How do you convert a slice into an array?

Question

I am trying to write an application that reads RPM files. The start of each block has a Magic char of [4]byte.

Here is my struct

type Lead struct {   Magic        [4]byte   Major, Minor byte   Type         uint16   Arch         uint16   Name         string   OS           uint16   SigType      uint16 } 

I am trying to do the following:

lead := Lead{} lead.Magic = buffer[0:4] 

I am searching online and not sure how to go from a slice to an array (without copying). I can always make the Magic []byte (or even uint64), but I was more curious on how would I go from type []byte to [4]byte if needed to?

Answer 1

The built in method copy will only copy a slice to a slice NOT a slice to an array.

You must trick copy into thinking the array is a slice

copy(varLead.Magic[:], someSlice[0:4]) 

Or use a for loop to do the copy:

for index, b := range someSlice {      varLead.Magic[index] = b  } 

Or do as zupa has done using literals. I have added onto their working example.

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