valid.h
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/* GNU Mailutils -- a suite of utilities for electronic mail
Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
GNU Mailutils is free software; you can redistribute it and/or modify
it under the terms of the GNU General Library Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU Mailutils 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 Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with GNU Mailutils; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
/* Credits to the c-client and its Authors
* The notorius c-client VALID() macro, was written by Mark Crispin.
*/
/* From the C-Client, part of pine */
/* You are not expected to understand this macro, but read the next page if
* you are not faint of heart.
*
* Known formats to the VALID macro are:
* From user Wed Dec 2 05:53 1992
* BSD From user Wed Dec 2 05:53:22 1992
* SysV From user Wed Dec 2 05:53 PST 1992
* rn From user Wed Dec 2 05:53:22 PST 1992
* From user Wed Dec 2 05:53 -0700 1992
* From user Wed Dec 2 05:53:22 -0700 1992
* From user Wed Dec 2 05:53 1992 PST
* From user Wed Dec 2 05:53:22 1992 PST
* From user Wed Dec 2 05:53 1992 -0700
* Solaris From user Wed Dec 2 05:53:22 1992 -0700
*
* Plus all of the above with `` remote from xxx'' after it. Thank you very
* much, smail and Solaris, for making my life considerably more complicated.
*/
/*
* What? You want to understand the VALID macro anyway? Alright, since you
* insist. Actually, it isn't really all that difficult, provided that you
* take it step by step.
*
* Line 1 Initializes the return ti value to failure (0);
* Lines 2-3 Validates that the 1st-5th characters are ``From ''.
* Lines 4-6 Validates that there is an end of line and points x at it.
* Lines 7-14 First checks to see if the line is at least 41 characters long
.
* If so, it scans backwards to find the rightmost space. From
* that point, it scans backwards to see if the string matches
* `` remote from''. If so, it sets x to point to the space at
* the start of the string.
* Line 15 Makes sure that there are at least 27 characters in the line.
* Lines 16-21 Checks if the date/time ends with the year (there is a space
* five characters back). If there is a colon three characters
* further back, there is no timezone field, so zn is set to 0
* and ti is set in front of the year. Otherwise, there must
* either to be a space four characters back for a three-letter
* timezone, or a space six characters back followed by a + or -
* for a numeric timezone; in either case, zn and ti become the
* offset of the space immediately before it.
* Lines 22-24 Are the failure case for line 14. If there is a space four
* characters back, it is a three-letter timezone; there must be
a
* space for the year nine characters back. zn is the zone
* offset; ti is the offset of the space.
* Lines 25-28 Are the failure case for line 20. If there is a space six
* characters back, it is a numeric timezone; there must be a
* space eleven characters back and a + or - five characters back
.
* zn is the zone offset; ti is the offset of the space.
* Line 29-32 If ti is valid, make sure that the string before ti is of the
* form www mmm dd hh:mm or www mmm dd hh:mm:ss, otherwise
* invalidate ti. There must be a colon three characters back
* and a space six or nine characters back (depending upon
* whether or not the character six characters back is a colon).
* There must be a space three characters further back (in front
* of the day), one seven characters back (in front of the month)
,
* and one eleven characters back (in front of the day of week).
* ti is set to be the offset of the space before the time.
*
* Why a macro? It gets invoked a *lot* in a tight loop. On some of the
* newer pipelined machines it is faster being open-coded than it would be if
* subroutines are called.
*
* Why does it scan backwards from the end of the line, instead of doing the
* much easier forward scan? There is no deterministic way to parse the
* ``user'' field, because it may contain unquoted spaces! Yes, I tested it t
o
* see if unquoted spaces were possible. They are, and I've encountered enoug
h
* evil mail to be totally unwilling to trust that ``it will never happen''.
*/
#define VALID(s,x,ti,zn) { \
ti = 0; \
if ((*s == 'F') && (s[1] == 'r') && (s[2] == 'o') && (s[3] == 'm') && \
(s[4] == ' ')) { \
for (x = s + 5; *x && *x != '\n'; x++); \
if (x) { \
if (x - s >= 41) { \
for (zn = -1; x[zn] != ' '; zn--); \
if ((x[zn-1] == 'm') && (x[zn-2] == 'o') && (x[zn-3] == 'r') && \
(x[zn-4] == 'f') && (x[zn-5] == ' ') && (x[zn-6] == 'e') && \
(x[zn-7] == 't') && (x[zn-8] == 'o') && (x[zn-9] == 'm') && \
(x[zn-10] == 'e') && (x[zn-11] == 'r') && (x[zn-12] == ' '))\
x += zn - 12; \
} \
if (x - s >= 27) { \
if (x[-5] == ' ') { \
if (x[-8] == ':') zn = 0,ti = -5; \
else if (x[-9] == ' ') ti = zn = -9; \
else if ((x[-11] == ' ') && ((x[-10]=='+') || (x[-10]=='-'))) \
ti = zn = -11; \
} \
else if (x[-4] == ' ') { \
if (x[-9] == ' ') zn = -4,ti = -9; \
} \
else if (x[-6] == ' ') { \
if ((x[-11] == ' ') && ((x[-5] == '+') || (x[-5] == '-'))) \
zn = -6,ti = -11; \
} \
if (ti && !((x[ti - 3] == ':') && \
(x[ti -= ((x[ti - 6] == ':') ? 9 : 6)] == ' ') && \
(x[ti - 3] == ' ') && (x[ti - 7] == ' ') && \
(x[ti - 11] == ' '))) ti = 0; \
} \
} \
} \
}