/*
 * conversion between BIG5 and Mule Internal Code(CNS 116643-1992
 * plane 1 and plane 2).
 * This program is partially copied from lv(Multilingual file viewer)
 * and slightly modified. lv is written and copyrighted by NARITA Tomio
 * (nrt@web.ad.jp).
 *
 * 1999/1/15 Tatsuo Ishii
 *
 * $Id: big5.c,v 1.7 2001/02/10 02:31:27 tgl Exp $
 */

/* can be used in either frontend or backend */
#include "postgres_fe.h"

#include "mb/pg_wchar.h"

typedef struct
{
	unsigned short code,
				peer;
}			codes_t;

/* map Big5 Level 1 to CNS 11643-1992 Plane 1 */
static codes_t big5Level1ToCnsPlane1[25] = {	/* range */
	{0xA140, 0x2121},
	{0xA1F6, 0x2258},
	{0xA1F7, 0x2257},
	{0xA1F8, 0x2259},
	{0xA2AF, 0x2421},
	{0xA3C0, 0x4221},
	{0xa3e1, 0x0000},
	{0xA440, 0x4421},
	{0xACFE, 0x5753},
	{0xacff, 0x0000},
	{0xAD40, 0x5323},
	{0xAFD0, 0x5754},
	{0xBBC8, 0x6B51},
	{0xBE52, 0x6B50},
	{0xBE53, 0x6F5C},
	{0xC1AB, 0x7536},
	{0xC2CB, 0x7535},
	{0xC2CC, 0x7737},
	{0xC361, 0x782E},
	{0xC3B9, 0x7865},
	{0xC3BA, 0x7864},
	{0xC3BB, 0x7866},
	{0xC456, 0x782D},
	{0xC457, 0x7962},
	{0xc67f, 0x0000}
};

/* map CNS 11643-1992 Plane 1 to Big5 Level 1 */
static codes_t cnsPlane1ToBig5Level1[26] = {	/* range */
	{0x2121, 0xA140},
	{0x2257, 0xA1F7},
	{0x2258, 0xA1F6},
	{0x2259, 0xA1F8},
	{0x234f, 0x0000},
	{0x2421, 0xA2AF},
	{0x2571, 0x0000},
	{0x4221, 0xA3C0},
	{0x4242, 0x0000},
	{0x4421, 0xA440},
	{0x5323, 0xAD40},
	{0x5753, 0xACFE},
	{0x5754, 0xAFD0},
	{0x6B50, 0xBE52},
	{0x6B51, 0xBBC8},
	{0x6F5C, 0xBE53},
	{0x7535, 0xC2CB},
	{0x7536, 0xC1AB},
	{0x7737, 0xC2CC},
	{0x782D, 0xC456},
	{0x782E, 0xC361},
	{0x7864, 0xC3BA},
	{0x7865, 0xC3B9},
	{0x7866, 0xC3BB},
	{0x7962, 0xC457},
	{0x7d4c, 0x0000}
};

/* map Big5 Level 2 to CNS 11643-1992 Plane 2 */
static codes_t big5Level2ToCnsPlane2[48] = {	/* range */
	{0xC940, 0x2121},
	{0xc94a, 0x0000},
	{0xC94B, 0x212B},
	{0xC96C, 0x214D},
	{0xC9BE, 0x214C},
	{0xC9BF, 0x217D},
	{0xC9ED, 0x224E},
	{0xCAF7, 0x224D},
	{0xCAF8, 0x2439},
	{0xD77A, 0x3F6A},
	{0xD77B, 0x387E},
	{0xDBA7, 0x3F6B},
	{0xDDFC, 0x4176},
	{0xDDFD, 0x4424},
	{0xE8A3, 0x554C},
	{0xE976, 0x5723},
	{0xEB5B, 0x5A29},
	{0xEBF1, 0x554B},
	{0xEBF2, 0x5B3F},
	{0xECDE, 0x5722},
	{0xECDF, 0x5C6A},
	{0xEDAA, 0x5D75},
	{0xEEEB, 0x642F},
	{0xEEEC, 0x6039},
	{0xF056, 0x5D74},
	{0xF057, 0x6243},
	{0xF0CB, 0x5A28},
	{0xF0CC, 0x6337},
	{0xF163, 0x6430},
	{0xF16B, 0x6761},
	{0xF16C, 0x6438},
	{0xF268, 0x6934},
	{0xF269, 0x6573},
	{0xF2C3, 0x664E},
	{0xF375, 0x6762},
	{0xF466, 0x6935},
	{0xF4B5, 0x664D},
	{0xF4B6, 0x6962},
	{0xF4FD, 0x6A4C},
	{0xF663, 0x6A4B},
	{0xF664, 0x6C52},
	{0xF977, 0x7167},
	{0xF9C4, 0x7166},
	{0xF9C5, 0x7234},
	{0xF9C6, 0x7240},
	{0xF9C7, 0x7235},
	{0xF9D2, 0x7241},
	{0xf9d6, 0x0000}
};

/* map CNS 11643-1992 Plane 2 to Big5 Level 2 */
static codes_t cnsPlane2ToBig5Level2[49] = {	/* range */
	{0x2121, 0xC940},
	{0x212B, 0xC94B},
	{0x214C, 0xC9BE},
	{0x214D, 0xC96C},
	{0x217D, 0xC9BF},
	{0x224D, 0xCAF7},
	{0x224E, 0xC9ED},
	{0x2439, 0xCAF8},
	{0x387E, 0xD77B},
	{0x3F6A, 0xD77A},
	{0x3F6B, 0xDBA7},
	{0x4424, 0x0000},
	{0x4176, 0xDDFC},
	{0x4177, 0x0000},
	{0x4424, 0xDDFD},
	{0x554B, 0xEBF1},
	{0x554C, 0xE8A3},
	{0x5722, 0xECDE},
	{0x5723, 0xE976},
	{0x5A28, 0xF0CB},
	{0x5A29, 0xEB5B},
	{0x5B3F, 0xEBF2},
	{0x5C6A, 0xECDF},
	{0x5D74, 0xF056},
	{0x5D75, 0xEDAA},
	{0x6039, 0xEEEC},
	{0x6243, 0xF057},
	{0x6337, 0xF0CC},
	{0x642F, 0xEEEB},
	{0x6430, 0xF163},
	{0x6438, 0xF16C},
	{0x6573, 0xF269},
	{0x664D, 0xF4B5},
	{0x664E, 0xF2C3},
	{0x6761, 0xF16B},
	{0x6762, 0xF375},
	{0x6934, 0xF268},
	{0x6935, 0xF466},
	{0x6962, 0xF4B6},
	{0x6A4B, 0xF663},
	{0x6A4C, 0xF4FD},
	{0x6C52, 0xF664},
	{0x7166, 0xF9C4},
	{0x7167, 0xF977},
	{0x7234, 0xF9C5},
	{0x7235, 0xF9C7},
	{0x7240, 0xF9C6},
	{0x7241, 0xF9D2},
	{0x7245, 0x0000}
};

/* Big Five Level 1 Correspondence to CNS 11643-1992 Plane 4 */
static unsigned short b1c4[][2] = {
	{0xC879, 0x2123},
	{0xC87B, 0x2124},
	{0xC87D, 0x212A},
	{0xC8A2, 0x2152}
};

/* Big Five Level 2 Correspondence to CNS 11643-1992 Plane 3 */
static unsigned short b2c3[][2] = {
	{0xF9D6, 0x4337},
	{0xF9D7, 0x4F50},
	{0xF9D8, 0x444E},
	{0xF9D9, 0x504A},
	{0xF9DA, 0x2C5D},
	{0xF9DB, 0x3D7E},
	{0xF9DC, 0x4B5C}
};

static unsigned short BinarySearchRange
			(codes_t * array, int high, unsigned short code)
{
	int			low,
				mid,
				distance,
				tmp;

	low = 0;
	mid = high >> 1;

	for (; low <= high; mid = (low + high) >> 1)
	{
		if ((array[mid].code <= code) && (array[mid + 1].code > code))
		{
			if (0 == array[mid].peer)
				return 0;
			if (code >= 0xa140U)
			{
				/* big5 to cns */
				tmp = ((code & 0xff00) - (array[mid].code & 0xff00)) >> 8;
				high = code & 0x00ff;
				low = array[mid].code & 0x00ff;

				/*
				 * NOTE: big5 high_byte: 0xa1-0xfe, low_byte: 0x40-0x7e,
				 * 0xa1-0xfe (radicals: 0x00-0x3e, 0x3f-0x9c) big5 radix
				 * is 0x9d.						[region_low, region_high]
				 * We should remember big5 has two different regions
				 * (above). There is a bias for the distance between these
				 * regions. 0xa1 - 0x7e + bias = 1 (Distance between 0xa1
				 * and 0x7e is 1.) bias = - 0x22.
				 */
				distance = tmp * 0x9d + high - low +
					(high >= 0xa1 ? (low >= 0xa1 ? 0 : -0x22)
					 : (low >= 0xa1 ? +0x22 : 0));

				/*
				 * NOTE: we have to convert the distance into a code
				 * point. The code point's low_byte is 0x21 plus mod_0x5e.
				 * In the first, we extract the mod_0x5e of the starting
				 * code point, subtracting 0x21, and add distance to it.
				 * Then we calculate again mod_0x5e of them, and restore
				 * the final codepoint, adding 0x21.
				 */
				tmp = (array[mid].peer & 0x00ff) + distance - 0x21;
				tmp = (array[mid].peer & 0xff00) + ((tmp / 0x5e) << 8)
					+ 0x21 + tmp % 0x5e;
				return tmp;
			}
			else
			{
				/* cns to big5 */
				tmp = ((code & 0xff00) - (array[mid].code & 0xff00)) >> 8;

				/*
				 * NOTE: ISO charsets ranges between 0x21-0xfe
				 * (94charset). Its radix is 0x5e. But there is no
				 * distance bias like big5.
				 */
				distance = tmp * 0x5e
					+ ((int) (code & 0x00ff) - (int) (array[mid].code & 0x00ff));

				/*
				 * NOTE: Similar to big5 to cns conversion, we extract
				 * mod_0x9d and restore mod_0x9d into a code point.
				 */
				low = array[mid].peer & 0x00ff;
				tmp = low + distance - (low >= 0xa1 ? 0x62 : 0x40);
				low = tmp % 0x9d;
				tmp = (array[mid].peer & 0xff00) + ((tmp / 0x9d) << 8)
					+ (low > 0x3e ? 0x62 : 0x40) + low;
				return tmp;
			}
		}
		else if (array[mid].code > code)
			high = mid - 1;
		else
			low = mid + 1;
	}

	return 0;
}


unsigned short
BIG5toCNS(unsigned short big5, unsigned char *lc)
{
	unsigned short cns = 0;
	int			i;

	if (big5 < 0xc940U)
	{
		/* level 1 */

		for (i = 0; i < sizeof(b1c4) / sizeof(unsigned short); i++)
		{
			if (b1c4[i][0] == big5)
			{
				*lc = LC_CNS11643_4;
				return (b1c4[i][1] | 0x8080U);
			}
		}

		if (0 < (cns = BinarySearchRange(big5Level1ToCnsPlane1, 23, big5)))
			*lc = LC_CNS11643_1;
	}
	else if (big5 == 0xc94aU)
	{
		/* level 2 */
		*lc = LC_CNS11643_1;
		cns = 0x4442;
	}
	else
	{
		/* level 2 */
		for (i = 0; i < sizeof(b2c3) / sizeof(unsigned short); i++)
		{
			if (b2c3[i][0] == big5)
			{
				*lc = LC_CNS11643_3;
				return (b2c3[i][1] | 0x8080U);
			}
		}

		if (0 < (cns = BinarySearchRange(big5Level2ToCnsPlane2, 46, big5)))
			*lc = LC_CNS11643_2;
	}

	if (0 == cns)
	{							/* no mapping Big5 to CNS 11643-1992 */
		*lc = 0;
		return (unsigned short) '?';
	}

	return cns | 0x8080;
}

unsigned short
CNStoBIG5(unsigned short cns, unsigned char lc)
{
	int			i;
	unsigned int big5 = 0;

	cns &= 0x7f7f;

	switch (lc)
	{
		case LC_CNS11643_1:
			big5 = BinarySearchRange(cnsPlane1ToBig5Level1, 24, cns);
			break;
		case LC_CNS11643_2:
			big5 = BinarySearchRange(cnsPlane2ToBig5Level2, 47, cns);
			break;
		case LC_CNS11643_3:
			for (i = 0; i < sizeof(b2c3) / sizeof(unsigned short); i++)
			{
				if (b2c3[i][1] == cns)
					return (b2c3[i][0]);
			}
			break;
		case LC_CNS11643_4:
			for (i = 0; i < sizeof(b1c4) / sizeof(unsigned short); i++)
			{
				if (b1c4[i][1] == cns)
					return (b1c4[i][0]);
			}
		default:
			break;
	}
	return big5;
}