ins_typebuf(
    char_u	*str,
    int		noremap,
    int		offset,
    int		nottyped,
    int		silent)
{
    char_u	*s1, *s2;
    int		newlen;
    int		addlen;
    int		i;
    int		newoff;
    int		val;
    int		nrm;

    init_typebuf();
    if (++typebuf.tb_change_cnt == 0)
	typebuf.tb_change_cnt = 1;
    state_no_longer_safe("ins_typebuf()");

    addlen = (int)STRLEN(str);

    if (offset == 0 && addlen <= typebuf.tb_off)
    {
	/*
	 * Easy case: there is room in front of typebuf.tb_buf[typebuf.tb_off]
	 */
	typebuf.tb_off -= addlen;
	mch_memmove(typebuf.tb_buf + typebuf.tb_off, str, (size_t)addlen);
    }
    else if (typebuf.tb_len == 0 && typebuf.tb_buflen
					       >= addlen + 3 * (MAXMAPLEN + 4))
    {
	/*
	 * Buffer is empty and string fits in the existing buffer.
	 * Leave some space before and after, if possible.
	 */
	typebuf.tb_off = (typebuf.tb_buflen - addlen - 3 * (MAXMAPLEN + 4)) / 2;
	mch_memmove(typebuf.tb_buf + typebuf.tb_off, str, (size_t)addlen);
    }
    else
    {
	int extra;

	/*
	 * Need to allocate a new buffer.
	 * In typebuf.tb_buf there must always be room for 3 * (MAXMAPLEN + 4)
	 * characters.  We add some extra room to avoid having to allocate too
	 * often.
	 */
	newoff = MAXMAPLEN + 4;
	extra = addlen + newoff + 4 * (MAXMAPLEN + 4);
	if (typebuf.tb_len > 2147483647 - extra)
	{
	    // string is getting too long for a 32 bit int
	    emsg(_(e_command_too_complex));    // also calls flush_buffers
	    setcursor();
	    return FAIL;
	}
	newlen = typebuf.tb_len + extra;
	s1 = alloc(newlen);
	if (s1 == NULL)		    // out of memory
	    return FAIL;
	s2 = alloc(newlen);
	if (s2 == NULL)		    // out of memory
	{
	    vim_free(s1);
	    return FAIL;
	}
	typebuf.tb_buflen = newlen;

	// copy the old chars, before the insertion point
	mch_memmove(s1 + newoff, typebuf.tb_buf + typebuf.tb_off,
							      (size_t)offset);
	// copy the new chars
	mch_memmove(s1 + newoff + offset, str, (size_t)addlen);
	// copy the old chars, after the insertion point, including the	NUL at
	// the end
	mch_memmove(s1 + newoff + offset + addlen,
				     typebuf.tb_buf + typebuf.tb_off + offset,
				       (size_t)(typebuf.tb_len - offset + 1));
	if (typebuf.tb_buf != typebuf_init)
	    vim_free(typebuf.tb_buf);
	typebuf.tb_buf = s1;

	mch_memmove(s2 + newoff, typebuf.tb_noremap + typebuf.tb_off,
							      (size_t)offset);
	mch_memmove(s2 + newoff + offset + addlen,
		   typebuf.tb_noremap + typebuf.tb_off + offset,
					   (size_t)(typebuf.tb_len - offset));
	if (typebuf.tb_noremap != noremapbuf_init)
	    vim_free(typebuf.tb_noremap);
	typebuf.tb_noremap = s2;

	typebuf.tb_off = newoff;
    }
    typebuf.tb_len += addlen;

    // If noremap == REMAP_SCRIPT: do remap script-local mappings.
    if (noremap == REMAP_SCRIPT)
	val = RM_SCRIPT;
    else if (noremap == REMAP_SKIP)
	val = RM_ABBR;
    else
	val = RM_NONE;

    /*
     * Adjust typebuf.tb_noremap[] for the new characters:
     * If noremap == REMAP_NONE or REMAP_SCRIPT: new characters are
     *			(sometimes) not remappable
     * If noremap == REMAP_YES: all the new characters are mappable
     * If noremap  > 0: "noremap" characters are not remappable, the rest
     *			mappable
     */
    if (noremap == REMAP_SKIP)
	nrm = 1;
    else if (noremap < 0)
	nrm = addlen;
    else
	nrm = noremap;
    for (i = 0; i < addlen; ++i)
	typebuf.tb_noremap[typebuf.tb_off + i + offset] =
						  (--nrm >= 0) ? val : RM_YES;

    // tb_maplen and tb_silent only remember the length of mapped and/or
    // silent mappings at the start of the buffer, assuming that a mapped
    // sequence doesn't result in typed characters.
    if (nottyped || typebuf.tb_maplen > offset)
	typebuf.tb_maplen += addlen;
    if (silent || typebuf.tb_silent > offset)
    {
	typebuf.tb_silent += addlen;
	cmd_silent = TRUE;
    }
    if (typebuf.tb_no_abbr_cnt && offset == 0)	// and not used for abbrev.s
	typebuf.tb_no_abbr_cnt += addlen;

    return OK;
}