text: // Copyright 2013 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.
  
  // +build ignore
  
  package main
  
  // This program generates tables.go:
  //	go run maketables.go | gofmt > tables.go
  
  // TODO: Emoji extensions?
  // https://www.unicode.org/faq/emoji_dingbats.html
  // https://www.unicode.org/Public/UNIDATA/EmojiSources.txt
  
  import (
  	"bufio"
  	"fmt"
  	"log"
  	"net/http"
  	"sort"
  	"strings"
  )
  
  type entry struct {
  	jisCode, table int
  }
  
  func main() {
  	fmt.Printf("// generated by go run maketables.go; DO NOT EDIT\n\n")
  	fmt.Printf("// Package japanese provides Japanese encodings such as EUC-JP and Shift JIS.\n")
  	fmt.Printf(`package japanese // import "golang.org/x/text/encoding/japanese"` + "\n\n")
  
  	reverse := [65536]entry{}
  	for i := range reverse {
  		reverse[i].table = -1
  	}
  
  	tables := []struct {
  		url  string
  		name string
  	}{
  		{"http://encoding.spec.whatwg.org/index-jis0208.txt", "0208"},
  		{"http://encoding.spec.whatwg.org/index-jis0212.txt", "0212"},
  	}
  	for i, table := range tables {
  		res, err := http.Get(table.url)
  		if err != nil {
  			log.Fatalf("%q: Get: %v", table.url, err)
  		}
  		defer res.Body.Close()
  
  		mapping := [65536]uint16{}
  
  		scanner := bufio.NewScanner(res.Body)
  		for scanner.Scan() {
  			s := strings.TrimSpace(scanner.Text())
  			if s == "" || s[0] == '#' {
  				continue
  			}
  			x, y := 0, uint16(0)
  			if _, err := fmt.Sscanf(s, "%d 0x%x", &x, &y); err != nil {
  				log.Fatalf("%q: could not parse %q", table.url, s)
  			}
  			if x < 0 || 120*94 <= x {
  				log.Fatalf("%q: JIS code %d is out of range", table.url, x)
  			}
  			mapping[x] = y
  			if reverse[y].table == -1 {
  				reverse[y] = entry{jisCode: x, table: i}
  			}
  		}
  		if err := scanner.Err(); err != nil {
  			log.Fatalf("%q: scanner error: %v", table.url, err)
  		}
  
  		fmt.Printf("// jis%sDecode is the decoding table from JIS %s code to Unicode.\n// It is defined at %s\n",
  			table.name, table.name, table.url)
  		fmt.Printf("var jis%sDecode = [...]uint16{\n", table.name)
  		for i, m := range mapping {
  			if m != 0 {
  				fmt.Printf("\t%d: 0x%04X,\n", i, m)
  			}
  		}
  		fmt.Printf("}\n\n")
  	}
  
  	// Any run of at least separation continuous zero entries in the reverse map will
  	// be a separate encode table.
  	const separation = 1024
  
  	intervals := []interval(nil)
  	low, high := -1, -1
  	for i, v := range reverse {
  		if v.table == -1 {
  			continue
  		}
  		if low < 0 {
  			low = i
  		} else if i-high >= separation {
  			if high >= 0 {
  				intervals = append(intervals, interval{low, high})
  			}
  			low = i
  		}
  		high = i + 1
  	}
  	if high >= 0 {
  		intervals = append(intervals, interval{low, high})
  	}
  	sort.Sort(byDecreasingLength(intervals))
  
  	fmt.Printf("const (\n")
  	fmt.Printf("\tjis0208    = 1\n")
  	fmt.Printf("\tjis0212    = 2\n")
  	fmt.Printf("\tcodeMask   = 0x7f\n")
  	fmt.Printf("\tcodeShift  = 7\n")
  	fmt.Printf("\ttableShift = 14\n")
  	fmt.Printf(")\n\n")
  
  	fmt.Printf("const numEncodeTables = %d\n\n", len(intervals))
  	fmt.Printf("// encodeX are the encoding tables from Unicode to JIS code,\n")
  	fmt.Printf("// sorted by decreasing length.\n")
  	for i, v := range intervals {
  		fmt.Printf("// encode%d: %5d entries for runes in [%5d, %5d).\n", i, v.len(), v.low, v.high)
  	}
  	fmt.Printf("//\n")
  	fmt.Printf("// The high two bits of the value record whether the JIS code comes from the\n")
  	fmt.Printf("// JIS0208 table (high bits == 1) or the JIS0212 table (high bits == 2).\n")
  	fmt.Printf("// The low 14 bits are two 7-bit unsigned integers j1 and j2 that form the\n")
  	fmt.Printf("// JIS code (94*j1 + j2) within that table.\n")
  	fmt.Printf("\n")
  
  	for i, v := range intervals {
  		fmt.Printf("const encode%dLow, encode%dHigh = %d, %d\n\n", i, i, v.low, v.high)
  		fmt.Printf("var encode%d = [...]uint16{\n", i)
  		for j := v.low; j < v.high; j++ {
  			x := reverse[j]
  			if x.table == -1 {
  				continue
  			}
  			fmt.Printf("\t%d - %d: jis%s<<14 | 0x%02X<<7 | 0x%02X,\n",
  				j, v.low, tables[x.table].name, x.jisCode/94, x.jisCode%94)
  		}
  		fmt.Printf("}\n\n")
  	}
  }
  
  // interval is a half-open interval [low, high).
  type interval struct {
  	low, high int
  }
  
  func (i interval) len() int { return i.high - i.low }
  
  // byDecreasingLength sorts intervals by decreasing length.
  type byDecreasingLength []interval
  
  func (b byDecreasingLength) Len() int           { return len(b) }
  func (b byDecreasingLength) Less(i, j int) bool { return b[i].len() > b[j].len() }
  func (b byDecreasingLength) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
  