日文ISO-2022-JP编码支持的【JIS X0208保留领域13区】

区点	JIS	SJIS	+0	+1	+2	+3	+4	+5	+6	+7	+8	+9	+A	+B	+C	+D	+E	+F
13区	2D20	873F		①	②	③	④	⑤	⑥	⑦	⑧	⑨	⑩	⑪	⑫	⑬	⑭	⑮
	2D30	874F	⑯	⑰	⑱	⑲	⑳	Ⅰ	Ⅱ	Ⅲ	Ⅳ	Ⅴ	Ⅵ	Ⅶ	Ⅷ	Ⅸ	Ⅹ
	2D40	875F	㍉	㌔	㌢	㍍	㌘	㌧	㌃	㌶	㍑	㍗	㌍	㌦	㌣	㌫	㍊	㌻
	2D50	876F	㎜	㎝	㎞	㎎	㎏	㏄	㎡									㍻
	2D60	8780	〝	〟	№	㏍	℡	㊤	㊥	㊦	㊧	㊨	㈱	㈲	㈹	㍾	㍽	㍼
	2D70	8790	≒	≡	∫	∮	∑	√	⊥	∠	∟	⊿	∵	∩	∪

libiconvxxx/lib/目录下的jisx0208.h文件

增加代码：

/*
 *Windows的机种依存文字 PC-9800系列等，NEC的电脑在日本主流的时候曾独自被定义了文字13区分配。
 **/
static const unsigned short jisx0208_2uni_page2D[96] = {
	/* 0x2D20 - 0x2D2F */
	0xfffd, 0x2460, 0x2461, 0x2462, 0x2463, 0x2464, 0x2465, 0x2466,
	0x2467,	0x2468, 0x2469, 0x246A, 0x246B, 0x246C, 0x246D, 0x246E,
	/* 0x2D30 - 0x2D3F */
	0x246F,	0x2470, 0x2471, 0x2472, 0x2473, 0x2160, 0x2161, 0x2162,
	0x2163,	0x2164,	0x2165, 0x2166, 0x2167, 0x2168, 0x2169, 0xfffd,
	/* 0x2D40 - 0x2D4F */
	0x3349, 0x3314,	0x3322, 0x334D, 0x3318, 0x3327, 0x3303, 0x3336,
	0x3351,	0x3357,	0x330D, 0x3326, 0x3323, 0x332B, 0x334A, 0x333B,
	/* 0x2D50 - 0x2D5F */
	0x339C, 0x339D, 0x339E, 0x338E, 0x338F, 0x33C4, 0x33A1, 0xfffd,
	0xfffd, 0xfffd, 0xfffd, 0xfffd, 0xfffd, 0xfffd, 0xfffd, 0x337B,
	/* 0x2D60 - 0x2D6F */
	0x301D, 0x301F, 0x2116, 0x33CD, 0x2121, 0x32A4, 0x32A5, 0x32A6,
	0x32A7, 0x32A8, 0x3231, 0x3232, 0x3239, 0x337E, 0x337D, 0x337C,
	/* 0x2D70 - 0x2D7F */
	0x2252, 0x2261, 0x222B, 0x222E, 0x2211, 0x221A, 0x22A5, 0x2220,
	0x221F, 0x22BF, 0x2235, 0x2229, 0x222A, 0xfffd, 0xfffd, 0xfffd
};

修改原函数：

static int
jisx0208_mbtowc (conv_t conv, ucs4_t *pwc, const unsigned char *s, int n)
{
  unsigned char c1 = s[0];

  /* 增加jp 对 [Windows的机种依存文字] 解码的支持*/
  if (c1 == 0x2D)
  {
	  if (n >= 2)
	  {
		unsigned char c2 = s[1];
		if (c2 >= 0x20 && c2 < 0x7F) {
		  unsigned int i = (c2 - 0x20);
		  unsigned short wc = jisx0208_2uni_page2D[i];
		  *pwc = (ucs4_t) wc;
		  return 2;
		}
		return RET_ILSEQ;
	  }
	  return RET_TOOFEW(0);
  }
  /* end */

  if ((c1 >= 0x21 && c1 <= 0x28) || (c1 >= 0x30 && c1 <= 0x74)) {
    if (n >= 2) {
      unsigned char c2 = s[1];
      if (c2 >= 0x21 && c2 < 0x7f) {
        unsigned int i = 94 * (c1 - 0x21) + (c2 - 0x21);
        unsigned short wc = 0xfffd;
        if (i < 1410) {
          if (i < 690)
            wc = jisx0208_2uni_page21[i];
        } else {
          if (i < 7808)
            wc = jisx0208_2uni_page30[i-1410];
        }
        if (wc != 0xfffd) {
          *pwc = (ucs4_t) wc;
          return 2;
        }
      }
      return RET_ILSEQ;
    }
    return RET_TOOFEW(0);
  }
  return RET_ILSEQ;
}