Documentation

swapbytes

Swap byte ordering

Description

example

Y = swapbytes(X) swaps the byte ordering of each element in array X from little endian to big endian (or vice versa). All elements of the input array must be full, noncomplex, and numeric.

Examples

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Swap the byte ordering for a scalar 32-bit value. Use hexadecimal representation to show the conversion from little endian to big endian.

X = uint32(hex2dec('4D3C2B1A'));
Y = dec2hex(swapbytes(X))
Y =
'1A2B3C4D'

Starting in R2019b, you can also write a hexadecimal value as a literal using the 0x or 0X prefix (for more information, see Hexadecimal and Binary Values). Specify the number X as a hexadecimal literal. Swap the byte ordering.

X = 0x4D3C2B1A;
Y = dec2hex(swapbytes(X))
Y =
'1A2B3C4D'

Swap the byte ordering for each element of a 1-by-4 vector.

format short
X = uint16([0 1 128 65535])
X = 1x4 uint16 row vector

0       1     128   65535

Y = swapbytes(X)
Y = 1x4 uint16 row vector

0     256   32768   65535

Examine the output in hexadecimal notation to show the endian conversion.

format hex
X
X = 1x4 uint16 row vector

0000   0001   0080   ffff

Y
Y = 1x4 uint16 row vector

0000   0100   8000   ffff

Create a three-dimensional array A of 16-bit integers. Swap the byte ordering of each element. Use hexadecimal representation to show the endian conversion.

format hex
X = uint16(magic(3)*150);
X(:,:,2) = X*40;
X
X = 3x3x2 uint16 array
X(:,:,1) =

04b0   0096   0384
01c2   02ee   041a
0258   0546   012c

X(:,:,2) =

bb80   1770   8ca0
4650   7530   a410
5dc0   d2f0   2ee0

Y = swapbytes(X)
Y = 3x3x2 uint16 array
Y(:,:,1) =

b004   9600   8403
c201   ee02   1a04
5802   4605   2c01

Y(:,:,2) =

80bb   7017   a08c
5046   3075   10a4
c05d   f0d2   e02e

Input Arguments

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Numeric value, specified as a scalar, vector, matrix, or multidimensional array. The swapbytes operation is elementwise when X is nonscalar.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

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Convert Little Endian to Big Endian

Computer systems store data in pieces of bytes. There are two ways to store a numeric value in computer memory: little endian and big endian. In little-endian style, the bytes are written from left to right in increasing significance. In big-endian style, the bytes are written from left to right in decreasing significance. The swapbytes function swaps the byte ordering in memory, converting little endian to big endian (and vice versa).

The following figure illustrates the conversion for a 32-bit (4-byte) hexadecimal number, 4D3C2B1A. In hexadecimal notation, one byte is represented by two digits. Each box in the little-endian picture shows one byte of data (4D, 3C, 2B, and 1A). The swapbytes function swaps the order of these boxes or bytes. 