by shakeel.mahate:

According to godoc: "binary.Read reads structured binary data from r into data.
Data must be a pointer to a fixed-size value or a slice of fixed-size values."

You can ask binary.Read() to read a slice of structs which works, but if you have a
slice as a member of struct, it returns an error "binary.Read: invalid type "

This works:
type S struct {
  Index int32
  Ticks int32
  Analogs [3]int16
  Digitals [8]byte
}
s := make([]S, 1024) // Slice of S works
binary.Read(buf, binary.LittleEndian, s)

This does not work:
type S struct {
  Index int32
  Ticks int32
  Analogs []int16 // This is offending slice
  Digitals []byte // And so is this
}
s := make([]S, 1024)
for i := range s {
  s[i].Analogs = make([]int16, 3) // Create the backing store for slices
  s[i].Digitals = make([]byte, 8) // Ditto
}
binary.Read(buf, binary.LittleEndian, s) // Returns binary.Read: invalid type error
message

First of all the error message is very cryptic, because it is not clear why the read
failed. It would be better to point out the actual member that failed, S.Analogs

Secondly the syntax for array and slice are very similar and we are encouraged to think
of them as one and the same. But you can only define an array's length as a constant
expression, there is no way to specify the length of an array using non-const
expressions. http://golang.org/ref/spec#Constant_expressions

Since we truly cannot create non-const arrays, the binary.Read API should support slices
as members.

I really like the terseness and elegance of the binary.Read API, I create slice of
structs and ask read to populate it. I just wish that the structs itself could have a
slice as a member or provide a better error message.

I had to resort reading each member of the struct individually in order to work around
this problem

Work around:
var Index, Ticks int32
Analogs := make([]int16, 3)
Digitals := make([]byte, 8)
for i := range 1024 {
  binary.Read(buf, binary.LittleEndian, &Index)
  // move the buf+4
  binary.Read(buf, binary.LittleEndian, &Ticks)
  // move the buf+4
  binary.Read(buf, binary.LittleEndian, Analogs)
  // move the buf+(3*2)
  binary.Read(buf, binary.LittleEndian, Digitals)
  // move the buf+(8*1)
}


Go version 1.0.3
Windows 7