path: root/WWW/Library/Implementation/HTParse.c

/*
 * $LynxId: HTParse.c,v 1.75 2014/02/12 23:15:42 tom Exp $
 *
 *		Parse HyperText Document Address		HTParse.c
 *		================================
 */

#include <HTUtils.h>
#include <HTParse.h>

#include <LYUtils.h>
#include <LYLeaks.h>
#include <LYStrings.h>
#include <LYCharUtils.h>
#include <LYGlobalDefs.h>

#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#else
#ifdef __MINGW32__
#include <malloc.h>
#endif /* __MINGW32__ */
#endif

#ifdef USE_IDNA
#include <idna.h>
#include <idn-free.h>
#endif

#define HEX_ESCAPE '%'

struct struct_parts {
    char *access;
    char *host;
    char *absolute;
    char *relative;
    char *search;		/* treated normally as part of path */
    char *anchor;
};

#if 0				/* for debugging */
static void show_parts(const char *name, struct struct_parts *parts, int line)
{
    if (TRACE) {
	CTRACE((tfp, "struct_parts(%s) %s@%d\n", name, __FILE__, line));
	CTRACE((tfp, "   access   '%s'\n", NONNULL(parts->access)));
	CTRACE((tfp, "   host     '%s'\n", NONNULL(parts->host)));
	CTRACE((tfp, "   absolute '%s'\n", NONNULL(parts->absolute)));
	CTRACE((tfp, "   relative '%s'\n", NONNULL(parts->relative)));
	CTRACE((tfp, "   search   '%s'\n", NONNULL(parts->search)));
	CTRACE((tfp, "   anchor   '%s'\n", NONNULL(parts->anchor)));
    }
}
#define SHOW_PARTS(name) show_parts(#name, &name, __LINE__)
#else
#define SHOW_PARTS(name)	/* nothing */
#endif

/*	Strip white space off a string.				HTStrip()
 *	-------------------------------
 *
 * On exit,
 *	Return value points to first non-white character, or to 0 if none.
 *	All trailing white space is OVERWRITTEN with zero.
 */
char *HTStrip(char *s)
{
#define SPACE(c) ((c == ' ') || (c == '\t') || (c == '\n'))
    char *p;

    for (p = s; *p; p++) {	/* Find end of string */
	;
    }
    for (p--; p >= s; p--) {
	if (SPACE(*p))
	    *p = '\0';		/* Zap trailing blanks */
	else
	    break;
    }
    while (SPACE(*s))
	s++;			/* Strip leading blanks */
    return s;
}

/*	Scan a filename for its constituents.			scan()
 *	-------------------------------------
 *
 * On entry,
 *	name	points to a document name which may be incomplete.
 * On exit,
 *	absolute or relative may be nonzero (but not both).
 *	host, anchor and access may be nonzero if they were specified.
 *	Any which are nonzero point to zero terminated strings.
 */
static void scan(char *name,
		 struct struct_parts *parts)
{
    char *after_access;
    char *p;

    parts->access = NULL;
    parts->host = NULL;
    parts->absolute = NULL;
    parts->relative = NULL;
    parts->search = NULL;	/* normally not used - kw */
    parts->anchor = NULL;

    /*
     * Scan left-to-right for a scheme (access).
     */
    after_access = name;
    for (p = name; *p; p++) {
	if (*p == ':') {
	    *p = '\0';
	    parts->access = name;	/* Access name has been specified */
	    after_access = (p + 1);
	    break;
	}
	if (*p == '/' || *p == '#' || *p == ';' || *p == '?')
	    break;
    }

    /*
     * Scan left-to-right for a fragment (anchor).
     */
    for (p = after_access; *p; p++) {
	if (*p == '#') {
	    parts->anchor = (p + 1);
	    *p = '\0';		/* terminate the rest */
	    break;		/* leave things after first # alone - kw */
	}
    }

    /*
     * Scan left-to-right for a host or absolute path.
     */
    p = after_access;
    if (*p == '/') {
	if (p[1] == '/') {
	    parts->host = (p + 2);	/* host has been specified    */
	    *p = '\0';		/* Terminate access           */
	    p = StrChr(parts->host, '/');	/* look for end of host name if any */
	    if (p != NULL) {
		*p = '\0';	/* Terminate host */
		parts->absolute = (p + 1);	/* Root has been found */
	    } else {
		p = StrChr(parts->host, '?');
		if (p != NULL) {
		    *p = '\0';	/* Terminate host */
		    parts->search = (p + 1);
		}
	    }
	} else {
	    parts->absolute = (p + 1);	/* Root found but no host */
	}
    } else {
	parts->relative = (*after_access) ?
	    after_access : NULL;	/* NULL for "" */
    }

    /*
     * Check schemes that commonly have unescaped hashes.
     */
    if (parts->access && parts->anchor &&
    /* optimize */ StrChr("lnsdLNSD", *parts->access) != NULL) {
	if ((!parts->host && strcasecomp(parts->access, "lynxcgi")) ||
	    !strcasecomp(parts->access, "nntp") ||
	    !strcasecomp(parts->access, "snews") ||
	    !strcasecomp(parts->access, "news") ||
	    !strcasecomp(parts->access, "data")) {
	    /*
	     * Access specified but no host and not a lynxcgi URL, so the
	     * anchor may not really be one, e.g., news:j462#36487@foo.bar, or
	     * it's an nntp or snews URL, or news URL with a host.  Restore the
	     * '#' in the address.
	     */
	    /* but only if we have found a path component of which this will
	     * become part. - kw  */
	    if (parts->relative || parts->absolute) {
		*(parts->anchor - 1) = '#';
		parts->anchor = NULL;
	    }
	}
    }
}				/*scan */

#if defined(HAVE_ALLOCA) && !defined(LY_FIND_LEAKS)
#define LYalloca(x)        alloca(x)
#define LYalloca_free(x)   {}
#else
#define LYalloca(x)        malloc(x)
#define LYalloca_free(x)   free(x)
#endif

static char *strchr_or_end(char *string, int ch)
{
    char *result = StrChr(string, ch);

    if (result == 0) {
	result = string + strlen(string);
    }
    return result;
}

/*
 * Given a host specification that may end with a port number, e.g.,
 *	foobar:123
 * point to the ':' which begins the ":port" to make it simple to handle the
 * substring.
 *
 * If no port is found (or a syntax error), return null.
 */
char *HTParsePort(char *host, int *portp)
{
    int brackets = 0;
    char *result = NULL;

    *portp = 0;
    if (host != NULL) {
	while (*host != '\0' && result == 0) {
	    switch (*host++) {
	    case ':':
		if (brackets == 0 && isdigit(UCH(*host))) {
		    char *next = NULL;

		    *portp = (int) strtol(host, &next, 10);
		    if (next != 0 && next != host && *next == '\0') {
			result = (host - 1);
			CTRACE((tfp, "HTParsePort %d\n", *portp));
		    }
		}
		break;
	    case '[':		/* for ipv6 */
		++brackets;
		break;
	    case ']':		/* for ipv6 */
		--brackets;
		break;
	    }
	}
    }
    return result;
}

#ifdef USE_IDNA
static int hex_decode(int ch)
{
    int result = -1;

    if (ch >= '0' && ch <= '9')
	result = (ch - '0');
    else if (ch >= 'a' && ch <= 'f')
	result = (ch - 'a') + 10;
    else if (ch >= 'A' && ch <= 'F')
	result = (ch - 'A') + 10;
    return result;
}

/*
 * Convert in-place the given hostname to IDNA form.  That requires up to 64
 * characters, and we've allowed for that, with MIN_PARSE.
 */
static void convert_to_idna(char *host)
{
    size_t length = strlen(host);
    char *endhost = host + length;
    char *buffer = malloc(length + 1);
    char *output = NULL;
    char *src, *dst;
    int code;
    int hi, lo;

    if (buffer != 0) {
	code = TRUE;
	for (dst = buffer, src = host; src < endhost; ++dst) {
	    int ch = *src++;

	    if (ch == HEX_ESCAPE) {
		if ((src + 1) < endhost
		    && (hi = hex_decode(src[0])) >= 0
		    && (lo = hex_decode(src[1])) >= 0) {

		    *dst = (char) ((hi << 4) | lo);
		    src += 2;
		} else {
		    CTRACE((tfp, "convert_to_idna: `%s' is malformed\n", host));
		    code = FALSE;
		    break;
		}
	    } else {
		*dst = (char) ch;
	    }
	}
	if (code) {
	    *dst = '\0';
	    code = idna_to_ascii_8z(buffer, &output, IDNA_USE_STD3_ASCII_RULES);
	    if (code == IDNA_SUCCESS) {
		strcpy(host, output);
	    } else {
		CTRACE((tfp, "convert_to_idna: `%s': %s\n",
			buffer,
			idna_strerror((Idna_rc) code)));
	    }
	    if (output)
		idn_free (output);
	}
	free(buffer);
    }
}
#define MIN_PARSE 80
#else
#define MIN_PARSE 8
#endif

/*	Parse a Name relative to another name.			HTParse()
 *	--------------------------------------
 *
 *	This returns those parts of a name which are given (and requested)
 *	substituting bits from the related name where necessary.
 *
 * On entry,
 *	aName		A filename given
 *	relatedName	A name relative to which aName is to be parsed
 *	wanted		A mask for the bits which are wanted.
 *
 * On exit,
 *     returns         A pointer to a malloc'd string which MUST BE FREED
 */
char *HTParse(const char *aName,
	      const char *relatedName,
	      int wanted)
{
    char *result = NULL;
    char *tail = NULL;		/* a pointer to the end of the 'result' string */
    char *return_value = NULL;
    size_t len, len1, len2;
    size_t need;
    char *name = NULL;
    char *rel = NULL;
    char *p, *q;
    char *acc_method;
    struct struct_parts given, related;

    CTRACE((tfp, "HTParse: aName:`%s'\n", aName));
    CTRACE((tfp, "   relatedName:`%s'\n", relatedName));

    if (wanted & (PARSE_STRICTPATH | PARSE_QUERY)) {	/* if detail wanted... */
	if ((wanted & (PARSE_STRICTPATH | PARSE_QUERY))
	    == (PARSE_STRICTPATH | PARSE_QUERY))	/* if strictpath AND query */
	    wanted |= PARSE_PATH;	/* then treat as if PARSE_PATH wanted */
	if (wanted & PARSE_PATH)	/* if PARSE_PATH wanted */
	    wanted &= ~(PARSE_STRICTPATH | PARSE_QUERY);	/* ignore details */
    }
/* *INDENT-OFF* */
    CTRACE((tfp, "   want:%s%s%s%s%s%s%s\n",
	    wanted & PARSE_PUNCTUATION ? " punc"   : "",
	    wanted & PARSE_ANCHOR      ? " anchor" : "",
	    wanted & PARSE_PATH        ? " path"   : "",
	    wanted & PARSE_HOST        ? " host"   : "",
	    wanted & PARSE_ACCESS      ? " access" : "",
	    wanted & PARSE_STRICTPATH  ? " PATH"   : "",
	    wanted & PARSE_QUERY       ? " QUERY"  : ""));
/* *INDENT-ON* */

    /*
     * Allocate the temporary string. Optimized.
     */
    len1 = strlen(aName) + 1;
    len2 = strlen(relatedName) + 1;
    len = len1 + len2 + MIN_PARSE;	/* Lots of space: more than enough */

    need = (len * 2 + len1 + len2);
    if (need > (size_t) max_uri_size ||
	(int) need < (int) len1 ||
	(int) need < (int) len2)
	return StrAllocCopy(return_value, "");

    result = tail = (char *) LYalloca(need);
    if (result == NULL) {
	outofmem(__FILE__, "HTParse");

	assert(result != NULL);
    }
    *result = '\0';
    name = result + len;
    rel = name + len1;

    /*
     * Make working copy of the input string to cut up.
     */
    MemCpy(name, aName, len1);

    /*
     * Cut up the string into URL fields.
     */
    scan(name, &given);
    SHOW_PARTS(given);

    /*
     * Now related string.
     */
    if ((given.access && given.host && given.absolute) || !*relatedName) {
	/*
	 * Inherit nothing!
	 */
	related.access = NULL;
	related.host = NULL;
	related.absolute = NULL;
	related.relative = NULL;
	related.search = NULL;
	related.anchor = NULL;
    } else {
	MemCpy(rel, relatedName, len2);
	scan(rel, &related);
    }
    SHOW_PARTS(related);

    /*
     * Handle the scheme (access) field.
     */
    if (given.access && given.host && !given.relative && !given.absolute) {
	if (!strcmp(given.access, "http") ||
	    !strcmp(given.access, "https") ||
	    !strcmp(given.access, "ftp")) {

	    /*
	     * Assume root.
	     */
	    given.absolute = empty_string;
	}
    }
    acc_method = given.access ? given.access : related.access;
    if (wanted & PARSE_ACCESS) {
	if (acc_method) {
	    strcpy(tail, acc_method);
	    tail += strlen(tail);
	    if (wanted & PARSE_PUNCTUATION) {
		*tail++ = ':';
		*tail = '\0';
	    }
	}
    }

    /*
     * If different schemes, inherit nothing.
     *
     * We'll try complying with RFC 1808 and the Fielding draft, and inherit
     * nothing if both schemes are given, rather than only when they differ,
     * except for file URLs - FM
     *
     * After trying it for a while, it's still premature, IHMO, to go along
     * with it, so this is back to inheriting for identical schemes whether or
     * not they are "file".  If you want to try it again yourself, uncomment
     * the strcasecomp() below.  - FM
     */
    if ((given.access && related.access) &&
	(			/* strcasecomp(given.access, "file") || */
	    strcmp(given.access, related.access))) {
	related.host = NULL;
	related.absolute = NULL;
	related.relative = NULL;
	related.search = NULL;
	related.anchor = NULL;
    }

    /*
     * Handle the host field.
     */
    if (wanted & PARSE_HOST) {
	if (given.host || related.host) {
	    if (wanted & PARSE_PUNCTUATION) {
		*tail++ = '/';
		*tail++ = '/';
	    }
	    strcpy(tail, given.host ? given.host : related.host);
#define CLEAN_URLS
#ifdef CLEAN_URLS
	    /*
	     * Ignore default port numbers, and trailing dots on FQDNs, which
	     * will only cause identical addresses to look different.  (related
	     * is already a clean url).
	     */
	    {
		char *p2, *h;
		int portnumber;

		if ((p2 = StrChr(result, '@')) != NULL)
		    tail = (p2 + 1);
		p2 = HTParsePort(result, &portnumber);
		if (p2 != NULL && acc_method != NULL) {
		    /*
		     * Port specified.
		     */
#define ACC_METHOD(a,b) (!strcmp(acc_method, a) && (portnumber == b))
		    if (ACC_METHOD("http", 80) ||
			ACC_METHOD("https", 443) ||
			ACC_METHOD("gopher", 70) ||
			ACC_METHOD("ftp", 21) ||
			ACC_METHOD("wais", 210) ||
			ACC_METHOD("nntp", 119) ||
			ACC_METHOD("news", 119) ||
			ACC_METHOD("newspost", 119) ||
			ACC_METHOD("newsreply", 119) ||
			ACC_METHOD("snews", 563) ||
			ACC_METHOD("snewspost", 563) ||
			ACC_METHOD("snewsreply", 563) ||
			ACC_METHOD("finger", 79) ||
			ACC_METHOD("telnet", 23) ||
			ACC_METHOD("tn3270", 23) ||
			ACC_METHOD("rlogin", 513) ||
			ACC_METHOD("cso", 105))
			*p2 = '\0';	/* It is the default: ignore it */
		}
		if (p2 == NULL) {
		    int len3 = (int) strlen(tail);

		    if (len3 > 0) {
			h = tail + len3 - 1;	/* last char of hostname */
			if (*h == '.')
			    *h = '\0';	/* chop final . */
		    }
		} else if (p2 != result) {
		    h = p2;
		    h--;	/* End of hostname */
		    if (*h == '.') {
			/*
			 * Slide p2 over h.
			 */
			while (*p2 != '\0')
			    *h++ = *p2++;
			*h = '\0';	/* terminate */
		    }
		}
	    }
#ifdef USE_IDNA
	    /*
	     * Depending on locale-support, we could have a literal UTF-8
	     * string as a host name, or a URL-encoded form of that.
	     */
	    convert_to_idna(tail);
#endif
#endif /* CLEAN_URLS */
	}
    }

    /*
     * Trim any blanks from the result so far - there's no excuse for blanks
     * in a hostname.  Also update the tail here.
     */
    tail = LYRemoveBlanks(result);

    /*
     * If host in given or related was ended directly with a '?' (no slash),
     * fake the search part into absolute.  This is the only case search is
     * returned from scan.  A host must have been present.  this restores the
     * '?' at which the host part had been truncated in scan, we have to do
     * this after host part handling is done.  - kw
     */
    if (given.search && *(given.search - 1) == '\0') {
	given.absolute = given.search - 1;
	given.absolute[0] = '?';
    } else if (related.search && !related.absolute &&
	       *(related.search - 1) == '\0') {
	related.absolute = related.search - 1;
	related.absolute[0] = '?';
    }

    /*
     * If different hosts, inherit no path.
     */
    if (given.host && related.host)
	if (strcmp(given.host, related.host) != 0) {
	    related.absolute = NULL;
	    related.relative = NULL;
	    related.anchor = NULL;
	}

    /*
     * Handle the path.
     */
    if (wanted & (PARSE_PATH | PARSE_STRICTPATH | PARSE_QUERY)) {
	int want_detail = (wanted & (PARSE_STRICTPATH | PARSE_QUERY));

	if (acc_method && !given.absolute && given.relative) {
	    /*
	     * Treat all given nntp or snews paths, or given paths for news
	     * URLs with a host, as absolute.
	     */
	    switch (*acc_method) {
	    case 'N':
	    case 'n':
		if (!strcasecomp(acc_method, "nntp") ||
		    (!strcasecomp(acc_method, "news") &&
		     !strncasecomp(result, "news://", 7))) {
		    given.absolute = given.relative;
		    given.relative = NULL;
		}
		break;
	    case 'S':
	    case 's':
		if (!strcasecomp(acc_method, "snews")) {
		    given.absolute = given.relative;
		    given.relative = NULL;
		}
		break;
	    }
	}

	if (given.absolute) {	/* All is given */
	    if (wanted & PARSE_PUNCTUATION)
		*tail++ = '/';
	    strcpy(tail, given.absolute);
	    CTRACE((tfp, "HTParse: (ABS)\n"));
	} else if (related.absolute) {	/* Adopt path not name */
	    char *base = tail;

	    *tail++ = '/';
	    strcpy(tail, related.absolute);
	    if (given.relative) {
		/* RFC 1808 part 4 step 5 (if URL path is empty) */
		/* a) if given has params, add/replace that */
		if (given.relative[0] == ';') {
		    strcpy(strchr_or_end(tail, ';'), given.relative);
		}
		/* b) if given has query, add/replace that */
		else if (given.relative[0] == '?') {
		    strcpy(strchr_or_end(tail, '?'), given.relative);
		}
		/* otherwise fall through to RFC 1808 part 4 step 6 */
		else {
		    p = StrChr(tail, '?');	/* Search part? */
		    if (p == NULL)
			p = (tail + strlen(tail) - 1);
		    for (; *p != '/'; p--) ;	/* last / */
		    p[1] = '\0';	/* Remove filename */
		    strcat(p, given.relative);	/* Add given one */
		}
		HTSimplify(base);
		if (*base == '\0')
		    strcpy(base, "/");
	    }
	    CTRACE((tfp, "HTParse: (Related-ABS)\n"));
	} else if (given.relative) {
	    strcpy(tail, given.relative);	/* what we've got */
	    CTRACE((tfp, "HTParse: (REL)\n"));
	} else if (related.relative) {
	    strcpy(tail, related.relative);
	    CTRACE((tfp, "HTParse: (Related-REL)\n"));
	} else {		/* No inheritance */
	    if (!isLYNXCGI(aName) &&
		!isLYNXEXEC(aName) &&
		!isLYNXPROG(aName)) {
		*tail++ = '/';
		*tail = '\0';
	    }
	    if (!strcmp(result, "news:/"))
		result[5] = '*';
	    CTRACE((tfp, "HTParse: (No inheritance)\n"));
	}
	if (want_detail) {
	    p = StrChr(tail, '?');	/* Search part? */
	    if (p) {
		if (PARSE_STRICTPATH) {
		    *p = '\0';
		} else {
		    if (!(wanted & PARSE_PUNCTUATION))
			p++;
		    do {
			*tail++ = *p;
		    } while (*p++);
		}
	    } else {
		if (wanted & PARSE_QUERY)
		    *tail = '\0';
	    }
	}
    }

    /*
     * Handle the fragment (anchor).  Never inherit.
     */
    if (wanted & PARSE_ANCHOR) {
	if (given.anchor && *given.anchor) {
	    tail += strlen(tail);
	    if (wanted & PARSE_PUNCTUATION)
		*tail++ = '#';
	    strcpy(tail, given.anchor);
	}
    }

    /*
     * If there are any blanks remaining in the string, escape them as needed.
     * See the discussion in LYLegitimizeHREF() for example.
     */
    if ((p = StrChr(result, ' ')) != 0) {
	switch (is_url(result)) {
	case UNKNOWN_URL_TYPE:
	    CTRACE((tfp, "HTParse:      ignore:`%s'\n", result));
	    break;
	case LYNXEXEC_URL_TYPE:
	case LYNXPROG_URL_TYPE:
	case LYNXCGI_URL_TYPE:
	case LYNXPRINT_URL_TYPE:
	case LYNXHIST_URL_TYPE:
	case LYNXDOWNLOAD_URL_TYPE:
	case LYNXKEYMAP_URL_TYPE:
	case LYNXIMGMAP_URL_TYPE:
	case LYNXCOOKIE_URL_TYPE:
	case LYNXCACHE_URL_TYPE:
	case LYNXDIRED_URL_TYPE:
	case LYNXOPTIONS_URL_TYPE:
	case LYNXCFG_URL_TYPE:
	case LYNXCOMPILE_OPTS_URL_TYPE:
	case LYNXMESSAGES_URL_TYPE:
	    CTRACE((tfp, "HTParse:      spaces:`%s'\n", result));
	    break;
	case NOT_A_URL_TYPE:
	default:
	    CTRACE((tfp, "HTParse:      encode:`%s'\n", result));
	    do {
		q = p + strlen(p) + 2;

		while (q != p + 1) {
		    q[0] = q[-2];
		    --q;
		}
		p[0] = HEX_ESCAPE;
		p[1] = '2';
		p[2] = '0';
	    } while ((p = StrChr(result, ' ')) != 0);
	    break;
	}
    }
    CTRACE((tfp, "HTParse:      result:`%s'\n", result));

    StrAllocCopy(return_value, result);
    LYalloca_free(result);

    /* FIXME: could be optimized using HTParse() internals */
    if (*relatedName &&
	((wanted & PARSE_ALL_WITHOUT_ANCHOR) == PARSE_ALL_WITHOUT_ANCHOR)) {
	/*
	 * Check whether to fill in localhost.  - FM
	 */
	LYFillLocalFileURL(&return_value, relatedName);
	CTRACE((tfp, "pass LYFillLocalFile:`%s'\n", return_value));
    }

    return return_value;	/* exactly the right length */
}

/*	HTParseAnchor(), fast HTParse() specialization
 *	----------------------------------------------
 *
 * On exit,
 *	returns		A pointer within input string (probably to its end '\0')
 */
const char *HTParseAnchor(const char *aName)
{
    const char *p = aName;

    for (; *p && *p != '#'; p++) {
	;
    }
    if (*p == '#') {
	/* the safe way based on HTParse() -
	 * keeping in mind scan() peculiarities on schemes:
	 */
	struct struct_parts given;
	size_t need = ((unsigned) ((p - aName) + (int) strlen(p) + 1));
	char *name;

	if (need > (size_t) max_uri_size) {
	    p += strlen(p);
	} else {
	    name = (char *) LYalloca(need);

	    if (name == NULL) {
		outofmem(__FILE__, "HTParseAnchor");

		assert(name != NULL);
	    }
	    strcpy(name, aName);
	    scan(name, &given);
	    LYalloca_free(name);

	    p++;		/*next to '#' */
	    if (given.anchor == NULL) {
		for (; *p; p++)	/*scroll to end '\0' */
		    ;
	    }
	}
    }
    return p;
}

/*	Simplify a filename.				HTSimplify()
 *	--------------------
 *
 *  A unix-style file is allowed to contain the sequence xxx/../ which may
 *  be replaced by "" , and the sequence "/./" which may be replaced by "/".
 *  Simplification helps us recognize duplicate filenames.
 *
 *	Thus,	/etc/junk/../fred	becomes /etc/fred
 *		/etc/junk/./fred	becomes /etc/junk/fred
 *
 *	but we should NOT change
 *		http://fred.xxx.edu/../..
 *
 *	or	../../albert.html
 */
void HTSimplify(char *filename)
{
    char *p;
    char *q, *q1;

    if (filename == NULL)
	return;

    if (!(filename[0] && filename[1]) ||
	filename[0] == '?' || filename[1] == '?' || filename[2] == '?')
	return;

    if (StrChr(filename, '/') != NULL) {
	for (p = (filename + 2); *p; p++) {
	    if (*p == '?') {
		/*
		 * We're still treating a ?searchpart as part of the path in
		 * HTParse() and scan(), but if we encounter a '?' here, assume
		 * it's the delimiter and break.  We also could check for a
		 * parameter delimiter (';') here, but the current Fielding
		 * draft (wisely or ill-advisedly :) says that it should be
		 * ignored and collapsing be allowed in it's value).  The only
		 * defined parameter at present is ;type=[A, I, or D] for ftp
		 * URLs, so if there's a "/..", "/../", "/./", or terminal '.'
		 * following the ';', it must be due to the ';' being an
		 * unescaped path character and not actually a parameter
		 * delimiter.  - FM
		 */
		break;
	    }
	    if (*p == '/') {
		if ((p[1] == '.') && (p[2] == '.') &&
		    (p[3] == '/' || p[3] == '?' || p[3] == '\0')) {
		    /*
		     * Handle "../", "..?" or "..".
		     */
		    for (q = (p - 1); (q >= filename) && (*q != '/'); q--)
			/*
			 * Back up to previous slash or beginning of string.
			 */
			;
		    if ((q[0] == '/') &&
			(StrNCmp(q, "/../", 4) &&
			 StrNCmp(q, "/..?", 4)) &&
			!((q - 1) > filename && q[-1] == '/')) {
			/*
			 * Not at beginning of string or in a host field, so
			 * remove the "/xxx/..".
			 */
			q1 = (p + 3);
			p = q;
			while (*q1 != '\0')
			    *p++ = *q1++;
			*p = '\0';	/* terminate */
			/*
			 * Start again with previous slash.
			 */
			p = (q - 1);
		    }
		} else if (p[1] == '.' && p[2] == '/') {
		    /*
		     * Handle "./" by removing both characters.
		     */
		    q = p;
		    q1 = (p + 2);
		    while (*q1 != '\0')
			*q++ = *q1++;
		    *q = '\0';	/* terminate */
		    p--;
		} else if (p[1] == '.' && p[2] == '?') {
		    /*
		     * Handle ".?" by removing the dot.
		     */
		    q = (p + 1);
		    q1 = (p + 2);
		    while (*q1 != '\0')
			*q++ = *q1++;
		    *q = '\0';	/* terminate */
		    p--;
		} else if (p[1] == '.' && p[2] == '\0') {
		    /*
		     * Handle terminal "." by removing the character.
		     */
		    p[1] = '\0';
		}
	    }
	}
	if (p >= filename + 2 && *p == '?' && *(p - 1) == '.') {
	    if (*(p - 2) == '/') {
		/*
		 * Handle "/.?" by removing the dot.
		 */
		q = p - 1;
		q1 = p;
		while (*q1 != '\0')
		    *q++ = *q1++;
		*q = '\0';
	    } else if (*(p - 2) == '.' &&
		       p >= filename + 4 && *(p - 3) == '/' &&
		       (*(p - 4) != '/' ||
			(p > filename + 4 && *(p - 5) != ':'))) {
		/*
		 * Handle "xxx/..?"
		 */
		for (q = (p - 4); (q > filename) && (*q != '/'); q--)
		    /*
		     * Back up to previous slash or beginning of string.
		     */
		    ;
		if (*q == '/') {
		    if (q > filename && *(q - 1) == '/' &&
			!(q > filename + 1 && *(q - 1) != ':'))
			return;
		    q++;
		}
		if (StrNCmp(q, "../", 3) && StrNCmp(q, "./", 2)) {
		    /*
		     * Not after "//" at beginning of string or after "://",
		     * and xxx is not ".." or ".", so remove the "xxx/..".
		     */
		    q1 = p;
		    p = q;
		    while (*q1 != '\0')
			*p++ = *q1++;
		    *p = '\0';	/* terminate */
		}
	    }
	}
    }
}

/*	Make Relative Name.					HTRelative()
 *	-------------------
 *
 * This function creates and returns a string which gives an expression of
 * one address as related to another.  Where there is no relation, an absolute
 * address is returned.
 *
 *  On entry,
 *	Both names must be absolute, fully qualified names of nodes
 *	(no anchor bits)
 *
 *  On exit,
 *	The return result points to a newly allocated name which, if
 *	parsed by HTParse relative to relatedName, will yield aName.
 *	The caller is responsible for freeing the resulting name later.
 *
 */
char *HTRelative(const char *aName,
		 const char *relatedName)
{
    char *result = NULL;
    const char *p = aName;
    const char *q = relatedName;
    const char *after_access = NULL;
    const char *path = NULL;
    const char *last_slash = NULL;
    int slashes = 0;

    for (; *p; p++, q++) {	/* Find extent of match */
	if (*p != *q)
	    break;
	if (*p == ':')
	    after_access = p + 1;
	if (*p == '/') {
	    last_slash = p;
	    slashes++;
	    if (slashes == 3)
		path = p;
	}
    }

    /* q, p point to the first non-matching character or zero */

    if (!after_access) {	/* Different access */
	StrAllocCopy(result, aName);
    } else if (slashes < 3) {	/* Different nodes */
	StrAllocCopy(result, after_access);
    } else if (slashes == 3) {	/* Same node, different path */
	StrAllocCopy(result, path);
    } else {			/* Some path in common */
	unsigned levels = 0;

	for (; *q && (*q != '#'); q++)
	    if (*q == '/')
		levels++;
	result = typecallocn(char, 3 * levels + strlen(last_slash) + 1);

	if (result == NULL)
	    outofmem(__FILE__, "HTRelative");

	assert(result != NULL);

	result[0] = '\0';
	for (; levels; levels--)
	    strcat(result, "../");
	strcat(result, last_slash + 1);
    }
    CTRACE((tfp,
	    "HTparse: `%s' expressed relative to\n   `%s' is\n   `%s'.\n",
	    aName, relatedName, result));
    return result;
}

#define AlloCopy(next,base,extra) \
	typecallocn(char, ((next - base) + ((int) extra)))

/*	Escape undesirable characters using %			HTEscape()
 *	-------------------------------------
 *
 *	This function takes a pointer to a string in which
 *	some characters may be unacceptable unescaped.
 *	It returns a string which has these characters
 *	represented by a '%' character followed by two hex digits.
 *
 *	Unlike HTUnEscape(), this routine returns a calloc'd string.
 */
/* *INDENT-OFF* */
static const unsigned char isAcceptable[96] =

/*	Bit 0		xalpha		-- see HTFile.h
 *	Bit 1		xpalpha		-- as xalpha but with plus.
 *	Bit 2 ...	path		-- as xpalphas but with /
 */
    /*	 0 1 2 3 4 5 6 7 8 9 A B C D E F */
    {	 0,0,0,0,0,0,0,0,0,0,7,6,0,7,7,4,	/* 2x	!"#$%&'()*+,-./  */
	 7,7,7,7,7,7,7,7,7,7,0,0,0,0,0,0,	/* 3x  0123456789:;<=>?  */
	 7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,	/* 4x  @ABCDEFGHIJKLMNO  */
	 7,7,7,7,7,7,7,7,7,7,7,0,0,0,0,7,	/* 5X  PQRSTUVWXYZ[\]^_  */
	 0,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,	/* 6x  `abcdefghijklmno  */
	 7,7,7,7,7,7,7,7,7,7,7,0,0,0,0,0 };	/* 7X  pqrstuvwxyz{|}~	DEL */
/* *INDENT-ON* */

static const char *hex = "0123456789ABCDEF";

#define ACCEPTABLE(a)	( a>=32 && a<128 && ((isAcceptable[a-32]) & mask))

char *HTEscape(const char *str,
	       unsigned mask)
{
    const char *p;
    char *q;
    char *result;
    size_t unacceptable = 0;

    for (p = str; *p; p++)
	if (!ACCEPTABLE(UCH(TOASCII(*p))))
	    unacceptable++;
    result = AlloCopy(p, str, (unacceptable * 2) + 1);

    if (result == NULL)
	outofmem(__FILE__, "HTEscape");

    assert(result != NULL);

    for (q = result, p = str; *p; p++) {
	unsigned char a = UCH(TOASCII(*p));

	if (!ACCEPTABLE(a)) {
	    *q++ = HEX_ESCAPE;	/* Means hex coming */
	    *q++ = hex[a >> 4];
	    *q++ = hex[a & 15];
	} else
	    *q++ = *p;
    }
    *q = '\0';			/* Terminate */
    return result;
}

/*	Escape unsafe characters using %			HTEscapeUnsafe()
 *	--------------------------------
 *
 *	This function takes a pointer to a string in which
 *	some characters may be that may be unsafe are unescaped.
 *	It returns a string which has these characters
 *	represented by a '%' character followed by two hex digits.
 *
 *	Unlike HTUnEscape(), this routine returns a malloc'd string.
 */
#define UNSAFE(ch) (((ch) <= 32) || ((ch) >= 127))

char *HTEscapeUnsafe(const char *str)
{
    const char *p;
    char *q;
    char *result;
    size_t unacceptable = 0;

    for (p = str; *p; p++)
	if (UNSAFE(UCH(TOASCII(*p))))
	    unacceptable++;
    result = AlloCopy(p, str, (unacceptable * 2) + 1);

    if (result == NULL)
	outofmem(__FILE__, "HTEscapeUnsafe");

    assert(result != NULL);

    for (q = result, p = str; *p; p++) {
	unsigned char a = UCH(TOASCII(*p));

	if (UNSAFE(a)) {
	    *q++ = HEX_ESCAPE;	/* Means hex coming */
	    *q++ = hex[a >> 4];
	    *q++ = hex[a & 15];
	} else
	    *q++ = *p;
    }
    *q = '\0';			/* Terminate */
    return result;
}

/*	Escape undesirable characters using % but space to +.	HTEscapeSP()
 *	-----------------------------------------------------
 *
 *	This function takes a pointer to a string in which
 *	some characters may be unacceptable unescaped.
 *	It returns a string which has these characters
 *	represented by a '%' character followed by two hex digits,
 *	except that spaces are converted to '+' instead of %2B.
 *
 *	Unlike HTUnEscape(), this routine returns a calloced string.
 */
char *HTEscapeSP(const char *str,
		 unsigned mask)
{
    const char *p;
    char *q;
    char *result;
    size_t unacceptable = 0;

    for (p = str; *p; p++)
	if (!(*p == ' ' || ACCEPTABLE(UCH(TOASCII(*p)))))
	    unacceptable++;
    result = AlloCopy(p, str, (unacceptable * 2) + 1);

    if (result == NULL)
	outofmem(__FILE__, "HTEscape");

    assert(result != NULL);

    for (q = result, p = str; *p; p++) {
	unsigned char a = UCH(TOASCII(*p));

	if (a == 32) {
	    *q++ = '+';
	} else if (!ACCEPTABLE(a)) {
	    *q++ = HEX_ESCAPE;	/* Means hex coming */
	    *q++ = hex[a >> 4];
	    *q++ = hex[a & 15];
	} else {
	    *q++ = *p;
	}
    }
    *q = '\0';			/* Terminate */
    return result;
}

/*	Decode %xx escaped characters.				HTUnEscape()
 *	------------------------------
 *
 *	This function takes a pointer to a string in which some
 *	characters may have been encoded in %xy form, where xy is
 *	the ASCII hex code for character 16x+y.
 *	The string is converted in place, as it will never grow.
 */
static char from_hex(int c)
{
    return (char) (c >= '0' && c <= '9' ? c - '0'
		   : c >= 'A' && c <= 'F' ? c - 'A' + 10
		   : c - 'a' + 10);	/* accept small letters just in case */
}

char *HTUnEscape(char *str)
{
    char *p = str;
    char *q = str;

    if (!(p && *p))
	return str;

    while (*p != '\0') {
	if (*p == HEX_ESCAPE &&
	/*
	 * Tests shouldn't be needed, but better safe than sorry.
	 */
	    p[1] && p[2] &&
	    isxdigit(UCH(p[1])) &&
	    isxdigit(UCH(p[2]))) {
	    p++;
	    if (*p)
		*q = (char) (from_hex(*p++) * 16);
	    if (*p) {
		/*
		 * Careful! FROMASCII() may evaluate its arg more than once!
		 */
		/* S/390 -- gil -- 0221 */
		*q = (char) (*q + from_hex(*p++));
	    }
	    *q = FROMASCII(*q);
	    q++;
	} else {
	    *q++ = *p++;
	}
    }

    *q = '\0';
    return str;

}				/* HTUnEscape */

/*	Decode some %xx escaped characters.		      HTUnEscapeSome()
 *	-----------------------------------			Klaus Weide
 *							    (kweide@tezcat.com)
 *	This function takes a pointer to a string in which some
 *	characters may have been encoded in %xy form, where xy is
 *	the ASCII hex code for character 16x+y, and a pointer to
 *	a second string containing one or more characters which
 *	should be unescaped if escaped in the first string.
 *	The first string is converted in place, as it will never grow.
 */
char *HTUnEscapeSome(char *str,
		     const char *do_trans)
{
    char *p = str;
    char *q = str;
    char testcode;

    if (p == NULL || *p == '\0' || do_trans == NULL || *do_trans == '\0')
	return str;

    while (*p != '\0') {
	if (*p == HEX_ESCAPE &&
	    p[1] && p[2] &&	/* tests shouldn't be needed, but.. */
	    isxdigit(UCH(p[1])) &&
	    isxdigit(UCH(p[2])) &&
	    (testcode = (char) FROMASCII(from_hex(p[1]) * 16 +
					 from_hex(p[2]))) &&	/* %00 no good */
	    StrChr(do_trans, testcode)) {	/* it's one of the ones we want */
	    *q++ = testcode;
	    p += 3;
	} else {
	    *q++ = *p++;
	}
    }

    *q = '\0';
    return str;

}				/* HTUnEscapeSome */
/* *INDENT-OFF* */
static const unsigned char crfc[96] =

/*	Bit 0		xalpha		-- need "quoting"
 *	Bit 1		xpalpha		-- need \escape if quoted
 */
    /*	 0 1 2 3 4 5 6 7 8 9 A B C D E F */
    {	 1,0,3,0,0,0,0,0,1,1,0,0,1,0,1,0,	/* 2x	!"#$%&'()*+,-./  */
	 0,0,0,0,0,0,0,0,0,0,1,1,1,0,1,0,	/* 3x  0123456789:;<=>?  */
	 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,	/* 4x  @ABCDEFGHIJKLMNO  */
	 0,0,0,0,0,0,0,0,0,0,0,1,2,1,0,0,	/* 5X  PQRSTUVWXYZ[\]^_  */
	 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,	/* 6x  `abcdefghijklmno  */
	 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3 };	/* 7X  pqrstuvwxyz{|}~	DEL */
/* *INDENT-ON* */

#define ASCII_TAB '\011'
#define ASCII_LF  '\012'
#define ASCII_CR  '\015'
#define ASCII_SPC '\040'
#define ASCII_BAK '\134'

/*
 *  Turn a string which is not a RFC 822 token into a quoted-string. - KW
 *  The "quoted" parameter tells whether we need the beginning/ending quote
 *  marks.  If not, the caller will provide them -TD
 */
void HTMake822Word(char **str,
		   int quoted)
{
    const char *p;
    char *q;
    char *result;
    unsigned char a;
    unsigned added = 0;

    if (isEmpty(*str)) {
	StrAllocCopy(*str, quoted ? "\"\"" : "");
	return;
    }
    for (p = *str; *p; p++) {
	a = UCH(TOASCII(*p));	/* S/390 -- gil -- 0240 */
	if (a < 32 || a >= 128 ||
	    ((crfc[a - 32]) & 1)) {
	    if (!added)
		added = 2;
	    if (a >= 160 || a == '\t')
		continue;
	    if (a == '\r' || a == '\n')
		added += 2;
	    else if ((a & 127) < 32 || ((crfc[a - 32]) & 2))
		added++;
	}
    }
    if (!added)
	return;
    result = AlloCopy(p, *str, added + 1);
    if (result == NULL)
	outofmem(__FILE__, "HTMake822Word");

    assert(result != NULL);

    q = result;
    if (quoted)
	*q++ = '"';
    /*
     * Having converted the character to ASCII, we can't use symbolic
     * escape codes, since they're in the host character set, which
     * is not necessarily ASCII.  Thus we use octal escape codes instead.
     * -- gil (Paul Gilmartin) <pg@sweng.stortek.com>
     */
    /* S/390 -- gil -- 0268 */
    for (p = *str; *p; p++) {
	a = UCH(TOASCII(*p));
	if ((a != ASCII_TAB) &&
	    ((a & 127) < ASCII_SPC ||
	     (a < 128 && ((crfc[a - 32]) & 2))))
	    *q++ = ASCII_BAK;
	*q++ = *p;
	if (a == ASCII_LF ||
	    (a == ASCII_CR && (TOASCII(*(p + 1)) != ASCII_LF)))
	    *q++ = ' ';
    }
    if (quoted)
	*q++ = '"';
    *q = '\0';			/* Terminate */
    FREE(*str);
    *str = result;
}