Mathew Kimmel <kimmel@umvlsi.ecs.umass.edu> (06/08/91)
Submitted-by: Mathew Kimmel <kimmel@umvlsi.ecs.umass.edu>
Posting-number: Volume 20, Issue 45
Archive-name: ftok/part01
Environment: Coherent
This is a clone of the ftok() function used with interprocess
communications functions. This is a standard function on most unixes,
but Coherent lacks it, so I wrote my own version. Basically, what it
does is return a unique key to be used with the {msg,sem,shm}get
functions, based on a filename and an integer. For details about the
algorithm and usage, see the man page and comments at the beginning of
ftok.c
-Matt
---cut here---
#! /bin/sh
# This is a shell archive. Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file". To overwrite existing
# files, type "sh file -c". You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g.. If this archive is complete, you
# will see the following message at the end:
# "End of shell archive."
# Contents: ftok.c ftok.man
# Wrapped by kimmel@umvlsi.ecs.umass.edu on Fri Jun 7 01:44:52 1991
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f ftok.c -a "${1}" != "-c" ; then
echo shar: Will not over-write existing file \"ftok.c\"
else
echo shar: Extracting \"ftok.c\" \(1216 characters\)
sed "s/^X//" >ftok.c <<'END_OF_ftok.c'
X/* key_t ftok(filename,c) - Create a unique IPC key based on a filename
X * and an 8-bit number.
X *
X * This function takes as parameters a pointer to an ascii string
X * containing the pathname of a file, and an integer. It then returns
X * a (hopefully) unique IPC key. The key is a 32-bit integer, and is
X * constructed as follows: the lower 8 bits are the low 8 bits of c.
X * The next 8 bits are the low 8 bits of the device descriptor of the
X * device the file is located on. The upper 16 bits are the inode
X * of the file.
X *
X * This code copyright (c) Matt Kimmel 1991. Permission granted for
X * unrestricted use in non-commercial products.
X */
X#include <sys/ipc.h>
X#include <sys/stat.h>
X
Xkey_t ftok(filename,c)
Xchar *filename;
Xint c;
X{
X struct stat fs;
X union {
X key_t key;
X struct {
X char c;
X char dev;
X int inode;
X } info;
X } keyval;
X
X /* First attempt to stat the file */
X if(stat(filename,&fs) == -1) {
X perror("ftok");
X exit(1); /* Best to exit if this happens, or we may have a major IPC collision... */
X }
X
X keyval.info.c = (char)c;
X keyval.info.dev = (char)fs.st_dev;
X keyval.info.inode = (int)fs.st_ino;
X return(keyval.key);
X}
X
END_OF_ftok.c
if test 1216 -ne `wc -c <ftok.c`; then
echo shar: \"ftok.c\" unpacked with wrong size!
fi
# end of overwriting check
fi
if test -f ftok.man -a "${1}" != "-c" ; then
echo shar: Will not over-write existing file \"ftok.man\"
else
echo shar: Extracting \"ftok.man\" \(496 characters\)
sed "s/^X//" >ftok.man <<'END_OF_ftok.man'
X.TH ftok
X.SH USAGE
X.PP
Xkey_t ftok(pathname,c);
Xchar *pathname;
Xint c;
X.SH SYNOPSIS
X.PP
Xftok() takes as parameters the pathname of
Xan existing file or directory, and a number.
XFrom these, it assembles a (hopefully) unique
Xkey to be used with the interprocess communcation
Xsystem calls (specifically, msgget(), semget() and
Xshmget()). The method used for generating this
Xkey is complex; note, however, that only the lower
X8 bits of c are used.
X.SH SEE ALSO
X.PP
Xipc.h, msgget(), semget(), shmget()
END_OF_ftok.man
if test 496 -ne `wc -c <ftok.man`; then
echo shar: \"ftok.man\" unpacked with wrong size!
fi
# end of overwriting check
fi
echo shar: End of shell archive.
exit 0
exit 0 # Just in case...
--
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