/usr/share/gocode/src/golang.org/x/text/collate/build/trie.go is in golang-golang-x-text-dev 0.0~git20170627.0.6353ef0-1ubuntu2.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 | // Copyright 2012 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.
// The trie in this file is used to associate the first full character
// in a UTF-8 string to a collation element.
// All but the last byte in a UTF-8 byte sequence are
// used to look up offsets in the index table to be used for the next byte.
// The last byte is used to index into a table of collation elements.
// This file contains the code for the generation of the trie.
package build
import (
"fmt"
"hash/fnv"
"io"
"reflect"
)
const (
blockSize = 64
blockOffset = 2 // Subtract 2 blocks to compensate for the 0x80 added to continuation bytes.
)
type trieHandle struct {
lookupStart uint16 // offset in table for first byte
valueStart uint16 // offset in table for first byte
}
type trie struct {
index []uint16
values []uint32
}
// trieNode is the intermediate trie structure used for generating a trie.
type trieNode struct {
index []*trieNode
value []uint32
b byte
refValue uint16
refIndex uint16
}
func newNode() *trieNode {
return &trieNode{
index: make([]*trieNode, 64),
value: make([]uint32, 128), // root node size is 128 instead of 64
}
}
func (n *trieNode) isInternal() bool {
return n.value != nil
}
func (n *trieNode) insert(r rune, value uint32) {
const maskx = 0x3F // mask out two most-significant bits
str := string(r)
if len(str) == 1 {
n.value[str[0]] = value
return
}
for i := 0; i < len(str)-1; i++ {
b := str[i] & maskx
if n.index == nil {
n.index = make([]*trieNode, blockSize)
}
nn := n.index[b]
if nn == nil {
nn = &trieNode{}
nn.b = b
n.index[b] = nn
}
n = nn
}
if n.value == nil {
n.value = make([]uint32, blockSize)
}
b := str[len(str)-1] & maskx
n.value[b] = value
}
type trieBuilder struct {
t *trie
roots []*trieHandle
lookupBlocks []*trieNode
valueBlocks []*trieNode
lookupBlockIdx map[uint32]*trieNode
valueBlockIdx map[uint32]*trieNode
}
func newTrieBuilder() *trieBuilder {
index := &trieBuilder{}
index.lookupBlocks = make([]*trieNode, 0)
index.valueBlocks = make([]*trieNode, 0)
index.lookupBlockIdx = make(map[uint32]*trieNode)
index.valueBlockIdx = make(map[uint32]*trieNode)
// The third nil is the default null block. The other two blocks
// are used to guarantee an offset of at least 3 for each block.
index.lookupBlocks = append(index.lookupBlocks, nil, nil, nil)
index.t = &trie{}
return index
}
func (b *trieBuilder) computeOffsets(n *trieNode) *trieNode {
hasher := fnv.New32()
if n.index != nil {
for i, nn := range n.index {
var vi, vv uint16
if nn != nil {
nn = b.computeOffsets(nn)
n.index[i] = nn
vi = nn.refIndex
vv = nn.refValue
}
hasher.Write([]byte{byte(vi >> 8), byte(vi)})
hasher.Write([]byte{byte(vv >> 8), byte(vv)})
}
h := hasher.Sum32()
nn, ok := b.lookupBlockIdx[h]
if !ok {
n.refIndex = uint16(len(b.lookupBlocks)) - blockOffset
b.lookupBlocks = append(b.lookupBlocks, n)
b.lookupBlockIdx[h] = n
} else {
n = nn
}
} else {
for _, v := range n.value {
hasher.Write([]byte{byte(v >> 24), byte(v >> 16), byte(v >> 8), byte(v)})
}
h := hasher.Sum32()
nn, ok := b.valueBlockIdx[h]
if !ok {
n.refValue = uint16(len(b.valueBlocks)) - blockOffset
n.refIndex = n.refValue
b.valueBlocks = append(b.valueBlocks, n)
b.valueBlockIdx[h] = n
} else {
n = nn
}
}
return n
}
func (b *trieBuilder) addStartValueBlock(n *trieNode) uint16 {
hasher := fnv.New32()
for _, v := range n.value[:2*blockSize] {
hasher.Write([]byte{byte(v >> 24), byte(v >> 16), byte(v >> 8), byte(v)})
}
h := hasher.Sum32()
nn, ok := b.valueBlockIdx[h]
if !ok {
n.refValue = uint16(len(b.valueBlocks))
n.refIndex = n.refValue
b.valueBlocks = append(b.valueBlocks, n)
// Add a dummy block to accommodate the double block size.
b.valueBlocks = append(b.valueBlocks, nil)
b.valueBlockIdx[h] = n
} else {
n = nn
}
return n.refValue
}
func genValueBlock(t *trie, n *trieNode) {
if n != nil {
for _, v := range n.value {
t.values = append(t.values, v)
}
}
}
func genLookupBlock(t *trie, n *trieNode) {
for _, nn := range n.index {
v := uint16(0)
if nn != nil {
if n.index != nil {
v = nn.refIndex
} else {
v = nn.refValue
}
}
t.index = append(t.index, v)
}
}
func (b *trieBuilder) addTrie(n *trieNode) *trieHandle {
h := &trieHandle{}
b.roots = append(b.roots, h)
h.valueStart = b.addStartValueBlock(n)
if len(b.roots) == 1 {
// We insert a null block after the first start value block.
// This ensures that continuation bytes UTF-8 sequences of length
// greater than 2 will automatically hit a null block if there
// was an undefined entry.
b.valueBlocks = append(b.valueBlocks, nil)
}
n = b.computeOffsets(n)
// Offset by one extra block as the first byte starts at 0xC0 instead of 0x80.
h.lookupStart = n.refIndex - 1
return h
}
// generate generates and returns the trie for n.
func (b *trieBuilder) generate() (t *trie, err error) {
t = b.t
if len(b.valueBlocks) >= 1<<16 {
return nil, fmt.Errorf("maximum number of value blocks exceeded (%d > %d)", len(b.valueBlocks), 1<<16)
}
if len(b.lookupBlocks) >= 1<<16 {
return nil, fmt.Errorf("maximum number of lookup blocks exceeded (%d > %d)", len(b.lookupBlocks), 1<<16)
}
genValueBlock(t, b.valueBlocks[0])
genValueBlock(t, &trieNode{value: make([]uint32, 64)})
for i := 2; i < len(b.valueBlocks); i++ {
genValueBlock(t, b.valueBlocks[i])
}
n := &trieNode{index: make([]*trieNode, 64)}
genLookupBlock(t, n)
genLookupBlock(t, n)
genLookupBlock(t, n)
for i := 3; i < len(b.lookupBlocks); i++ {
genLookupBlock(t, b.lookupBlocks[i])
}
return b.t, nil
}
func (t *trie) printArrays(w io.Writer, name string) (n, size int, err error) {
p := func(f string, a ...interface{}) {
nn, e := fmt.Fprintf(w, f, a...)
n += nn
if err == nil {
err = e
}
}
nv := len(t.values)
p("// %sValues: %d entries, %d bytes\n", name, nv, nv*4)
p("// Block 2 is the null block.\n")
p("var %sValues = [%d]uint32 {", name, nv)
var printnewline bool
for i, v := range t.values {
if i%blockSize == 0 {
p("\n\t// Block %#x, offset %#x", i/blockSize, i)
}
if i%4 == 0 {
printnewline = true
}
if v != 0 {
if printnewline {
p("\n\t")
printnewline = false
}
p("%#04x:%#08x, ", i, v)
}
}
p("\n}\n\n")
ni := len(t.index)
p("// %sLookup: %d entries, %d bytes\n", name, ni, ni*2)
p("// Block 0 is the null block.\n")
p("var %sLookup = [%d]uint16 {", name, ni)
printnewline = false
for i, v := range t.index {
if i%blockSize == 0 {
p("\n\t// Block %#x, offset %#x", i/blockSize, i)
}
if i%8 == 0 {
printnewline = true
}
if v != 0 {
if printnewline {
p("\n\t")
printnewline = false
}
p("%#03x:%#02x, ", i, v)
}
}
p("\n}\n\n")
return n, nv*4 + ni*2, err
}
func (t *trie) printStruct(w io.Writer, handle *trieHandle, name string) (n, sz int, err error) {
const msg = "trie{ %sLookup[%d:], %sValues[%d:], %sLookup[:], %sValues[:]}"
n, err = fmt.Fprintf(w, msg, name, handle.lookupStart*blockSize, name, handle.valueStart*blockSize, name, name)
sz += int(reflect.TypeOf(trie{}).Size())
return
}
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