// Arrays and slices in Go
// looking at them from the allocation perspective.
// author: gtowell
// Created: Nov 12, 2021

package main

import (
	"encoding/binary"
	"fmt"
	"unsafe"
)


func main() {
	var aInt int = 5
	var aInt8 int8 = 5
	var aInt16 int16 = 5

	fmt.Printf("%d %d %d\n", aInt, aInt8, aInt16)
	fmt.Printf("%d %d %d\n", unsafe.Sizeof(aInt), unsafe.Sizeof(aInt8), unsafe.Sizeof(aInt16));


	// sizeof give the number of bytes used by the "top level descriptor"
	// binary.size the size of the contents of a slice
	
	var ar5Int16 [5]int16
	fmt.Printf("Array of 5 int16 == %d   total=%d\n", unsafe.Sizeof(ar5Int16), binary.Size(ar5Int16))
	var ar5Int64 [5]int64
	fmt.Printf("Array of 5 int64 == %d   total=%d\n", unsafe.Sizeof(ar5Int64), binary.Size(ar5Int64))

	var ar5x5Int64 [5][5]int64
	fmt.Printf("Array of 5x5 int64 == %d   total=%d\n", unsafe.Sizeof(ar5x5Int64), binary.Size(ar5x5Int64))
	for i:=0; i<5; i++ {
		for j:=0; j<5; j++ {
			fmt.Printf("in 5x5 array%d %d %p\n", i, j, &ar5x5Int64[i][j])
		}
	}


	var sl5Int16 []int16 = make([]int16, 5)
	fmt.Printf("slice of 5 int16 == %d   total=%d\n", unsafe.Sizeof(sl5Int16),binary.Size(sl5Int16))
	var sl5Int64 []int64 = make([]int64, 6)
	fmt.Printf("slice of 5 int64 == %d   total=%d\n", unsafe.Sizeof(sl5Int64), binary.Size(sl5Int64))


}