package main

/*

#include <stdlib.h>

#include <stdint.h>

typedef void* (*alloc_f)(char* t, int64_t n);

static void* call_alloc_f(alloc_f f, char* t, int64_t n) {return f(t,n);}

*/

import "C"

import (

"fmt"

"math"

"unsafe"

)

func main() {}

//export sqrts

func sqrts(alloc C.alloc_f, n int64) {

allocString(alloc, fmt.Sprintf("Square roots up to %d:", n))

floats := allocFloats(alloc, int(n))

for i := range floats {

floats[i] = math.Sqrt(float64(i + 1))

}

}

func allocFloats(alloc C.alloc_f, n int) []float64 {

return allocSlice[float64](alloc, n, "d")

}

func allocInts(alloc C.alloc_f, n int) []int64 {

return allocSlice[int64](alloc, n, "q")

}

func allocBytes(alloc C.alloc_f, n int) []byte {

return allocSlice[byte](alloc, n, "B")

}

func allocString(alloc C.alloc_f, s string) {

b := allocBytes(alloc, len(s))

copy(b, s)

}

// Calls the Python alloc callback and returns the allocated buffer

// as a slice.

func allocSlice[T any](alloc C.alloc_f, n int, typeCode string) []T {

t := C.CString(typeCode) // Make a c-string type code.

ptr := C.call_alloc_f(alloc, t, C.int64_t(n)) // Allocate the buffer.

C.free(unsafe.Pointer(t)) // Release c-string.

return unsafe.Slice((*T)(ptr), n) // Wrap with a go-slice.

}