ch2-cgo/ch2-06-qsort

[giscus[bot]]

ch2-cgo/ch2-06-qsort

Go语言高级编程

https://chai2010.cn/advanced-go-programming-book/ch2-cgo/ch2-06-qsort.html

[Future2100]

最后一段代码应该把Slice改成Sort吧

[PaiGack]

函数以及由 Sort 改成了 Slice ，所以这个地方应该是没有问题的

[flyflyhe]

package qsort

/*
#include <stdlib.h>

typedef int (qsort_cmp_func_t)(const void a, const void* b);
extern int _cgo_qsort_compare(void* a, void* b);
*/
import "C"
import (
"fmt"
"reflect"
"runtime"
"strconv"
"strings"
"sync"
"unsafe"
)

type GoQsortCompareInfo struct {
base unsafe.Pointer
elemnum int
elemsize int
less func(a, b int) bool
}

var m sync.Map

//export _cgo_qsort_compare
func _cgo_qsort_compare(a, b unsafe.Pointer) C.int {
go_qsort_compare_infoTmp, _ := m.Load(GetGoid())
go_qsort_compare_info := go_qsort_compare_infoTmp.(GoQsortCompareInfo)
var (
// array memory is locked
base = uintptr(go_qsort_compare_info.base)
elemsize = uintptr(go_qsort_compare_info.elemsize)
)

i := int((uintptr(a) - base) / elemsize)
j := int((uintptr(b) - base) / elemsize)

switch {
case go_qsort_compare_info.less(i, j): // v[i] < v[j]
	return -1
case go_qsort_compare_info.less(j, i): // v[i] > v[j]
	return +1
default:
	return 0
}

}

func Slice(slice interface{}, less func(a, b int) bool) {
sv := reflect.ValueOf(slice)
if sv.Kind() != reflect.Slice {
panic(fmt.Sprintf("qsort called with non-slice value of type %T", slice))
}
if sv.Len() == 0 {
return
}

go_qsort_compare_info := GoQsortCompareInfo{}

// baseMem = unsafe.Pointer(sv.Index(0).Addr().Pointer())
// baseMem maybe moved, so must saved after call C.fn
go_qsort_compare_info.base = unsafe.Pointer(sv.Index(0).Addr().Pointer())
go_qsort_compare_info.elemnum = sv.Len()
go_qsort_compare_info.elemsize = int(sv.Type().Elem().Size())
go_qsort_compare_info.less = less

m.Store(GetGoid(), go_qsort_compare_info)
defer m.Delete(GetGoid())
C.qsort(
	go_qsort_compare_info.base,
	C.size_t(go_qsort_compare_info.elemnum),
	C.size_t(go_qsort_compare_info.elemsize),
	C.qsort_cmp_func_t(C._cgo_qsort_compare),
)

}

func GetGoid() int64 {
var (
buf [64]byte
n = runtime.Stack(buf[:], false)
stk = strings.TrimPrefix(string(buf[:n]), "goroutine")
)

idField := strings.Fields(stk)[0]
id, err := strconv.Atoi(idField)
if err != nil {
	panic(fmt.Errorf("can not get goroutine id: %v", err))
}

return int64(id)

}
加了个sync.map 并发调用通过协程id并发调用 一时想不到其他的办法。。