forked from TrueCloudLab/lego
260 lines
6.6 KiB
Go
260 lines
6.6 KiB
Go
// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package rangetable
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import (
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"unicode"
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)
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// atEnd is used to mark a completed iteration.
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const atEnd = unicode.MaxRune + 1
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// Merge returns a new RangeTable that is the union of the given tables.
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// It can also be used to compact user-created RangeTables. The entries in
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// R16 and R32 for any given RangeTable should be sorted and non-overlapping.
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//
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// A lookup in the resulting table can be several times faster than using In
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// directly on the ranges. Merge is an expensive operation, however, and only
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// makes sense if one intends to use the result for more than a couple of
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// hundred lookups.
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func Merge(ranges ...*unicode.RangeTable) *unicode.RangeTable {
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rt := &unicode.RangeTable{}
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if len(ranges) == 0 {
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return rt
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}
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iter := tablesIter(make([]tableIndex, len(ranges)))
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for i, t := range ranges {
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iter[i] = tableIndex{t, 0, atEnd}
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if len(t.R16) > 0 {
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iter[i].next = rune(t.R16[0].Lo)
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}
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}
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if r0 := iter.next16(); r0.Stride != 0 {
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for {
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r1 := iter.next16()
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if r1.Stride == 0 {
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rt.R16 = append(rt.R16, r0)
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break
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}
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stride := r1.Lo - r0.Hi
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if (r1.Lo == r1.Hi || stride == r1.Stride) && (r0.Lo == r0.Hi || stride == r0.Stride) {
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// Fully merge the next range into the previous one.
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r0.Hi, r0.Stride = r1.Hi, stride
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continue
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} else if stride == r0.Stride {
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// Move the first element of r1 to r0. This may eliminate an
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// entry.
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r0.Hi = r1.Lo
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r0.Stride = stride
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r1.Lo = r1.Lo + r1.Stride
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if r1.Lo > r1.Hi {
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continue
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}
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}
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rt.R16 = append(rt.R16, r0)
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r0 = r1
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}
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}
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for i, t := range ranges {
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iter[i] = tableIndex{t, 0, atEnd}
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if len(t.R32) > 0 {
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iter[i].next = rune(t.R32[0].Lo)
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}
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}
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if r0 := iter.next32(); r0.Stride != 0 {
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for {
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r1 := iter.next32()
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if r1.Stride == 0 {
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rt.R32 = append(rt.R32, r0)
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break
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}
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stride := r1.Lo - r0.Hi
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if (r1.Lo == r1.Hi || stride == r1.Stride) && (r0.Lo == r0.Hi || stride == r0.Stride) {
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// Fully merge the next range into the previous one.
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r0.Hi, r0.Stride = r1.Hi, stride
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continue
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} else if stride == r0.Stride {
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// Move the first element of r1 to r0. This may eliminate an
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// entry.
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r0.Hi = r1.Lo
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r1.Lo = r1.Lo + r1.Stride
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if r1.Lo > r1.Hi {
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continue
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}
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}
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rt.R32 = append(rt.R32, r0)
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r0 = r1
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}
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}
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for i := 0; i < len(rt.R16) && rt.R16[i].Hi <= unicode.MaxLatin1; i++ {
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rt.LatinOffset = i + 1
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}
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return rt
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}
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type tableIndex struct {
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t *unicode.RangeTable
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p uint32
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next rune
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}
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type tablesIter []tableIndex
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// sortIter does an insertion sort using the next field of tableIndex. Insertion
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// sort is a good sorting algorithm for this case.
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func sortIter(t []tableIndex) {
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for i := range t {
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for j := i; j > 0 && t[j-1].next > t[j].next; j-- {
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t[j], t[j-1] = t[j-1], t[j]
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}
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}
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}
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// next16 finds the ranged to be added to the table. If ranges overlap between
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// multiple tables it clips the result to a non-overlapping range if the
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// elements are not fully subsumed. It returns a zero range if there are no more
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// ranges.
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func (ti tablesIter) next16() unicode.Range16 {
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sortIter(ti)
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t0 := ti[0]
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if t0.next == atEnd {
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return unicode.Range16{}
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}
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r0 := t0.t.R16[t0.p]
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r0.Lo = uint16(t0.next)
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// We restrict the Hi of the current range if it overlaps with another range.
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for i := range ti {
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tn := ti[i]
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// Since our tableIndices are sorted by next, we can break if the there
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// is no overlap. The first value of a next range can always be merged
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// into the current one, so we can break in case of equality as well.
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if rune(r0.Hi) <= tn.next {
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break
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}
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rn := tn.t.R16[tn.p]
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rn.Lo = uint16(tn.next)
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// Limit r0.Hi based on next ranges in list, but allow it to overlap
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// with ranges as long as it subsumes it.
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m := (rn.Lo - r0.Lo) % r0.Stride
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if m == 0 && (rn.Stride == r0.Stride || rn.Lo == rn.Hi) {
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// Overlap, take the min of the two Hi values: for simplicity's sake
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// we only process one range at a time.
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if r0.Hi > rn.Hi {
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r0.Hi = rn.Hi
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}
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} else {
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// Not a compatible stride. Set to the last possible value before
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// rn.Lo, but ensure there is at least one value.
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if x := rn.Lo - m; r0.Lo <= x {
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r0.Hi = x
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}
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break
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}
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}
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// Update the next values for each table.
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for i := range ti {
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tn := &ti[i]
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if rune(r0.Hi) < tn.next {
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break
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}
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rn := tn.t.R16[tn.p]
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stride := rune(rn.Stride)
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tn.next += stride * (1 + ((rune(r0.Hi) - tn.next) / stride))
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if rune(rn.Hi) < tn.next {
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if tn.p++; int(tn.p) == len(tn.t.R16) {
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tn.next = atEnd
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} else {
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tn.next = rune(tn.t.R16[tn.p].Lo)
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}
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}
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}
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if r0.Lo == r0.Hi {
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r0.Stride = 1
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}
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return r0
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}
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// next32 finds the ranged to be added to the table. If ranges overlap between
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// multiple tables it clips the result to a non-overlapping range if the
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// elements are not fully subsumed. It returns a zero range if there are no more
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// ranges.
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func (ti tablesIter) next32() unicode.Range32 {
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sortIter(ti)
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t0 := ti[0]
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if t0.next == atEnd {
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return unicode.Range32{}
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}
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r0 := t0.t.R32[t0.p]
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r0.Lo = uint32(t0.next)
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// We restrict the Hi of the current range if it overlaps with another range.
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for i := range ti {
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tn := ti[i]
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// Since our tableIndices are sorted by next, we can break if the there
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// is no overlap. The first value of a next range can always be merged
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// into the current one, so we can break in case of equality as well.
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if rune(r0.Hi) <= tn.next {
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break
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}
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rn := tn.t.R32[tn.p]
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rn.Lo = uint32(tn.next)
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// Limit r0.Hi based on next ranges in list, but allow it to overlap
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// with ranges as long as it subsumes it.
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m := (rn.Lo - r0.Lo) % r0.Stride
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if m == 0 && (rn.Stride == r0.Stride || rn.Lo == rn.Hi) {
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// Overlap, take the min of the two Hi values: for simplicity's sake
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// we only process one range at a time.
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if r0.Hi > rn.Hi {
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r0.Hi = rn.Hi
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}
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} else {
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// Not a compatible stride. Set to the last possible value before
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// rn.Lo, but ensure there is at least one value.
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if x := rn.Lo - m; r0.Lo <= x {
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r0.Hi = x
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}
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break
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}
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}
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// Update the next values for each table.
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for i := range ti {
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tn := &ti[i]
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if rune(r0.Hi) < tn.next {
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break
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}
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rn := tn.t.R32[tn.p]
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stride := rune(rn.Stride)
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tn.next += stride * (1 + ((rune(r0.Hi) - tn.next) / stride))
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if rune(rn.Hi) < tn.next {
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if tn.p++; int(tn.p) == len(tn.t.R32) {
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tn.next = atEnd
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} else {
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tn.next = rune(tn.t.R32[tn.p].Lo)
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}
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}
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}
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if r0.Lo == r0.Hi {
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r0.Stride = 1
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}
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return r0
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}
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