/* $Id: unicode.c,v 2.0 1995/01/29 08:10:04 ygz Exp $ */

#ifndef lint
static char *rcs_id="$Id: unicode.c,v 2.0 1995/01/29 08:10:04 ygz Exp $";
#endif /* lint */

#include "config.h"
#include "io.h"

/*** UTF8 => UNICODE ***/

static int u8toun(p, len, pu1, pu2)
    char *p;
    int len;
    unsigned char *pu1, *pu2;
{
  register unsigned char c1 = p[0], c2 = p[1], c3 = p[2];

	if ((c1 & 0x80) == 0) {	/* ASCII character */
		*pu1 = 0;
		*pu2 = c1;
		return 1;
	}
	if ((c1 & 0xc0) == 0x80) {	/* unexpected tail character */
		return -1;
	}
	if ((c1 & 0xe0) == 0xc0) {	/* 110vvvvv 10vvvvvv */
		if (len < 2)	/* at least two characters are expected */
			return 0;	/* dangling */
		if ((c2 & 0xc0) != 0x80)  /* unexpected head character */
			return -2;
		*pu1 = (c1 & 0x1c) >> 2;
		*pu2 = ((c1 & 0x03) << 6) | (c2 & 0x3f);
		return 2;
	}
	if ((c1 & 0xf0) == 0xe0) {	/* 1110vvvv 10vvvvvv 10vvvvvv */
		if (len < 3)	/* at least three characters are expected */
			return 0;	/* dangling */
		if ((c2 & 0xc0) != 0x80)  /* unexpected head character */
			return -2;
		if ((c3 & 0xc0) != 0x80)  /* unexpected head character */
			return -3;
		*pu1 = ((c1 & 0x0f) << 4) | ((c2 & 0x3c) >> 2);
		*pu2 = ((c2 & 0x03) << 6) | (c3 & 0x3f);
		return 3;
	}
}

static char utf8_uni_savec[MAX_MODULE][2];

int utf8_uni_init (arg)
     char *arg;
{
  static int utf8_uni_inst = 0;

	utf8_uni_savec[utf8_uni_inst][0] = '\0';
	utf8_uni_savec[utf8_uni_inst][1] = '\0';
	return (utf8_uni_inst++);
}

#define CODE_ERROR	0x80

char *utf8_uni (s,plen,inst)
     char *s;
     int *plen;
     int inst;
{
  char buf[4096];
  char *s_start = s;
  register int len = *plen;
  register char *p = buf;

	if (len == 0)
                return (s);
	if (utf8_uni_savec[inst][0]) {
		if (utf8_uni_savec[inst][1]) {
			*(--s) = utf8_uni_savec[inst][1];
			len++;
			utf8_uni_savec[inst][1] = 0;
		}
		*(--s) = utf8_uni_savec[inst][0];
		len++;
		utf8_uni_savec[inst][0] = 0;
	}
	bcopy(s, p, len);

	s = s_start;
	while (len > 0) {
		int nc = u8toun(p, len, s, s+1);

		if (nc > 0) {
			s++; s++;
			p += nc;
			len -= nc;
		} else if (nc < 0) { 	/* bad character */
			*s++ = 0;
			*s++ = CODE_ERROR;
			p += (-nc);
			len -= (-nc);
		} else {	/* dangling */
			if (len <= 2)
				utf8_uni_savec[inst][0] = *p++;
			if (len == 1)
				utf8_uni_savec[inst][1] = *p++;
			break;
		}
	}
	*plen = s - s_start;
	return s_start;
}

/*** UNICODE => UTF8 ***/

static char uni_utf8_savec[MAX_MODULE];
static char uni_utf8_saved[MAX_MODULE];

int uni_utf8_init (arg)
     char *arg;
{
  static int uni_utf8_inst = 0;

	uni_utf8_saved[uni_utf8_inst] = 0;
	return (uni_utf8_inst++);
}

char *uni_utf8 (s,plen,inst)
     char *s;
     int *plen;
     int inst;
{
  char buf[4096];
  char *s_start = s;
  register int len = *plen;
  register char *p = buf;

	if (len == 0)
                return (s);
	if (uni_utf8_saved[inst]) {
		*(--s) = uni_utf8_savec[inst];
		len++;
		uni_utf8_saved[inst] = 0;
	}
	bcopy(s, p, len);

	s = s_start;
	while (len >= 2) {
		if ((p[0] == 0) && ((p[1] & 0x80) == 0)) {	/* ASCII */
			*s++ = p[1];
		} else if ((p[0] & 0xf8) == 0) {	/* 0x0080 - 0x07ff */
			*s++ = 0xc0 | (p[0] << 2) | ((p[1] >> 6) & 0x03);
			*s++ = 0x80 | (p[1] & 0x3f);
		} else {				/* 0x0800 - 0xffff */
			*s++ = 0xe0 | ((p[0] >> 4) & 0x0f);
			*s++ = 0x80 | ((p[0] & 0x0f) << 2) |
					((p[1] >> 6) & 0x03);
			*s++ = 0x80 | (p[1] & 0x3f);
		}
		p++;  p++;
		len--;  len--;
	}
	if (len == 1) {		/* dangling */
		uni_utf8_saved[inst] = 1;
		uni_utf8_savec[inst] = *p;
	}
	*plen = s - s_start;
	return s_start;
}

/*********** UTF 7 **************/

/* ASCII subsets */
static	unsigned char	base64[] =
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

#define	SAFE_CHARS	"'(),-.:?"
#define	SPACE_CHARS	" \t\n\r"

/* character classes */
#define	BASE64		0x01
#define	SAFE		0x02
#define	SPACE		0x04

/* base64 state */
#define	IN_ASCII	0
#define	IN_BASE64	1
#define AFTER_PLUS	2

static	char	inv_base64[128];
static	char	char_type[256];

static void init_utf7_tables()
{
  register unsigned char *s;
  static first_time = 1;

	if (! first_time)
		return;

	for (s = base64; *s != '\0'; s++) {
		char_type[*s] |= BASE64;
		inv_base64[*s] = s - base64;
	}
	for (s = SAFE_CHARS;  *s != '\0';  s++)
		char_type[*s] |= SAFE;
	for (s = SPACE_CHARS;  *s != '\0';  s++)
		char_type[*s] |= SPACE;

	first_time = 0;
}

struct utf7_context {
    short int state;		/* state in the base64 */
    short int nbits;		/* number of bits in the bit buffer */
    unsigned long bit_buffer;
};

static int u7toun(c, pu1, pu2, ctx)	/* return 1 if a unicode is produced */
    unsigned char c;		/* a char in utf7 stream */
    unsigned char *pu1, *pu2;	/* the unicode */
    struct utf7_context *ctx;	/* the context */
{
	if (ctx->state == IN_ASCII) {
		if (c == '+') {
			ctx->state = AFTER_PLUS;
			return 0;
		} else {
			*pu1 = 0;  *pu2 = c;
			return 1;
		}
	}
	if (ctx->state == AFTER_PLUS) {
		if (c == '-') {
			*pu1 = 0;  *pu2 = '+';
			return 1;
		} else {
			ctx->state = IN_BASE64;
			ctx->nbits = 0;
			/* don't return yet, continue to the IN_BASE64 mode */
		}
	}

	/* now we're in Base64 mode */
	if (char_type[c]&BASE64) {
		ctx->bit_buffer <<= 6;
		ctx->bit_buffer |= inv_base64[c];
		ctx->nbits += 6;
		if (ctx->nbits >= 16) {
			ctx->nbits -= 16;
			*pu1 = (char)((ctx->bit_buffer >> (ctx->nbits + 8))
					& 0x00ff);
			*pu2 = (char)((ctx->bit_buffer >>  ctx->nbits     )
					& 0x00ff);
			return 1;
		}
		return 0;
	}
	ctx->state = IN_ASCII;
	if (c != '-') {
		*pu1 = 0;  *pu2 = c;
		return 1;
	}
	return 0;
}

static int untou7(u1, u2, s, ctx)	/* return the # of char written to s */
    unsigned char u1, u2;	/* the unicode */
    unsigned char *s;		/* store here */
    struct utf7_context *ctx;	/* the context */
{
  unsigned char *prev_s = s;

	if ( ((u1 == 0) && ((u2 & 0x80) == 0)) &&
	     (char_type[u2] & (BASE64|SAFE|SPACE)) ) {	/* safe ASCII */
		if (ctx->state == IN_BASE64) {
			if (ctx->nbits > 0)
				*s++ = base64[
				    (ctx->bit_buffer<<(6 - ctx->nbits)) & 0x3f
				];
			if ((char_type[u2] & BASE64) || u2 == '-')						*s++ = '-';
			ctx->state = IN_ASCII;
		}
		*s++ = u2;
		if (u2 == '+')
			*s++ = '-';
	} else {
		if (ctx->state == IN_ASCII) {
			*s++ = '+';
			ctx->state = IN_BASE64;
			ctx->nbits = 0;
		}
		ctx->bit_buffer <<= 8;
		ctx->bit_buffer |= u1;
		ctx->bit_buffer <<= 8;
		ctx->bit_buffer |= u2;
		ctx->nbits += 16;
		while (ctx->nbits >= 6) {
			ctx->nbits -= 6;
			*s++ = base64[(ctx->bit_buffer >> ctx->nbits) & 0x3f];
		}
	}
	return (s - prev_s);	/* return the length */
}

/***** UTF7 => UNICODE *****/

static struct utf7_context utf7_uni_context[MAX_MODULE];

int utf7_uni_init (arg)
     char *arg;
{
  static int utf7_uni_inst = 0;

	init_utf7_tables();
	utf7_uni_context[utf7_uni_inst].state = IN_ASCII;
	utf7_uni_context[utf7_uni_inst].nbits = 0;
	utf7_uni_context[utf7_uni_inst].bit_buffer = 0L;
	return (utf7_uni_inst++);
}

char *utf7_uni (s,plen,inst)
     char *s;
     int *plen;
     int inst;
{
  char buf[4096];
  char *s_start = s;
  register int len = *plen;
  register char *p = buf;

	if (len == 0)
                return (s);
	bcopy(s, p, len);

	while (len-- > 0) {
		if (u7toun(*p++, s, s+1, &(utf7_uni_context[inst]))) {
			s++;  s++;
		}
	}
	*plen = s - s_start;
	return s_start;
}

/***** UNICODE => UTF7 *****/

static char uni_utf7_savec[MAX_MODULE];
static char uni_utf7_saved[MAX_MODULE];
static struct utf7_context uni_utf7_context[MAX_MODULE];

int uni_utf7_init (arg)
     char *arg;
{
  static int uni_utf7_inst = 0;

	init_utf7_tables();
	uni_utf7_saved[uni_utf7_inst] = 0;
	uni_utf7_context[uni_utf7_inst].state = IN_ASCII;
	uni_utf7_context[uni_utf7_inst].nbits = 0;
	uni_utf7_context[uni_utf7_inst].bit_buffer = 0L;
	return (uni_utf7_inst++);
}

char *uni_utf7 (s,plen,inst)
     char *s;
     int *plen;
     int inst;
{
  char buf[4096];
  char *s_start = s;
  register int len = *plen;
  register char *p = buf;
  
	if (len == 0)
                return (s);
	if (uni_utf7_saved[inst]) {
		*(--s) = uni_utf7_savec[inst];
		len++;
		uni_utf7_saved[inst] = 0;
	}
	bcopy(s, p, len);

	s = s_start;
	while (len >= 2) {
		s += untou7(p[0], p[1], s, &(uni_utf7_context[inst]));
		len --;  len --;
		p++;  p++;
	}
	if (len == 1) {		/* dangling */
		uni_utf7_saved[inst] = 1;
		uni_utf7_savec[inst] = *p;
	}
	*plen = s - s_start;
	return s_start;
}