes);
bytes[] bytesBack = BitArrayToByteArray(bits);
string textBack = System.Text.Encoding.ASCII.GetString(bytesBack);
// bytes == bytesBack
// text = textBack
.
回答3:
A poor man's solution:
protected byte ConvertToByte(BitArray bits)
{
if (bits.Count != 8)
{
throw new ArgumentException("illegal number of bits");
}
byte b = 0;
if (bits.Get(7)) b++;
if (bits.Get(6)) b += 2;
if (bits.Get(5)) b += 4;
if (bits.Get(4)) b += 8;
if (bits.Get(3)) b += 16;
if (bits.Get(2)) b += 32;
if (bits.Get(1)) b += 64;
if (bits.Get(0)) b += 128;
return b;
}
回答4:
This should do the trick. However the previous answer is quite likely the better option.
public byte ConvertToByte(BitArray bits)
{
if (bits.Count > 8)
throw new ArgumentException("ConvertToByte can only work with a BitArray containing a maximum of 8 values");
byte result = 0;
for (byte i = 0; i < bits.Count; i++)
{
if (bits[i])
result |= (byte)(1 << i);
}
return result;
}
In the example you posted the resulting byte will be 0x80. In other words the first value in the BitArray coresponds to the first bit in the returned byte.
回答5:
That's should be the ultimate one. Works with any length of array.
private List<byte> BoolList2ByteList(List<bool> values)
{
List<byte> ret = new List<byte>();
int count = 0;
byte currentByte = 0;
foreach (bool b in values)
{
if (b) currentByte |= (byte)(1 << count);
count++;
if (count == 7) { ret.Add(currentByte); currentByte = 0; count = 0; };
}
if (count < 7) ret.Add(currentByte);
return ret;
}
回答6:
In addition to @JonSkeet answer you can use Generic Method as blow:
public static byte ToByte(this BitArray bits)
{
if (bits.Count != 8)
{
throw new ArgumentException("bits");
}
byte[] bytes = new byte[1];
bits.CopyTo(bytes, 0);
return bytes[0];
}
And use like:
BitArray foo = new BitArray(new bool[]
{
false, false, false, false,false, false, false, true
});
foo.ToByte();
回答7:
Unfortunately, the BitArray class is partially implemented in .Net Core class (UWP). For example BitArray class is unable to call the CopyTo() and Count() methods. I wrote this extension to fill the gap:
public static IEnumerable<byte> ToBytes(this BitArray bits, bool MSB = false)
{
int bitCount = 7;
int outByte = 0;
foreach (bool bitValue in bits)
{
if (bitValue)
outByte |= MSB ? 1 << bitCount : 1 << (7 - bitCount);
if (bitCount == 0)
{
yield return (byte) outByte;
bitCount = 8;
outByte = 0;
}
bitCount--;
}
// Last partially decoded byte
if (bitCount < 7)
yield return (byte) outByte;
}
The method decodes the BitArray to a byte array using LSB (Less Significant Byte) logic. This is the same logic used by the BitArray class. Calling the method with the MSB parameter set on true will produce a MSB decoded byte sequence. In this case, remember that you maybe also need to reverse the final output byte collection.
回答8:
byte GetByte(BitArray input)
{
int len = input.Length;
if (len > 8)
len = 8;
int output = 0;
for (int i = 0; i < len; i++)
if (input.Get(i))
output += (1 << (len - 1 - i)); //this part depends on your system (Big/Little)
//output += (1 << i); //depends on system
return (byte)output;
}
Cheers!
回答9:
Little endian byte array converter : First bit (indexed with "0") in the BitArray assumed to represents least significant bit (rightmost bit in the bit-octet) which interpreted as "zero" or "one" as binary.
public static class BitArrayExtender {
public static byte[] ToByteArray( this BitArray bits ) {
const int BYTE = 8;
int length = ( bits.Count / BYTE ) + ( (bits.Count % BYTE == 0) ? 0 : 1 );
var bytes = new byte[ length ];
for ( int i = 0; i < bits.Length; i++ ) {
int bitIndex = i % BYTE;
int byteIndex = i / BYTE;
int mask = (bits[ i ] ? 1 : 0) << bitIndex;
bytes[ byteIndex ] |= (byte)mask;
}//for
return bytes;
}//ToByteArray
}//class
回答10:
A sample from my codes:
Public Shared Function BytesXor(a1 As Byte(), a2 As Byte()) As Byte()
Dim ba1 As BitArray = New BitArray(a1)
Dim ba2 As BitArray = New BitArray(a2)
Dim intLength As Integer = System.Math.Min(a1.Length, a2.Length)
Dim RetrunValue(intLength - 1) As Byte
If ba1.Length > ba2.Length Then ba1.Length = ba2.Length
If ba2.Length > ba1.Length Then ba2.Length = ba1.Length
Dim ba3 As BitArray = ba1.Xor(ba2)
Dim p As Integer = 0
For i As Integer = 0 To intLength - 1
Dim v As Integer = 0
For j As Integer = 0 To 7
If ba3.Get(p) Then
'BitArray(Byte()) sorts bits from lower to higher
'"BitArray to Byte" must be put by reverse order
v += 1 << j
End If
p += 1
Next
RetrunValue(i) = CByte(v)
Next
Return RetrunValue
End Function
来源：https://stackoverflow.com/questions/560123/convert-from-bitarray-to-byte