Encoding — 符号化法

8.1.1. ~UTF-8~decoder

各［ `UTF-8$n の`~decoder$ ］には、次のものが結付けられる ⇒＃ `~UTF-8~cp@（初期~時 0 ）, `~UTF-8出現~byte数@（初期~時 0 ）, `~UTF-8要~byte数@（初期~時 0 ）, `~UTF-8下限@（初期~時 `80^X ）, `~UTF-8上限@（初期~時 `BF^X ） ◎ UTF-8’s decoder’s has an associated UTF-8 code point, UTF-8 bytes seen, and UTF-8 bytes needed (all initially 0), a UTF-8 lower boundary (initially 0x80), and a UTF-8 upper boundary (initially 0xBF).

`UTF-8$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ UTF-8’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］~AND［ `~UTF-8要~byte数$ ~NEQ 0 ］ ⇒＃ `~UTF-8要~byte数$ ~SET 0； ~RET `~error$ ◎ If byte is end-of-stream and UTF-8 bytes needed is not 0, set UTF-8 bytes needed to 0 and return error.
2. ~IF［ %~byte ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If byte is end-of-stream, return finished.

3. ~IF［ `~UTF-8要~byte数$ ~EQ 0 ］： ◎ If UTF-8 bytes needed is 0, based on byte:

   1. %~byte に応じて： ◎ ↑

      `00^X 〜 `7F^X

      ~RET ~cp [ %~byte ] ◎ Return a code point whose value is byte.

      `C2^X 〜 `DF^X

      1. `~UTF-8要~byte数$ ~SET 1 ◎ Set UTF-8 bytes needed to 1.
      2. `~UTF-8~cp$ ~SET %~byte ~bAND `1F^X （ %~byte の下位 5 ~bit ） ◎ Set UTF-8 code point to byte & 0x1F. ◎ The five least significant bits of byte.

      `E0^X 〜 `EF^X

      1. ~IF［ %~byte ~EQ `E0^X ］ ⇒ `~UTF-8下限$ ~SET `A0^X ◎ If byte is 0xE0, set UTF-8 lower boundary to 0xA0.
      2. ~IF［ %~byte ~EQ `ED^X ］ ⇒ `~UTF-8上限$ ~SET `9F^X ◎ If byte is 0xED, set UTF-8 upper boundary to 0x9F.
      3. `~UTF-8要~byte数$ ~SET 2 ◎ Set UTF-8 bytes needed to 2.
      4. `~UTF-8~cp$ ~SET %~byte ~bAND `F^X （ %~byte の下位 4 ~bit ） ◎ Set UTF-8 code point to byte & 0xF. ◎ The four least significant bits of byte.

      `F0^X 〜 `F4^X

      1. ~IF［ %~byte ~EQ `F0^X ］ ⇒ `~UTF-8下限$ ~SET `90^X ◎ If byte is 0xF0, set UTF-8 lower boundary to 0x90.
      2. ~IF［ %~byte ~EQ `F4^X ］ ⇒ `~UTF-8上限$ ~SET `8F^X ◎ If byte is 0xF4, set UTF-8 upper boundary to 0x8F.
      3. `~UTF-8要~byte数$ ~SET 3 ◎ Set UTF-8 bytes needed to 3.
      4. `~UTF-8~cp$ ~SET %~byte ~bAND `7^X （ %~byte の下位 3 ~bit ） ◎ Set UTF-8 code point to byte & 0x7. ◎ The three least significant bits of byte.

      ~OTHER◎ Otherwise

      ~RET `~error$ ◎ Return error.

   2. ~RET `継続$ ◎ Return continue.

4. ~IF［ %~byte ~NIN { `~UTF-8下限$ 〜 `~UTF-8上限$ } ］： ◎ If byte is not in the range UTF-8 lower boundary to UTF-8 upper boundary, inclusive, then:

   1. ( `~UTF-8~cp$, `~UTF-8要~byte数$, `~UTF-8出現~byte数$ ) ~SET ( 0, 0, 0 ) ◎ Set UTF-8 code point, UTF-8 bytes needed, and UTF-8 bytes seen to 0,＼
   2. ( `~UTF-8下限$, `~UTF-8上限$ ) ~SET ( `80^X, `BF^X ) ◎ set UTF-8 lower boundary to 0x80, and set UTF-8 upper boundary to 0xBF.
   3. %~byte を %~stream に`前付加する$ ◎ Prepend byte to stream.
   4. ~RET `~error$ ◎ Return error.
5. ( `~UTF-8下限$, `~UTF-8上限$ ) ~SET ( `80^X, `BF^X ) ◎ Set UTF-8 lower boundary to 0x80 and UTF-8 upper boundary to 0xBF.

6. `~UTF-8~cp$ ~SET (`~UTF-8~cp$ ~Lshift 6) ~bOR (%~byte ~bAND `3F^X) ◎ Set UTF-8 code point to (UTF-8 code point << 6) | (byte & 0x3F)

   `~UTF-8~cp$内の既存の~bitを左へ 6 ~bit ~shiftして，~~空いた下位 6 ~bitに %~byte の下位 6 ~bitをあてがう。 ◎ Shift the existing bits of UTF-8 code point left by six places and set the newly-vacated six least significant bits to the six least significant bits of byte.

7. `~UTF-8出現~byte数$ ~INCBY 1 ◎ Increase UTF-8 bytes seen by one.
8. ~IF［ `~UTF-8出現~byte数$ ~NEQ `~UTF-8要~byte数$ ］ ⇒ ~RET `継続$ ◎ If UTF-8 bytes seen is not equal to UTF-8 bytes needed, return continue.
9. %~cp ~LET `~UTF-8~cp$ ◎ Let code point be UTF-8 code point.
10. ( `~UTF-8~cp$, `~UTF-8要~byte数$, `~UTF-8出現~byte数$ ) ~SET ( 0, 0, 0 ) ◎ Set UTF-8 code point, UTF-8 bytes needed, and UTF-8 bytes seen to 0.
11. ~RET ~cp [ %~cp ] ◎ Return a code point whose value is code point.

注記： 上の`~UTF-8~decoder$における拘束は、~Unicode標準の “Best Practices for Using U+FFFD” に準じる。 他のふるまいは Encoding 標準の下では許可されない（同じ結果が得られるなら、他の~algoでも~~十分であり，むしろ奨励される）。 `UNICODE$r ◎ The constraints in the UTF-8 decoder above match “Best Practices for Using U+FFFD” from the Unicode standard. No other behavior is permitted per the Encoding Standard (other algorithms that achieve the same result are fine, even encouraged). [UNICODE]

8.1.2. ~UTF-8~encoder

`UTF-8$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ UTF-8’s encoder’s handler, given a stream and code point, runs these steps:

1. ~IF［ %~cp ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If code point is end-of-stream, return finished.
2. ~IF［ %~cp ~IN `~ASCII~cp$ ］ ⇒ ~RET ~byte列 [ %~cp ] ◎ If code point is an ASCII code point, return a byte whose value is code point.

3. ( %count, %~offset ) ~SET %~cp が属する範囲に応じて ⇒＃ { `0080^U 〜 `07FF^U } ならば ( 1, `C0^X ) ／ { `0800^U 〜 `FFFF^U } ならば ( 2, `E0^X ) ／ { `10000^U 〜 `10FFFF^U } ならば ( 3, `F0^X ) ◎ Set count and offset based on the range code point is in: ◎ U+0080 to U+07FF, inclusive • 1 and 0xC0 U+0800 to U+FFFF, inclusive • 2 and 0xE0 U+10000 to U+10FFFF, inclusive • 3 and 0xF0

4. %~byte列 ~LET ~byte列 [ ( %~cp ~Rshift ( 6 ~MUL %count ) ) ~PLUS %~offset ] ◎ Let bytes be a byte sequence whose first byte is (code point >> (6 × count)) + offset.

5. ~WHILE %count ~GT 0 ： ◎ While count is greater than 0:

   1. %temp ~SET %~cp ~Rshift ( 6 ~MUL ( %count ~MINUS 1 ) ) ◎ Set temp to code point >> (6 × (count − 1)).
   2. %~byte列 に ( `80^X ~bOR ( %temp ~bAND `3F^X ) ) を付加する ◎ Append to bytes 0x80 | (temp & 0x3F).
   3. %count ~DECBY 1 ◎ Decrease count by one.
6. ~RET %~byte列 ◎ Return bytes bytes, in order.

この~algoは、~Unicode標準に述べられるものと一致する結果を得るが、完全さのためここに含められている。 `UNICODE$r ◎ This algorithm has identical results to the one described in the Unicode standard. It is included here for completeness. [UNICODE]

10.1.1 ~GBK~decoder

`GBK$n の`~decoder$は，`gb18030$n の`~decoder$である。 ◎ GBK’s decoder is gb18030’s decoder.

10.1.2 ~GBK~encoder

`GBK$n の~encoderは，［ `~GBK~flag$ ~SET ~ON ］にされた`gb18030$n の`~encoder$である。 ◎ GBK’s encoder is gb18030’s encoder with its GBK flag set.

注記： `GBK$n を`gb18030$nに対する全くの別名にしないのは、 `GBK$n の`~encoder$により生成された内容を，旧来の~serverや他の消費者をなるべく壊すことなく，保守的に移行するためである。 ◎ Not fully aliasing GBK with gb18030 is a conservative move to decrease the chances of breaking legacy servers and other consumers of content generated with GBK’s encoder.

10.2.1. ~gb18030~decoder

各［ `gb18030$n の`~decoder$ ］には、次のものが結付けられる ⇒＃ `~gb1@（初期~時 0 ）, `~gb2@（初期~時 0 ）, `~gb3@（初期~時 0 ） ◎ gb18030’s decoder has an associated gb18030 first, gb18030 second, and gb18030 third (all initially 0x00).

`gb18030$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ gb18030’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ ( `~gb1$, `~gb2$, `~gb3$ ) ~EQ ( `00^X, `00^X, `00^X ) ］ ⇒ ~RET `完遂$ ◎ If byte is end-of-stream and gb18030 first, gb18030 second, and gb18030 third are 0x00, return finished.
   2. ( `~gb1$, `~gb2$, `~gb3$ ) ~SET ( `00^X, `00^X, `00^X ) ◎ If byte is end-of-stream, and gb18030 first, gb18030 second, or gb18030 third is not 0x00, set gb18030 first, gb18030 second, and gb18030 third to 0x00, and＼
   3. ~RET `~error$ ◎ return error.

2. ~IF［ `~gb3$ ~NEQ `00^X ］： ◎ If gb18030 third is not 0x00, then:

   1. ~IF［ %~byte ~NIN { `30^X 〜 `39^X } ］： ◎ If byte is not in the range 0x30 to 0x39, inclusive, then:

      1. ~byte列 [ `~gb2$, `~gb3$, %~byte ] を %~stream に`前付加する$ ◎ Prepend gb18030 second, gb18030 third, and byte to stream.
      2. ( `~gb1$, `~gb2$, `~gb3$ ) ~SET ( `00^X, `00^X, `00^X ) ◎ Set gb18030 first, gb18030 second, and gb18030 third to 0x00.
      3. ~RET `~error$ ◎ Return error.
   2. %~cp ~LET 次に与える~pointerが指す`索引~gb18030範囲集~cp$ ⇒ (( `~gb1$ ~MINUS `81^X ) ~MUL ( 10 ~MUL 126 ~MUL 10 )) ~PLUS (( `~gb2$ ~MINUS `30^X ) ~MUL ( 10 ~MUL 126 )) ~PLUS (( `~gb3$ ~MINUS `81^X ) ~MUL 10 ) ~PLUS ( %~byte ~MINUS `30^X ) ◎ Let code point be the index gb18030 ranges code point for ((gb18030 first − 0x81) × (10 × 126 × 10)) + ((gb18030 second − 0x30) × (10 × 126)) + ((gb18030 third − 0x81) × 10) + byte − 0x30.
   3. ~IF［ %~cp ~EQ ~NULL ］ ⇒ ~RET `~error$ ◎ If code point is null, return error.
   4. ~RET ~cp [ %~cp ] ◎ Return a code point whose value is code point.

3. ~IF［ `~gb2$ ~NEQ `00^X ］： ◎ If gb18030 second is not 0x00, then:

   1. ~IF［ %~byte ~IN { `81^X 〜 `FE^X } ］ ⇒＃ `~gb3$ ~SET %~byte ； ~RET `継続$ ◎ If byte is in the range 0x81 to 0xFE, inclusive, set gb18030 third to byte and return continue.
   2. ~byte列 [ `~gb2$, %~byte ] を %~stream に`前付加する$ ◎ Prepend gb18030 second followed by byte to stream,＼
   3. ( `~gb1$, `~gb2$ ) ~SET ( `00^X, `00^X ) ◎ set gb18030 first and gb18030 second to 0x00, and＼
   4. ~RET `~error$ ◎ return error.

4. ~IF［ `~gb1$ ~NEQ `00^X ］： ◎ If gb18030 first is not 0x00, then:

   1. ~IF［ %~byte ~IN { `30^X 〜 `39^X } ］ ⇒＃ `~gb2$ ~SET %~byte ； ~RET `継続$ ◎ If byte is in the range 0x30 to 0x39, inclusive, set gb18030 second to byte and return continue.
   2. %~lead ~LET `~gb1$ ◎ Let lead be gb18030 first,＼
   3. %~pointer ~LET ~NULL ◎ let pointer be null, and＼
   4. `~gb1$ ~SET `00^X ◎ set gb18030 first to 0x00.
   5. %~offset ~LET ［ %~byte ~IN { `00^X 〜 `7E^X } ならば `40^X ／ ~ELSE_ `41^X ］ ◎ Let offset be 0x40 if byte is less than 0x7F and 0x41 otherwise.
   6. ~IF［ %~byte ~IN { `40^X 〜 `7E^X, `80^X 〜 `FE^X } ］ ⇒ %~pointer ~SET ( %~lead ~MINUS `81^X ) ~MUL 190 ~PLUS ( %~byte ~MINUS %~offset ) ◎ If byte is in the range 0x40 to 0x7E, inclusive, or 0x80 to 0xFE, inclusive, set pointer to (lead − 0x81) × 190 + (byte − offset).
   7. %~cp ~LET %~pointer に応じて ⇒ ~NULL ならば ~NULL ／ ~ELSE_ `索引~gb18030$ の中で %~pointer が指す`索引~cp$ ◎ Let code point be null if pointer is null and the index code point for pointer in index gb18030 otherwise.
   8. ~IF［ %~cp ~NEQ ~NULL ］ ⇒ ~RET ~cp [ %~cp ] ◎ If code point is non-null, return a code point whose value is code point.
   9. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ %~byte を %~stream に`前付加する$ ◎ If byte is an ASCII byte, prepend byte to stream.
   10. ~RET `~error$ ◎ Return error.
5. ~IF［ %~byte ~IN { `81^X 〜 `FE^X } ］ ⇒＃ `~gb1$ ~SET %~byte ； ~RET `継続$ ◎ ↓
6. ~RET %~byte に応じて ⇒＃ `~ASCII~byte$ならば ~cp [ %~byte ] ／ `80^X ならば ~cp [ `20AC^U ] ／ `FF^X ならば `~error$ ◎ If byte is an ASCII byte, return a code point whose value is byte. ◎ If byte is 0x80, return code point U+20AC. ◎ If byte is in the range 0x81 to 0xFE, inclusive, set gb18030 first to byte and return continue. ◎ Return error.

10.2.2. ~gb18030~encoder

各［ `gb18030$n の`~encoder$ ］には、次のものが結付けられる ⇒ `~GBK~flag@（初期~時 ~OFF ） ◎ gb18030’s encoder has an associated GBK flag (initially unset).

`gb18030$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ gb18030’s encoder’s handler, given a stream and code point, runs these steps:

1. ~IF［ %~cp ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If code point is end-of-stream, return finished.
2. ~IF［ %~cp ~IN `~ASCII~cp$ ］ ⇒ ~RET ~byte列 [ %~cp ] ◎ If code point is an ASCII code point, return a byte whose value is code point.

3. ~IF［ %~cp ~EQ `E5E5^U ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If code point is U+E5E5, return error with code point.

   注記： 配備-済みの内容との互換性をとるため、 `索引~gb18030$ は［ `A3^X `A0^X ］を `E5E5^U ではなく `3000^U に対応付けている。 したがって往来できない。 ◎ Index gb18030 maps 0xA3 0xA0 to U+3000 rather than U+E5E5 for compatibility with deployed content. Therefore it cannot roundtrip.

4. ~IF［ `~GBK~flag$ ~EQ ~ON ］~AND［ %~cp ~EQ `20AC^U ］ ⇒ ~RET ~byte列 [ `80^X ] ◎ If the GBK flag is set and code point is U+20AC, return byte 0x80.
5. %~pointer ~LET `索引~gb18030$ の中で %~cp を指す`索引~pointer$ ◎ Let pointer be the index pointer for code point in index gb18030.

6. ~IF［ %~pointer ~NEQ ~NULL ］： ◎ If pointer is non-null, then:

   1. %~lead ~LET ( %~pointer ~DIV 190 ) ~PLUS `81^X ◎ Let lead be pointer / 190 + 0x81.
   2. %~trail ~LET %~pointer ~MOD 190 ◎ Let trail be pointer % 190.
   3. %~offset ~LET ［ %~trail ~IN { `00^X 〜 `3E^X } ならば `40^X ／ ~ELSE_ `41^X ］ ◎ Let offset be 0x40 if trail is less than 0x3F and 0x41 otherwise.
   4. ~RET ~byte列 [ %~lead, ( %~trail ~PLUS %~offset ) ] ◎ Return two bytes whose values are lead and trail + offset.
7. ~IF［ `~GBK~flag$ ~EQ ~ON ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If GBK flag is set, return error with code point.
8. %~pointer ~SET %~cp を指す`索引~gb18030範囲集~pointer$ ◎ Set pointer to the index gb18030 ranges pointer for code point.
9. %byte1 ~LET %~pointer ~DIV ( 10 ~MUL 126 ~MUL 10 ) ◎ Let byte1 be pointer / (10 × 126 × 10).
10. %~pointer ~SET %~pointer ~MOD ( 10 ~MUL 126 ~MUL 10 ) ◎ Set pointer to pointer % (10 × 126 × 10).
11. %byte2 ~LET %~pointer ~DIV ( 10 ~MUL 126 ) ◎ Let byte2 be pointer / (10 × 126).
12. %~pointer ~SET %~pointer ~MOD ( 10 ~MUL 126 ) ◎ Set pointer to pointer % (10 × 126).
13. %byte3 ~LET %~pointer ~DIV 10 ◎ Let byte3 be pointer / 10.
14. %byte4 ~LET %~pointer ~MOD 10 ◎ Let byte4 be pointer % 10.
15. ~RET ~byte列 [ ( %byte1 ~PLUS `81^X ), ( %byte2 ~PLUS `30^X ), ( %byte3 ~PLUS `81^X ), ( %byte4 ~PLUS `30^X ) ] ◎ Return four bytes whose values are byte1 + 0x81, byte2 + 0x30, byte3 + 0x81, byte4 + 0x30.

11.1.1. ~Big5~decoder

各［ `Big5$n の`~decoder$ ］には、次のものが結付けられる ⇒ `~Big5~lead@（初期~時 `00^X ） ◎ Big5’s decoder has an associated Big5 lead (initially 0x00).

`Big5$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ Big5’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］：

   1. ~IF［ `~Big5~lead$ ~NEQ `00^X ］ ⇒＃ `~Big5~lead$ ~SET `00^X ； ~RET `~error$
   2. ~RET `完遂$
   ◎ If byte is end-of-stream and Big5 lead is not 0x00, set Big5 lead to 0x00 and return error. ◎ If byte is end-of-stream and Big5 lead is 0x00, return finished.

2. ~IF［ `~Big5~lead$ ~NEQ `00^X ］： ◎ If Big5 lead is not 0x00,＼

   1. %~lead ~LET `~Big5~lead$ ◎ let lead be Big5 lead,＼
   2. %~pointer ~LET ~NULL ◎ let pointer be null,＼
   3. `~Big5~lead$ ~SET `00^X ◎ set Big5 lead to 0x00, and then:
   4. %~offset ~LET ［ %~byte ~IN { `00^X 〜 `7E^X } ならば `40^X ／ ~ELSE_ `62^X ］ ◎ Let offset be 0x40 if byte is less than 0x7F and 0x62 otherwise.
   5. ~IF［ %~byte ~IN { `40^X 〜 `7E^X, `A1^X 〜 `FE^X } ］ ⇒ %~pointer ~SET ( %~lead ~MINUS `81^X ) ~MUL 157 ~PLUS ( %~byte ~MINUS %~offset ) ◎ If byte is in the range 0x40 to 0x7E, inclusive, or 0xA1 to 0xFE, inclusive, set pointer to (lead − 0x81) × 157 ~PLUS (byte − offset).

   6. ~IF［ 下の表の中で， 1 列目が %~pointer に等しい行がある ］ ⇒ ~RET 同じ行の 2 列目の 2 個の ~cpからなる`~token$列 ◎ If there is a row in the table below whose first column is pointer, return the two code points listed in its second column (the third column is irrelevant):

      ~pointer◎ Pointer	~cp◎ Code points	説明（この段には関係ない）◎ Notes
      1133	`00CA^U `0304^U	Ê̄ (LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND MACRON)
      1135	`00CA^U `030C^U	Ê̌ (LATIN CAPITAL LETTER E WITH CIRCUMFLEX AND CARON)
      1164	`00EA^U `0304^U	ê̄ (LATIN SMALL LETTER E WITH CIRCUMFLEX AND MACRON)
      1166	`00EA^U `030C^U	ê̌ (LATIN SMALL LETTER E WITH CIRCUMFLEX AND CARON)

      注記： `索引$ は単独の~cpに制限されるので、これらの~pointerにはこの表が利用される。 ◎ Since indexes are limited to single code points this table is used for these pointers.

   7. %~cp ~LET ［ %~pointer ~EQ ~NULL ならば ~NULL ／ ~ELSE_ `索引~Big5$ の中で %~pointer が指す`索引~cp$ ］ ◎ Let code point be null if pointer is null and the index code point for pointer in index Big5 otherwise.
   8. ~IF［ %~cp ~NEQ ~NULL ］ ⇒ ~RET ~cp [ %~cp ] ◎ If code point is non-null, return a code point whose value is code point.
   9. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ %~byte を %~stream に`前付加する$ ◎ If byte is an ASCII byte, prepend byte to stream.
   10. ~RET `~error$ ◎ Return error.
3. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ ~RET ~cp [ %~byte ] ◎ If byte is an ASCII byte, return a code point whose value is byte.
4. ~IF［ %~byte ~IN { `81^X 〜 `FE^X } ］ ⇒＃ `~Big5~lead$ ~SET %~byte ； ~RET `継続$ ◎ If byte is in the range 0x81 to 0xFE, inclusive, set Big5 lead to byte and return continue.
5. ~RET `~error$ ◎ Return error.

11.1.2. ~Big5~encoder

`Big5$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ Big5’s encoder’s handler, given a stream and code point, runs these steps:

1. ~IF［ %~cp ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If code point is end-of-stream, return finished.
2. ~IF［ %~cp ~IN `~ASCII~cp$ ］ ⇒ ~RET ~byte列 [ %~cp ] ◎ If code point is an ASCII code point, return a byte whose value is code point.
3. %~pointer ~LET %~cp を指す`索引~Big5~pointer$ ◎ Let pointer be the index Big5 pointer for code point.
4. ~IF［ %~pointer ~EQ ~NULL ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If pointer is null, return error with code point.
5. %~lead ~LET ( %~pointer ~DIV 157 ) ~PLUS `81^X ◎ Let lead be pointer / 157 + 0x81.
6. %~trail ~LET %~pointer ~MOD 157 ◎ Let trail be pointer % 157.
7. %~offset ~LET ［ %~trail ~IN { `00^X 〜 `3E^X } ならば `40^X ／ ~ELSE_ `62^X ］ ◎ Let offset be 0x40 if trail is less than 0x3F and 0x62 otherwise.
8. ~RET ~byte列 [ %~lead, ( %~trail ~PLUS %~offset) ] ◎ Return two bytes whose values are lead and trail + offset.

12.1.1. ~EUC-JP~decoder

各［ `EUC-JP$n の`~decoder$ ］には、次のものが結付けられる ⇒＃ `~EUC-JP~jis0212~flag@（初期~時 ~OFF ）； `~EUC-JP~lead@（初期~時 `00^X） ◎ EUC-JP’s decoder has an associated EUC-JP jis0212 flag (initially unset) and EUC-JP lead (initially 0x00).

`EUC-JP$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ EUC-JP’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ `~EUC-JP~lead$ ~NEQ `00^X ］ ⇒＃ `~EUC-JP~lead$ ~SET `00^X ； ~RET `~error$ ◎ If byte is end-of-stream and EUC-JP lead is not 0x00, set EUC-JP lead to 0x00, and return error.
   2. ~ELSE ⇒ ~RET `完遂$ ◎ If byte is end-of-stream and EUC-JP lead is 0x00, return finished.
2. ~IF［ `~EUC-JP~lead$ ~EQ `8E^X ］~AND［ %~byte ~IN { `A1^X 〜 `DF^X } ］ ⇒＃ `~EUC-JP~lead$ ~SET `00^X ； ~RET ~cp [ `FF61^X ~MINUS `A1^X ~PLUS %~byte ] ◎ If EUC-JP lead is 0x8E and byte is in the range 0xA1 to 0xDF, inclusive, set EUC-JP lead to 0x00 and return a code point whose value is 0xFF61 − 0xA1 + byte.
3. ~IF［ `~EUC-JP~lead$ ~EQ `8F^X ］~AND［ %~byte ~IN { `A1^X 〜 `FE^X } ］ ⇒＃ `~EUC-JP~jis0212~flag$ ~SET ~ON ； `~EUC-JP~lead$ ~SET %~byte ； ~RET `継続$ ◎ If EUC-JP lead is 0x8F and byte is in the range 0xA1 to 0xFE, inclusive, set the EUC-JP jis0212 flag, set EUC-JP lead to byte, and return continue.

4. ~IF［ `~EUC-JP~lead$ ~NEQ `00^X ］： ◎ If EUC-JP lead is not 0x00,＼

   1. %~lead ~LET `~EUC-JP~lead$ ◎ let lead be EUC-JP lead,＼
   2. `~EUC-JP~lead$ ~SET `00^X ◎ set EUC-JP lead to 0x00, and then:
   3. %~cp ~LET ~NULL ◎ Let code point be null.

   4. ~IF［ %~lead ~IN { `A1^X 〜 `FE^X } ］~AND［ %~byte ~IN { `A1^X 〜 `FE^X } ］：

      1. %索引 ~LET `~EUC-JP~jis0212~flag$に応じて ⇒＃ ~OFF ならば`索引~jis0208$ ／ ~ON ならば `索引~jis0212$
      2. %~cp ~SET %索引 の中で ( ( %~lead ~MINUS `A1^X ) ~MUL 94 ~PLUS %~byte ~MINUS `A1^X ) が指す`索引~cp$
      ◎ If lead and byte are both in the range 0xA1 to 0xFE, inclusive, set code point to the index code point for (lead − 0xA1) × 94 + byte − 0xA1 in index jis0208 if the EUC-JP jis0212 flag is unset and in index jis0212 otherwise.
   5. `~EUC-JP~jis0212~flag$ ~SET ~OFF ◎ Unset the EUC-JP jis0212 flag.
   6. ~IF［ %~cp ~NEQ ~NULL ］ ⇒ ~RET ~cp [ %~cp ] ◎ If code point is non-null, return a code point whose value is code point.
   7. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ %~byte を %~stream に`前付加する$ ◎ If byte is an ASCII byte, prepend byte to stream.
   8. ~RET `~error$ ◎ Return error.
5. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ ~RET ~cp [ %~byte ] ◎ If byte is an ASCII byte, return a code point whose value is byte.
6. ~IF［ %~byte ~IN { `8E^X, `8F^X, `A1^X 〜 `FE^X } ］ ⇒＃ `~EUC-JP~lead$ ~SET %~byte ； ~RET `継続$ ◎ If byte is 0x8E, 0x8F, or in the range 0xA1 to 0xFE, inclusive, set EUC-JP lead to byte and return continue.
7. ~RET `~error$ ◎ Return error.

12.1.2. ~EUC-JP~encoder

`EUC-JP$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ EUC-JP’s encoder’s handler, given a stream and code point, runs these steps:

1. %結果 ~LET %~cp に応じて ⇒＃ `~EoS$ ならば `完遂$ ／ `~ASCII~cp$ならば ~byte列 [ %~cp ] ／ `00A5^U ならば ~byte列 [ `5C^X ] ／ `203E^U ならば ~byte列 [ `7E^X ] ／ `FF61^U 〜 `FF9F^U ならば ~byte列 [ `8E^X, ( %~cp ~MINUS `FF61^X ~PLUS `A1^X ) ] ／ ~ELSE_ ~NULL ◎ If code point is end-of-stream, return finished. ◎ If code point is an ASCII code point, return a byte whose value is code point. ◎ If code point is U+00A5, return byte 0x5C. ◎ If code point is U+203E, return byte 0x7E. ◎ If code point is in the range U+FF61 to U+FF9F, inclusive, return two bytes whose values are 0x8E and code point − 0xFF61 + 0xA1.
2. ~IF［ %結果 ~NEQ ~NULL ］ ⇒ ~RET %結果 ◎ ↑
3. ~IF［ %~cp ~EQ `2212^U ］ ⇒ %~cp ~SET `FF0D^U ◎ If code point is U+2212, set it to U+FF0D.

4. %~pointer ~LET `索引~jis0208$ の中で %~cp を指す`索引~pointer$ ◎ Let pointer be the index pointer for code point in index jis0208.

   注記： %~pointer は、 ~NULL でなければ，`索引~jis0208$と~pointer演算の資質に因り 8836 未満になる。 ◎ If pointer is non-null, it is less than 8836 due to the nature of index jis0208 and the index pointer operation.

5. ~IF［ %~pointer ~EQ ~NULL ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If pointer is null, return error with code point.
6. %~lead ~LET ( %~pointer ~DIV 94 ) ~PLUS `A1^X ◎ Let lead be pointer / 94 + 0xA1.
7. %~trail ~LET ( %~pointer ~MOD 94 ) ~PLUS `A1^X ◎ Let trail be pointer % 94 + 0xA1.
8. ~RET ~byte列 [ %~lead, %~trail ] ◎ Return two bytes whose values are lead and trail.

12.2.1. ~ISO-2022-JP~decoder

各［ `ISO-2022-JP$n の`~decoder$ ］には、次のものが結付けられる ⇒＃ `~ISO-2022-JP~decoder状態@（初期~時 `ASCII$i）, `~ISO-2022-JP~decoder出力~状態@（初期~時 `ASCII$i ）, `~ISO-2022-JP~lead@（初期~時 `00^X ）, `~ISO-2022-JP出力~flag@（初期~時 ~OFF ） ◎ ISO-2022-JP’s decoder has an associated ISO-2022-JP decoder state (initially ASCII), ISO-2022-JP decoder output state (initially ASCII), ISO-2022-JP lead (initially 0x00), and ISO-2022-JP output flag (initially unset).

`ISO-2022-JP$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，`~ISO-2022-JP~decoder状態$に応じて 次を走らす： ◎ ISO-2022-JP’s decoder’s handler, given a stream and byte, runs these steps, switching on ISO-2022-JP decoder state:

`ASCII@i

%~byte に応じて： ◎ Based on byte:

1. `1B^X ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~escape開始$i ； ~RET `継続$ ◎ 0x1B • Set ISO-2022-JP decoder state to escape start and return continue.
2. `0E^X, `0F^X, `1B^X 以外の`~ASCII~byte$ ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET ~cp [ %~byte ] ◎ 0x00 to 0x7F, excluding 0x0E, 0x0F, and 0x1B • Unset the ISO-2022-JP output flag and return a code point whose value is byte.
3. `~EoS$ ⇒＃ ~RET `完遂$ ◎ end-of-stream • Return finished.
4. ~OTHER ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET `~error$ ◎ Otherwise • Unset the ISO-2022-JP output flag and return error.

`Roman@i

%~byte に応じて： ◎ Based on byte:

1. `1B^X ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~escape開始$i ； ~RET `継続$ ◎ 0x1B • Set ISO-2022-JP decoder state to escape start and return continue.
2. `5C^X ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET ~cp [ `00A5^U ] ◎ 0x5C • Unset the ISO-2022-JP output flag and return code point U+00A5.
3. `7E^X ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET ~cp [ `203E^U ] ◎ 0x7E • Unset the ISO-2022-JP output flag and return code point U+203E.
4. `0E^X, `0F^X, `1B^X, `5C^X, `7E^X 以外の`~ASCII~byte$ ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET ~cp [ %~byte ] ◎ 0x00 to 0x7F, excluding 0x0E, 0x0F, 0x1B, 0x5C, and 0x7E • Unset the ISO-2022-JP output flag and return a code point whose value is byte.
5. `~EoS$ ⇒＃ ~RET `完遂$ ◎ end-of-stream • Return finished.
6. ~OTHER ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET `~error$ ◎ Otherwise • Unset the ISO-2022-JP output flag and return error.

`katakana@i

%~byte に応じて： ◎ Based on byte:

1. `1B^X ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~escape開始$i ； ~RET `継続$ ◎ 0x1B • Set ISO-2022-JP decoder state to escape start and return continue.
2. `21^X 〜 `5F^X ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET ~cp [ `FF61^X ~MINUS `21^X ~PLUS %~byte ] ◎ 0x21 to 0x5F • Unset the ISO-2022-JP output flag and return a code point whose value is 0xFF61 − 0x21 + byte.
3. `~EoS$ ⇒＃ ~RET `完遂$ ◎ end-of-stream • Return finished.
4. ~OTHER ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET `~error$ ◎ Otherwise • Unset the ISO-2022-JP output flag and return error.

`~lead~byte@i

%~byte に応じて： ◎ Based on byte:

1. `1B^X ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~escape開始$i ； ~RET `継続$ ◎ 0x1B • Set ISO-2022-JP decoder state to escape start and return continue.
2. `21^X 〜 `7E^X ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； `~ISO-2022-JP~lead$ ~SET %~byte ； `~ISO-2022-JP~decoder状態$ ~SET `~trail~byte$i ； ~RET `継続$ ◎ 0x21 to 0x7E • Unset the ISO-2022-JP output flag, set ISO-2022-JP lead to byte, ISO-2022-JP decoder state to trail byte, and return continue.
3. `~EoS$ ⇒＃ ~RET `完遂$ ◎ end-of-stream • Return finished.
4. ~OTHER ⇒＃ `~ISO-2022-JP出力~flag$ ~SET ~OFF ； ~RET `~error$ ◎ Otherwise • Unset the ISO-2022-JP output flag and return error.

`~trail~byte@i

%~byte に応じて： ◎ Based on byte:

1. `1B^X ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~escape開始$i ； ~RET `~error$ ◎ 0x1B • Set ISO-2022-JP decoder state to escape start and return error.

2. `21^X 〜 `7E^X ： ◎ 0x21 to 0x7E

   1. `~ISO-2022-JP~decoder状態$ ~SET `~lead~byte$i ◎ Set the ISO-2022-JP decoder state to lead byte.
   2. %pointer ~LET ( `~ISO-2022-JP~lead$ ~MINUS `21^X ) ~MUL 94 ~PLUS %~byte ~MINUS `21^X ◎ Let pointer be (ISO-2022-JP lead − 0x21) × 94 + byte − 0x21.
   3. %~cp ~LET `索引~jis0208$ の中で %~pointer が指す`索引~cp$ ◎ Let code point be the index code point for pointer in index jis0208.
   4. ~IF［ %~cp ~EQ ~NULL ］ ⇒ ~RET `~error$ ◎ If code point is null, return error.
   5. ~RET ~cp [ %~cp ] ◎ Return a code point whose value is code point.
3. `~EoS$ ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~lead~byte$i ； %~byte を %~stream に`前付加する$ ； ~RET `~error$ ◎ end-of-stream • Set the ISO-2022-JP decoder state to lead byte, prepend byte to stream, and return error.
4. ~OTHER ⇒＃ `~ISO-2022-JP~decoder状態$ ~SET `~lead~byte$i ； ~RET `~error$ ◎ Otherwise • Set ISO-2022-JP decoder state to lead byte and return error.

`~escape開始@i

1. ~IF［ %~byte ~IN { `24^X, `28^X } ］ ⇒＃ `~ISO-2022-JP~lead$ ~SET %~byte ； `~ISO-2022-JP~decoder状態$ ~SET `~escape$i ； ~RET `継続$ ◎ If byte is either 0x24 or 0x28, set ISO-2022-JP lead to byte, ISO-2022-JP decoder state to escape, and return continue.
2. %~byte を %~stream に`前付加する$ ◎ Prepend byte to stream.
3. `~ISO-2022-JP出力~flag$ ~SET ~OFF ◎ Unset the ISO-2022-JP output flag,＼
4. `~ISO-2022-JP~decoder状態$ ~SET `~ISO-2022-JP~decoder出力~状態$ ◎ set ISO-2022-JP decoder state to ISO-2022-JP decoder output state, and＼
5. ~RET `~error$ ◎ return error.

`~escape@i

1. %~lead ~LET `~ISO-2022-JP~lead$ ◎ Let lead be ISO-2022-JP lead and＼
2. `~ISO-2022-JP~lead$ ~SET `00^X ◎ set ISO-2022-JP lead to 0x00.
3. %状態 ~LET ( %~lead, %~byte ) に応じて ⇒＃ ( `28^X, `42^X ) ならば `ASCII$i ／ ( `28^X, `4A^X ) ならば `Roman$i1 ／ ( `28^X, `49^X ) ならば `katakana$i ／ ( `24^X, `40^X ) ならば `~lead~byte$i ／ ( `24^X, `42^X ) ならば `~lead~byte$i ~ELSE_ ~NULL ◎ Let state be null. ◎ If lead is 0x28 and byte is 0x42, set state to ASCII. ◎ If lead is 0x28 and byte is 0x4A, set state to Roman. ◎ If lead is 0x28 and byte is 0x49, set state to katakana. ◎ If lead is 0x24 and byte is either 0x40 or 0x42, set state to lead byte.

4. ~IF［ %状態 ~NEQ ~NULL ］： ◎ If state is non-null, then:

   1. `~ISO-2022-JP~decoder状態$ ~SET %状態 ◎ ↓
   2. `~ISO-2022-JP~decoder出力~状態$ ~SET %状態 ◎ Set ISO-2022-JP decoder state and ISO-2022-JP decoder output state to state.
   3. %出力~flag ~LET `~ISO-2022-JP出力~flag$ ◎ Let output flag be the ISO-2022-JP output flag.
   4. `~ISO-2022-JP出力~flag$ ~SET ~ON ◎ Set the ISO-2022-JP output flag.
   5. ~RET ［ %出力~flag ~EQ ~OFF ならば `継続$ ／ ~ELSE_ `~error$ ］ ◎ Return continue, if output flag is unset, and error otherwise.
5. ~byte列 [ %~lead, %~byte ] を %~stream に`前付加する$ ◎ Prepend lead and byte to stream.
6. `~ISO-2022-JP出力~flag$ ~SET ~OFF ◎ Unset the ISO-2022-JP output flag,＼
7. `~ISO-2022-JP~decoder状態$ ~SET `~ISO-2022-JP~decoder出力~状態$ ◎ set ISO-2022-JP decoder state to ISO-2022-JP decoder output state and＼
8. ~RET `~error$ ◎ return error.

12.2.2. ~ISO-2022-JP~encoder

各［ `ISO-2022-JP$n の`~encoder$ ］には、次のものが結付けられる ⇒ `~ISO-2022-JP~encoder状態@ — 次のいずれかをとり得る（初期~時 `ASCII$i1 ） ⇒ `ASCII@i1 ／ `Roman@i1 ／ `jis0208@i1 ◎ ISO-2022-JP’s encoder has an associated ISO-2022-JP encoder state which is ASCII, Roman, or jis0208 (initially ASCII).

`ISO-2022-JP$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ ISO-2022-JP’s encoder’s handler, given a stream and code point, runs these steps:

1. ~IF［ %~cp ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ `~ISO-2022-JP~encoder状態$ ~NEQ `ASCII$i1 ］ ⇒＃ %~cp を %~stream に`前付加する$ ； `~ISO-2022-JP~encoder状態$ ~SET `ASCII$i1 ； ~RET ~byte列 [ `1B^X, `28^X, `42^X ] ◎ If code point is end-of-stream and ISO-2022-JP encoder state is not ASCII, prepend code point to stream, set ISO-2022-JP encoder state to ASCII, and return three bytes 0x1B 0x28 0x42.
   2. ~RET `完遂$ ◎ If code point is end-of-stream and ISO-2022-JP encoder state is ASCII, return finished.

2. ~IF［ `~ISO-2022-JP~encoder状態$ ~IN { `ASCII$i1, `Roman$i1 } ］~AND［ %~cp ~IN { `000E^U, `000F^U, `001B^U } ］ ⇒ ~RET `FFFD^U を伴う`~error$ ◎ If ISO-2022-JP encoder state is ASCII or Roman, and code point is U+000E, U+000F, or U+001B, return error with U+FFFD.

   攻撃を防ぐため、これは %~cp ではなく， `FFFD^U を返す。 ◎ This returns U+FFFD rather than code point to prevent attacks.

3. ~IF［ `~ISO-2022-JP~encoder状態$ ~EQ `ASCII$i1 ］~AND［ %~cp ~IN `~ASCII~cp$ ］ ⇒ ~RET ~byte列 [ %~cp ] ◎ If ISO-2022-JP encoder state is ASCII and code point is an ASCII code point, return a byte whose value is code point.

4. ~IF［ `~ISO-2022-JP~encoder状態$ ~EQ `Roman$i1 ］：

   1. %結果 ~LET %~cp に応じて ⇒＃ `005C^U, `007E^U 以外の`~ASCII~cp$ならば ~byte列 [ %~cp ] ／ `00A5^U ならば ~byte列 [ `5C^X ] ／ `203E^U ならば ~byte列 [ `7E^X ] ／ ~ELSE_ ~NULL
   2. ~IF［ %結果 ~NEQ ~NULL ］ ⇒ ~RET %結果 ◎ ↑
   ◎ If ISO-2022-JP encoder state is Roman and code point is an ASCII code point, excluding U+005C and U+007E, or is U+00A5 or U+203E, then: • If code point is an ASCII code point, return a byte whose value is code point. • If code point is U+00A5, return byte 0x5C. • If code point is U+203E, return byte 0x7E.
5. ~IF［ %~cp ~IN `~ASCII~cp$ ］~AND［ `~ISO-2022-JP~encoder状態$ ~NEQ `ASCII$i1 ］ ⇒＃ %~cp を %~stream に`前付加する$ ； `~ISO-2022-JP~encoder状態$ ~SET `ASCII$i1 ； ~RET ~byte列 [ `1B^X, `28^X, `42^X ] ◎ If code point is an ASCII code point, and ISO-2022-JP encoder state is not ASCII, prepend code point to stream, set ISO-2022-JP encoder state to ASCII, and return three bytes 0x1B 0x28 0x42.
6. ~IF［ %~cp ~NIN { `00A5^U, `203E^U } ］~AND［ `~ISO-2022-JP~encoder状態$ ~NEQ `Roman$i1 ］ ⇒＃ %~cp を %~stream に`前付加する$ ； `~ISO-2022-JP~encoder状態$ ~SET `Roman$i1 ； ~RET ~byte列 [ `1B^X, `28^X, `4A^X ] ◎ If code point is either U+00A5 or U+203E, and ISO-2022-JP encoder state is not Roman, prepend code point to stream, set ISO-2022-JP encoder state to Roman, and return three bytes 0x1B 0x28 0x4A.
7. ~IF［ %~cp ~EQ `2212^U ］ ⇒ %~cp ~SET `FF0D^U ◎ If code point is U+2212, set it to U+FF0D.
8. ~IF［ %~cp ~IN { `FF61^U 〜 `FF9F^U } ］ ⇒ %~cp ~SET `索引~ISO-2022-JP~katakana$の中で ( %~cp ~MINUS `FF61^X ) が指す`索引~cp$ ◎ If code point is in the range U+FF61 to U+FF9F, inclusive, set it to the index code point for code point − 0xFF61 in index ISO-2022-JP katakana.

9. %~pointer ~LET `索引~jis0208$ の中で %~cp を指す`索引~pointer$ ◎ Let pointer be the index pointer for code point in index jis0208.

   注記： %~pointer は、 ~NULL でなければ，`索引~jis0208$と~pointer演算の資質に因り 8836 未満になる。 ◎ If pointer is non-null, it is less than 8836 due to the nature of index jis0208 and the index pointer operation.

10. ~IF［ %~pointer ~EQ ~NULL ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If pointer is null, return error with code point.
11. ~IF［ `~ISO-2022-JP~encoder状態$ ~NEQ `jis0208$i1 ］ ⇒＃ %~cp を %~stream に`前付加する$ ； `~ISO-2022-JP~encoder状態$ ~SET `jis0208$i1 ； ~RET ~byte列 [ `1B^X, `24^X, `42^X ] ◎ If ISO-2022-JP encoder state is not jis0208, prepend code point to stream, set ISO-2022-JP encoder state to jis0208, and return three bytes 0x1B 0x24 0x42.
12. %~lead ~LET ( %~pointer ~DIV 94 ) ~PLUS `21^X ◎ Let lead be pointer / 94 + 0x21.
13. %~trail ~LET ( %~pointer ~MOD 94 ) ~PLUS `21^X ◎ Let trail be pointer % 94 + 0x21.
14. ~RET ~byte列 [ %~lead, %~trail ] ◎ Return two bytes whose values are lead and trail.

12.3.1. ~Shift_JIS~decoder

各［ `Shift_JIS$n の`~decoder$ ］には、次のものが結付けられる ⇒ `~Shift_JIS~lead@（初期~時 `00^X ） ◎ Shift_JIS’s decoder has an associated Shift_JIS lead (initially 0x00).

`Shift_JIS$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ Shift_JIS’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ `~Shift_JIS~lead$ ~NEQ `00^X ］ ⇒＃ `~Shift_JIS~lead$ ~SET `00^X ； ~RET `~error$ ◎ If byte is end-of-stream and Shift_JIS lead is not 0x00, set Shift_JIS lead to 0x00 and return error.
   2. ~ELSE ⇒ ~RET `完遂$ ◎ If byte is end-of-stream and Shift_JIS lead is 0x00, return finished.

2. ~IF［ `~Shift_JIS~lead$ ~NEQ `00^X ］： ◎ If Shift_JIS lead is not 0x00,＼

   1. %~lead ~LET `~Shift_JIS~lead$ ◎ let lead be Shift_JIS lead,＼
   2. %~pointer ~LET ~NULL ◎ let pointer be null,＼
   3. `~Shift_JIS~lead$ ~SET `00^X ◎ set Shift_JIS lead to 0x00, and then:
   4. %~offset ~LET ［ %~byte ~IN { `00^X 〜 `7E^X } ならば `40^X ／ ~ELSE_ `41^X ］ ◎ Let offset be 0x40, if byte is less than 0x7F, and 0x41 otherwise.
   5. %~lead~offset ~LET ［ %~lead ~IN { `00^X 〜 `BF^X } ならば `81^X ／ ~ELSE_ `C1^X ］ ◎ Let lead offset be 0x81, if lead is less than 0xA0, and 0xC1 otherwise.
   6. ~IF［ %~byte ~IN { `40^X 〜 `7E^X, `80^X 〜 `FC^X } ］ ⇒ %~pointer ~SET ( %~lead ~MINUS %~lead~offset ) ~MUL 188 ~PLUS %~byte ~MINUS %~offset ◎ If byte is in the range 0x40 to 0x7E, inclusive, or 0x80 to 0xFC, inclusive, set pointer to (lead − lead offset) × 188 + byte − offset.

   7. ~IF［ %~pointer ~IN { 8836 〜 10715 } ］ ⇒ ~RET ~cp [ `E000^X ~MINUS 8836 ~PLUS %~pointer ] ◎ If pointer is in the range 8836 to 10715, inclusive, return a code point whose value is 0xE000 − 8836 + pointer.

      注記： これは EUDC として周知の，旧来の Windows によるものと相互運用可能にする。 ◎ This is interoperable legacy from Windows known as EUDC.

      【 EUDC — いわゆる外字のための機能。 】【 8836 = 94 ~MUL 94 は~Shift_JIS（ JIS X 0208 ）の `区点番号^_ の総数。 結果の~cpは~Unicode私用領域に入る。 】

   8. %~cp ~LET ［ %~pointer ~EQ ~NULL ならば ~NULL ／ ~ELSE_ `索引~jis0208$ の中で %~pointer が指す`索引~cp$ ］ ◎ Let code point be null, if pointer is null, and the index code point for pointer in index jis0208 otherwise.
   9. ~IF［ %~cp ~NEQ ~NULL ］ ⇒ ~RET ~cp [ %~cp ] ◎ If code point is non-null, return a code point whose value is code point.
   10. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ %~byte を %~stream に`前付加する$ ◎ If byte is an ASCII byte, prepend byte to stream.
   11. ~RET `~error$ ◎ Return error.
3. ~IF［ %~byte ~IN { `~ASCII~byte$, `80^X} ］ ⇒ ~RET ~cp [ %~byte ] ◎ If byte is an ASCII byte or 0x80, return a code point whose value is byte.
4. ~IF［ %~byte ~IN { `A1^X 〜 `DF^X } ］ ⇒ ~RET ~cp [ `FF61^X ~PLUS ( %~byte ~MINUS `A1^X ) ] ◎ If byte is in the range 0xA1 to 0xDF, inclusive, return a code point whose value is 0xFF61 − 0xA1 + byte.
5. ~IF［ %~byte ~IN { `81^X 〜 `9F^X, `E0^X 〜 `FC^X } ］ ⇒＃ `~Shift_JIS~lead$ ~SET %~byte ； ~RET `継続$ ◎ If byte is in the range 0x81 to 0x9F, inclusive, or 0xE0 to 0xFC, inclusive, set Shift_JIS lead to byte and return continue.
6. ~RET `~error$ ◎ Return error.

12.3.2. ~Shift_JIS~encoder

`Shift_JIS$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ Shift_JIS’s encoder’s handler, given a stream and code point, runs these steps:

1. %結果 ~LET %~cp に応じて ⇒＃ `~EoS$ ならば `完遂$ ／ `~ASCII~cp$ならば ~byte列 [ %~cp ] ／ `0080^U ならば ~byte列 [ %~cp ] ／ `00A5^U ならば ~byte列 [ `5C^X ] ／ `203E^U ならば ~byte列 [ `7E^X ] ／ `FF61^U 〜 `FF9F^U ならば ~byte列 [ ( %~cp ~MINUS `FF61^X ) ~PLUS `A1^X ] ／ ~ELSE_ ~NULL ◎ If code point is end-of-stream, return finished. ◎ If code point is an ASCII code point or U+0080, return a byte whose value is code point. ◎ If code point is U+00A5, return byte 0x5C. ◎ If code point is U+203E, return byte 0x7E. ◎ If code point is in the range U+FF61 to U+FF9F, inclusive, return a byte whose value is code point − 0xFF61 + 0xA1.
2. ~IF［ %結果 ~NEQ ~NULL ］ ⇒ ~RET %結果 ◎ ↑
3. ~IF［ %~cp ~EQ `2212^U ］ ⇒ %~cp ~SET `FF0D^U ◎ If code point is U+2212, set it to U+FF0D.
4. %~pointer ~LET %~cp を指す`索引~Shift_JIS~pointer$ ◎ Let pointer be the index Shift_JIS pointer for code point.
5. ~IF［ %~pointer ~EQ ~NULL ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If pointer is null, return error with code point.
6. %~lead ~LET ( %~pointer ~DIV 188 ) ◎ Let lead be pointer / 188.
7. %~lead~offset ~LET ［ %~lead ~IN { `00^X 〜 `1E^X } ならば `81^X ／ ~ELSE_ `C1^X ］ ◎ Let lead offset be 0x81, if lead is less than 0x1F, and 0xC1 otherwise.
8. %~trail ~LET %~pointer ~MOD 188 ◎ Let trail be pointer % 188.
9. %~offset ~LET ［ %~trail ~IN { `00^X 〜 `3E^X } ならば `40^X ／ ~ELSE_ `41^X ］ ◎ Let offset be 0x40, if trail is less than 0x3F, and 0x41 otherwise.
10. ~RET ~byte列 [ ( %~lead ~PLUS %~lead~offset ), ( %~trail ~PLUS %~offset ) ] ◎ Return two bytes whose values are lead + lead offset and trail + offset.

13.1.1. ~EUC-KR~decoder

各［ `EUC-KR$n の`~decoder$ ］には、次のものが結付けられる ⇒ `~EUC-KR~lead@（初期~時 `00^X ） ◎ EUC-KR’s decoder has an associated EUC-KR lead (initially 0x00).

`EUC-KR$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ EUC-KR’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ `~EUC-KR~lead$ ~NEQ `00^X ］ ⇒＃ `~EUC-KR~lead$ ~SET `00^X ； ~RET `~error$ ◎ If byte is end-of-stream and EUC-KR lead is not 0x00, set EUC-KR lead to 0x00 and return error.
   2. ~ELSE ⇒ ~RET `完遂$ ◎ If byte is end-of-stream and EUC-KR lead is 0x00, return finished.

2. ~IF［ `~EUC-KR~lead$ ~NEQ `00^X ］： ◎ If EUC-KR lead is not 0x00,＼

   1. %~lead ~LET `~EUC-KR~lead$ ◎ let lead be EUC-KR lead,＼
   2. %~pointer ~LET ~NULL ◎ let pointer be null,＼
   3. `~EUC-KR~lead$ ~SET `00^X ◎ set EUC-KR lead to 0x00, and then:
   4. ~IF［ %~byte ~IN { `41^X 〜 `FE^X } ］ ⇒ %~pointer ~SET ( %~lead ~MINUS `81^X ) ~MUL 190 ~PLUS ( %~byte ~MINUS `41^X ) ◎ If byte is in the range 0x41 to 0xFE, inclusive, set pointer to (lead − 0x81) × 190 + (byte − 0x41).
   5. %~cp ~LET ［ %~pointer ~EQ ~NULL ならば ~NULL ／ ~ELSE_ `索引~EUC-KR$ の中で %~pointer が指す`索引~cp$ ］ ◎ Let code point be null, if pointer is null, and the index code point for pointer in index EUC-KR otherwise.
   6. ~IF［ %~cp ~NEQ ~NULL ］ ⇒ ~RET ~cp [ %~cp ] ◎ If code point is non-null, return a code point whose value is code point.
   7. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ %~byte を %~stream に`前付加する$ ◎ If byte is an ASCII byte, prepend byte to stream.
   8. ~RET `~error$ ◎ Return error.
3. ~IF［ %~byte ~IN `~ASCII~byte$ ］ ⇒ ~RET ~cp [ %~byte ] ◎ If byte is an ASCII byte, return a code point whose value is byte.
4. ~IF［ %~byte ~IN { `81^X 〜 `FE^X } ］ ⇒＃ `~EUC-KR~lead$ ~SET %~byte ； ~RET `継続$ ◎ If byte is in the range 0x81 to 0xFE, inclusive, set EUC-KR lead to byte and return continue.
5. ~RET `~error$ ◎ Return error.

13.1.2. ~EUC-KR~encoder

`EUC-KR$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ EUC-KR’s encoder’s handler, given a stream and code point, runs these steps:

1. ~IF［ %~cp ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If code point is end-of-stream, return finished.
2. ~IF［ %~cp ~IN `~ASCII~cp$ ］ ⇒ ~RET ~byte列 [ %~cp ] ◎ If code point is an ASCII code point, return a byte whose value is code point.
3. %~pointer ~LET `索引~EUC-KR$ の中で %~cp を指す`索引~pointer$ ◎ Let pointer be the index pointer for code point in index EUC-KR.
4. ~IF［ %~pointer ~EQ ~NULL ］ ⇒ ~RET %~cp を伴う`~error$ ◎ If pointer is null, return error with code point.
5. %~lead ~LET ( %~pointer ~DIV 190 ) ~PLUS `81^X ◎ Let lead be pointer / 190 + 0x81.
6. %~trail ~LET ( %~pointer ~MOD 190 ) ~PLUS `41^X ◎ Let trail be pointer % 190 + 0x41.
7. ~RET ~byte列 [ %~lead, %~trail ] ◎ Return two bytes whose values are lead and trail.

14.1.1. ~replacement~decoder

各［ `replacement$n の`~decoder$ ］には、次のものが結付けられる ⇒ `~replacementによる~errorはすでに返した~flag@（初期~時 ~OFF ） ◎ replacement’s decoder has an associated replacement error returned flag (initially unset).

`replacement$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ replacement’s decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］ ⇒ ~RET `完遂$ ◎ If byte is end-of-stream, return finished.
2. ~IF［ `~replacementによる~errorはすでに返した~flag$ ~EQ ~OFF ］ ⇒＃ `~replacementによる~errorはすでに返した~flag$ ~SET ~ON ； ~RET `~error$ ◎ If replacement error returned flag is unset, set the replacement error returned flag and return error.
3. ~RET `完遂$ ◎ Return finished.

【 `replacement$n には、`~encoder$はない。 】

14.2.1. 共用~UTF-16~decoder

注記： ~BOM（ byte order mark, “バイト順マーク” ）は`~label$より優先される。 それは，配備-済みの内容において、どの`~label$よりも正確aであることが見出されているので。 したがって それは、`共用~UTF-16~decoder$の一部ではなく，`~decode$ ~algoの一部になる。 ◎ A byte order mark has priority over a label as it has been found to be more accurate in deployed content. Therefore it is not part of the shared UTF-16 decoder algorithm but rather the decode algorithm.

各［ `共用~UTF-16~decoder$ ］には、次のものが結付けられる ⇒＃ `~UTF-16~lead~byte@（初期~時 ~NULL ）, `~UTF-16~lead~surrogate@（初期~時 ~NULL ）, `~UTF-16BE~decoder~flag@（初期~時 ~OFF ） ◎ shared UTF-16 decoder has an associated UTF-16 lead byte and UTF-16 lead surrogate (both initially null), and UTF-16BE decoder flag (initially unset).

`共用~UTF-16~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ shared UTF-16 decoder’s handler, given a stream and byte, runs these steps:

1. ~IF［ %~byte ~EQ `~EoS$ ］： ◎ ↓

   1. ~IF［ `~UTF-16~lead~byte$ ~NEQ ~NULL ］~OR［ `~UTF-16~lead~surrogate$ ~NEQ ~NULL ］ ⇒＃ `~UTF-16~lead~byte$ ~SET ~NULL； `~UTF-16~lead~surrogate$ ~SET ~NULL； ~RET `~error$ ◎ If byte is end-of-stream and either UTF-16 lead byte or UTF-16 lead surrogate is non-null, set UTF-16 lead byte and UTF-16 lead surrogate to null, and return error.
   2. ~ELSE ⇒ ~RET `完遂$ ◎ If byte is end-of-stream and UTF-16 lead byte and UTF-16 lead surrogate are null, return finished.
2. ~IF［ `~UTF-16~lead~byte$ ~EQ ~NULL ］ ⇒＃ `~UTF-16~lead~byte$ ~SET %~byte ； ~RET `継続$ ◎ If UTF-16 lead byte is null, set UTF-16 lead byte to byte and return continue.
3. %~cu ~LET `~UTF-16BE~decoder~flag$に応じて ⇒＃ ~ON ならば ( ( `~UTF-16~lead~byte$ ~Lshift 8 ) ~PLUS %~byte ) ／ ~OFF ならば ( ( %~byte ~Lshift 8 ) ~PLUS `~UTF-16~lead~byte$ ) ◎ Let code unit be the result of: • UTF-16BE decoder flag is set •• (UTF-16 lead byte << 8) + byte. • UTF-16BE decoder flag is unset •• (byte << 8) + UTF-16 lead byte.
4. `~UTF-16~lead~byte$ ~SET ~NULL ◎ Then set UTF-16 lead byte to null.

5. ~IF［ `~UTF-16~lead~surrogate$ ~NEQ ~NULL ］： ◎ If UTF-16 lead surrogate is non-null,＼

   1. %~lead~surrogate ~LET `~UTF-16~lead~surrogate$ ◎ let lead surrogate be UTF-16 lead surrogate,＼
   2. `~UTF-16~lead~surrogate$ ~SET ~NULL ◎ set UTF-16 lead surrogate to null, and then:
   3. ~IF［ %~cu ~IN { `DC00^U 〜 `DFFF^U } ］ ⇒ ~RET ~cp [ `10000^X ~PLUS ( ( %~lead~surrogate ~MINUS `D800^X ) ~Lshift 10 ) ~PLUS ( %~cu ~MINUS `DC00^X ) ] ◎ If code unit is in the range U+DC00 to U+DFFF, inclusive, return a code point whose value is 0x10000 + ((lead surrogate − 0xD800) << 10) + (code unit − 0xDC00).
   4. %byte1 ~LET %~cu ~Rshift 8 ◎ Let byte1 be code unit >> 8.
   5. %byte2 ~LET %~cu ~bAND `00FF^X ◎ Let byte2 be code unit & 0x00FF.
   6. %~byte列 ~LET %~utf-16be~flag に応じて ⇒＃ ~ON ならば ~byte列 [ %byte1, %byte2 ] ／ ~OFF ならば ~byte列 [ %byte2, %byte1 ] ◎ Let bytes be two bytes whose values are byte1 and byte2, if the UTF-16BE decoder flag is set, and byte2 and byte1 otherwise.
   7. %~byte列 を %~stream に`前付加する$ ◎ Prepend the bytes to stream and return error.
   8. ~RET `~error$ ◎ ↑
6. ~IF［ %~cu ~IN { `D800^U 〜 `DBFF^U } ］ ⇒＃ `~UTF-16~lead~surrogate$ ~SET %~cu ； ~RET `継続$ ◎ If code unit is in the range U+D800 to U+DBFF, inclusive, set UTF-16 lead surrogate to code unit and return continue.
7. ~IF［ %~cu ~IN { `DC00^U 〜 `DFFF^U } ］ ⇒ ~RET `~error$ ◎ If code unit is in the range U+DC00 to U+DFFF, inclusive, return error.
8. ~RET ~cp [ %~cu ] ◎ Return code point code unit.

14.3.1. ~UTF-16BE~decoder

`UTF-16BE$n の`~decoder$は、［ `~UTF-16BE~decoder~flag$ ~SET ~ON ］にされた`共用~UTF-16~decoder$である。 ◎ UTF-16BE’s decoder is shared UTF-16 decoder with its UTF-16BE decoder flag set.

14.4.1. ~UTF-16LE~decoder

`UTF-16BE$n の`~decoder$は、`共用~UTF-16~decoder$である。 ◎ UTF-16LE’s decoder is shared UTF-16 decoder.

14.5.1. ~x-user-defined~decoder

`x-user-defined$n の`~decoder$の`~handler$は、所与の ( %~stream, %~byte ) に対し，次を走らす： ◎ x-user-defined’s decoder’s handler, given a stream and byte, runs these steps:

1. ~RET %~byte に応じて ⇒＃ `~EoS$ならば `完遂$ ／ `~ASCII~byte$であるならば ~cp [ %~byte ] ／ ~ELSE_ ~cp [ `F780^X ~PLUS %~byte ~MINUS `80^X ] ◎ If byte is end-of-stream, return finished. ◎ If byte is an ASCII byte, return a code point whose value is byte. ◎ Return a code point whose value is 0xF780 + byte − 0x80.

14.5.2. ~x-user-defined~encoder

`x-user-defined$n の`~encoder$の`~handler$は、所与の ( %~stream, %~cp ) に対し，次を走らす： ◎ x-user-defined’s encoder’s handler, given a stream and code point, runs these steps:

1. ~RET %~cp に応じて ⇒＃ `~EoS$ならば `完遂$ ／ `~ASCII~cp$ならば ~byte列 [ %~cp ] ／ `F780^U 〜 `F7FF^U ならば ~byte列 [ %~cp ~MINUS `F780^X ~PLUS `80^X ] ／ ~ELSE_ %~cp を伴う`~error$ ◎ If code point is end-of-stream, return finished. ◎ If code point is an ASCII code point, return a byte whose value is code point. ◎ If code point is in the range U+F780 to U+F7FF, inclusive, return a byte whose value is code point − 0xF780 + 0x80. ◎ Return error with code point.