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Diffstat (limited to 'vendor/github.com/mattermost/rsc/regexp/regmerge/sort.go')
-rw-r--r-- | vendor/github.com/mattermost/rsc/regexp/regmerge/sort.go | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/vendor/github.com/mattermost/rsc/regexp/regmerge/sort.go b/vendor/github.com/mattermost/rsc/regexp/regmerge/sort.go new file mode 100644 index 000000000..e40f87714 --- /dev/null +++ b/vendor/github.com/mattermost/rsc/regexp/regmerge/sort.go @@ -0,0 +1,199 @@ +// Copyright 2012 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. + +// Copy of go/src/pkg/sort/sort.go, specialized for []int +// and to remove some array indexing. + +package main + +func min(a, b int) int { + if a < b { + return a + } + return b +} + +// Insertion sort +func insertionSort(data []int, 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] + } + } +} + +// siftDown implements the heap property on data[lo, hi). +// first is an offset into the array where the root of the heap lies. +func siftDown(data []int, 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 heapSort(data []int, 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-- { + siftDown(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] + siftDown(data, lo, i, first) + } +} + +// Quicksort, following Bentley and McIlroy, +// ``Engineering a Sort Function,'' SP&E November 1993. + +// medianOfThree moves the median of the three values data[a], data[b], data[c] into data[a]. +func medianOfThree(data []int, a, b, c int) { + m0 := b + m1 := a + m2 := c + // bubble sort on 3 elements + if data[m1] < data[m0] { + data[m1], data[m0] = data[m0], data[m1] + } + if data[m2] < data[m1] { + data[m2], data[m1] = 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 swapRange(data []int, a, b, n int) { + for i := 0; i < n; i++ { + data[a+i], data[b+i] = data[b+i], data[a+i] + } +} + +func doPivot(data []int, lo, hi int) (midlo, midhi int) { + m := lo + (hi-lo)/2 // Written like this to avoid integer overflow. + if hi-lo > 40 { + // Tukey's ``Ninther,'' median of three medians of three. + s := (hi - lo) / 8 + medianOfThree(data, lo, lo+s, lo+2*s) + medianOfThree(data, m, m-s, m+s) + medianOfThree(data, hi-1, hi-1-s, hi-1-2*s) + } + medianOfThree(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] is unexamined + // data[c <= i < d] > pivot + // data[d <= i < hi] = pivot + // + // Once b meets c, can swap the "= pivot" sections + // into the middle of the slice. + pivot := lo + a, b, c, d := lo+1, lo+1, hi, hi + dpivot := data[pivot] + db, dc1 := data[b], data[c-1] + for b < c { + if db < dpivot { // data[b] < pivot + b++ + if b < c { + db = data[b] + } + continue + } + if !(dpivot < db) { // data[b] = pivot + data[a], data[b] = db, data[a] + a++ + b++ + if b < c { + db = data[b] + } + continue + } + if dpivot < dc1 { // data[c-1] > pivot + c-- + if c > 0 { + dc1 = data[c-1] + } + continue + } + if !(dc1 < dpivot) { // data[c-1] = pivot + data[c-1], data[d-1] = data[d-1], dc1 + c-- + d-- + if c > 0 { + dc1 = data[c-1] + } + continue + } + // data[b] > pivot; data[c-1] < pivot + data[b], data[c-1] = dc1, db + b++ + c-- + if b < c { + db = data[b] + dc1 = data[c-1] + } + } + + n := min(b-a, a-lo) + swapRange(data, lo, b-n, n) + + n = min(hi-d, d-c) + swapRange(data, c, hi-n, n) + + return lo + b - a, hi - (d - c) +} + +func quickSort(data []int, a, b, maxDepth int) { + for b-a > 7 { + if maxDepth == 0 { + heapSort(data, a, b) + return + } + maxDepth-- + mlo, mhi := doPivot(data, a, b) + // Avoiding recursion on the larger subproblem guarantees + // a stack depth of at most lg(b-a). + if mlo-a < b-mhi { + quickSort(data, a, mlo, maxDepth) + a = mhi // i.e., quickSort(data, mhi, b) + } else { + quickSort(data, mhi, b, maxDepth) + b = mlo // i.e., quickSort(data, a, mlo) + } + } + if b-a > 1 { + insertionSort(data, a, b) + } +} + +func sortInts(data []int) { + // Switch to heapsort if depth of 2*ceil(lg(n)) is reached. + n := len(data) + maxDepth := 0 + for 1<<uint(maxDepth) < n { + maxDepth++ + } + maxDepth *= 2 + quickSort(data, 0, n, maxDepth) +} |