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