1 files changed, 211 insertions, 0 deletions
diff --git a/src/pkg/exp/norm/triegen.go b/src/pkg/exp/norm/triegen.go
new file mode 100644
index 000000000..2b7eeee17
--- /dev/null
+++ b/src/pkg/exp/norm/triegen.go
@@ -0,0 +1,211 @@
+// 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
+}