pk stuff

Some C functions accept more than one type of struct, so I wanted a Go wrapper able to pass a uintptr derived from an interface{}. Go’s reflect package makes this easy:

package main

import (
  "fmt"
  "reflect"
)

type USN_JOURNAL_DATA struct {
  UsnJournalID    int
  FirstUsn        uint32
  NextUsn         uint32
  LowestValidUsn  uint32
  MaxUsn          uint32
  MaximumSize     uint32
  AllocationDelta uint32
}

func doitA(ujd *USN_JOURNAL_DATA) (size uintptr, align int, p uintptr) {
  v := reflect.ValueOf(ujd)
  t := v.Elem().Type()
  size = t.Size()
  align = t.Align()
  p = v.Pointer()
  return
}

func doitB(i interface{}) (size uintptr, align int, p uintptr) {
  v := reflect.ValueOf(i)
  t := v.Elem().Type()
  size = t.Size()
  align = t.Align()
  p = v.Pointer()
  return
}

func main() {
  a := USN_JOURNAL_DATA{1, 2, 3, 4, 5, 6, 7}
  size, align, p := doitA(&a)
  fmt.Println(size, align, p)
  size, align, p = doitB(&a)
  fmt.Println(size, align, p)
}

Interestingly, as demonstrated above, the same implementation can be used for a func accepting either a struct pointer or an interface{}.