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https://github.com/chai2010/advanced-go-programming-book.git
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84 lines
1.9 KiB
Go
84 lines
1.9 KiB
Go
// Copyright © 2018 ChaiShushan <chaishushan{AT}gmail.com>.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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package qsort
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/*
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#include <stdlib.h>
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typedef int (*qsort_cmp_func_t)(const void* a, const void* b);
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extern int _cgo_qsort_compare(void* a, void* b);
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*/
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import "C"
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import (
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"fmt"
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"reflect"
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"sync"
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"unsafe"
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)
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var go_qsort_compare_info struct {
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base unsafe.Pointer
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elemnum int
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elemsize int
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less func(a, b int) bool
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sync.Mutex
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}
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//export _cgo_qsort_compare
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func _cgo_qsort_compare(a, b unsafe.Pointer) C.int {
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var (
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// array memory is locked
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base = uintptr(go_qsort_compare_info.base)
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elemsize = uintptr(go_qsort_compare_info.elemsize)
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)
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i := int((uintptr(a) - base) / elemsize)
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j := int((uintptr(b) - base) / elemsize)
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switch {
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case go_qsort_compare_info.less(i, j): // v[i] < v[j]
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return -1
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case go_qsort_compare_info.less(j, i): // v[i] > v[j]
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return +1
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default:
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return 0
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}
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}
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func Slice(slice interface{}, less func(a, b int) bool) {
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sv := reflect.ValueOf(slice)
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if sv.Kind() != reflect.Slice {
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panic(fmt.Sprintf("qsort called with non-slice value of type %T", slice))
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}
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if sv.Len() == 0 {
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return
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}
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go_qsort_compare_info.Lock()
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defer go_qsort_compare_info.Unlock()
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defer func() {
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go_qsort_compare_info.base = nil
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go_qsort_compare_info.elemnum = 0
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go_qsort_compare_info.elemsize = 0
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go_qsort_compare_info.less = nil
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}()
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// baseMem = unsafe.Pointer(sv.Index(0).Addr().Pointer())
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// baseMem maybe moved, so must saved after call C.fn
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go_qsort_compare_info.base = unsafe.Pointer(sv.Index(0).Addr().Pointer())
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go_qsort_compare_info.elemnum = sv.Len()
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go_qsort_compare_info.elemsize = int(sv.Type().Elem().Size())
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go_qsort_compare_info.less = less
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C.qsort(
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go_qsort_compare_info.base,
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C.size_t(go_qsort_compare_info.elemnum),
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C.size_t(go_qsort_compare_info.elemsize),
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C.qsort_cmp_func_t(C._cgo_qsort_compare),
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)
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}
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