1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// +build ignore
6
7// This program generates the trie for width operations. The generated table
8// includes width category information as well as the normalization mappings.
9package main
10
11import (
12	"bytes"
13	"fmt"
14	"io"
15	"log"
16	"math"
17	"unicode/utf8"
18
19	"golang.org/x/text/internal/gen"
20	"golang.org/x/text/internal/triegen"
21)
22
23// See gen_common.go for flags.
24
25func main() {
26	gen.Init()
27	genTables()
28	genTests()
29	gen.Repackage("gen_trieval.go", "trieval.go", "width")
30	gen.Repackage("gen_common.go", "common_test.go", "width")
31}
32
33func genTables() {
34	t := triegen.NewTrie("width")
35	// fold and inverse mappings. See mapComment for a description of the format
36	// of each entry. Add dummy value to make an index of 0 mean no mapping.
37	inverse := [][4]byte{{}}
38	mapping := map[[4]byte]int{[4]byte{}: 0}
39
40	getWidthData(func(r rune, tag elem, alt rune) {
41		idx := 0
42		if alt != 0 {
43			var buf [4]byte
44			buf[0] = byte(utf8.EncodeRune(buf[1:], alt))
45			s := string(r)
46			buf[buf[0]] ^= s[len(s)-1]
47			var ok bool
48			if idx, ok = mapping[buf]; !ok {
49				idx = len(mapping)
50				if idx > math.MaxUint8 {
51					log.Fatalf("Index %d does not fit in a byte.", idx)
52				}
53				mapping[buf] = idx
54				inverse = append(inverse, buf)
55			}
56		}
57		t.Insert(r, uint64(tag|elem(idx)))
58	})
59
60	w := &bytes.Buffer{}
61	gen.WriteUnicodeVersion(w)
62
63	sz, err := t.Gen(w)
64	if err != nil {
65		log.Fatal(err)
66	}
67
68	sz += writeMappings(w, inverse)
69
70	fmt.Fprintf(w, "// Total table size %d bytes (%dKiB)\n", sz, sz/1024)
71
72	gen.WriteVersionedGoFile(*outputFile, "width", w.Bytes())
73}
74
75const inverseDataComment = `
76// inverseData contains 4-byte entries of the following format:
77//   <length> <modified UTF-8-encoded rune> <0 padding>
78// The last byte of the UTF-8-encoded rune is xor-ed with the last byte of the
79// UTF-8 encoding of the original rune. Mappings often have the following
80// pattern:
81//   Ａ -> A  (U+FF21 -> U+0041)
82//   Ｂ -> B  (U+FF22 -> U+0042)
83//   ...
84// By xor-ing the last byte the same entry can be shared by many mappings. This
85// reduces the total number of distinct entries by about two thirds.
86// The resulting entry for the aforementioned mappings is
87//   { 0x01, 0xE0, 0x00, 0x00 }
88// Using this entry to map U+FF21 (UTF-8 [EF BC A1]), we get
89//   E0 ^ A1 = 41.
90// Similarly, for U+FF22 (UTF-8 [EF BC A2]), we get
91//   E0 ^ A2 = 42.
92// Note that because of the xor-ing, the byte sequence stored in the entry is
93// not valid UTF-8.`
94
95func writeMappings(w io.Writer, data [][4]byte) int {
96	fmt.Fprintln(w, inverseDataComment)
97	fmt.Fprintf(w, "var inverseData = [%d][4]byte{\n", len(data))
98	for _, x := range data {
99		fmt.Fprintf(w, "{ 0x%02x, 0x%02x, 0x%02x, 0x%02x },\n", x[0], x[1], x[2], x[3])
100	}
101	fmt.Fprintln(w, "}")
102	return len(data) * 4
103}
104
105func genTests() {
106	w := &bytes.Buffer{}
107	fmt.Fprintf(w, "\nvar mapRunes = map[rune]struct{r rune; e elem}{\n")
108	getWidthData(func(r rune, tag elem, alt rune) {
109		if alt != 0 {
110			fmt.Fprintf(w, "\t0x%X: {0x%X, 0x%X},\n", r, alt, tag)
111		}
112	})
113	fmt.Fprintln(w, "}")
114	gen.WriteGoFile("runes_test.go", "width", w.Bytes())
115}
116