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From: Wolfram Schneider <wosch@cs.tu-berlin.de>
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Date: Mon, 8 Jan 1996 12:15:47 +0100
Message-Id: <199601081115.MAA16136@caramba.cs.tu-berlin.de>
To: hackers@freebsd.org
Subject: large files
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On FreeBSD 2.0 I can mmap only file less than 2GB (SSIZE_MAX alias
INT_MAX). On FreeBSD 2.1 I can't write(2) to files larger than 2GB
(and don't test if mmap works with 2GB files).

Why?

Wolfram


Example:
# This is a shell archive.  Save it in a file, remove anything before
# this line, and then unpack it by entering "sh file".  Note, it may
# create directories; files and directories will be owned by you and
# have default permissions.
#
# This archive contains:
#
#	Makefile
#	mmap.c
#
echo x - Makefile
sed 's/^X//' >Makefile << 'END-of-Makefile'
XFILE=mmap.c
XALL=mmap1 mmap2
X
Xall: test
X
Xmmap1:
X	cc -Wall -DSIZE=SIZE_T_MAX -DFILENAME=\"/tmp/$@\" ${FILE} -o $@
X
Xmmap2:
X	cc -Wall -DSIZE=SSIZE_MAX -DFILENAME=\"/tmp/$@\" ${FILE} -o $@
X
Xtest: ${ALL}
X	-@for i in $>; do ./$$i; ls -l /tmp/$$i; done
X
Xclean:
X	rm -f ${ALL}; cd /tmp; rm -f ${ALL}
X
END-of-Makefile
echo x - mmap.c
sed 's/^X//' >mmap.c << 'END-of-mmap.c'
X#include <fcntl.h>
X#include <sys/types.h>
X#include <sys/mman.h>
X#include <sys/stat.h>
X#include <unistd.h>
X#include <limits.h>
X
X#include <err.h>
X#include <stdio.h>
X
X#ifndef SIZE
X#define SIZE (SIZE_T_MAX)
X#endif
X
Xchar *filename = 
X#ifndef FILENAME
X                   "/tmp/bla";
X#else
X                   FILENAME;
X#endif
X
Xvoid 
Xmain(argc, argv)
X    int argc;
X    char **argv;
X{
X    struct stat sb;
X    int fd;
X    caddr_t p;
X    off_t len;
X    char buf[256];
X
X
X
X    if ((fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666)) == -1)
X	err(1, "``%s''", filename);
X
X    /* make a long seek */
X    if (lseek(fd, (off_t)SIZE - 16, SEEK_SET) == -1)
X	err(1, "lseek");
X    
X    strcpy(buf, "foobar\n");
X
X    /* write something into file */
X    if (write(fd, buf, strlen(buf)) == -1)
X	err(1, "write");
X
X    if (fstat(fd, &sb) < 0)
X	err(1, "``%s''", filename);
X    len = sb.st_size;
X
X
X    if ((p = mmap((caddr_t)0, (size_t)len,
X		  PROT_READ, MAP_SHARED,
X		  fd, (off_t)0)) == (caddr_t)-1)
X	err(1, "mmap ``%s''", filename);
X
X    /* print "foobar" */
X    printf("%s", p+len-7); 
X
X    close(fd);
X}
END-of-mmap.c
exit