| // Copyright 2011 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. |
| |
| // Trie table generator. |
| // Used by make*tables tools to generate a go file with trie data structures |
| // for mapping UTF-8 to a 16-bit value. All but the last byte in a UTF-8 byte |
| // sequence are used to lookup offsets in the index table to be used for the |
| // next byte. The last byte is used to index into a table with 16-bit values. |
| |
| package main |
| |
| import ( |
| "fmt" |
| "hash/crc32" |
| "log" |
| "utf8" |
| ) |
| |
| // Intermediate trie structure |
| type trieNode struct { |
| table [256]*trieNode |
| value uint16 |
| b byte |
| leaf bool |
| } |
| |
| func newNode() *trieNode { |
| return new(trieNode) |
| } |
| |
| func (n trieNode) String() string { |
| s := fmt.Sprint("trieNode{table: { non-nil at index: ") |
| for i, v := range n.table { |
| if v != nil { |
| s += fmt.Sprintf("%d, ", i) |
| } |
| } |
| s += fmt.Sprintf("}, value:%#x, b:%#x leaf:%v}", n.value, n.b, n.leaf) |
| return s |
| } |
| |
| func (n trieNode) isInternal() bool { |
| internal := true |
| for i := 0; i < 256; i++ { |
| if nn := n.table[i]; nn != nil { |
| if !internal && !nn.leaf { |
| log.Fatalf("triegen: isInternal: node contains both leaf and non-leaf children (%v)", n) |
| } |
| internal = internal && !nn.leaf |
| } |
| } |
| return internal |
| } |
| |
| func (n *trieNode) insert(rune int, value uint16) { |
| var p [utf8.UTFMax]byte |
| sz := utf8.EncodeRune(p[:], rune) |
| |
| for i := 0; i < sz; i++ { |
| if n.leaf { |
| log.Fatalf("triegen: insert: node (%#v) should not be a leaf", n) |
| } |
| nn := n.table[p[i]] |
| if nn == nil { |
| nn = newNode() |
| nn.b = p[i] |
| n.table[p[i]] = nn |
| } |
| n = nn |
| } |
| n.value = value |
| n.leaf = true |
| } |
| |
| type nodeIndex struct { |
| lookupBlocks []*trieNode |
| valueBlocks []*trieNode |
| |
| lookupBlockIdx map[uint32]uint16 |
| valueBlockIdx map[uint32]uint16 |
| } |
| |
| func newIndex() *nodeIndex { |
| index := &nodeIndex{} |
| index.lookupBlocks = make([]*trieNode, 0) |
| index.valueBlocks = make([]*trieNode, 0) |
| index.lookupBlockIdx = make(map[uint32]uint16) |
| index.valueBlockIdx = make(map[uint32]uint16) |
| return index |
| } |
| |
| func computeOffsets(index *nodeIndex, n *trieNode) uint16 { |
| if n.leaf { |
| return n.value |
| } |
| hasher := crc32.New(crc32.MakeTable(crc32.IEEE)) |
| // We only index continuation bytes. |
| for i := 0; i < 64; i++ { |
| var v uint16 = 0 |
| if nn := n.table[0x80+i]; nn != nil { |
| v = computeOffsets(index, nn) |
| } |
| hasher.Write([]byte{uint8(v >> 8), uint8(v)}) |
| } |
| h := hasher.Sum32() |
| if n.isInternal() { |
| v, ok := index.lookupBlockIdx[h] |
| if !ok { |
| v = uint16(len(index.lookupBlocks)) |
| index.lookupBlocks = append(index.lookupBlocks, n) |
| index.lookupBlockIdx[h] = v |
| } |
| n.value = v |
| } else { |
| v, ok := index.valueBlockIdx[h] |
| if !ok { |
| v = uint16(len(index.valueBlocks)) |
| index.valueBlocks = append(index.valueBlocks, n) |
| index.valueBlockIdx[h] = v |
| } |
| n.value = v |
| } |
| return n.value |
| } |
| |
| func printValueBlock(nr int, n *trieNode, offset int) { |
| boff := nr * 64 |
| fmt.Printf("\n// Block %#x, offset %#x", nr, boff) |
| var printnewline bool |
| for i := 0; i < 64; i++ { |
| if i%6 == 0 { |
| printnewline = true |
| } |
| v := uint16(0) |
| if nn := n.table[i+offset]; nn != nil { |
| v = nn.value |
| } |
| if v != 0 { |
| if printnewline { |
| fmt.Printf("\n") |
| printnewline = false |
| } |
| fmt.Printf("%#04x:%#04x, ", nr*64+i, v) |
| } |
| } |
| } |
| |
| func printLookupBlock(nr int, n *trieNode, offset int) { |
| boff := nr * 64 |
| fmt.Printf("\n// Block %#x, offset %#x", nr, boff) |
| var printnewline bool |
| for i := 0; i < 64; i++ { |
| if i%8 == 0 { |
| printnewline = true |
| } |
| v := uint16(0) |
| if nn := n.table[i+offset]; nn != nil { |
| v = nn.value |
| } |
| if v != 0 { |
| if printnewline { |
| fmt.Printf("\n") |
| printnewline = false |
| } |
| fmt.Printf("%#03x:%#02x, ", boff+i, v) |
| } |
| } |
| } |
| |
| // printTables returns the size in bytes of the generated tables. |
| func (t *trieNode) printTables(name string) int { |
| index := newIndex() |
| // Values for 7-bit ASCII are stored in first two block, followed by nil block. |
| index.valueBlocks = append(index.valueBlocks, nil, nil, nil) |
| // First byte of multi-byte UTF-8 codepoints are indexed in 4th block. |
| index.lookupBlocks = append(index.lookupBlocks, nil, nil, nil, nil) |
| // Index starter bytes of multi-byte UTF-8. |
| for i := 0xC0; i < 0x100; i++ { |
| if t.table[i] != nil { |
| computeOffsets(index, t.table[i]) |
| } |
| } |
| |
| nv := len(index.valueBlocks) * 64 |
| fmt.Printf("// %sValues: %d entries, %d bytes\n", name, nv, nv*2) |
| fmt.Printf("// Block 2 is the null block.\n") |
| fmt.Printf("var %sValues = [%d]uint16 {", name, nv) |
| printValueBlock(0, t, 0) |
| printValueBlock(1, t, 64) |
| printValueBlock(2, newNode(), 0) |
| for i := 3; i < len(index.valueBlocks); i++ { |
| printValueBlock(i, index.valueBlocks[i], 0x80) |
| } |
| fmt.Print("\n}\n\n") |
| |
| ni := len(index.lookupBlocks) * 64 |
| fmt.Printf("// %sLookup: %d bytes\n", name, ni) |
| fmt.Printf("// Block 0 is the null block.\n") |
| fmt.Printf("var %sLookup = [%d]uint8 {", name, ni) |
| printLookupBlock(0, newNode(), 0) |
| printLookupBlock(1, newNode(), 0) |
| printLookupBlock(2, newNode(), 0) |
| printLookupBlock(3, t, 0xC0) |
| for i := 4; i < len(index.lookupBlocks); i++ { |
| printLookupBlock(i, index.lookupBlocks[i], 0x80) |
| } |
| fmt.Print("\n}\n\n") |
| fmt.Printf("var %sTrie = trie{ %sLookup[:], %sValues[:] }\n\n", name, name, name) |
| return nv*2 + ni |
| } |