encoding/base64 and encoding/hex both support nearly the same set of functions, but base64
uses a class-based encoder, whereas hex exports the methods at the top level. Is there a simple way to create a wrapper around hex so that you can work with an abstracted encoding interface? More generally, is there a way to do the equivalent of binding a method to a struct? (e.g., SomeStruct.Encode = hex.Encode)
So far, I had to define functions on a hexEncoder
struct with the same signature as the hex
functions. I created an interface like this:
type Encoding interface {
Decode(dst, src []byte) (n int, err error)
DecodedLen(n int) int
Encode(dst, src []byte) // base64 returns nothing, hex returns int
EncodedLen(n int) int
}
which works perfectly with base64.StdEncoding
, but I wasn't clear on how to wrap the hex methods. I created an empty struct for hex:
// wrap hex encoding/decoding so that it can be used interchangeably with base64 encoding
type hexEncoder struct {}
func (h hexEncoder) Decode(dst, src []byte) (n int, err error) {
return hex.Decode(dst, src)
}
func (h hexEncoder) DecodedLen(n int) int {
return hex.DecodedLen(n)
}
func (h hexEncoder) Encode(dst, src []byte) {
hex.Encode(dst, src) // don't return the int to match Encoding
}
func (h hexEncoder) EncodedLen(n int) int {
return hex.EncodedLen(n)
}
This works, but it's a bunch of extra boiler plate (where all that really needs to be wrapped is hex.Encode
). Is there a better way to do this? Ultimately, the goal is to be able to use hex and base64 interchangeably with encoding/decoding, like in something like this:
func convert(src []byte, decoder Encoding, encoder Encoding) ([]byte, error) {
temp := make([]byte, decoder.DecodedLen(len(src)))
n, err := decoder.Decode(temp, src)
if err != nil {
return temp, err
}
dst := make([]byte, encoder.EncodedLen(len(src)))
encoder.Encode(dst, temp[:n])
return dst, nil
}
A struct can have its own static and instance methods (or functions) but are not created within the struct itself. These methods exist in a separate block using impl and they can be either static or instance methods.
C++ 2. Static Members: C structures cannot have static members but are allowed in C++.
There is no such thing as a "static struct" in C++, static is a storage-class-specifier and applies to variables or functions, not types. You should not revert back to using a struct with named members instead an array of unnamed elements.. it should be the other way around..
Static variable isn't allowed in struct because C requires the whole stucture elements to be placed "together". To withdraw a element value from a structure is counted by the offset of the element from the beginning address of the structure. Note: You can have a static member in C++ structure.
No, there is no better way to implement an interface that dispatches to functions in another package, and to be honest I cannot really imagine how a better way would look like.
What you're saying in that wrapper is:
type myType struct{}
func (myType) WhenCalledLikeThis() { DoThat() }
Which seems optimal. It doesn't need any backing memory, allows slight changes in naming and return values (as you've done for Encode
), and dispatches with a single call.
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