swapbytes

Swap byte ordering

Syntax

Y = swapbytes(X)

Description

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

Swap Byte Ordering of Scalar

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 Byte Ordering of Vector

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

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

X = 1×4 uint16 row vector

       0       1     128   65535

Y = swapbytes(X)

Y = 1×4 uint16 row vector

       0     256   32768   65535

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

format hex
X

X = 1×4 uint16 row vector

   0000   0001   0080   ffff

Y

Y = 1×4 uint16 row vector

   0000   0100   8000   ffff

Swap Byte Ordering of 3-D Array

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 = 3×3×2 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 = 3×3×2 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

X — Numeric value

scalar | vector | matrix | multidimensional array

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

More About

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.

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

The swapbytes function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Inheritance of the class of the input to swapbytes in a MATLAB Function block is supported only when the class of the input is double. For non-double inputs, the input port data types must be specified, not inherited.

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

Inheritance of the class of the input to swapbytes in a MATLAB Function block is supported only when the class of the input is double. For non-double inputs, the input port data types must be specified, not inherited.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The swapbytes function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced before R2006a