Remove reflect.SliceHeader usage

reflect.SliceHeader is deprecated in favor of unsafe functions introduced in go 1.20

alloc's fheader was unused, so remove, leaving only unsafeFastStringToReadOnlyBytes to port

Author: serprex

alloc.go

@@ -1,7 +1,6 @@
 package lua
 
 import (
-	"reflect"
 	"unsafe"
 )
 
@@ -13,9 +12,6 @@ type iface struct {
 
 const preloadLimit LNumber = 128
 
-var _fv float64
-var _uv uintptr
-
 var preloads [int(preloadLimit)]LValue
 
 func init() {
@@ -26,21 +22,18 @@ func init() {
 
 // allocator is a fast bulk memory allocator for the LValue.
 type allocator struct {
-	size    int
-	fptrs   []float64
-	fheader *reflect.SliceHeader
+	size  int
+	fptrs []float64
 
 	scratchValue  LValue
 	scratchValueP *iface
 }
 
 func newAllocator(size int) *allocator {
 	al := &allocator{
-		size:    size,
-		fptrs:   make([]float64, 0, size),
-		fheader: nil,
+		size:  size,
+		fptrs: make([]float64, 0, size),
 	}
-	al.fheader = (*reflect.SliceHeader)(unsafe.Pointer(&al.fptrs))
 	al.scratchValue = LNumber(0)
 	al.scratchValueP = (*iface)(unsafe.Pointer(&al.scratchValue))
 
@@ -63,7 +56,6 @@ func (al *allocator) LNumber2I(v LNumber) LValue {
 	// check if we need a new alloc page
 	if cap(al.fptrs) == len(al.fptrs) {
 		al.fptrs = make([]float64, 0, al.size)
-		al.fheader = (*reflect.SliceHeader)(unsafe.Pointer(&al.fptrs))
 	}
 
 	// alloc a new float, and store our value into it

go.mod

@@ -1,6 +1,6 @@
 module github.com/yuin/gopher-lua
 
-go 1.17
+go 1.20
 
 require github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e
 

utils.go

@@ -4,7 +4,6 @@ import (
 	"bufio"
 	"fmt"
 	"io"
-	"reflect"
 	"strconv"
 	"strings"
 	"time"
@@ -255,11 +254,6 @@ func strCmp(s1, s2 string) int {
 	}
 }
 
-func unsafeFastStringToReadOnlyBytes(s string) (bs []byte) {
-	sh := (*reflect.StringHeader)(unsafe.Pointer(&s))
-	bh := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
-	bh.Data = sh.Data
-	bh.Cap = sh.Len
-	bh.Len = sh.Len
-	return
+func unsafeFastStringToReadOnlyBytes(s string) []byte {
+	return unsafe.Slice(unsafe.StringData(s), len(s))
 }