Convert the box drawing characters of PC codepage 437 to Unicode

437toutf8.go

/*
Convert the box drawing characters of PC codepage 437 to Unicode
and encode as UTF-8.

If no argument is provided then program reads from stdin. These are equivalent:
	437toutf8 437in.txt > utf8out.txt
	437toutf8 < 437in.txt > utf8out.txt
*/

package main

import (
	"bufio"
	"log"
	"os"
)

// Just the box drawing characters for now
var cp437 = map[byte]rune{
	169: '⌐',
	170: '¬',
	174: '«',
	175: '»',
	176: '░',
	177: '▒',
	178: '▓',
	179: '│',
	180: '┤',
	181: '╡',
	182: '╢',
	183: '╖',
	184: '╕',
	185: '╣',
	186: '║',
	187: '╗',
	188: '╝',
	189: '╜',
	190: '╛',
	191: '┐',
	192: '└',
	193: '┴',
	194: '┬',
	195: '├',
	196: '─',
	197: '┼',
	198: '╞',
	199: '╟',
	200: '╚',
	201: '╔',
	202: '╩',
	203: '╦',
	204: '╠',
	205: '═',
	206: '╬',
	207: '╧',
	208: '╨',
	209: '╤',
	210: '╥',
	211: '╙',
	212: '╘',
	213: '╒',
	214: '╓',
	215: '╫',
	216: '╪',
	217: '┘',
	218: '┌',
	219: '█',
	220: '▄',
	221: '▌',
	222: '▐',
	223: '▀',
	254: '■',
}

func main() {
	r := bufio.NewReader(os.Stdin)
	if len(os.Args) > 1 {
		rf, err := os.Open(os.Args[1])
		if err != nil {
			log.Fatal(err)
		}
		r = bufio.NewReader(rf)
	}
	w := bufio.NewWriter(os.Stdout)

	for {
		if b, err := r.ReadByte(); err == nil {
			if r, ok := cp437[b]; ok {
				w.WriteRune(r)
			} else {
				w.WriteByte(b)
			}
		} else {
			break
		}
	}
	w.Flush()
}