netsurf/utils/utf8.c

/*
 * This file is part of NetSurf, http://netsurf.sourceforge.net/
 * Licensed under the GNU General Public License,
 *                http://www.opensource.org/licenses/gpl-license
 * Copyright 2005 John M Bell <jmb202@ecs.soton.ac.uk>
 */

/**
 * \file UTF-8 manipulation functions (implementation)
 */

#include <assert.h>
#include <stdlib.h>
#include <string.h>

#include <iconv.h>

#include "netsurf/utils/utf8.h"

static char *utf8_convert(const char *string, size_t len, const char *from,
		const char *to);

/**
 * Convert a UTF-8 multibyte sequence into a single UCS4 character
 *
 * Encoding of UCS values outside the UTF-16 plane has been removed from
 * RFC3629. This function conforms to RFC2279, however, as it is possible
 * that the platform specific keyboard input handler will generate a UCS4
 * value outside the UTF-16 plane.
 *
 * \param s  The sequence to process
 * \param l  Length of sequence
 * \return   UCS4 character
 */
size_t utf8_to_ucs4(const char *s, size_t l)
{
	size_t c = 0;

	if (!s)
		assert(0);
	else if (l > 0 && *s < 0x80)
		c = *s;
	else if (l > 1 && (*s & 0xE0) == 0xC0 && (*(s+1) & 0xC0) == 0x80)
		c = ((*s & 0x1F) << 6) | (*(s+1) & 0x3F);
	else if (l > 2 && (*s & 0xF0) == 0xE0 && (*(s+1) & 0xC0) == 0x80 &&
			(*(s+2) & 0xC0) == 0x80)
		c = ((*s & 0x0F) << 12) | ((*(s+1) & 0x3F) << 6) |
							(*(s+2) & 0x3F);
	else if (l > 3 && (*s & 0xF8) == 0xF0 && (*(s+1) & 0xC0) == 0x80 &&
			(*(s+2) & 0xC0) == 0x80 && (*(s+3) & 0xC0) == 0x80)
		c = ((*s & 0x0F) << 18) | ((*(s+1) & 0x3F) << 12) |
				((*(s+2) & 0x3F) << 6) | (*(s+3) & 0x3F);
	else if (l > 4 && (*s & 0xFC) == 0xF8 && (*(s+1) & 0xC0) == 0x80 &&
			(*(s+2) & 0xC0) == 0x80 && (*(s+3) & 0xC0) == 0x80 &&
			(*(s+4) & 0xC0) == 0x80)
		c = ((*s & 0x0F) << 24) | ((*(s+1) & 0x3F) << 18) |
			((*(s+2) & 0x3F) << 12) | ((*(s+3) & 0x3F) << 6) |
			(*(s+4) & 0x3F);
	else if (l > 5 && (*s & 0xFE) == 0xFC && (*(s+1) & 0xC0) == 0x80 &&
			(*(s+2) & 0xC0) == 0x80 && (*(s+3) & 0xC0) == 0x80 &&
			(*(s+4) & 0xC0) == 0x80 && (*(s+5) & 0xC0) == 0x80)
		c = ((*s & 0x0F) << 28) | ((*(s+1) & 0x3F) << 24) |
			((*(s+2) & 0x3F) << 18) | ((*(s+3) & 0x3F) << 12) |
			((*(s+4) & 0x3F) << 6) | (*(s+5) & 0x3F);
	else
		assert(0);

	return c;
}

/**
 * Convert a single UCS4 character into a UTF-8 multibyte sequence
 *
 * Encoding of UCS values outside the UTF-16 plane has been removed from
 * RFC3629. This function conforms to RFC2279, however, as it is possible
 * that the platform specific keyboard input handler will generate a UCS4
 * value outside the UTF-16 plane.
 *
 * \param c  The character to process (0 <= c <= 0x7FFFFFFF)
 * \param s  Pointer to 6 byte long output buffer
 * \return   Length of multibyte sequence
 */
size_t utf8_from_ucs4(size_t c, char *s)
{
	size_t l = 0;

	if (c > 0x7FFFFFFF)
		assert(0);
	else if (c < 0x80) {
		*s = (char)c;
		l = 1;
	}
	else if (c < 0x800) {
		*s = 0xC0 | ((c >> 6) & 0x1F);
		*(s+1) = 0x80 | (c & 0x3F);
		l = 2;
	}
	else if (c < 0x10000) {
		*s = 0xE0 | ((c >> 12) & 0xF);
		*(s+1) = 0x80 | ((c >> 6) & 0x3F);
		*(s+2) = 0x80 | (c & 0x3F);
		l = 3;
	}
	else if (c < 0x200000) {
		*s = 0xF0 | ((c >> 18) & 0x7);
		*(s+1) = 0x80 | ((c >> 12) & 0x3F);
		*(s+2) = 0x80 | ((c >> 6) & 0x3F);
		*(s+3) = 0x80 | (c & 0x3F);
		l = 4;
	}
	else if (c < 0x4000000) {
		*s = 0xF8 | ((c >> 24) & 0x3);
		*(s+1) = 0x80 | ((c >> 18) & 0x3F);
		*(s+2) = 0x80 | ((c >> 12) & 0x3F);
		*(s+3) = 0x80 | ((c >> 6) & 0x3F);
		*(s+4) = 0x80 | (c & 0x3F);
		l = 5;
	}
	else if (c <= 0x7FFFFFFF) {
		*s = 0xFC | ((c >> 30) & 0x1);
		*(s+1) = 0x80 | ((c >> 24) & 0x3F);
		*(s+2) = 0x80 | ((c >> 18) & 0x3F);
		*(s+3) = 0x80 | ((c >> 12) & 0x3F);
		*(s+4) = 0x80 | ((c >> 6) & 0x3F);
		*(s+5) = 0x80 | (c & 0x3F);
		l = 6;
	}

	return l;
}

/**
 * Calculate the length (in characters) of a NULL-terminated UTF-8 string
 *
 * \param s  The string
 * \return   Length of string
 */
size_t utf8_length(const char *s)
{
	const char *__s = s;
	int l = 0;
	while (*__s != '\0') {
		if ((*__s & 0x80) == 0x00)
			__s += 1;
		else if ((*__s & 0xE0) == 0xC0)
			__s += 2;
		else if ((*__s & 0xF0) == 0xE0)
			__s += 3;
		else if ((*__s & 0xF8) == 0xF0)
			__s += 4;
		else if ((*__s & 0xFC) == 0xF8)
			__s += 5;
		else if ((*__s & 0xFE) == 0xFC)
			__s += 6;
		else
			assert(0);
		l++;
	}

	return l;
}

/**
 * Find previous legal UTF-8 char in string
 *
 * \param s  The string
 * \param o  Offset in the string to start at
 * \return Offset of first byte of previous legal character
 */
size_t utf8_prev(const char *s, size_t o)
{
	while (o != 0 && !(((s[--o] & 0x80) == 0x00) ||
			((s[o] & 0xC0) == 0xC0)))
		/* do nothing */;

	return o;
}

/**
 * Find next legal UTF-8 char in string
 *
 * \param s  The string
 * \param l  Maximum offset in string
 * \param o  Offset in the string to start at
 * \return Offset of first byte of next legal character
 */
size_t utf8_next(const char *s, size_t l, size_t o)
{
	while (o != l && !(((s[++o] & 0x80) == 0x00) ||
			((s[o] & 0xC0) == 0xC0)))
		/* do nothing */;

	return o;
}


/**
 * Convert a UTF8 string into the named encoding
 *
 * \param string  The NULL-terminated string to convert
 * \param encname The encoding name (suitable for passing to iconv)
 * \param len     Length of input string to consider (in bytes), or 0
 * \return Pointer to converted string (on heap) or NULL on error
 */
char *utf8_to_enc(const char *string, const char *encname, size_t len)
{
	return utf8_convert(string, len, "UTF-8", encname);
}

/**
 * Convert a UTF8 string into the named encoding
 *
 * \param string  The NULL-terminated string to convert
 * \param encname The encoding name (suitable for passing to iconv)
 * \param len     Length of input string to consider (in bytes), or 0
 * \return Pointer to converted string (on heap) or NULL on error
 */
char *utf8_from_enc(const char *string, const char *encname, size_t len)
{
	return utf8_convert(string, len, encname, "UTF-8");
}

/**
 * Convert a string from one encoding to another
 *
 * \param string  The NULL-terminated string to convert
 * \param len     Length of input string to consider (in bytes)
 * \param from    The encoding name to convert from
 * \param to      The encoding name to convert to
 * \return Pointer to converted string (on heap) or NULL on error
 */
char *utf8_convert(const char *string, size_t len, const char *from,
		const char *to)
{
	iconv_t cd;
	char *ret, *temp, *out, *in;
	size_t slen, rlen;

	if (!string || !from || !to)
		return NULL;

	in = (char *)string;

	cd = iconv_open(to, from);
	if (cd == (iconv_t)-1)
		return NULL;

	slen = len ? len : strlen(string);
	/* Worst case = ACSII -> UCS4, so allocate an output buffer
	 * 4 times larger than the input buffer, and add 4 bytes at
	 * the end for the NULL terminator
	 */
	rlen = slen * 4 + 4;

	temp = out = calloc(rlen, sizeof(char));
	if (!out) {
		iconv_close(cd);
		return NULL;
	}

	/* perform conversion */
	if (iconv(cd, &in, &slen, &out, &rlen) == (size_t)-1) {
		free(temp);
		iconv_close(cd);
		return NULL;
	}

	iconv_close(cd);

	if (rlen > 64 /* allow 64bytes wasted space */) {
		/* and allocate a more sensibly sized output buffer */
		ret = calloc(out - temp + 4, sizeof(char));
		memcpy(ret, temp, out - temp);
		free(temp);
	}
	else
		ret = temp;

	return ret;
}