252 lines
7.3 KiB
Go
252 lines
7.3 KiB
Go
// Copyright 2014 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 triegen
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import (
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"bytes"
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"fmt"
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"io"
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"strings"
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"text/template"
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)
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// print writes all the data structures as well as the code necessary to use the
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// trie to w.
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func (b *builder) print(w io.Writer) error {
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b.Stats.NValueEntries = len(b.ValueBlocks) * blockSize
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b.Stats.NValueBytes = len(b.ValueBlocks) * blockSize * b.ValueSize
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b.Stats.NIndexEntries = len(b.IndexBlocks) * blockSize
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b.Stats.NIndexBytes = len(b.IndexBlocks) * blockSize * b.IndexSize
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b.Stats.NHandleBytes = len(b.Trie) * 2 * b.IndexSize
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// If we only have one root trie, all starter blocks are at position 0 and
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// we can access the arrays directly.
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if len(b.Trie) == 1 {
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// At this point we cannot refer to the generated tables directly.
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b.ASCIIBlock = b.Name + "Values"
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b.StarterBlock = b.Name + "Index"
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} else {
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// Otherwise we need to have explicit starter indexes in the trie
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// structure.
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b.ASCIIBlock = "t.ascii"
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b.StarterBlock = "t.utf8Start"
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}
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b.SourceType = "[]byte"
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if err := lookupGen.Execute(w, b); err != nil {
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return err
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}
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b.SourceType = "string"
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if err := lookupGen.Execute(w, b); err != nil {
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return err
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}
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if err := trieGen.Execute(w, b); err != nil {
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return err
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}
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for _, c := range b.Compactions {
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if err := c.c.Print(w); err != nil {
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return err
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}
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}
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return nil
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}
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func printValues(n int, values []uint64) string {
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w := &bytes.Buffer{}
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boff := n * blockSize
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fmt.Fprintf(w, "\t// Block %#x, offset %#x", n, boff)
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var newline bool
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for i, v := range values {
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if i%6 == 0 {
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newline = true
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}
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if v != 0 {
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if newline {
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fmt.Fprintf(w, "\n")
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newline = false
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}
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fmt.Fprintf(w, "\t%#02x:%#04x, ", boff+i, v)
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}
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}
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return w.String()
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}
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func printIndex(b *builder, nr int, n *node) string {
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w := &bytes.Buffer{}
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boff := nr * blockSize
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fmt.Fprintf(w, "\t// Block %#x, offset %#x", nr, boff)
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var newline bool
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for i, c := range n.children {
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if i%8 == 0 {
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newline = true
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}
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if c != nil {
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v := b.Compactions[c.index.compaction].Offset + uint32(c.index.index)
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if v != 0 {
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if newline {
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fmt.Fprintf(w, "\n")
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newline = false
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}
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fmt.Fprintf(w, "\t%#02x:%#02x, ", boff+i, v)
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}
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}
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}
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return w.String()
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}
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var (
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trieGen = template.Must(template.New("trie").Funcs(template.FuncMap{
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"printValues": printValues,
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"printIndex": printIndex,
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"title": strings.Title,
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"dec": func(x int) int { return x - 1 },
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"psize": func(n int) string {
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return fmt.Sprintf("%d bytes (%.2f KiB)", n, float64(n)/1024)
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},
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}).Parse(trieTemplate))
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lookupGen = template.Must(template.New("lookup").Parse(lookupTemplate))
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)
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// TODO: consider the return type of lookup. It could be uint64, even if the
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// internal value type is smaller. We will have to verify this with the
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// performance of unicode/norm, which is very sensitive to such changes.
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const trieTemplate = `{{$b := .}}{{$multi := gt (len .Trie) 1}}
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// {{.Name}}Trie. Total size: {{psize .Size}}. Checksum: {{printf "%08x" .Checksum}}.
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type {{.Name}}Trie struct { {{if $multi}}
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ascii []{{.ValueType}} // index for ASCII bytes
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utf8Start []{{.IndexType}} // index for UTF-8 bytes >= 0xC0
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{{end}}}
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func new{{title .Name}}Trie(i int) *{{.Name}}Trie { {{if $multi}}
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h := {{.Name}}TrieHandles[i]
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return &{{.Name}}Trie{ {{.Name}}Values[uint32(h.ascii)<<6:], {{.Name}}Index[uint32(h.multi)<<6:] }
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}
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type {{.Name}}TrieHandle struct {
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ascii, multi {{.IndexType}}
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}
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// {{.Name}}TrieHandles: {{len .Trie}} handles, {{.Stats.NHandleBytes}} bytes
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var {{.Name}}TrieHandles = [{{len .Trie}}]{{.Name}}TrieHandle{
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{{range .Trie}} { {{.ASCIIIndex}}, {{.StarterIndex}} }, // {{printf "%08x" .Checksum}}: {{.Name}}
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{{end}}}{{else}}
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return &{{.Name}}Trie{}
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}
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{{end}}
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// lookupValue determines the type of block n and looks up the value for b.
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func (t *{{.Name}}Trie) lookupValue(n uint32, b byte) {{.ValueType}}{{$last := dec (len .Compactions)}} {
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switch { {{range $i, $c := .Compactions}}
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{{if eq $i $last}}default{{else}}case n < {{$c.Cutoff}}{{end}}:{{if ne $i 0}}
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n -= {{$c.Offset}}{{end}}
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return {{print $b.ValueType}}({{$c.Handler}}){{end}}
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}
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}
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// {{.Name}}Values: {{len .ValueBlocks}} blocks, {{.Stats.NValueEntries}} entries, {{.Stats.NValueBytes}} bytes
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// The third block is the zero block.
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var {{.Name}}Values = [{{.Stats.NValueEntries}}]{{.ValueType}} {
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{{range $i, $v := .ValueBlocks}}{{printValues $i $v}}
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{{end}}}
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// {{.Name}}Index: {{len .IndexBlocks}} blocks, {{.Stats.NIndexEntries}} entries, {{.Stats.NIndexBytes}} bytes
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// Block 0 is the zero block.
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var {{.Name}}Index = [{{.Stats.NIndexEntries}}]{{.IndexType}} {
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{{range $i, $v := .IndexBlocks}}{{printIndex $b $i $v}}
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{{end}}}
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`
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// TODO: consider allowing zero-length strings after evaluating performance with
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// unicode/norm.
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const lookupTemplate = `
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// lookup{{if eq .SourceType "string"}}String{{end}} returns the trie value for the first UTF-8 encoding in s and
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// the width in bytes of this encoding. The size will be 0 if s does not
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// hold enough bytes to complete the encoding. len(s) must be greater than 0.
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func (t *{{.Name}}Trie) lookup{{if eq .SourceType "string"}}String{{end}}(s {{.SourceType}}) (v {{.ValueType}}, sz int) {
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c0 := s[0]
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switch {
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case c0 < 0x80: // is ASCII
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return {{.ASCIIBlock}}[c0], 1
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case c0 < 0xC2:
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return 0, 1 // Illegal UTF-8: not a starter, not ASCII.
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case c0 < 0xE0: // 2-byte UTF-8
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if len(s) < 2 {
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return 0, 0
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}
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i := {{.StarterBlock}}[c0]
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c1 := s[1]
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if c1 < 0x80 || 0xC0 <= c1 {
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return 0, 1 // Illegal UTF-8: not a continuation byte.
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}
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return t.lookupValue(uint32(i), c1), 2
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case c0 < 0xF0: // 3-byte UTF-8
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if len(s) < 3 {
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return 0, 0
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}
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i := {{.StarterBlock}}[c0]
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c1 := s[1]
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if c1 < 0x80 || 0xC0 <= c1 {
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return 0, 1 // Illegal UTF-8: not a continuation byte.
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}
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o := uint32(i)<<6 + uint32(c1)
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i = {{.Name}}Index[o]
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c2 := s[2]
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if c2 < 0x80 || 0xC0 <= c2 {
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return 0, 2 // Illegal UTF-8: not a continuation byte.
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}
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return t.lookupValue(uint32(i), c2), 3
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case c0 < 0xF8: // 4-byte UTF-8
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if len(s) < 4 {
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return 0, 0
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}
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i := {{.StarterBlock}}[c0]
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c1 := s[1]
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if c1 < 0x80 || 0xC0 <= c1 {
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return 0, 1 // Illegal UTF-8: not a continuation byte.
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}
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o := uint32(i)<<6 + uint32(c1)
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i = {{.Name}}Index[o]
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c2 := s[2]
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if c2 < 0x80 || 0xC0 <= c2 {
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return 0, 2 // Illegal UTF-8: not a continuation byte.
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}
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o = uint32(i)<<6 + uint32(c2)
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i = {{.Name}}Index[o]
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c3 := s[3]
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if c3 < 0x80 || 0xC0 <= c3 {
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return 0, 3 // Illegal UTF-8: not a continuation byte.
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}
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return t.lookupValue(uint32(i), c3), 4
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}
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// Illegal rune
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return 0, 1
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}
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// lookup{{if eq .SourceType "string"}}String{{end}}Unsafe returns the trie value for the first UTF-8 encoding in s.
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// s must start with a full and valid UTF-8 encoded rune.
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func (t *{{.Name}}Trie) lookup{{if eq .SourceType "string"}}String{{end}}Unsafe(s {{.SourceType}}) {{.ValueType}} {
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c0 := s[0]
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if c0 < 0x80 { // is ASCII
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return {{.ASCIIBlock}}[c0]
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}
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i := {{.StarterBlock}}[c0]
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if c0 < 0xE0 { // 2-byte UTF-8
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return t.lookupValue(uint32(i), s[1])
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}
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i = {{.Name}}Index[uint32(i)<<6+uint32(s[1])]
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if c0 < 0xF0 { // 3-byte UTF-8
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return t.lookupValue(uint32(i), s[2])
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}
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i = {{.Name}}Index[uint32(i)<<6+uint32(s[2])]
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if c0 < 0xF8 { // 4-byte UTF-8
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return t.lookupValue(uint32(i), s[3])
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}
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return 0
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}
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`
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