每日一抄 Go语言封装qsort快速排序函数

package qsort

/*

《GO语言高级编程》设计中案例，仅作为笔记进行收藏。

qsort快速排序函数是C语⾔的⾼阶函数，⽀持⽤于⾃定义排序⽐较函数，可以对任意类型的数组进⾏排序。

*/

//sort.go支持包

/*

#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"

	"sync"

	"unsafe"

)

var go_qsort_compare_info struct {

	base     unsafe.Pointer

	elemnum  int

	elemsize int

	less     func(a, b int) bool

	sync.Mutex

}

//export _cgo_qsort_compare

func _cgo_qsort_compare(a, b unsafe.Pointer) C.int {

	var (

		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(i, j):

		//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.Lock()

	defer go_qsort_compare_info.Unlock()

	defer func() {

		go_qsort_compare_info.base = nil

		go_qsort_compare_info.elemnum = 0

		go_qsort_compare_info.elemsize = 0

		go_qsort_compare_info.less = nil

	}()

	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

	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),

	)

}
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每日一抄 Go语言封装qsort快速排序函数

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