#include <stdio.h>

#include "gb18030.h"

/* GB18030-2000 is an encoding of Unicode character used in China

 *

 * {0x00-0x7f} are one byte characters identical to US-ASCII

 * {0x80} is properly undefined, but many GB18030 encodings make

 *      it the Euro sign (Unicode 0x20AC), so use that

 * {0x81-0xFE}{0x40-0x7E,0x80-0xFE} a full superset of GBK (with fallback 

 *      mappings)

 * {0x81-0xFE}{0x30-0x39}{0x81-0xFE}{0x30-0x39} maps linearly to ISO 10646

 *      GB+81308130 = U+0080 up to U+FFFF

 *      GB+90308130 = U+10000 up to U+10FFFF skipping mappings already

 *                     defined in 1-byte and 2-byte areas.

 *

 * Truth is it's a bit of a mess algorithmically as it doesn't multiply

 * encode characters, so there are holes in the Unicode mapping that

 * should be avoided.

 */

/* This is a "small" region that needs explicit enumeration */

#include "gb18030_enumeration.c"

static int

in_range( unsigned char n, unsigned char low, unsigned char high )

{

	if ( n < low || n > high ) return 0;

	return 1;

}

/* Get GB 18030 from Unicode Value in Table */

static int

gb18030_unicode_table_lookup( unsigned int unicode, unsigned char out[4] )

{

	int i, j;

	if ( unicode >= 0x0080 && unicode <= 0xFFE5 ) {

		/* list is sorted, so should do binary search here */

		for ( i=0; i

			if ( unicode == gb18030_enums[i].unicode ) {

				for ( j=0; j

					out[j] = gb18030_enums[i].bytes[j];

				return gb18030_enums[i].len;

			}

		}

	}

	return 0;

}

static int

gb18030_match( unsigned char *s, const unsigned char *bytes, unsigned char len )

{

	int i;

	for ( i=0; i

		if ( ( s[i])!=bytes[i] ) return 0;

	return 1;

}

static unsigned int

gb18030_table_lookup( unsigned char *uc, unsigned char len, int *found )

{

	unsigned int i;

	*found = 0;

	for ( i=0; i

		if ( gb18030_enums[i].len!=len ) continue;

		if ( gb18030_match( &(uc[0]), gb18030_enums[i].bytes, len ) ) {

			*found = 1;

			return gb18030_enums[i].unicode;

		}

	}

	return '?';

}

static int

gb18030_unicode_range_lookup( unsigned int unicode, unsigned char out[4] ) 

{

	return 0;

}

static int

gb18030_range_lookup( unsigned char *s, /* unsigned char len = 4 only */ int *found )

{

	*found = 0;

	return 0;

#if 0

       Note that GB 18030 defines roundtrip mappings for all Unicode code points U+0000..U+10ffff.

       This would require 1.1 million  elements.

       However, most four-byte GB 18030 mappings can be enumerated efficiently within distinct ranges.

       Therefore, we use <range> elements for all but the 31000 or so assignments above.

    -->

  <range uFirst="0452" uLast="200F"  bFirst="81 30 D3 30" bLast="81 36 A5 31"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="2643" uLast="2E80"  bFirst="81 37 A8 39" bLast="81 38 FD 38"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="361B" uLast="3917"  bFirst="82 30 A6 33" bLast="82 30 F2 37"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="3CE1" uLast="4055"  bFirst="82 31 D4 38" bLast="82 32 AF 32"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="4160" uLast="4336"  bFirst="82 32 C9 37" bLast="82 32 F8 37"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="44D7" uLast="464B"  bFirst="82 33 A3 39" bLast="82 33 C9 31"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="478E" uLast="4946"  bFirst="82 33 E8 38" bLast="82 34 96 38"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="49B8" uLast="4C76"  bFirst="82 34 A1 31" bLast="82 34 E7 33"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="9FA6" uLast="D7FF"  bFirst="82 35 8F 33" bLast="83 36 C7 38"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="E865" uLast="F92B"  bFirst="83 36 D0 30" bLast="84 30 85 34"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="FA2A" uLast="FE2F"  bFirst="84 30 9C 38" bLast="84 31 85 37"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="FFE6" uLast="FFFF"  bFirst="84 31 A2 34" bLast="84 31 A4 39"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

  <range uFirst="10000" uLast="10FFFF"  bFirst="90 30 81 30" bLast="E3 32 9A 35"  bMin="81 30 81 30" bMax="FE 39 FE 39"/>

#endif

}

unsigned int

gb18030_to_unicode( unsigned char *s, unsigned char len )

{

	unsigned int ret;

	int found;

	ret = gb18030_table_lookup( s, len, &found );

	if ( !found && len==4 ) {

		ret = gb18030_range_lookup( s, &found );

		if ( !found ) ret = '?';

	}

	return ret;

}

/*

 * Convert unicode character to gb18030

 *

 * returns number of characters for output

 */

int

gb18030_encode( unsigned int unicode, unsigned char out[4] )

{

	int len;

	if ( unicode < 0x80 ) {

		out[0] = unicode;

		len = 1;

	} else {

		len = gb18030_unicode_table_lookup( unicode, out );

		if ( !len )

			len = gb18030_unicode_range_lookup( unicode, out ); 

	}

	return len;

}

/*

 * Decode a gb18030 character into unicode

 */

unsigned int

gb18030_decode( char *s, unsigned int *pi )

{

	unsigned int c;

	unsigned char uc[4];

	int i = *pi;

	uc[0] = ( unsigned char ) s[i];

	if ( ( uc[0] & 128 ) == 0 ) {

		c = ( unsigned int ) uc[0];

		i += 1;

	} else if ( uc[0] == 0x80 ) {

		c = 0x20AC;

		i += 1;

	} else if ( uc[0] != 0xFF ) { /* multi-byte character */

		uc[1] = ( unsigned char ) s[i+1];

		uc[2] = ( unsigned char ) s[i+2];

		uc[3]= ( unsigned char ) s[i+3];

		if ( in_range( uc[1], 0x40, 0x7e ) || in_range( uc[1], 0x80, 0xfe ) ) {

			/* two-byte character */

			c = gb18030_to_unicode( &(uc[0]), 2 );

			i += 2;

		} else if ( in_range( uc[1], 0x30, 0x39 ) &&

		            in_range( uc[2], 0x81, 0xfe ) &&

		            in_range( uc[3], 0x30, 0x39 ) ) {

			/* four-byte character */

			c = gb18030_to_unicode( &(uc[0]), 4 );

			i += 4;

		} else {

			/* this is an illegal character */

			c = '?';

			i += 1;

		}

	} else { /* s[i]==0xFF */

		/* this is an illegal character */

		c = '?';

		i += 1;

	}

	*pi = i;

	return c;

}