Documentation

typecast

Convert data types without changing underlying data

Syntax

y = typecast(x,键入)

Description

y = typecast(x,键入)converts a numeric value inXto the data type specified bytype. InputXmust be a full, noncomplex, numeric scalar or vector. Thetype输入是一个字符串设置为以下之一:'uint8','int8','uint16','int16','uint32','int32','uint64','int64','single', or'double'.

typecast与matlab不同®castfunction in that it does not alter the input data.typecastalways returns the same number of bytes in the outputYas were in the inputX. For example, casting the 16-bit integer 1000 touint8withtypecastreturns the full 16 bits in two 8-bit segments (3 and 232) thus keeping its original value (3*256 + 232 = 1000). Thecast另一方面,函数将输入值截断为255。

The output oftypecastcan be formatted differently depending on what system you use it on. Some computer systems store data starting with its most significant byte (an ordering called大端口), while others start with the least significant byte (calledlittle-endian).

不te

MATLAB issues an error ifXcontains fewer values than are needed to make an output value.

Examples

Example 1

此示例在相同大小的数据类型之间转换:

TypeCast(UINT8(255),'INT8')ANS = -1键盘(INT16(-1),'UINT16')ANS = 65535

Example 2

Set X to a 1-by-3 vector of 32-bit integers, then cast it to an 8-bit integer type:

X = uint32([1 255 256]) X = 1 255 256

Running this on a little-endian system produces the following results. Each 32-bit value is divided up into four 8-bit segments:

Y = typecast(X, 'uint8') Y = 1 0 0 0 255 0 0 0 0 1 0 0

The third element ofX, 256, exceeds the 8 bits that it is being converted to inY(9)因此溢出到Y(10):

Y(9:12) ans = 0 1 0 0

不te thatlength(Y)is equal to4.*length(X). Also note the difference between the output oftypecastversus that ofcast:

Z = cast(X, 'uint8') Z = 1 255 255

Example 3

此示例投用了较小的数据类型(uint8)进入一个更大的人(uint16). Displaying the numbers in hexadecimal format makes it easier to see just how the data is being rearranged:

十六进制格式X = uint8 ([44 55 66 77]) X = 2c 37 42 4d

The firsttypecastis done on a big-endian system. The four 8-bit segments of the input data are combined to produce two 16-bit segments:

Y = typecast(X, 'uint16') Y = 2c37 424d

The second is done on a little-endian system. Note the difference in byte ordering:

Y = typecast(X, 'uint16') Y = 372c 4d42

You can format the little-endian output into big-endian (and vice versa) using theswapbytesfunction:

y = swapbytes(typecast(x,'uint16'))y = 2c37 424d

Example 4

This example attempts to make a 32-bit value from a vector of three 8-bit values. MATLAB issues an error because there are an insufficient number of bytes in the input:

format hex typecast(uint8([120 86 52]), 'uint32') Error using typecast Too few input values to make output type.

Repeat the example, but with a vector of four 8-bit values, and it returns the expected answer:

TypeCast(UINT8([120 86 52 18]),'UINT32')ANS = 12345678

Extended Capabilities

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