added disk quota

This commit is contained in:
ston1th 2022-03-17 00:47:45 +01:00
commit 9cc2b04342
26 changed files with 1376 additions and 61 deletions

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// Copyright 2021 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 slices defines various functions useful with slices of any type.
// Unless otherwise specified, these functions all apply to the elements
// of a slice at index 0 <= i < len(s).
package slices
import "golang.org/x/exp/constraints"
// Equal reports whether two slices are equal: the same length and all
// elements equal. If the lengths are different, Equal returns false.
// Otherwise, the elements are compared in increasing index order, and the
// comparison stops at the first unequal pair.
// Floating point NaNs are not considered equal.
func Equal[E comparable](s1, s2 []E) bool {
if len(s1) != len(s2) {
return false
}
for i := range s1 {
if s1[i] != s2[i] {
return false
}
}
return true
}
// EqualFunc reports whether two slices are equal using a comparison
// function on each pair of elements. If the lengths are different,
// EqualFunc returns false. Otherwise, the elements are compared in
// increasing index order, and the comparison stops at the first index
// for which eq returns false.
func EqualFunc[E1, E2 any](s1 []E1, s2 []E2, eq func(E1, E2) bool) bool {
if len(s1) != len(s2) {
return false
}
for i, v1 := range s1 {
v2 := s2[i]
if !eq(v1, v2) {
return false
}
}
return true
}
// Compare compares the elements of s1 and s2.
// The elements are compared sequentially, starting at index 0,
// until one element is not equal to the other.
// The result of comparing the first non-matching elements is returned.
// If both slices are equal until one of them ends, the shorter slice is
// considered less than the longer one.
// The result is 0 if s1 == s2, -1 if s1 < s2, and +1 if s1 > s2.
// Comparisons involving floating point NaNs are ignored.
func Compare[E constraints.Ordered](s1, s2 []E) int {
s2len := len(s2)
for i, v1 := range s1 {
if i >= s2len {
return +1
}
v2 := s2[i]
switch {
case v1 < v2:
return -1
case v1 > v2:
return +1
}
}
if len(s1) < s2len {
return -1
}
return 0
}
// CompareFunc is like Compare but uses a comparison function
// on each pair of elements. The elements are compared in increasing
// index order, and the comparisons stop after the first time cmp
// returns non-zero.
// The result is the first non-zero result of cmp; if cmp always
// returns 0 the result is 0 if len(s1) == len(s2), -1 if len(s1) < len(s2),
// and +1 if len(s1) > len(s2).
func CompareFunc[E1, E2 any](s1 []E1, s2 []E2, cmp func(E1, E2) int) int {
s2len := len(s2)
for i, v1 := range s1 {
if i >= s2len {
return +1
}
v2 := s2[i]
if c := cmp(v1, v2); c != 0 {
return c
}
}
if len(s1) < s2len {
return -1
}
return 0
}
// Index returns the index of the first occurrence of v in s,
// or -1 if not present.
func Index[E comparable](s []E, v E) int {
for i, vs := range s {
if v == vs {
return i
}
}
return -1
}
// IndexFunc returns the first index i satisfying f(s[i]),
// or -1 if none do.
func IndexFunc[E any](s []E, f func(E) bool) int {
for i, v := range s {
if f(v) {
return i
}
}
return -1
}
// Contains reports whether v is present in s.
func Contains[E comparable](s []E, v E) bool {
return Index(s, v) >= 0
}
// Insert inserts the values v... into s at index i,
// returning the modified slice.
// In the returned slice r, r[i] == v[0].
// Insert panics if i is out of range.
// This function is O(len(s) + len(v)).
func Insert[S ~[]E, E any](s S, i int, v ...E) S {
tot := len(s) + len(v)
if tot <= cap(s) {
s2 := s[:tot]
copy(s2[i+len(v):], s[i:])
copy(s2[i:], v)
return s2
}
s2 := make(S, tot)
copy(s2, s[:i])
copy(s2[i:], v)
copy(s2[i+len(v):], s[i:])
return s2
}
// Delete removes the elements s[i:j] from s, returning the modified slice.
// Delete panics if s[i:j] is not a valid slice of s.
// Delete modifies the contents of the slice s; it does not create a new slice.
// Delete is O(len(s)-(j-i)), so if many items must be deleted, it is better to
// make a single call deleting them all together than to delete one at a time.
func Delete[S ~[]E, E any](s S, i, j int) S {
return append(s[:i], s[j:]...)
}
// Clone returns a copy of the slice.
// The elements are copied using assignment, so this is a shallow clone.
func Clone[S ~[]E, E any](s S) S {
// Preserve nil in case it matters.
if s == nil {
return nil
}
return append(S([]E{}), s...)
}
// Compact replaces consecutive runs of equal elements with a single copy.
// This is like the uniq command found on Unix.
// Compact modifies the contents of the slice s; it does not create a new slice.
func Compact[S ~[]E, E comparable](s S) S {
if len(s) == 0 {
return s
}
i := 1
last := s[0]
for _, v := range s[1:] {
if v != last {
s[i] = v
i++
last = v
}
}
return s[:i]
}
// CompactFunc is like Compact but uses a comparison function.
func CompactFunc[S ~[]E, E any](s S, eq func(E, E) bool) S {
if len(s) == 0 {
return s
}
i := 1
last := s[0]
for _, v := range s[1:] {
if !eq(v, last) {
s[i] = v
i++
last = v
}
}
return s[:i]
}
// Grow increases the slice's capacity, if necessary, to guarantee space for
// another n elements. After Grow(n), at least n elements can be appended
// to the slice without another allocation. Grow may modify elements of the
// slice between the length and the capacity. If n is negative or too large to
// allocate the memory, Grow panics.
func Grow[S ~[]E, E any](s S, n int) S {
return append(s, make(S, n)...)[:len(s)]
}
// Clip removes unused capacity from the slice, returning s[:len(s):len(s)].
func Clip[S ~[]E, E any](s S) S {
return s[:len(s):len(s)]
}

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// Copyright 2022 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 slices
import "golang.org/x/exp/constraints"
// Sort sorts a slice of any ordered type in ascending order.
func Sort[Elem constraints.Ordered](x []Elem) {
n := len(x)
quickSortOrdered(x, 0, n, maxDepth(n))
}
// Sort sorts the slice x in ascending order as determined by the less function.
// This sort is not guaranteed to be stable.
func SortFunc[Elem any](x []Elem, less func(a, b Elem) bool) {
n := len(x)
quickSortLessFunc(x, 0, n, maxDepth(n), less)
}
// SortStable sorts the slice x while keeping the original order of equal
// elements, using less to compare elements.
func SortStableFunc[Elem any](x []Elem, less func(a, b Elem) bool) {
stableLessFunc(x, len(x), less)
}
// IsSorted reports whether x is sorted in ascending order.
func IsSorted[Elem constraints.Ordered](x []Elem) bool {
for i := len(x) - 1; i > 0; i-- {
if x[i] < x[i-1] {
return false
}
}
return true
}
// IsSortedFunc reports whether x is sorted in ascending order, with less as the
// comparison function.
func IsSortedFunc[Elem any](x []Elem, less func(a, b Elem) bool) bool {
for i := len(x) - 1; i > 0; i-- {
if less(x[i], x[i-1]) {
return false
}
}
return true
}
// BinarySearch searches for target in a sorted slice and returns the smallest
// index at which target is found. If the target is not found, the index at
// which it could be inserted into the slice is returned; therefore, if the
// intention is to find target itself a separate check for equality with the
// element at the returned index is required.
func BinarySearch[Elem constraints.Ordered](x []Elem, target Elem) int {
return search(len(x), func(i int) bool { return x[i] >= target })
}
// BinarySearchFunc uses binary search to find and return the smallest index i
// in [0, n) at which ok(i) is true, assuming that on the range [0, n),
// ok(i) == true implies ok(i+1) == true. That is, BinarySearchFunc requires
// that ok is false for some (possibly empty) prefix of the input range [0, n)
// and then true for the (possibly empty) remainder; BinarySearchFunc returns
// the first true index. If there is no such index, BinarySearchFunc returns n.
// (Note that the "not found" return value is not -1 as in, for instance,
// strings.Index.) Search calls ok(i) only for i in the range [0, n).
func BinarySearchFunc[Elem any](x []Elem, ok func(Elem) bool) int {
return search(len(x), func(i int) bool { return ok(x[i]) })
}
// 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
}
func search(n int, f func(int) bool) int {
// Define f(-1) == false and f(n) == true.
// Invariant: f(i-1) == false, f(j) == true.
i, j := 0, n
for i < j {
h := int(uint(i+j) >> 1) // avoid overflow when computing h
// i ≤ h < j
if !f(h) {
i = h + 1 // preserves f(i-1) == false
} else {
j = h // preserves f(j) == true
}
}
// i == j, f(i-1) == false, and f(j) (= f(i)) == true => answer is i.
return i
}

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// Code generated by gen_sort_variants.go; DO NOT EDIT.
// Copyright 2022 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 slices
// insertionSortLessFunc sorts data[a:b] using insertion sort.
func insertionSortLessFunc[Elem any](data []Elem, a, b int, less func(a, b Elem) bool) {
for i := a + 1; i < b; i++ {
for j := i; j > a && less(data[j], data[j-1]); j-- {
data[j], data[j-1] = data[j-1], data[j]
}
}
}
// siftDownLessFunc implements the heap property on data[lo:hi].
// first is an offset into the array where the root of the heap lies.
func siftDownLessFunc[Elem any](data []Elem, lo, hi, first int, less func(a, b Elem) bool) {
root := lo
for {
child := 2*root + 1
if child >= hi {
break
}
if child+1 < hi && less(data[first+child], data[first+child+1]) {
child++
}
if !less(data[first+root], data[first+child]) {
return
}
data[first+root], data[first+child] = data[first+child], data[first+root]
root = child
}
}
func heapSortLessFunc[Elem any](data []Elem, a, b int, less func(a, b Elem) bool) {
first := a
lo := 0
hi := b - a
// Build heap with greatest element at top.
for i := (hi - 1) / 2; i >= 0; i-- {
siftDownLessFunc(data, i, hi, first, less)
}
// Pop elements, largest first, into end of data.
for i := hi - 1; i >= 0; i-- {
data[first], data[first+i] = data[first+i], data[first]
siftDownLessFunc(data, lo, i, first, less)
}
}
// Quicksort, loosely following Bentley and McIlroy,
// "Engineering a Sort Function" SP&E November 1993.
// medianOfThreeLessFunc moves the median of the three values data[m0], data[m1], data[m2] into data[m1].
func medianOfThreeLessFunc[Elem any](data []Elem, m1, m0, m2 int, less func(a, b Elem) bool) {
// sort 3 elements
if less(data[m1], data[m0]) {
data[m1], data[m0] = data[m0], data[m1]
}
// data[m0] <= data[m1]
if less(data[m2], data[m1]) {
data[m2], data[m1] = data[m1], data[m2]
// data[m0] <= data[m2] && data[m1] < data[m2]
if less(data[m1], data[m0]) {
data[m1], data[m0] = data[m0], data[m1]
}
}
// now data[m0] <= data[m1] <= data[m2]
}
func swapRangeLessFunc[Elem any](data []Elem, a, b, n int, less func(a, b Elem) bool) {
for i := 0; i < n; i++ {
data[a+i], data[b+i] = data[b+i], data[a+i]
}
}
func doPivotLessFunc[Elem any](data []Elem, lo, hi int, less func(a, b Elem) bool) (midlo, midhi int) {
m := int(uint(lo+hi) >> 1) // Written like this to avoid integer overflow.
if hi-lo > 40 {
// Tukey's "Ninther" median of three medians of three.
s := (hi - lo) / 8
medianOfThreeLessFunc(data, lo, lo+s, lo+2*s, less)
medianOfThreeLessFunc(data, m, m-s, m+s, less)
medianOfThreeLessFunc(data, hi-1, hi-1-s, hi-1-2*s, less)
}
medianOfThreeLessFunc(data, lo, m, hi-1, less)
// Invariants are:
// data[lo] = pivot (set up by ChoosePivot)
// data[lo < i < a] < pivot
// data[a <= i < b] <= pivot
// data[b <= i < c] unexamined
// data[c <= i < hi-1] > pivot
// data[hi-1] >= pivot
pivot := lo
a, c := lo+1, hi-1
for ; a < c && less(data[a], data[pivot]); a++ {
}
b := a
for {
for ; b < c && !less(data[pivot], data[b]); b++ { // data[b] <= pivot
}
for ; b < c && less(data[pivot], data[c-1]); c-- { // data[c-1] > pivot
}
if b >= c {
break
}
// data[b] > pivot; data[c-1] <= pivot
data[b], data[c-1] = data[c-1], data[b]
b++
c--
}
// If hi-c<3 then there are duplicates (by property of median of nine).
// Let's be a bit more conservative, and set border to 5.
protect := hi-c < 5
if !protect && hi-c < (hi-lo)/4 {
// Lets test some points for equality to pivot
dups := 0
if !less(data[pivot], data[hi-1]) { // data[hi-1] = pivot
data[c], data[hi-1] = data[hi-1], data[c]
c++
dups++
}
if !less(data[b-1], data[pivot]) { // data[b-1] = pivot
b--
dups++
}
// m-lo = (hi-lo)/2 > 6
// b-lo > (hi-lo)*3/4-1 > 8
// ==> m < b ==> data[m] <= pivot
if !less(data[m], data[pivot]) { // data[m] = pivot
data[m], data[b-1] = data[b-1], data[m]
b--
dups++
}
// if at least 2 points are equal to pivot, assume skewed distribution
protect = dups > 1
}
if protect {
// Protect against a lot of duplicates
// Add invariant:
// data[a <= i < b] unexamined
// data[b <= i < c] = pivot
for {
for ; a < b && !less(data[b-1], data[pivot]); b-- { // data[b] == pivot
}
for ; a < b && less(data[a], data[pivot]); a++ { // data[a] < pivot
}
if a >= b {
break
}
// data[a] == pivot; data[b-1] < pivot
data[a], data[b-1] = data[b-1], data[a]
a++
b--
}
}
// Swap pivot into middle
data[pivot], data[b-1] = data[b-1], data[pivot]
return b - 1, c
}
func quickSortLessFunc[Elem any](data []Elem, a, b, maxDepth int, less func(a, b Elem) bool) {
for b-a > 12 { // Use ShellSort for slices <= 12 elements
if maxDepth == 0 {
heapSortLessFunc(data, a, b, less)
return
}
maxDepth--
mlo, mhi := doPivotLessFunc(data, a, b, less)
// Avoiding recursion on the larger subproblem guarantees
// a stack depth of at most lg(b-a).
if mlo-a < b-mhi {
quickSortLessFunc(data, a, mlo, maxDepth, less)
a = mhi // i.e., quickSortLessFunc(data, mhi, b)
} else {
quickSortLessFunc(data, mhi, b, maxDepth, less)
b = mlo // i.e., quickSortLessFunc(data, a, mlo)
}
}
if b-a > 1 {
// Do ShellSort pass with gap 6
// It could be written in this simplified form cause b-a <= 12
for i := a + 6; i < b; i++ {
if less(data[i], data[i-6]) {
data[i], data[i-6] = data[i-6], data[i]
}
}
insertionSortLessFunc(data, a, b, less)
}
}
func stableLessFunc[Elem any](data []Elem, n int, less func(a, b Elem) bool) {
blockSize := 20 // must be > 0
a, b := 0, blockSize
for b <= n {
insertionSortLessFunc(data, a, b, less)
a = b
b += blockSize
}
insertionSortLessFunc(data, a, n, less)
for blockSize < n {
a, b = 0, 2*blockSize
for b <= n {
symMergeLessFunc(data, a, a+blockSize, b, less)
a = b
b += 2 * blockSize
}
if m := a + blockSize; m < n {
symMergeLessFunc(data, a, m, n, less)
}
blockSize *= 2
}
}
// symMergeLessFunc merges the two sorted subsequences data[a:m] and data[m:b] using
// the SymMerge algorithm from Pok-Son Kim and Arne Kutzner, "Stable Minimum
// Storage Merging by Symmetric Comparisons", in Susanne Albers and Tomasz
// Radzik, editors, Algorithms - ESA 2004, volume 3221 of Lecture Notes in
// Computer Science, pages 714-723. Springer, 2004.
//
// Let M = m-a and N = b-n. Wolog M < N.
// The recursion depth is bound by ceil(log(N+M)).
// The algorithm needs O(M*log(N/M + 1)) calls to data.Less.
// The algorithm needs O((M+N)*log(M)) calls to data.Swap.
//
// The paper gives O((M+N)*log(M)) as the number of assignments assuming a
// rotation algorithm which uses O(M+N+gcd(M+N)) assignments. The argumentation
// in the paper carries through for Swap operations, especially as the block
// swapping rotate uses only O(M+N) Swaps.
//
// symMerge assumes non-degenerate arguments: a < m && m < b.
// Having the caller check this condition eliminates many leaf recursion calls,
// which improves performance.
func symMergeLessFunc[Elem any](data []Elem, a, m, b int, less func(a, b Elem) bool) {
// Avoid unnecessary recursions of symMerge
// by direct insertion of data[a] into data[m:b]
// if data[a:m] only contains one element.
if m-a == 1 {
// Use binary search to find the lowest index i
// such that data[i] >= data[a] for m <= i < b.
// Exit the search loop with i == b in case no such index exists.
i := m
j := b
for i < j {
h := int(uint(i+j) >> 1)
if less(data[h], data[a]) {
i = h + 1
} else {
j = h
}
}
// Swap values until data[a] reaches the position before i.
for k := a; k < i-1; k++ {
data[k], data[k+1] = data[k+1], data[k]
}
return
}
// Avoid unnecessary recursions of symMerge
// by direct insertion of data[m] into data[a:m]
// if data[m:b] only contains one element.
if b-m == 1 {
// Use binary search to find the lowest index i
// such that data[i] > data[m] for a <= i < m.
// Exit the search loop with i == m in case no such index exists.
i := a
j := m
for i < j {
h := int(uint(i+j) >> 1)
if !less(data[m], data[h]) {
i = h + 1
} else {
j = h
}
}
// Swap values until data[m] reaches the position i.
for k := m; k > i; k-- {
data[k], data[k-1] = data[k-1], data[k]
}
return
}
mid := int(uint(a+b) >> 1)
n := mid + m
var start, r int
if m > mid {
start = n - b
r = mid
} else {
start = a
r = m
}
p := n - 1
for start < r {
c := int(uint(start+r) >> 1)
if !less(data[p-c], data[c]) {
start = c + 1
} else {
r = c
}
}
end := n - start
if start < m && m < end {
rotateLessFunc(data, start, m, end, less)
}
if a < start && start < mid {
symMergeLessFunc(data, a, start, mid, less)
}
if mid < end && end < b {
symMergeLessFunc(data, mid, end, b, less)
}
}
// rotateLessFunc rotates two consecutive blocks u = data[a:m] and v = data[m:b] in data:
// Data of the form 'x u v y' is changed to 'x v u y'.
// rotate performs at most b-a many calls to data.Swap,
// and it assumes non-degenerate arguments: a < m && m < b.
func rotateLessFunc[Elem any](data []Elem, a, m, b int, less func(a, b Elem) bool) {
i := m - a
j := b - m
for i != j {
if i > j {
swapRangeLessFunc(data, m-i, m, j, less)
i -= j
} else {
swapRangeLessFunc(data, m-i, m+j-i, i, less)
j -= i
}
}
// i == j
swapRangeLessFunc(data, m-i, m, i, less)
}

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// Code generated by gen_sort_variants.go; DO NOT EDIT.
// Copyright 2022 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 slices
import "golang.org/x/exp/constraints"
// insertionSortOrdered sorts data[a:b] using insertion sort.
func insertionSortOrdered[Elem constraints.Ordered](data []Elem, a, b int) {
for i := a + 1; i < b; i++ {
for j := i; j > a && (data[j] < data[j-1]); j-- {
data[j], data[j-1] = data[j-1], data[j]
}
}
}
// siftDownOrdered implements the heap property on data[lo:hi].
// first is an offset into the array where the root of the heap lies.
func siftDownOrdered[Elem constraints.Ordered](data []Elem, lo, hi, first int) {
root := lo
for {
child := 2*root + 1
if child >= hi {
break
}
if child+1 < hi && (data[first+child] < data[first+child+1]) {
child++
}
if !(data[first+root] < data[first+child]) {
return
}
data[first+root], data[first+child] = data[first+child], data[first+root]
root = child
}
}
func heapSortOrdered[Elem constraints.Ordered](data []Elem, a, b int) {
first := a
lo := 0
hi := b - a
// Build heap with greatest element at top.
for i := (hi - 1) / 2; i >= 0; i-- {
siftDownOrdered(data, i, hi, first)
}
// Pop elements, largest first, into end of data.
for i := hi - 1; i >= 0; i-- {
data[first], data[first+i] = data[first+i], data[first]
siftDownOrdered(data, lo, i, first)
}
}
// Quicksort, loosely following Bentley and McIlroy,
// "Engineering a Sort Function" SP&E November 1993.
// medianOfThreeOrdered moves the median of the three values data[m0], data[m1], data[m2] into data[m1].
func medianOfThreeOrdered[Elem constraints.Ordered](data []Elem, m1, m0, m2 int) {
// sort 3 elements
if data[m1] < data[m0] {
data[m1], data[m0] = data[m0], data[m1]
}
// data[m0] <= data[m1]
if data[m2] < data[m1] {
data[m2], data[m1] = data[m1], data[m2]
// data[m0] <= data[m2] && data[m1] < data[m2]
if data[m1] < data[m0] {
data[m1], data[m0] = data[m0], data[m1]
}
}
// now data[m0] <= data[m1] <= data[m2]
}
func swapRangeOrdered[Elem constraints.Ordered](data []Elem, a, b, n int) {
for i := 0; i < n; i++ {
data[a+i], data[b+i] = data[b+i], data[a+i]
}
}
func doPivotOrdered[Elem constraints.Ordered](data []Elem, lo, hi int) (midlo, midhi int) {
m := int(uint(lo+hi) >> 1) // Written like this to avoid integer overflow.
if hi-lo > 40 {
// Tukey's "Ninther" median of three medians of three.
s := (hi - lo) / 8
medianOfThreeOrdered(data, lo, lo+s, lo+2*s)
medianOfThreeOrdered(data, m, m-s, m+s)
medianOfThreeOrdered(data, hi-1, hi-1-s, hi-1-2*s)
}
medianOfThreeOrdered(data, lo, m, hi-1)
// Invariants are:
// data[lo] = pivot (set up by ChoosePivot)
// data[lo < i < a] < pivot
// data[a <= i < b] <= pivot
// data[b <= i < c] unexamined
// data[c <= i < hi-1] > pivot
// data[hi-1] >= pivot
pivot := lo
a, c := lo+1, hi-1
for ; a < c && (data[a] < data[pivot]); a++ {
}
b := a
for {
for ; b < c && !(data[pivot] < data[b]); b++ { // data[b] <= pivot
}
for ; b < c && (data[pivot] < data[c-1]); c-- { // data[c-1] > pivot
}
if b >= c {
break
}
// data[b] > pivot; data[c-1] <= pivot
data[b], data[c-1] = data[c-1], data[b]
b++
c--
}
// If hi-c<3 then there are duplicates (by property of median of nine).
// Let's be a bit more conservative, and set border to 5.
protect := hi-c < 5
if !protect && hi-c < (hi-lo)/4 {
// Lets test some points for equality to pivot
dups := 0
if !(data[pivot] < data[hi-1]) { // data[hi-1] = pivot
data[c], data[hi-1] = data[hi-1], data[c]
c++
dups++
}
if !(data[b-1] < data[pivot]) { // data[b-1] = pivot
b--
dups++
}
// m-lo = (hi-lo)/2 > 6
// b-lo > (hi-lo)*3/4-1 > 8
// ==> m < b ==> data[m] <= pivot
if !(data[m] < data[pivot]) { // data[m] = pivot
data[m], data[b-1] = data[b-1], data[m]
b--
dups++
}
// if at least 2 points are equal to pivot, assume skewed distribution
protect = dups > 1
}
if protect {
// Protect against a lot of duplicates
// Add invariant:
// data[a <= i < b] unexamined
// data[b <= i < c] = pivot
for {
for ; a < b && !(data[b-1] < data[pivot]); b-- { // data[b] == pivot
}
for ; a < b && (data[a] < data[pivot]); a++ { // data[a] < pivot
}
if a >= b {
break
}
// data[a] == pivot; data[b-1] < pivot
data[a], data[b-1] = data[b-1], data[a]
a++
b--
}
}
// Swap pivot into middle
data[pivot], data[b-1] = data[b-1], data[pivot]
return b - 1, c
}
func quickSortOrdered[Elem constraints.Ordered](data []Elem, a, b, maxDepth int) {
for b-a > 12 { // Use ShellSort for slices <= 12 elements
if maxDepth == 0 {
heapSortOrdered(data, a, b)
return
}
maxDepth--
mlo, mhi := doPivotOrdered(data, a, b)
// Avoiding recursion on the larger subproblem guarantees
// a stack depth of at most lg(b-a).
if mlo-a < b-mhi {
quickSortOrdered(data, a, mlo, maxDepth)
a = mhi // i.e., quickSortOrdered(data, mhi, b)
} else {
quickSortOrdered(data, mhi, b, maxDepth)
b = mlo // i.e., quickSortOrdered(data, a, mlo)
}
}
if b-a > 1 {
// Do ShellSort pass with gap 6
// It could be written in this simplified form cause b-a <= 12
for i := a + 6; i < b; i++ {
if data[i] < data[i-6] {
data[i], data[i-6] = data[i-6], data[i]
}
}
insertionSortOrdered(data, a, b)
}
}
func stableOrdered[Elem constraints.Ordered](data []Elem, n int) {
blockSize := 20 // must be > 0
a, b := 0, blockSize
for b <= n {
insertionSortOrdered(data, a, b)
a = b
b += blockSize
}
insertionSortOrdered(data, a, n)
for blockSize < n {
a, b = 0, 2*blockSize
for b <= n {
symMergeOrdered(data, a, a+blockSize, b)
a = b
b += 2 * blockSize
}
if m := a + blockSize; m < n {
symMergeOrdered(data, a, m, n)
}
blockSize *= 2
}
}
// symMergeOrdered merges the two sorted subsequences data[a:m] and data[m:b] using
// the SymMerge algorithm from Pok-Son Kim and Arne Kutzner, "Stable Minimum
// Storage Merging by Symmetric Comparisons", in Susanne Albers and Tomasz
// Radzik, editors, Algorithms - ESA 2004, volume 3221 of Lecture Notes in
// Computer Science, pages 714-723. Springer, 2004.
//
// Let M = m-a and N = b-n. Wolog M < N.
// The recursion depth is bound by ceil(log(N+M)).
// The algorithm needs O(M*log(N/M + 1)) calls to data.Less.
// The algorithm needs O((M+N)*log(M)) calls to data.Swap.
//
// The paper gives O((M+N)*log(M)) as the number of assignments assuming a
// rotation algorithm which uses O(M+N+gcd(M+N)) assignments. The argumentation
// in the paper carries through for Swap operations, especially as the block
// swapping rotate uses only O(M+N) Swaps.
//
// symMerge assumes non-degenerate arguments: a < m && m < b.
// Having the caller check this condition eliminates many leaf recursion calls,
// which improves performance.
func symMergeOrdered[Elem constraints.Ordered](data []Elem, a, m, b int) {
// Avoid unnecessary recursions of symMerge
// by direct insertion of data[a] into data[m:b]
// if data[a:m] only contains one element.
if m-a == 1 {
// Use binary search to find the lowest index i
// such that data[i] >= data[a] for m <= i < b.
// Exit the search loop with i == b in case no such index exists.
i := m
j := b
for i < j {
h := int(uint(i+j) >> 1)
if data[h] < data[a] {
i = h + 1
} else {
j = h
}
}
// Swap values until data[a] reaches the position before i.
for k := a; k < i-1; k++ {
data[k], data[k+1] = data[k+1], data[k]
}
return
}
// Avoid unnecessary recursions of symMerge
// by direct insertion of data[m] into data[a:m]
// if data[m:b] only contains one element.
if b-m == 1 {
// Use binary search to find the lowest index i
// such that data[i] > data[m] for a <= i < m.
// Exit the search loop with i == m in case no such index exists.
i := a
j := m
for i < j {
h := int(uint(i+j) >> 1)
if !(data[m] < data[h]) {
i = h + 1
} else {
j = h
}
}
// Swap values until data[m] reaches the position i.
for k := m; k > i; k-- {
data[k], data[k-1] = data[k-1], data[k]
}
return
}
mid := int(uint(a+b) >> 1)
n := mid + m
var start, r int
if m > mid {
start = n - b
r = mid
} else {
start = a
r = m
}
p := n - 1
for start < r {
c := int(uint(start+r) >> 1)
if !(data[p-c] < data[c]) {
start = c + 1
} else {
r = c
}
}
end := n - start
if start < m && m < end {
rotateOrdered(data, start, m, end)
}
if a < start && start < mid {
symMergeOrdered(data, a, start, mid)
}
if mid < end && end < b {
symMergeOrdered(data, mid, end, b)
}
}
// rotateOrdered rotates two consecutive blocks u = data[a:m] and v = data[m:b] in data:
// Data of the form 'x u v y' is changed to 'x v u y'.
// rotate performs at most b-a many calls to data.Swap,
// and it assumes non-degenerate arguments: a < m && m < b.
func rotateOrdered[Elem constraints.Ordered](data []Elem, a, m, b int) {
i := m - a
j := b - m
for i != j {
if i > j {
swapRangeOrdered(data, m-i, m, j)
i -= j
} else {
swapRangeOrdered(data, m-i, m+j-i, i)
j -= i
}
}
// i == j
swapRangeOrdered(data, m-i, m, i)
}