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iter_legacy.go
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iter_legacy.go
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/*
Copyright 2021 The Vitess Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package uca
import (
"vitess.io/vitess/go/mysql/collations/charset"
)
type WeightIteratorLegacy struct {
// Constant
*CollationLegacy
// Internal state
codepoint codepointIteratorLegacy
input []byte
length int
}
type codepointIteratorLegacy struct {
weights []uint16
scratch [2]uint16
}
func (it *codepointIteratorLegacy) next() (uint16, bool) {
if len(it.weights) == 0 {
return 0, false
}
weight := it.weights[0]
it.weights = it.weights[1:]
return weight, weight != 0x0
}
func (it *codepointIteratorLegacy) init(table Weights, cp rune) {
p, offset := PageOffset(cp)
page := table[p]
if page == nil {
UnicodeImplicitWeightsLegacy(it.scratch[:2], cp)
it.weights = it.scratch[:2]
return
}
stride := int((*page)[0])
position := 1 + stride*offset
it.weights = (*page)[position : position+stride]
}
func (it *codepointIteratorLegacy) initContraction(weights []uint16) {
it.weights = weights
}
func (it *WeightIteratorLegacy) reset(input []byte) {
it.input = input
it.length = 0
it.codepoint.weights = nil
}
func (it *WeightIteratorLegacy) DebugCodepoint() (rune, int) {
return it.charset.DecodeRune(it.input)
}
func (it *WeightIteratorLegacy) Next() (uint16, bool) {
for {
if w, ok := it.codepoint.next(); ok {
return w, true
}
cp, width := it.charset.DecodeRune(it.input)
if cp == charset.RuneError && width < 3 {
return 0, false
}
it.input = it.input[width:]
it.length++
if cp > it.maxCodepoint {
return 0xFFFD, true
}
if it.contract != nil {
if weights, remainder, skip := it.contract.Find(it.charset, cp, it.input); weights != nil {
it.codepoint.initContraction(weights)
it.input = remainder
it.length += skip
continue
}
}
it.codepoint.init(it.table, cp)
}
}
func (it *WeightIteratorLegacy) Length() int {
return it.length
}