How Expensive is the `[]byte(string)` Conversion in Go?

The Price of []byte(string)

The []byte(string) conversion in Go is a costly operation that involves copying. This is because strings in Go are immutable, while byte slices are mutable. Therefore, a copy of the string's bytes is created to ensure that subsequent slice operations will not modify the original string.

The conversion is not a cast, which would simply reinterpret the bits in place. Instead, it is a conversion that requires memory allocation and content transfer. This can be expensive in some scenarios.

To illustrate, consider the following code:

func toBytes(s string) []byte {
  return []byte(s)
}

This function takes a string as input and returns a byte slice. The conversion from string to byte slice requires copying all of the string's bytes to a new byte slice. If the string is large, this can be a costly operation.

Reverse Conversion

The reverse conversion from byte slice to string also involves copying. However, no encoding or decoding is performed. The bytes in the byte slice are simply copied to the string as they are.

Conclusion

The []byte(string) and string([]byte) conversions in Go are costly operations that involve copying. This is because strings in Go are immutable, while byte slices are mutable. When performing these conversions, it is important to be aware of the potential performance impact.

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