/* Generic support for headers.
   Copyright (C) 1997, 1998 Free Software Foundation, Inc.

This file is part of GNU Wget.

GNU Wget is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

GNU Wget is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Wget; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include <config.h>

#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_STRING_H
# include <string.h>
#else
# include <strings.h>
#endif

#include "wget.h"
#include "connect.h"
#include "rbuf.h"
#include "headers.h"

/* This file contains the generic routines for work with headers.
   Currently they are used only by HTTP in http.c, but they can be
   used by anything that cares about RFC822-style headers.

   Header is defined in RFC2068, as quoted below.  Note that this
   definition is not HTTP-specific -- it is virtually
   indistinguishable from the one given in RFC822 or RFC1036.

	message-header = field-name ":" [ field-value ] CRLF

	field-name     = token
	field-value    = *( field-content | LWS )

	field-content  = <the OCTETs making up the field-value
			 and consisting of either *TEXT or combinations
			 of token, tspecials, and quoted-string>

   The public functions are header_get() and header_process(), which
   see.  */


/* Get a header from read-buffer RBUF and return it in *HDR.

   As defined in RFC2068 and elsewhere, a header can be folded into
   multiple lines if the continuation line begins with a space or
   horizontal TAB.  Also, this function will accept a header ending
   with just LF instead of CRLF.

   The header may be of arbitrary length; the function will allocate
   as much memory as necessary for it to fit.  It need not contain a
   `:', thus you can use it to retrieve, say, HTTP status line.

   The trailing CRLF or LF are stripped from the header, and it is
   zero-terminated.   #### Is this well-behaved?  */
int
header_get (struct rbuf *rbuf, char **hdr, enum header_get_flags flags)
{
  int i;
  int bufsize = 80;

  *hdr = (char *)xmalloc (bufsize);
  for (i = 0; 1; i++)
    {
      int res;
      /* #### Use DO_REALLOC?  */
      if (i > bufsize - 1)
	*hdr = (char *)xrealloc (*hdr, (bufsize <<= 1));
      res = RBUF_READCHAR (rbuf, *hdr + i);
      if (res == 1)
	{
	  if ((*hdr)[i] == '\n')
	    {
	      if (!((flags & HG_NO_CONTINUATIONS)
		    || i == 0
		    || (i == 1 && (*hdr)[0] == '\r')))
		{
		  char next;
		  /* If the header is non-empty, we need to check if
		     it continues on to the other line.  We do that by
		     peeking at the next character.  */
		  res = rbuf_peek (rbuf, &next);
		  if (res == 0)
		    return HG_EOF;
		  else if (res == -1)
		    return HG_ERROR;
		  /*  If the next character is HT or SP, just continue.  */
		  if (next == '\t' || next == ' ')
		    continue;
		}
	      /* The header ends.  */
	      (*hdr)[i] = '\0';
	      /* Get rid of '\r'.  */
	      if (i > 0 && (*hdr)[i - 1] == '\r')
		(*hdr)[i - 1] = '\0';
	      break;
	    }
	}
      else if (res == 0)
	return HG_EOF;
      else
	return HG_ERROR;
    }
  DEBUGP (("%s\n", *hdr));
  return HG_OK;
}

/* Check whether HEADER begins with NAME and, if yes, skip the `:' and
   the whitespace, and call PROCFUN with the arguments of HEADER's
   contents (after the `:' and space) and ARG.  Otherwise, return 0.  */
int
header_process (const char *header, const char *name,
		int (*procfun) (const char *, void *),
		void *arg)
{
  /* Check whether HEADER matches NAME.  */
  while (*name && (TOLOWER (*name) == TOLOWER (*header)))
    ++name, ++header;
  if (*name || *header++ != ':')
    return 0;

  header += skip_lws (header);

  return ((*procfun) (header, arg));
}

/* Helper functions for use with header_process().  */

/* Extract a long integer from HEADER and store it to CLOSURE.  If an
   error is encountered, return 0, else 1.  */
int
header_extract_number (const char *header, void *closure)
{
  const char *p = header;
  long result;

  for (result = 0; ISDIGIT (*p); p++)
    result = 10 * result + (*p - '0');

  /* Failure if no number present. */
  if (p == header)
    return 0;

  /* Skip trailing whitespace. */
  p += skip_lws (p);

  /* Indicate failure if trailing garbage is present. */
  if (*p)
    return 0;

  *(long *)closure = result;
  return 1;
}

/* Strdup HEADER, and place the pointer to CLOSURE.  */
int
header_strdup (const char *header, void *closure)
{
  *(char **)closure = xstrdup (header);
  return 1;
}

/* Write the value 1 into the integer pointed to by CLOSURE.  */
int
header_exists (const char *header, void *closure)
{
  *(int *)closure = 1;
  return 1;
}

/* Skip LWS (linear white space), if present.  Returns number of
   characters to skip.  */
int
skip_lws (const char *string)
{
  const char *p = string;

  while (*p == ' ' || *p == '\t' || *p == '\r' || *p == '\n')
    ++p;
  return p - string;
}