File: HTParse.c

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/*              Parse HyperText Document Address                HTParse.c
   **           ================================
 */

#include "HTParse.h"
#define TRACE 0

#define FREE(x) if (x) {free(x); x = NULL;}

struct struct_parts
  {
    char *access;
    char *host;
    char *absolute;
    char *relative;
/*      char * search;          no - treated as part of path */
    char *anchor;
  };

/*      Strings of any length
   **      ---------------------
 */
PUBLIC int strcasecomp
ARGS2 (
	CONST char *, a,
	CONST char *, b)
{
  CONST char *p = a;
  CONST char *q = b;

  for (p = a, q = b; *p && *q; p++, q++)
    {
      int diff = TOLOWER (*p) - TOLOWER (*q);
      if (diff)
	return diff;
    }
  if (*p)
    return 1;			/* p was longer than q */
  if (*q)
    return -1;			/* p was shorter than q */
  return 0;			/* Exact match */
}

/*      With count limit
   **      ----------------
 */
PUBLIC int strncasecomp
ARGS3 (
	CONST char *, a,
	CONST char *, b,
	int, n)
{
  CONST char *p = a;
  CONST char *q = b;

  for (p = a, q = b;;
       p++, q++)
    {
      int diff;
      if (p == (a + n))
	return 0;		/*   Match up to n characters */
      if (!(*p && *q))
	return (*p - *q);
      diff = TOLOWER (*p) - TOLOWER (*q);
      if (diff)
	return diff;
    }
  /*NOTREACHED */
}

/*      Allocate a new copy of a string, and returns it
 */
PUBLIC char *HTSACopy
ARGS2 (
	char **, dest,
	CONST char *, src)
{
  FREE (*dest);
  if (src)
    {
      *dest = (char *) malloc (strlen (src) + 1);
      if (*dest == NULL)
	outofmem (__FILE__, "HTSACopy");
      strcpy (*dest, src);
    }
  return *dest;
}
/*      String Allocate and Concatenate
 */
PUBLIC char *HTSACat
ARGS2 (
	char **, dest,
	CONST char *, src)
{
  if (src && *src)
    {
      if (*dest)
	{
	  int length = strlen (*dest);
	  *dest = (char *) realloc (*dest, length + strlen (src) + 1);
	  if (*dest == NULL)
	    outofmem (__FILE__, "HTSACat");
	  strcpy (*dest + length, src);
	}
      else
	{
	  *dest = (char *) malloc (strlen (src) + 1);
	  if (*dest == NULL)
	    outofmem (__FILE__, "HTSACat");
	  strcpy (*dest, src);
	}
    }
  return *dest;
}



/*      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.
 */
PUBLIC char *HTStrip
ARGS1 (
	char *, s)
{
#define SPACE(c) ((c == ' ') || (c == '\t') || (c == '\n'))
  char *p = s;
  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 consituents.                    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.
 */
PRIVATE void scan
ARGS2 (
	char *, name,
	struct struct_parts *, parts)
{
  char *after_access;
  char *p;
  /* int length = strlen (name); */

  parts->access = NULL;
  parts->host = NULL;
  parts->absolute = NULL;
  parts->relative = NULL;
  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;
    }

#ifdef NOTDEFINED
  for (p = (name + length - 1); p >= name; p--)
    {
#endif /* NOTDEFINED */
      /*
         **  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 */
	    }
	}

      /*
         **  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
	    {
	      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)
	{
	  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.
	       */
	      *(parts->anchor - 1) = '#';
	      parts->anchor = NULL;
	    }
	}

#ifdef NOT_DEFINED		/* search is just treated as part of path */
      {
	char *p = (relative ? relative : absolute);
	if (p != NULL)
	  {
	    char *q = strchr (p, '?');	/* Any search string? */
	    if (q != NULL)
	      {
		*q = '\0';	/* If so, chop that off. */
		parts->search = (q + 1);
	      }
	  }
      }
#endif /* NOT_DEFINED */
    }				/*scan */


/*      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
 */
  PUBLIC char *HTParse ARGS3 (
			       CONST char *, aName,
			       CONST char *, relatedName,
			       int, wanted)
  {
    char *result = NULL;
    char *return_value = NULL;
    int len;
    char *name = NULL;
    char *rel = NULL;
    char *p;
    char *access;
    struct struct_parts given, related;

    if (TRACE)
        fprintf (stderr,
		 "HTParse: aName:%s   relatedName:%s\n", aName, relatedName);

    /*
       **  Allocate the output string.
     */
      len = strlen (aName) + strlen (relatedName) + 10;
      result = (char *) malloc (len);	/* Lots of space: more than enough */
    if (result == NULL)
        outofmem (__FILE__, "HTParse");
      result[0] = '\0';		/* Clear string  */

    /*
       **  Make working copies of the input strings to cut up.
     */
      StrAllocCopy (name, aName);
      StrAllocCopy (rel, relatedName);

    /*
       **  Cut up the strings into URL fields.
     */
      scan (name, &given);
      scan (rel, &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 = "";
      }
    access = given.access ? given.access : related.access;
    if (wanted & PARSE_ACCESS)
      {
	if (access)
	  {
	    strcat (result, access);
	    if (wanted & PARSE_PUNCTUATION)
	      strcat (result, ":");
	  }
      }

    /*
       **  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 strncasecomp() 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.anchor = NULL;
      }

    /*
       **  Handle the host field.
     */
    if (wanted & PARSE_HOST)
      if (given.host || related.host)
	{
	  char *tail = result + strlen (result);
	  if (wanted & PARSE_PUNCTUATION)
	    strcat (result, "//");
	  strcat (result, 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.
	   */
	  {
	    char *p, *h;
	    p = strchr (tail, ':');
	    if (p != NULL && !isdigit ((unsigned char) p[1]))
	      /*
	         **  Colon not followed by a port number.
	       */
	      *p = '\0';
	    if (p != NULL && p != '\0' && access != NULL)
	      {
		/*
		   **  Port specified.
		 */
		if ((!strcmp (access, "http") && !strcmp (p, ":80")) ||
		    (!strcmp (access, "gopher") && !strcmp (p, ":70")) ||
		    (!strcmp (access, "ftp") && !strcmp (p, ":21")) ||
		    (!strcmp (access, "wais") && !strcmp (p, ":210")) ||
		    (!strcmp (access, "nntp") && !strcmp (p, ":119")) ||
		    (!strcmp (access, "news") && !strcmp (p, ":119")) ||
		    (!strcmp (access, "snews") && !strcmp (p, ":563")) ||
		    (!strcmp (access, "finger") && !strcmp (p, ":79")) ||
		    (!strcmp (access, "cso") && !strcmp (p, ":105")))
		  *p = '\0';	/* It is the default: ignore it */
	      }
	    if (p == NULL)
	      {
		int len = strlen (tail);

		if (len > 0)
		  {
		    h = tail + len - 1;		/* last char of hostname */
		    if (*h == '.')
		      *h = '\0';	/* chop final . */
		  }
	      }
	    else
	      {
		h = p;
		h--;		/* End of hostname */
		if (*h == '.')
		  {
		    /*
		       **  Slide p over h.
		     */
		    while (*p != '\0')
		      *h++ = *p++;
		    *h = '\0';	/* terminate */
		  }
	      }
	  }
#endif /* CLEAN_URLS */
	}

    /*
       **  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)
      {
	if (access && !given.absolute && given.relative)
	  {
	    if (!strcasecomp (access, "nntp") ||
		!strcasecomp (access, "snews") ||
		(!strcasecomp (access, "news") &&
		 !strncasecomp (result, "news://", 7)))
	      {
		/*
		 *  Treat all given nntp or snews paths,
		 *  or given paths for news URLs with a host,
		 *  as absolute.
		 */
		given.absolute = given.relative;
		given.relative = NULL;
	      }
	  }
	if (given.absolute)
	  {			/* All is given */
	    if (wanted & PARSE_PUNCTUATION)
	      strcat (result, "/");
	    strcat (result, given.absolute);
	    if (TRACE)
	      fprintf (stderr, "1\n");
	  }
	else if (related.absolute)
	  {			/* Adopt path not name */
	    strcat (result, "/");
	    strcat (result, related.absolute);
	    if (given.relative)
	      {
		p = strchr (result, '?');	/* Search part? */
		if (p == NULL)
		  p = (result + strlen (result) - 1);
		for (; *p != '/'; p--)
		  ;		/* last / */
		p[1] = '\0';	/* Remove filename */
		strcat (result, given.relative);	/* Add given one */
		HTSimplify (result);
	      }
	    if (TRACE)
	      fprintf (stderr, "2\n");
	  }
	else if (given.relative)
	  {
	    strcat (result, given.relative);	/* what we've got */
	    if (TRACE)
	      fprintf (stderr, "3\n");
	  }
	else if (related.relative)
	  {
	    strcat (result, related.relative);
	    if (TRACE)
	      fprintf (stderr, "4\n");
	  }
	else
	  {			/* No inheritance */
	    if (strncasecomp (aName, "lynxcgi:", 8) &&
		strncasecomp (aName, "lynxexec:", 9) &&
		strncasecomp (aName, "lynxprog:", 9))
	      {
		strcat (result, "/");
	      }
	    if (!strcmp (result, "news:/"))
	      result[5] = '*';
	    if (TRACE)
	      fprintf (stderr, "5\n");
	  }
      }

    /*
       **  Handle the fragment (anchor).
     */
    if (wanted & PARSE_ANCHOR)
      if ((given.anchor && *given.anchor) ||
	  (!given.anchor && related.anchor))
	{
	  if (wanted & PARSE_PUNCTUATION)
	    strcat (result, "#");
	  strcat (result, (given.anchor) ?
		  given.anchor : related.anchor);
	}
    if (TRACE)
      fprintf (stderr, "HTParse: result:%s\n", result);
    FREE (rel);
    FREE (name);

    StrAllocCopy (return_value, result);
    FREE (result);

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

/*      Simplify a filename.                            HTSimplify()
   **   --------------------
   **
   **  A unix-style file is allowed to contain the seqeunce xxx/../ which may
   **  be replaced by "" , and the seqeunce "/./" 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
 */
  PUBLIC void HTSimplify ARGS1 (
				 char *, filename)
  {
    char *p;
    char *q, *q1;

    if (filename == NULL)
        return;

    if ((filename[0] && filename[1]) && strchr (filename, '/') != NULL)
      {
	for (p = (filename + 2); *p; p++)
	  {
	    if (*p == '/')
	      {
		if ((p[1] == '.') && (p[2] == '.') &&
		    (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) &&
			!((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 */
#ifdef NOTDEFINED
			/*
			   **  Make sure filename has at least one slash.
			 */
			if (*filename == '\0')
			  {
			    *filename = '/';
			    *(filename + 1) = '\0';
			  }
#endif				/* NOTDEFINED */
			/*
			   **  Start again with previous slash.
			 */
			p = (q - 1);
		      }
		  }
		else if (p[1] == '.' && p[2] == '/')
		  {
		    /*
		       **  Handle "./" by removing the characters.
		     */
		    q = p;
		    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';
		  }
	      }
	  }
      }
  }

/*      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 retured.
   **
   **  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.
   **
 */
  PUBLIC char *HTRelative ARGS2 (
				  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 */
	int levels = 0;
	for (; *q && (*q != '#'); q++)
	  if (*q == '/')
	    levels++;
	result = (char *) malloc (3 * levels + strlen (last_slash) + 1);
	if (result == NULL)
	  outofmem (__FILE__, "HTRelative");
	result[0] = '\0';
	for (; levels; levels--)
	  strcat (result, "../");
	strcat (result, last_slash + 1);
      }
    if (TRACE)
      fprintf (stderr, "HT: `%s' expressed relative to\n    `%s' is\n   `%s'.",
	       aName, relatedName, result);
    return result;
  }