maketables.go

Documentation: golang.org/x/text/encoding/traditionalchinese

     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  
     7  package main
     8  
     9  // This program generates tables.go:
    10  //	go run maketables.go | gofmt > tables.go
    11  
    12  import (
    13  	"bufio"
    14  	"fmt"
    15  	"log"
    16  	"net/http"
    17  	"sort"
    18  	"strings"
    19  )
    20  
    21  func main() {
    22  	fmt.Printf("// generated by go run maketables.go; DO NOT EDIT\n\n")
    23  	fmt.Printf("// Package traditionalchinese provides Traditional Chinese encodings such as Big5.\n")
    24  	fmt.Printf(`package traditionalchinese // import "golang.org/x/text/encoding/traditionalchinese"` + "\n\n")
    25  
    26  	res, err := http.Get("http://encoding.spec.whatwg.org/index-big5.txt")
    27  	if err != nil {
    28  		log.Fatalf("Get: %v", err)
    29  	}
    30  	defer res.Body.Close()
    31  
    32  	mapping := [65536]uint32{}
    33  	reverse := [65536 * 4]uint16{}
    34  
    35  	scanner := bufio.NewScanner(res.Body)
    36  	for scanner.Scan() {
    37  		s := strings.TrimSpace(scanner.Text())
    38  		if s == "" || s[0] == '#' {
    39  			continue
    40  		}
    41  		x, y := uint16(0), uint32(0)
    42  		if _, err := fmt.Sscanf(s, "%d 0x%x", &x, &y); err != nil {
    43  			log.Fatalf("could not parse %q", s)
    44  		}
    45  		if x < 0 || 126*157 <= x {
    46  			log.Fatalf("Big5 code %d is out of range", x)
    47  		}
    48  		mapping[x] = y
    49  
    50  		// The WHATWG spec http://encoding.spec.whatwg.org/#indexes says that
    51  		// "The index pointer for code point in index is the first pointer
    52  		// corresponding to code point in index", which would normally mean
    53  		// that the code below should be guarded by "if reverse[y] == 0", but
    54  		// last instead of first seems to match the behavior of
    55  		// "iconv -f UTF-8 -t BIG5". For example, U+8005 者 occurs twice in
    56  		// http://encoding.spec.whatwg.org/index-big5.txt, as index 2148
    57  		// (encoded as "\x8e\xcd") and index 6543 (encoded as "\xaa\xcc")
    58  		// and "echo 者 | iconv -f UTF-8 -t BIG5 | xxd" gives "\xaa\xcc".
    59  		c0, c1 := x/157, x%157
    60  		if c1 < 0x3f {
    61  			c1 += 0x40
    62  		} else {
    63  			c1 += 0x62
    64  		}
    65  		reverse[y] = (0x81+c0)<<8 | c1
    66  	}
    67  	if err := scanner.Err(); err != nil {
    68  		log.Fatalf("scanner error: %v", err)
    69  	}
    70  
    71  	fmt.Printf("// decode is the decoding table from Big5 code to Unicode.\n")
    72  	fmt.Printf("// It is defined at http://encoding.spec.whatwg.org/index-big5.txt\n")
    73  	fmt.Printf("var decode = [...]uint32{\n")
    74  	for i, v := range mapping {
    75  		if v != 0 {
    76  			fmt.Printf("\t%d: 0x%08X,\n", i, v)
    77  		}
    78  	}
    79  	fmt.Printf("}\n\n")
    80  
    81  	// Any run of at least separation continuous zero entries in the reverse map will
    82  	// be a separate encode table.
    83  	const separation = 1024
    84  
    85  	intervals := []interval(nil)
    86  	low, high := -1, -1
    87  	for i, v := range reverse {
    88  		if v == 0 {
    89  			continue
    90  		}
    91  		if low < 0 {
    92  			low = i
    93  		} else if i-high >= separation {
    94  			if high >= 0 {
    95  				intervals = append(intervals, interval{low, high})
    96  			}
    97  			low = i
    98  		}
    99  		high = i + 1
   100  	}
   101  	if high >= 0 {
   102  		intervals = append(intervals, interval{low, high})
   103  	}
   104  	sort.Sort(byDecreasingLength(intervals))
   105  
   106  	fmt.Printf("const numEncodeTables = %d\n\n", len(intervals))
   107  	fmt.Printf("// encodeX are the encoding tables from Unicode to Big5 code,\n")
   108  	fmt.Printf("// sorted by decreasing length.\n")
   109  	for i, v := range intervals {
   110  		fmt.Printf("// encode%d: %5d entries for runes in [%6d, %6d).\n", i, v.len(), v.low, v.high)
   111  	}
   112  	fmt.Printf("\n")
   113  
   114  	for i, v := range intervals {
   115  		fmt.Printf("const encode%dLow, encode%dHigh = %d, %d\n\n", i, i, v.low, v.high)
   116  		fmt.Printf("var encode%d = [...]uint16{\n", i)
   117  		for j := v.low; j < v.high; j++ {
   118  			x := reverse[j]
   119  			if x == 0 {
   120  				continue
   121  			}
   122  			fmt.Printf("\t%d-%d: 0x%04X,\n", j, v.low, x)
   123  		}
   124  		fmt.Printf("}\n\n")
   125  	}
   126  }
   127  
   128  // interval is a half-open interval [low, high).
   129  type interval struct {
   130  	low, high int
   131  }
   132  
   133  func (i interval) len() int { return i.high - i.low }
   134  
   135  // byDecreasingLength sorts intervals by decreasing length.
   136  type byDecreasingLength []interval
   137  
   138  func (b byDecreasingLength) Len() int           { return len(b) }
   139  func (b byDecreasingLength) Less(i, j int) bool { return b[i].len() > b[j].len() }
   140  func (b byDecreasingLength) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
   141
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