Converting 2 bytes to signed int

Question

Is their any way to convert 2 bytes to signed int? I know we can convert a byte to signed int in following way

byte B1= 0xFF;
int r = Convert.ToSbyte((sbyte)B1);

but what about 2 bytes to signed int? For example -260 is 0xFC, 0xFE

Solution 1

In case of one byte, just assign:

byte B1 = 0xFF;
int r = B1;

In case of two bytes - add shift and assign:

byte B1 = 0xFE;
byte B2 = 0xFC;

int r = (B1 << 8) | B2;

in case Int16 is wanted then cast:

// -260
short s = unchecked((short) ((B1 << 8) | B2));

Solution 2

Assuming the first byte is the msb:

byte b1 = 0xff;
byte b2 = 0xff;
var test = BitConverter.ToInt16(new byte[] { b1, b2 }, 0);

Otherwise:

byte b1 = 0xff;
byte b2 = 0xff;
var test = BitConverter.ToInt16(new byte[] { b2, b1 }, 0);

Edit: "signed"

Solution 3

Take a look at BitConverter class and its ToInt32() method.

Comments

[prattom]

That will convert to unsigned integer

[Groo]

OP probably wants a signed Int16.

[default]

@prattom BitConverter.ToInt32: Returns a 32-bit signed integer converted from four bytes at a specified position in a byte array.

[Groo]

OP probably wants a signed Int16.

[prattom]

sorry not unsigned integer but Bitconverter returns positive integer instead to negative integer for ex. 0xFC, 0xFE is returned as 65276 if I use BitConverter class while it should -260

[Gusman]

good old binary operators, for sure most efficient than any converter class :)

[Thomas]

ToInt32(array<Byte>^, Int32) Returns a 32-bit signed integer converted from four bytes at a specified position in a byte array. you should use this.

[Gusman]

@prattom that's becaue you used ToInt32 and only sent two bytes, an int32 has it's negative bit at the most significant bit of the dword, so there's no negative for two bytes, use ToInt16()