// Copyright (c) 2017 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package utf8
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import (
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"fmt"
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"unicode/utf8"
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)
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// Sequences is a collection of Sequence
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type Sequences []Sequence
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// NewSequences constructs a collection of Sequence which describe the
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// byte ranges covered between the start and end runes.
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func NewSequences(start, end rune) (Sequences, error) {
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rv, _, err := NewSequencesPrealloc(start, end, nil, nil, nil, nil)
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return rv, err
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}
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func NewSequencesPrealloc(start, end rune,
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preallocSequences Sequences,
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preallocRangeStack RangeStack,
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preallocStartBytes, preallocEndBytes []byte) (Sequences, RangeStack, error) {
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rv := preallocSequences[:0]
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startBytes := preallocStartBytes
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if cap(startBytes) < utf8.UTFMax {
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startBytes = make([]byte, utf8.UTFMax)
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}
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startBytes = startBytes[:utf8.UTFMax]
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endBytes := preallocEndBytes
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if cap(endBytes) < utf8.UTFMax {
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endBytes = make([]byte, utf8.UTFMax)
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}
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endBytes = endBytes[:utf8.UTFMax]
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rangeStack := preallocRangeStack[:0]
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rangeStack = rangeStack.Push(scalarRange{start, end})
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rangeStack, r := rangeStack.Pop()
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TOP:
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for r != nilScalarRange {
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INNER:
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for {
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r1, r2 := r.split()
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if r1 != nilScalarRange {
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rangeStack = rangeStack.Push(scalarRange{r2.start, r2.end})
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r.start = r1.start
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r.end = r1.end
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continue INNER
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}
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if !r.valid() {
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rangeStack, r = rangeStack.Pop()
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continue TOP
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}
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for i := 1; i < utf8.UTFMax; i++ {
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max := maxScalarValue(i)
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if r.start <= max && max < r.end {
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rangeStack = rangeStack.Push(scalarRange{max + 1, r.end})
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r.end = max
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continue INNER
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}
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}
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asciiRange := r.ascii()
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if asciiRange != nilRange {
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rv = append(rv, Sequence{
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asciiRange,
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})
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rangeStack, r = rangeStack.Pop()
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continue TOP
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}
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for i := uint(1); i < utf8.UTFMax; i++ {
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m := rune((1 << (6 * i)) - 1)
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if (r.start & ^m) != (r.end & ^m) {
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if (r.start & m) != 0 {
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rangeStack = rangeStack.Push(scalarRange{(r.start | m) + 1, r.end})
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r.end = r.start | m
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continue INNER
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}
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if (r.end & m) != m {
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rangeStack = rangeStack.Push(scalarRange{r.end & ^m, r.end})
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r.end = (r.end & ^m) - 1
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continue INNER
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}
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}
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}
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n, m := r.encode(startBytes, endBytes)
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seq, err := SequenceFromEncodedRange(startBytes[0:n], endBytes[0:m])
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if err != nil {
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return nil, nil, err
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}
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rv = append(rv, seq)
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rangeStack, r = rangeStack.Pop()
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continue TOP
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}
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}
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return rv, rangeStack, nil
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}
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// Sequence is a collection of Range
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type Sequence []Range
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// SequenceFromEncodedRange creates sequence from the encoded bytes
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func SequenceFromEncodedRange(start, end []byte) (Sequence, error) {
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if len(start) != len(end) {
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return nil, fmt.Errorf("byte slices must be the same length")
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}
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switch len(start) {
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case 2:
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return Sequence{
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Range{start[0], end[0]},
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Range{start[1], end[1]},
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}, nil
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case 3:
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return Sequence{
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Range{start[0], end[0]},
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Range{start[1], end[1]},
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Range{start[2], end[2]},
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}, nil
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case 4:
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return Sequence{
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Range{start[0], end[0]},
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Range{start[1], end[1]},
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Range{start[2], end[2]},
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Range{start[3], end[3]},
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}, nil
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}
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return nil, fmt.Errorf("invalid encoded byte length")
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}
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// Matches checks to see if the provided byte slice matches the Sequence
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func (u Sequence) Matches(bytes []byte) bool {
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if len(bytes) < len(u) {
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return false
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}
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for i := 0; i < len(u); i++ {
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if !u[i].matches(bytes[i]) {
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return false
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}
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}
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return true
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}
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func (u Sequence) String() string {
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switch len(u) {
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case 1:
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return fmt.Sprintf("%v", u[0])
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case 2:
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return fmt.Sprintf("%v%v", u[0], u[1])
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case 3:
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return fmt.Sprintf("%v%v%v", u[0], u[1], u[2])
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case 4:
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return fmt.Sprintf("%v%v%v%v", u[0], u[1], u[2], u[3])
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default:
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return fmt.Sprintf("invalid utf8 sequence")
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}
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}
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// Range describes a single range of byte values
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type Range struct {
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Start byte
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End byte
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}
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var nilRange = Range{0xff, 0}
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func (u Range) matches(b byte) bool {
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if u.Start <= b && b <= u.End {
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return true
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}
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return false
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}
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func (u Range) String() string {
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if u.Start == u.End {
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return fmt.Sprintf("[%X]", u.Start)
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}
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return fmt.Sprintf("[%X-%X]", u.Start, u.End)
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}
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type scalarRange struct {
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start rune
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end rune
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}
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var nilScalarRange = scalarRange{0xffff, 0}
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func (s *scalarRange) String() string {
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return fmt.Sprintf("ScalarRange(%d,%d)", s.start, s.end)
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}
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// split this scalar range if it overlaps with a surrogate codepoint
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func (s *scalarRange) split() (scalarRange, scalarRange) {
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if s.start < 0xe000 && s.end > 0xd7ff {
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return scalarRange{
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start: s.start,
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end: 0xd7ff,
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},
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scalarRange{
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start: 0xe000,
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end: s.end,
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}
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}
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return nilScalarRange, nilScalarRange
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}
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func (s *scalarRange) valid() bool {
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return s.start <= s.end
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}
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func (s *scalarRange) ascii() Range {
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if s.valid() && s.end <= 0x7f {
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return Range{
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Start: byte(s.start),
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End: byte(s.end),
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}
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}
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return nilRange
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}
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// start and end MUST have capacity for utf8.UTFMax bytes
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func (s *scalarRange) encode(start, end []byte) (int, int) {
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n := utf8.EncodeRune(start, s.start)
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m := utf8.EncodeRune(end, s.end)
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return n, m
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}
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type RangeStack []scalarRange
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func (s RangeStack) Push(v scalarRange) RangeStack {
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return append(s, v)
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}
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func (s RangeStack) Pop() (RangeStack, scalarRange) {
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l := len(s)
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if l < 1 {
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return s, nilScalarRange
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}
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return s[:l-1], s[l-1]
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}
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func maxScalarValue(nbytes int) rune {
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switch nbytes {
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case 1:
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return 0x007f
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case 2:
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return 0x07FF
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case 3:
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return 0xFFFF
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default:
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return 0x10FFFF
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}
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}
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