1// Copyright 2013 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//go:build ignore
6// +build ignore
7
8package main
9
10// This program generates tables.go:
11//	go run maketables.go | gofmt > tables.go
12
13// TODO: Emoji extensions?
14// https://www.unicode.org/faq/emoji_dingbats.html
15// https://www.unicode.org/Public/UNIDATA/EmojiSources.txt
16
17import (
18	"bufio"
19	"fmt"
20	"log"
21	"net/http"
22	"sort"
23	"strings"
24)
25
26type entry struct {
27	jisCode, table int
28}
29
30func main() {
31	fmt.Printf("// generated by go run maketables.go; DO NOT EDIT\n\n")
32	fmt.Printf("// Package japanese provides Japanese encodings such as EUC-JP and Shift JIS.\n")
33	fmt.Printf(`package japanese // import "golang.org/x/text/encoding/japanese"` + "\n\n")
34
35	reverse := [65536]entry{}
36	for i := range reverse {
37		reverse[i].table = -1
38	}
39
40	tables := []struct {
41		url  string
42		name string
43	}{
44		{"http://encoding.spec.whatwg.org/index-jis0208.txt", "0208"},
45		{"http://encoding.spec.whatwg.org/index-jis0212.txt", "0212"},
46	}
47	for i, table := range tables {
48		res, err := http.Get(table.url)
49		if err != nil {
50			log.Fatalf("%q: Get: %v", table.url, err)
51		}
52		defer res.Body.Close()
53
54		mapping := [65536]uint16{}
55
56		scanner := bufio.NewScanner(res.Body)
57		for scanner.Scan() {
58			s := strings.TrimSpace(scanner.Text())
59			if s == "" || s[0] == '#' {
60				continue
61			}
62			x, y := 0, uint16(0)
63			if _, err := fmt.Sscanf(s, "%d 0x%x", &x, &y); err != nil {
64				log.Fatalf("%q: could not parse %q", table.url, s)
65			}
66			if x < 0 || 120*94 <= x {
67				log.Fatalf("%q: JIS code %d is out of range", table.url, x)
68			}
69			mapping[x] = y
70			if reverse[y].table == -1 {
71				reverse[y] = entry{jisCode: x, table: i}
72			}
73		}
74		if err := scanner.Err(); err != nil {
75			log.Fatalf("%q: scanner error: %v", table.url, err)
76		}
77
78		fmt.Printf("// jis%sDecode is the decoding table from JIS %s code to Unicode.\n// It is defined at %s\n",
79			table.name, table.name, table.url)
80		fmt.Printf("var jis%sDecode = [...]uint16{\n", table.name)
81		for i, m := range mapping {
82			if m != 0 {
83				fmt.Printf("\t%d: 0x%04X,\n", i, m)
84			}
85		}
86		fmt.Printf("}\n\n")
87	}
88
89	// Any run of at least separation continuous zero entries in the reverse map will
90	// be a separate encode table.
91	const separation = 1024
92
93	intervals := []interval(nil)
94	low, high := -1, -1
95	for i, v := range reverse {
96		if v.table == -1 {
97			continue
98		}
99		if low < 0 {
100			low = i
101		} else if i-high >= separation {
102			if high >= 0 {
103				intervals = append(intervals, interval{low, high})
104			}
105			low = i
106		}
107		high = i + 1
108	}
109	if high >= 0 {
110		intervals = append(intervals, interval{low, high})
111	}
112	sort.Sort(byDecreasingLength(intervals))
113
114	fmt.Printf("const (\n")
115	fmt.Printf("\tjis0208    = 1\n")
116	fmt.Printf("\tjis0212    = 2\n")
117	fmt.Printf("\tcodeMask   = 0x7f\n")
118	fmt.Printf("\tcodeShift  = 7\n")
119	fmt.Printf("\ttableShift = 14\n")
120	fmt.Printf(")\n\n")
121
122	fmt.Printf("const numEncodeTables = %d\n\n", len(intervals))
123	fmt.Printf("// encodeX are the encoding tables from Unicode to JIS code,\n")
124	fmt.Printf("// sorted by decreasing length.\n")
125	for i, v := range intervals {
126		fmt.Printf("// encode%d: %5d entries for runes in [%5d, %5d).\n", i, v.len(), v.low, v.high)
127	}
128	fmt.Printf("//\n")
129	fmt.Printf("// The high two bits of the value record whether the JIS code comes from the\n")
130	fmt.Printf("// JIS0208 table (high bits == 1) or the JIS0212 table (high bits == 2).\n")
131	fmt.Printf("// The low 14 bits are two 7-bit unsigned integers j1 and j2 that form the\n")
132	fmt.Printf("// JIS code (94*j1 + j2) within that table.\n")
133	fmt.Printf("\n")
134
135	for i, v := range intervals {
136		fmt.Printf("const encode%dLow, encode%dHigh = %d, %d\n\n", i, i, v.low, v.high)
137		fmt.Printf("var encode%d = [...]uint16{\n", i)
138		for j := v.low; j < v.high; j++ {
139			x := reverse[j]
140			if x.table == -1 {
141				continue
142			}
143			fmt.Printf("\t%d - %d: jis%s<<14 | 0x%02X<<7 | 0x%02X,\n",
144				j, v.low, tables[x.table].name, x.jisCode/94, x.jisCode%94)
145		}
146		fmt.Printf("}\n\n")
147	}
148}
149
150// interval is a half-open interval [low, high).
151type interval struct {
152	low, high int
153}
154
155func (i interval) len() int { return i.high - i.low }
156
157// byDecreasingLength sorts intervals by decreasing length.
158type byDecreasingLength []interval
159
160func (b byDecreasingLength) Len() int           { return len(b) }
161func (b byDecreasingLength) Less(i, j int) bool { return b[i].len() > b[j].len() }
162func (b byDecreasingLength) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
163