How to Convert a Go Slice to a Fixed-Sized Array?

Converting a Slice to a Fixed Size Array

When working with slices and fixed size arrays in Go, it's important to understand how to perform conversions between them. This can be especially useful when you need to work with external libraries or interfaces that expect fixed-size arrays.

The issue arises when attempting to directly assign a slice to an array of a different size. As shown in the example provided, this results in a type mismatch error.

To convert a slice into a fixed-size array, the "copy" function can be employed. This function takes two arguments: a destination array and a source slice. It copies the contents of the source slice into the destination array, up to the minimum of their lengths.

For example:

slice := []byte("abcdefgh")
var arr [4]byte

copy(arr[:], slice[:4])

fmt.Println(arr)
// Output: [97 98 99 100]

Here, the copy function is used to copy the first four bytes from the slice into the arr array. Since the source slice is larger than the destination array, only the first four bytes are copied.

Another approach is to use the copy function without specifying the source slice's length. This will automatically copy the entire source slice into the destination array:

copy(arr[:], slice)

fmt.Println(arr)
// Output: [97 98 99 100]

In summary, using the copy function provides a reliable and efficient method for converting a slice to a fixed-size array in Go, ensuring that the array contains the desired subset of elements from the slice.

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