/*
   XDS - OSSP Extensible Data Serialization Library
   Copyright (c) 2001 The OSSP Project (http://www.ossp.org/)
   Copyright (c) 2001 Cable & Wireless Deutschland (http://www.cw.com/de/)

   This file is part of OSSP XDS, an extensible data serialization
   library which can be found at http://www.ossp.com/pkg/xds/.

   Permission to use, copy, modify, and distribute this software for
   any purpose with or without fee is hereby granted, provided that
   the above copyright notice and this permission notice appear in all
   copies.

   THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   SUCH DAMAGE.
*/

#include <stdio.h>
#include <string.h>
#include "xds.h"

#define	bits(c)	(0x80 | ((c) & 0x3F))
#define	put(c)	*strptr++ = (c);
#define	putbits(c)	put(bits(c))
#define	finish()	*strptr = '\0'

static char* sputu8(xds_uint32_t c, char* strptr)
    {
    if (strptr == NULL)
	return NULL;

    if (c < 0x80)
	{
	put(c);
	finish();
	}
    else if (c < 0x800)
	{
	put(0xC0 | (c >>  6));
	putbits(c);
	finish();
	}
    else if (c < 0x10000)
	{
	put(0xE0 | (c >> 12));
	putbits(c >>  6);
	putbits(c);
	finish();
	}
    else if (c < 0x200000)
	{
	put(0xF0 | (c >> 18));
	putbits(c >> 12);
	putbits(c >>  6);
	putbits(c);
	finish();
	}
    else if (c < 0x400000)
	{
	put(0xF8 | (c >> 24));
	putbits(c >> 18);
	putbits(c >> 12);
	putbits(c >>  6);
	putbits(c);
	finish();
	}
    else if (c < 0x80000000)
	{
	put(0xFC | (c >> 30));
	putbits(c >> 24);
	putbits(c >> 18);
	putbits(c >> 12);
	putbits(c >>  6);
	putbits(c);
	finish();
	}
    else
	finish();		/* Not a valid Unicode "character" */

    return strptr;
    }

static const char TAG_OPEN[] = "<string>";
static const char TAG_CLOSE[] = "</string>";
static const size_t TAG_OPEN_LEN = sizeof(TAG_OPEN)-1;
static const size_t TAG_CLOSE_LEN = sizeof(TAG_CLOSE)-1;

int xml_encode_string(xds_t* xds, void* engine_context,
		      void* buffer, size_t buffer_size, size_t* used_buffer_size,
		      va_list* args)
    {
    char*  src;
    size_t src_len;
    char*  dst;
    size_t dst_size;
    char*  tmp;

    /* Setup the engine. We need at least space for our tags; how long
       the actual content is going to be will be seen soon. */

    xds_init_encoding_engine(TAG_OPEN_LEN + TAG_CLOSE_LEN);

    /* Get the data from the stack. */

    src      = va_arg(*args, char*);
    xds_check_parameter(src != NULL);
    src_len  = strlen(src);

    /* Set up the target buffer. */

    dst      = buffer;
    dst_size = buffer_size;

    /* Write the opening tag. */

    memmove(dst, TAG_OPEN, TAG_OPEN_LEN);
    dst      += TAG_OPEN_LEN;
    dst_size -= TAG_OPEN_LEN;

    /* Format the data into the buffer. */

    while(src_len > 0 && dst_size > 0)
	{
	if (*((xds_uint8_t*)src) >= 0x80)
	    {			/* UTF-8ify it. */
	    if (dst_size >= 7)
		{
		tmp = sputu8((xds_uint32_t)*((xds_uint8_t*)src), dst);
		++src; --src_len;
		dst_size -= tmp - dst;
		dst = tmp;
		}
	    else
		dst_size = 0;
	    }
	else if (*src == '<')
	    {			/* Turn into "&lt;". */
	    if (dst_size >= 4)
		{
		*dst++ = '&'; --dst_size;
		*dst++ = 'l'; --dst_size;
		*dst++ = 't'; --dst_size;
		*dst++ = ';'; --dst_size;
		++src; --src_len;
		}
	    else
		dst_size = 0;
	    }
	else if (*src == '&')
	    {			/* Turn into "&amp;". */
	    if (dst_size >= 5)
		{
		*dst++ = '&'; --dst_size;
		*dst++ = 'a'; --dst_size;
		*dst++ = 'm'; --dst_size;
		*dst++ = 'p'; --dst_size;
		*dst++ = ';'; --dst_size;
		++src; --src_len;
		}
	    else
		dst_size = 0;
	    }
	else if (*src == '>')
	    {			/* Turn into "&gt;". */
	    if (dst_size >= 4)
		{
		*dst++ = '&'; --dst_size;
		*dst++ = 'g'; --dst_size;
		*dst++ = 't'; --dst_size;
		*dst++ = ';'; --dst_size;
		++src; --src_len;
		}
	    else
		dst_size = 0;
	    }
	else
	    {			/* No special character; just copy it. */
	    *dst++ = *src++;
	    --src_len; --dst_size;
	    }
	}
    if (src_len > 0)
	{			/* Target buffer was too small. */
	*used_buffer_size = buffer_size + 1;
	return XDS_ERR_OVERFLOW;
	}

    /* Write the closing tag. */

    memmove(dst, TAG_CLOSE, TAG_CLOSE_LEN);
    dst      += TAG_CLOSE_LEN;
    dst_size -= TAG_CLOSE_LEN;

    /* Done. */

    *used_buffer_size = dst - (char*)buffer;
    return XDS_OK;
    }