Category : C Source Code
Archive   : E_C_STR.ZIP
Filename : READ.ME

File : READ-ME
Author : Richard A. O'Keefe.
Updated: 1 June 1984.
Purpose: Explain the new strings package.

The UNIX string libraries (described in the string(3) manual page)
differ from UNIX to UNIX (e.g. strtok is not in V7 or 4.1bsd). Worse,
the sources are not in the public domain, so that if there is a string
routine which is nearly what you want but not quite you can't take a
copy and modify it. And of course C programmers on non-UNIX systems
are at the mercy of their supplier.

This package was designed to let me do reasonable things with C's
strings whatever UNIX (V7, PaNiX, UX63, 4.1bsd) I happen to be using.
Everything in the System III manual is here and does just what the S3
manual says it does. There are also lots of new goodies. I'm sorry
about the names, but the routines do have to work on asphyxiated-at-
birth systems which truncate identifiers. The convention is that a
routine is called
str [n] [c]
If there is an "n", it means that the function takes an (int) "length"
argument, which bounds the number of characters to be moved or looked
at. If the function has a "set" argument, a "c" in the name indicates
that the complement of the set is used. Functions or variables whose
names start with _ are support routines which aren't really meant for
general use. I don't know what the "p" is doing in "strpbrk", but it
is there in the S3 manual so it's here too. "istrtok" does not follow
this rule, but with 7 letters what can you do?

I have included new versions of atoi(3) and atol(3) as well. They
use a new primitive str2int, which takes a pair of bounds and a radix,
and does much more thorough checking than the normal atoi and atol do.
The result returned by atoi & atol is valid if and only if errno == 0.
There is also an output conversion routine int2str, with itoa and ltoa
as interface macros. Only after writing int2str did I notice that the
str2int routine has no provision for unsigned numbers. On reflection,
I don't greatly care. I'm afraid that int2str may depend on your "C"
compiler in unexpected ways. Do check the code with -S.

Several of these routines have "asm" inclusions conditional on the
VaxAsm option. These insertions can make the routines which have them
quite a bit faster, but there is a snag. The VAX architects, for some
reason best known to themselves and their therapists, decided that all
"strings" were shorter than 2^16 bytes. Even when the length operands
are in 32-bit registers, only 16 bits count. So the "asm" versions do
not work for long strings. If you can guarantee that all your strings
will be short, define VaxAsm in the makefile, but in general, and when
using other machines, do not define it.

Thanks to someone on the net who saw the first posting of strings,
and sent me a formatted copy of the System V memory(3C) manual page, I
have been able to include versions of these routines. The convention
is that they are called
mem{operation}([dst,] ... , len)
where operation is cpy, cmp, chr, and so on, and len is how many bytes
to move or test. Note that this is different from the strn functions,
str{operation} -- stop when you find a NUL character
strn{operation} -- stop when len is exhausted or you find NUL
mem{operation} -- stop when len is exhausted
b{operation} -- stop when len is exhausted
but the b family has different argument orders or different results or
both. In particular, note that my implementation of bcmp does conform
to the letter of the 4.2bsd manual page, but I decided to make it give
a value I have often wanted, which is not like the value of strcmp. As
the System V manual page is more explicit about the return code memcmp
DOES return a value like strcmp, so you may prefer to use it. BEWARE:
the "c" in the name mem-c-cpy doesn't mean what it does in the System3
names, it's more like mem-chr-cpy.

To use this library, you need the "strings.a" library file and the
"strings.h" header file. The other header files are for compiling the
library itself, though if you are hacking extensions you may find them
useful. General users really shouldn't see them. I've defined a few
macros I find useful in "strings.h"; if you have no need for "index",
"rindex", "streql", and "beql", just edit them out. On the 4.1bsd
system I am using, having all these functions 'extern' does not mean
that they will all be loaded; only the ones you call are. When using
lesser systems you may find it necessary to break strings.h up or you
could get by with just adding "extern" declarations for functions as
you need them. Note that as many of these functions have names
matching "standard C library" names (by design, this is after all a
replacement/reimplementation of part of that library) you may have to
talk the loader into loading this library first. Again, I've found no
problems on 4.1bsd.

A note on character comparison. The various UNIX manuals come out
and say explicitly that the *cmp and *chr routines use the computer's
"native" character comparison. That is, on a PDP-11, VAX-11, and some
other machines, signed character comparison is used, and the byte 0377
will never be located (use -1). On IBM 370s and many other machines,
unsigned character comparison is used, and the byte -1 can't be found.
(Use 0377.) If you have occasion to use 8-bit byte values in calls to
*chr functions, it would be nice if the package looked after making it
work portably. I thought about that, and decided not to do it, as you
might *want* to write VAX code that didn't find 128, and might rely on
the current effect. However, you should be able to use 8-bit values in
a portable fashion if you ask, and that the package DOES do for you.
There is a macro
int2char(c)
which takes the bottom 8 bits of c on a machine with unsigned character
comparison or sign-extends them on a machine with signed comparison. It
is up to you to use this macro in appropriate places. It is up to who-
ever installs the package to make sure that the right definition is put
in and the wrong one commented out.

You may wonder at my failure to provide manual pages for this code.
For the things in V7, 4.?, or SIII, you should be able to use whichever
manual page came with that system, and anything I might write would be
so like it as to raise suspicions of violating AT&T copyrights. In the
sources you will find comments which provide far more documentation for
these routines than AT&T ever provided for their strings stuff, I just
don't happen to have put it in nroff -man form. Had I done so, the *.3
files would have outbulked the .c files!

There is a manual page for the strx family of routines. It was the
work of Tony Hansen, of AT&T Information Systems Lincroft NJ. It is not
clear whether I should distribute this manual page or not, but as these
functions are not likely to documented anywhere else I decided to risk
it. There is no risk in the *code* however. His posting to net.sources
arrived at Edinburgh with just the reason for reposting, and the manual
page. The code is my own work based on his manual page. Indeed, I had
already written strx[n]mov, using different names.

These files are in the public domain. This includes getopt.c, which
is the work of Henry Spencer, University of Toronto Zoology, who says of
it "None of this software is derived from Bell software. I had no access
to the source for Bell's versions at the time I wrote it. This software
is hereby explicitly placed in the public domain. It may be used for
any purpose on any machine by anyone." I would greatly prefer it if *my*
material received no military use.