common: implement old version of func sort.Slice

common/sort/slice.go

@@ -0,0 +1,190 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package sort
+
+import "reflect"
+
+// any is an alias for interface{} and is equivalent to interface{} in all ways.
+type any = interface{}
+
+// lessSwap is a pair of Less and Swap function for use with the
+// auto-generated func-optimized variant of sort.go in
+// zfuncversion.go.
+type lessSwap struct {
+	Less func(i, j int) bool
+	Swap func(i, j int)
+}
+
+// Slice sorts the slice x given the provided less function.
+// It panics if x is not a slice.
+//
+// The sort is not guaranteed to be stable: equal elements
+// may be reversed from their original order.
+// For a stable sort, use SliceStable.
+//
+// The less function must satisfy the same requirements as
+// the Interface type's Less method.
+func Slice(x any, less func(i, j int) bool) {
+	rv := reflect.ValueOf(x)
+	swap := reflect.Swapper(x)
+	length := rv.Len()
+	quickSort_func(lessSwap{less, swap}, 0, length, maxDepth(length))
+}
+
+// maxDepth returns a threshold at which quicksort should switch
+// to heapsort. It returns 2*ceil(lg(n+1)).
+func maxDepth(n int) int {
+	var depth int
+	for i := n; i > 0; i >>= 1 {
+		depth++
+	}
+	return depth * 2
+}
+
+// Auto-generated variant of sort.go:quickSort
+func quickSort_func(data lessSwap, a, b, maxDepth int) {
+	for b-a > 12 {
+		if maxDepth == 0 {
+			heapSort_func(data, a, b)
+			return
+		}
+		maxDepth--
+		mlo, mhi := doPivot_func(data, a, b)
+		if mlo-a < b-mhi {
+			quickSort_func(data, a, mlo, maxDepth)
+			a = mhi
+		} else {
+			quickSort_func(data, mhi, b, maxDepth)
+			b = mlo
+		}
+	}
+	if b-a > 1 {
+		for i := a + 6; i < b; i++ {
+			if data.Less(i, i-6) {
+				data.Swap(i, i-6)
+			}
+		}
+		insertionSort_func(data, a, b)
+	}
+}
+
+// Auto-generated variant of sort.go:heapSort
+func heapSort_func(data lessSwap, a, b int) {
+	first := a
+	lo := 0
+	hi := b - a
+	for i := (hi - 1) / 2; i >= 0; i-- {
+		siftDown_func(data, i, hi, first)
+	}
+	for i := hi - 1; i >= 0; i-- {
+		data.Swap(first, first+i)
+		siftDown_func(data, lo, i, first)
+	}
+}
+
+// Auto-generated variant of sort.go:doPivot
+func doPivot_func(data lessSwap, lo, hi int) (midlo, midhi int) {
+	m := int(uint(lo+hi) >> 1)
+	if hi-lo > 40 {
+		s := (hi - lo) / 8
+		medianOfThree_func(data, lo, lo+s, lo+2*s)
+		medianOfThree_func(data, m, m-s, m+s)
+		medianOfThree_func(data, hi-1, hi-1-s, hi-1-2*s)
+	}
+	medianOfThree_func(data, lo, m, hi-1)
+	pivot := lo
+	a, c := lo+1, hi-1
+	for ; a < c && data.Less(a, pivot); a++ {
+	}
+	b := a
+	for {
+		for ; b < c && !data.Less(pivot, b); b++ {
+		}
+		for ; b < c && data.Less(pivot, c-1); c-- {
+		}
+		if b >= c {
+			break
+		}
+		data.Swap(b, c-1)
+		b++
+		c--
+	}
+	protect := hi-c < 5
+	if !protect && hi-c < (hi-lo)/4 {
+		dups := 0
+		if !data.Less(pivot, hi-1) {
+			data.Swap(c, hi-1)
+			c++
+			dups++
+		}
+		if !data.Less(b-1, pivot) {
+			b--
+			dups++
+		}
+		if !data.Less(m, pivot) {
+			data.Swap(m, b-1)
+			b--
+			dups++
+		}
+		protect = dups > 1
+	}
+	if protect {
+		for {
+			for ; a < b && !data.Less(b-1, pivot); b-- {
+			}
+			for ; a < b && data.Less(a, pivot); a++ {
+			}
+			if a >= b {
+				break
+			}
+			data.Swap(a, b-1)
+			a++
+			b--
+		}
+	}
+	data.Swap(pivot, b-1)
+	return b - 1, c
+}
+
+// Auto-generated variant of sort.go:insertionSort
+func insertionSort_func(data lessSwap, a, b int) {
+	for i := a + 1; i < b; i++ {
+		for j := i; j > a && data.Less(j, j-1); j-- {
+			data.Swap(j, j-1)
+		}
+	}
+}
+
+// Auto-generated variant of sort.go:siftDown
+func siftDown_func(data lessSwap, lo, hi, first int) {
+	root := lo
+	for {
+		child := 2*root + 1
+		if child >= hi {
+			break
+		}
+		if child+1 < hi && data.Less(first+child, first+child+1) {
+			child++
+		}
+		if !data.Less(first+root, first+child) {
+			return
+		}
+		data.Swap(first+root, first+child)
+		root = child
+	}
+}
+
+// Auto-generated variant of sort.go:medianOfThree
+func medianOfThree_func(data lessSwap, m1, m0, m2 int) {
+	if data.Less(m1, m0) {
+		data.Swap(m1, m0)
+	}
+	if data.Less(m2, m1) {
+		data.Swap(m2, m1)
+		if data.Less(m1, m0) {
+			data.Swap(m1, m0)
+		}
+	}
+}