How to Deep Copy a Slice in Go: Append vs. Copy?

How to Deep Copy a Slice in Go Concis and Efficiently

In Go, copying slices requires consideration for creating a new backing array to prevent unintentional modifications to the original array. There are several concise and well-performing ways to achieve this.

One approach is to use the append function:

copy := append([]T{}, orig...)

where T is the element type of the original slice orig. However, an alternative solution exists using the built-in copy function:

cpy := make([]T, len(orig))
copy(cpy, orig)

The copy function is optimized for copying slices within the language. From the Go documentation:

"The copy built-in function copies elements from a source slice into a destination slice. ... Copy returns the number of elements copied, which will be the minimum of len(src) and len(dst)."

Note:

It's important to remember that these solutions copy values in the slice. If the slice contains pointers or structs with pointer fields, those pointers will still point to the same values as the original slice.

Benchmark:

Testing the append and copy approaches reveals similar performance characteristics:

BenchmarkCopy     100000         24724 ns/op
BenchmarkAppend   100000         24967 ns/op

The benchmark results suggest that both methods are equally efficient for deep copying slices.

The above is the detailed content of How to Deep Copy a Slice in Go: Append vs. Copy?. For more information, please follow other related articles on the PHP Chinese website!