/* ================================================================ */
/*
File:   ConvertUTF7.c
Author: David B. Goldsmith
Copyright (C) 1994, 1996 Taligent, Inc. All rights reserved.

This code is copyrighted. Under the copyright laws, this code may not
be copied, in whole or part, without prior written consent of Taligent. 

Taligent grants the right to use this code as long as this ENTIRE
copyright notice is reproduced in the code.  The code is provided
AS-IS, AND TALIGENT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR
IMPLIED, INCLUDING, BUT NOT LIMITED TO IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT
WILL TALIGENT BE LIABLE FOR ANY DAMAGES WHATSOEVER (INCLUDING,
WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS PROFITS, BUSINESS
INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR OTHER PECUNIARY
LOSS) ARISING OUT OF THE USE OR INABILITY TO USE THIS CODE, EVEN
IF TALIGENT HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
BECAUSE SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF
LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES, THE ABOVE
LIMITATION MAY NOT APPLY TO YOU.

RESTRICTED RIGHTS LEGEND: Use, duplication, or disclosure by the
government is subject to restrictions as set forth in subparagraph
(c)(l)(ii) of the Rights in Technical Data and Computer Software
clause at DFARS 252.227-7013 and FAR 52.227-19.

This code may be protected by one or more U.S. and International
Patents.

TRADEMARKS: Taligent and the Taligent Design Mark are registered
trademarks of Taligent, Inc.
*/

#include "CVTUTF7.H"

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static short invbase64[128];

static char direct[] = 
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'(),-./:?";
static char optional[] = "!\"#$%&*;<=>@[]^_`{|}";
static char spaces[] = " \011\015\012";		/* space, tab, return, line feed */
static char mustshiftsafe[128];
static char mustshiftopt[128];

static int needtables = 1;

#define SHIFT_IN '+'
#define SHIFT_OUT '-'

static void
tabinit()
{
	int i, limit;

	for (i = 0; i < 128; ++i)
	{
		mustshiftopt[i] = mustshiftsafe[i] = 1;
		invbase64[i] = -1;
	}
	limit = strlen(direct);
	for (i = 0; i < limit; ++i)
		mustshiftopt[direct[i]] = mustshiftsafe[direct[i]] = 0;
	limit = strlen(spaces);
	for (i = 0; i < limit; ++i)
		mustshiftopt[spaces[i]] = mustshiftsafe[spaces[i]] = 0;
	limit = strlen(optional);
	for (i = 0; i < limit; ++i)
		mustshiftopt[optional[i]] = 0;
	limit = strlen(base64);
	for (i = 0; i < limit; ++i)
		invbase64[base64[i]] = i;

	needtables = 0;
}

#define DECLARE_BIT_BUFFER register unsigned long BITbuffer = 0, buffertemp = 0; int bufferbits = 0
#define BITS_IN_BUFFER bufferbits
#define WRITE_N_BITS(x, n) ((BITbuffer |= ( ((x) & ~(-1L<<(n))) << (32-(n)-bufferbits) ) ), bufferbits += (n) )
#define READ_N_BITS(n) ((buffertemp = (BITbuffer >> (32-(n)))), (BITbuffer <<= (n)), (bufferbits -= (n)), buffertemp)
#define TARGETCHECK  {if (target >= targetEnd) {result = targetExhausted; break;}}

ConversionResult ConvertUCS2toUTF7(
                UCS2** sourceStart, UCS2* sourceEnd, 
                char** targetStart, char* targetEnd,
                int optional, int verbose)
{
	ConversionResult result = ok;
	DECLARE_BIT_BUFFER;
	int shifted = 0, needshift = 0, done = 0;
	register UCS2 *source = *sourceStart;
	register char *target = *targetStart;
	char *mustshift;

	if (needtables)
		tabinit();

	if (optional)
		mustshift = mustshiftopt;
	else
		mustshift = mustshiftsafe;

	do
	{
		register UCS2 r;

		if (!(done = (source >= sourceEnd)))
			r = *source++;
		needshift = (!done && ((r > 0x7f) || mustshift[r]));

		if (needshift && !shifted)
		{
			TARGETCHECK;
			*target++ = SHIFT_IN;
			/* Special case handling of the SHIFT_IN character */
			if (r == (UCS2)SHIFT_IN) {
				TARGETCHECK;
				*target++ = SHIFT_OUT;
			}
			else
				shifted = 1;
		}

		if (shifted)
		{
			/* Either write the character to the bit buffer, or pad
			   the bit buffer out to a full base64 character.
			 */
			if (needshift)
				WRITE_N_BITS(r, 16);
			else
				WRITE_N_BITS(0, (6 - (BITS_IN_BUFFER % 6))%6);

			/* Flush out as many full base64 characters as possible
			   from the bit buffer.
			 */
			while ((target < targetEnd) && BITS_IN_BUFFER >= 6)
			{
				*target++ = base64[READ_N_BITS(6)];
			}

			if (BITS_IN_BUFFER >= 6)
				TARGETCHECK;

			if (!needshift)
			{
				/* Write the explicit shift out character if
				   1) The caller has requested we always do it, or
				   2) The directly encoded character is in the
				   base64 set, or
				   3) The directly encoded character is SHIFT_OUT.
				 */
				if (verbose || ((!done) && (invbase64[r] >=0 || r == SHIFT_OUT)))
				{
					TARGETCHECK;
					*target++ = SHIFT_OUT;
				}
				shifted = 0;
			}
		}

		/* The character can be directly encoded as ASCII. */
		if (!needshift && !done)
		{
			TARGETCHECK;
			*target++ = (char) r;
		}

	}
	while (!done);
	
    *sourceStart = source;
    *targetStart = target;
    return result;
}

ConversionResult ConvertUTF7toUCS2(
                char** sourceStart, char* sourceEnd, 
                UCS2** targetStart, UCS2* targetEnd)
{
	ConversionResult result = ok;
	DECLARE_BIT_BUFFER;
	int shifted = 0, first = 0, wroteone = 0, base64EOF, base64value, done;
	unsigned int c, prevc;
	unsigned long junk;
	register char *source = *sourceStart;
	register UCS2 *target = *targetStart;

	if (needtables)
		tabinit();

	do
	{
		/* read an ASCII character c */
		if (!(done = (source >= sourceEnd)))
			c = *source++;
		if (shifted)
		{
			/* We're done with a base64 string if we hit EOF, it's not a valid
			   ASCII character, or it's not in the base64 set.
			 */
			base64EOF = done || (c > 0x7f) || (base64value = invbase64[c]) < 0;
			if (base64EOF)
			{
				shifted = 0;
				/* If the character causing us to drop out was SHIFT_IN or
				   SHIFT_OUT, it may be a special escape for SHIFT_IN. The
				   test for SHIFT_IN is not necessary, but allows an alternate
				   form of UTF-7 where SHIFT_IN is escaped by SHIFT_IN. This
				   only works for some values of SHIFT_IN.
				 */
				if (!done && (c == SHIFT_IN || c == SHIFT_OUT))
				{
					/* get another character c */
					prevc = c;
					if (!(done = (source >= sourceEnd)))
						c = *source++;
					/* If no base64 characters were encountered, and the
					   character terminating the shift sequence was
					   SHIFT_OUT, then it's a special escape for SHIFT_IN.
					 */
					if (first && prevc == SHIFT_OUT)
					{
						/* write SHIFT_IN unicode */
						TARGETCHECK;
						*target++ = (UCS2)SHIFT_IN;
					}
					else if (!wroteone)
					{
						result = sourceCorrupt;
						/* fprintf(stderr, "UTF7: empty sequence near byte %ld in input\n", source-sourceStart) */;
					}
				}
				else if (!wroteone)
				{
					result = sourceCorrupt;
					/* fprintf(stderr, "UTF7: empty sequence near byte %ld in input\n", source-sourceStart) */;
				}
			}
			else
			{
				/* Add another 6 bits of base64 to the bit buffer. */
				WRITE_N_BITS(base64value, 6);
				first = 0;
			}

			/* Extract as many full 16 bit characters as possible from the
			   bit buffer.
			 */
			while (BITS_IN_BUFFER >= 16 && (target < targetEnd))
			{
				/* write a unicode */
				*target++ = READ_N_BITS(16);
				wroteone = 1;
			}

			if (BITS_IN_BUFFER >= 16)
				TARGETCHECK;

			if (base64EOF)
			{
				junk = READ_N_BITS(BITS_IN_BUFFER);
				if (junk)
				{
					result = sourceCorrupt;
					/* fprintf(stderr, "UTF7: non-zero pad bits near byte %ld in input\n", source-sourceStart) */;
				}
			}
		}

		if (!shifted && !done)
		{
			if (c == SHIFT_IN)
			{
				shifted = 1;
				first = 1;
				wroteone = 0;
			}
			else
			{
				/* It must be a directly encoded character. */
				if (c > 0x7f)
				{
					result = sourceCorrupt;
					/* fprintf(stderr, "UTF7: non-ASCII character near byte %ld in input\n", source-sourceStart) */;
				}
				/* write a unicode */
				TARGETCHECK;
				*target++ = c;
			}
		}
	}
	while (!done);

    *sourceStart = source;
    *targetStart = target;
    return result;
}