1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
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
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
|
<pre>Network Working Group M. Ohta
Request for Comments: 1554 Tokyo Institute of Technology
Category: Informational K. Handa
ETL
December 1993
<span class="h1">ISO-2022-JP-2: Multilingual Extension of ISO-2022-JP</span>
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Introduction
This memo describes a text encoding scheme: "ISO-2022-JP-2", which is
used experimentally for electronic mail [<a href="./rfc822" title=""Standard for the Format of ARPA Internet Text Messages"">RFC822</a>] and network news
[<a href="./rfc1036" title=""Standard for Interchange of USENET Messages"">RFC1036</a>] messages in several Japanese networks. The encoding is a
multilingual extension of "ISO-2022-JP", the existing encoding for
Japanese [<a href="#ref-2022JP" title=""Japanese Character Encoding for Internet Messages"">2022JP</a>]. The encoding is supported by an Emacs based
multilingual text editor: MULE [<a href="#ref-MULE" title=""Mule: MULtilingual Enhancement to GNU Emacs"">MULE</a>].
The name, "ISO-2022-JP-2", is intended to be used in the "charset"
parameter field of MIME headers (see [<a href="#ref-MIME1" title=""MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies"">MIME1</a>] and [<a href="#ref-MIME2" title=""MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text"">MIME2</a>]).
Description
The text with "ISO-2022-JP-2" starts in ASCII [<a href="#ref-ASCII" title=""Coded character set -- 7-bit American national standard code for information interchange"">ASCII</a>], and switches
to other character sets of ISO 2022 [<a href="#ref-ISO2022" title=""Information processing -- ISO 7-bit and 8-bit coded character sets -- Code extension techniques"">ISO2022</a>] through limited
combinations of escape sequences. All the characters are encoded
with 7 bits only.
At the beginning of text, the existence of an announcer sequence:
"ESC 2/0 4/1 ESC 2/0 4/6 ESC 2/0 5/10" is (though omitted) assumed.
Thus, characters of 94 character sets are designated to G0 and
invoked as GL. C1 control characters are represented with 7 bits.
Characters of 96 character sets are designated to G2 and invoked with
SS2 (single shift two, "ESC 4/14" or "ESC N").
For example, the escape sequence "ESC 2/4 2/8 4/3" or "ESC $ ( C"
indicates that the bytes following the escape sequence are Korean KSC
characters, which are encoded in two bytes each. The escape sequence
"ESC 2/14 4/1" or "ESC . A" indicates that ISO 8859-1 is designated
to G2. After the designation, the single shifted sequence "ESC 4/14
4/1" or "ESC N A" is interpreted to represent a character "A with
acute".
<span class="grey">Ohta & Handa [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc1554">RFC 1554</a> Multilingual Extension of ISO-2022-JP December 1993</span>
The following table gives the escape sequences and the character sets
used in "ISO-2022-JP-2" messages. The reg# is the registration number
in ISO's registry [<a href="#ref-ISOREG" title=""International Register of Coded Character Sets To Be Used With Escape Sequences"">ISOREG</a>].
94 character sets
reg# character set ESC sequence designated to
------------------------------------------------------------------
6 ASCII ESC 2/8 4/2 ESC ( B G0
42 JIS X 0208-1978 ESC 2/4 4/0 ESC $ @ G0
87 JIS X 0208-1983 ESC 2/4 4/2 ESC $ B G0
14 JIS X 0201-Roman ESC 2/8 4/10 ESC ( J G0
58 GB2312-1980 ESC 2/4 4/1 ESC $ A G0
149 KSC5601-1987 ESC 2/4 2/8 4/3 ESC $ ( C G0
159 JIS X 0212-1990 ESC 2/4 2/8 4/4 ESC $ ( D G0
96 character sets
reg# character set ESC sequence designated to
------------------------------------------------------------------
100 ISO8859-1 ESC 2/14 4/1 ESC . A G2
126 ISO8859-7(Greek) ESC 2/14 4/6 ESC . F G2
For further information about the character sets and the escape
sequences, see [<a href="#ref-ISO2022" title=""Information processing -- ISO 7-bit and 8-bit coded character sets -- Code extension techniques"">ISO2022</a>] and [<a href="#ref-ISOREG" title=""International Register of Coded Character Sets To Be Used With Escape Sequences"">ISOREG</a>].
If there is any G0 designation in text, there must be a switch to
ASCII or to JIS X 0201-Roman before a space character (but not
necessarily before "ESC 4/14 2/0" or "ESC N ' '") or control
characters such as tab or CRLF. This means that the next line starts
in the character set that was switched to before the end of the
previous line. Though the designation to JIS X 0201-Roman is allowed
for backward compatibility to "ISO-2022-JP", its use is discouraged.
Applications such as pagers and editors which randomly seek within a
text file encoded with "ISO-2022-JP-2" may assume that all the lines
begin with ASCII, not with JIS X 0201-Roman.
At the beginning of a line, information on G2 designation of the
previous line is cleared. New designation must be given before a
character in 96 character sets is used in the line.
The text must end in ASCII designated to G0.
As the "ISO-2022-JP", and thus, "ISO-2022-JP-2", is designed to
represent English and modern Japanese, left-to-right directionality
is assumed if the text is displayed horizontally.
Users of "ISO-2022-JP-2" must be aware that some common transport
such as old Bnews can not relay a 7-bit value 7/15 (decimal 127),
which is used to encode, say, "y with diaeresis" of ISO 8859-1.
<span class="grey">Ohta & Handa [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc1554">RFC 1554</a> Multilingual Extension of ISO-2022-JP December 1993</span>
Other restrictions are given in the Formal Syntax section below.
Formal Syntax
The notational conventions used here are identical to those used in
STD 11, <a href="./rfc822">RFC 822</a> [<a href="./rfc822" title=""Standard for the Format of ARPA Internet Text Messages"">RFC822</a>].
The * (asterisk) convention is as follows:
l*m something
meaning at least l and at most m somethings, with l and m taking
default values of 0 and infinity, respectively.
message = headers 1*(CRLF text)
; see also [<a href="#ref-MIME1" title=""MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies"">MIME1</a>] "body-part"
; note: must end in ASCII
text = *(single-byte-char /
g2-desig-seq /
single-shift-char)
[*segment
reset-seq
*(single-byte-char /
g2-desig-seq /
single-shift-char ) ]
; note: g2-desig-seq must
; precede single-shift-char
headers = <see [<a href="./rfc822" title=""Standard for the Format of ARPA Internet Text Messages"">RFC822</a>] "fields" and [<a href="#ref-MIME1" title=""MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies"">MIME1</a>] "body-part">
segment = single-byte-segment / double-byte-segment
single-byte-segment = single-byte-seq
*(single-byte-char /
g2-desig-seq /
single-shift-char )
double-byte-segment = double-byte-seq
*((one-of-94 one-of-94) /
g2-desig-seq /
single-shift-char )
reset-seq = ESC "(" ( "B" / "J" )
single-byte-seq = ESC "(" ( "B" / "J" )
double-byte-seq = (ESC "$" ( "@" / "A" / "B" )) /
<span class="grey">Ohta & Handa [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc1554">RFC 1554</a> Multilingual Extension of ISO-2022-JP December 1993</span>
(ESC "$" "(" ( "C" / "D" ))
g2-desig-seq = ESC "." ( "A" / "F" )
single-shift-seq = ESC "N"
single-shift-char = single-shift-seq one-of-96
CRLF = CR LF
; ( Octal, Decimal.)
ESC = <ISO 2022 ESC, escape> ; ( 33, 27.)
SI = <ISO 2022 SI, shift-in> ; ( 17, 15.)
SO = <ISO 2022 SO, shift-out> ; ( 16, 14.)
CR = <ASCII CR, carriage return>; ( 15, 13.)
LF = <ASCII LF, linefeed> ; ( 12, 10.)
one-of-94 = <any one of 94 values> ; (41-176, 33.-126.)
one-of-96 = <any one of 96 values> ; (40-177, 32.-127.)
7BIT = <any 7-bit value> ; ( 0-177, 0.-127.)
single-byte-char = <any 7BIT, including bare CR & bare LF, but NOT
including CRLF, and not including ESC, SI, SO>
MIME Considerations
The name given to the character encoding is "ISO-2022-JP-2". This
name is intended to be used in MIME messages as follows:
Content-Type: text/plain; charset=iso-2022-jp-2
The "ISO-2022-JP-2" encoding is already in 7-bit form, so it is not
necessary to use a Content-Transfer-Encoding header. It should be
noted that applying the Base64 or Quoted-Printable encoding will
render the message unreadable in non-MIME-compliant software.
"ISO-2022-JP-2" may also be used in MIME headers. Both "B" and "Q"
encoding could be useful with "ISO-2022-JP-2" text.
<span class="grey">Ohta & Handa [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc1554">RFC 1554</a> Multilingual Extension of ISO-2022-JP December 1993</span>
References
[<a id="ref-ASCII">ASCII</a>] American National Standards Institute, "Coded character set
-- 7-bit American national standard code for information
interchange", ANSI X3.4-1986.
[<a id="ref-ISO2022">ISO2022</a>] International Organization for Standardization (ISO),
"Information processing -- ISO 7-bit and 8-bit coded
character sets -- Code extension techniques",
International Standard, Ref. No. ISO 2022-1986 (E).
[<a id="ref-ISOREG">ISOREG</a>] International Organization for Standardization (ISO),
"International Register of Coded Character Sets To Be Used
With Escape Sequences".
[<a id="ref-MIME1">MIME1</a>] Borenstein, N., and N. Freed, "MIME (Multipurpose Internet
Mail Extensions) Part One: Mechanisms for Specifying and
Describing the Format of Internet Message Bodies", <a href="./rfc1521">RFC 1521</a>,
September 1993.
[<a id="ref-MIME2">MIME2</a>] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
Two: Message Header Extensions for Non-ASCII Text", <a href="./rfc1522">RFC 1522</a>,
September 1993.
[<a id="ref-RFC822">RFC822</a>] Crocker, D., "Standard for the Format of ARPA Internet Text
Messages", STD 11, <a href="./rfc1522">RFC 1522</a>, UDEL, August 1982.
[<a id="ref-RFC1036">RFC1036</a>] Horton M., and R. Adams, "Standard for Interchange of
USENET Messages", <a href="./rfc1036">RFC 1036</a>, AT&T Bell Laboratories, Center
for Seismic Studies, December 1987.
[<a id="ref-2022JP">2022JP</a>] Murai, J., Crispin, M., and E. van der Poel, "Japanese
Character Encoding for Internet Messages", <a href="./rfc1468">RFC 1468</a>, June
1993.
[<a id="ref-MULE">MULE</a>] Nishikimi, M., Handa, K., and S. Tomura, "Mule: MULtilingual
Enhancement to GNU Emacs", Proc. of INET'93, August, 1993.
Acknowledgements
This memo is the result of discussion between various people in a
news group: fj.kanji and is reviewed by a mailing list: jp-msg
@iij.ad.jp. The Authors wish to thank in particular Prof. Eiichi
Wada for his suggestions based on profound knowledge in ISO 2022 and
related standards.
<span class="grey">Ohta & Handa [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc1554">RFC 1554</a> Multilingual Extension of ISO-2022-JP December 1993</span>
Security Considerations
Security issues are not discussed in this memo.
Authors' Addresses
Masataka Ohta
Tokyo Institute of Technology
2-12-1, O-okayama, Meguro-ku,
Tokyo 152, JAPAN
Phone: +81-3-5499-7084
Fax: +81-3-3729-1940
EMail: mohta@cc.titech.ac.jp
Ken'ichi Handa
Electrotechnical Laboratory
Umezono 1-1-4, Tsukuba,
Ibaraki 305, JAPAN
Phone: +81-298-58-5916
Fax: +81-298-58-5918
EMail: handa@etl.go.jp
Ohta & Handa [Page 6]
</pre>
|
