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