#!/bin/sh # This is a shell archive (produced by GNU sharutils 4.2). # To extract the files from this archive, save it to some FILE, remove # everything before the `!/bin/sh' line above, then type `sh FILE'. # # Made on 1999-01-26 20:15 EST by . # Source directory was `/var/home/jcej/projects/ACE_wrappers/docs/tutorials/012'. # # Existing files will *not* be overwritten unless `-c' is specified. # # This shar contains: # length mode name # ------ ---------- ------------------------------------------ # 430 -rw-rw-r-- hdr # 56 -rw-rw-r-- bodies # 1093 -rw-rw-r-- page01.pre # 263 -rw-rw-r-- page02.pre # 397 -rw-rw-r-- page03.pre # 154 -rw-rw-r-- page04.pre # 183 -rw-rw-r-- page05.pre # 448 -rw-rw-r-- page06.pre # 395 -rw-rw-r-- page02.pst # 399 -rw-rw-r-- page03.pst # 162 -rw-rw-r-- page04.pst # 449 -rw-rw-r-- page05.pst # save_IFS="${IFS}" IFS="${IFS}:" gettext_dir=FAILED locale_dir=FAILED first_param="$1" for dir in $PATH do if test "$gettext_dir" = FAILED && test -f $dir/gettext \ && ($dir/gettext --version >/dev/null 2>&1) then set `$dir/gettext --version 2>&1` if test "$3" = GNU then gettext_dir=$dir fi fi if test "$locale_dir" = FAILED && test -f $dir/shar \ && ($dir/shar --print-text-domain-dir >/dev/null 2>&1) then locale_dir=`$dir/shar --print-text-domain-dir` fi done IFS="$save_IFS" if test "$locale_dir" = FAILED || test "$gettext_dir" = FAILED then echo=echo else TEXTDOMAINDIR=$locale_dir export TEXTDOMAINDIR TEXTDOMAIN=sharutils export TEXTDOMAIN echo="$gettext_dir/gettext -s" fi touch -am 1231235999 $$.touch >/dev/null 2>&1 if test ! -f 1231235999 && test -f $$.touch; then shar_touch=touch else shar_touch=: echo $echo 'WARNING: not restoring timestamps. Consider getting and' $echo "installing GNU \`touch', distributed in GNU File Utilities..." echo fi rm -f 1231235999 $$.touch # if mkdir _sh31139; then $echo 'x -' 'creating lock directory' else $echo 'failed to create lock directory' exit 1 fi # ============= hdr ============== if test -f 'hdr' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'hdr' '(file already exists)' else $echo 'x -' extracting 'hdr' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'hdr' && X X X ACE Tutorial 012 X
ACE Tutorial 012
X
Passing classes through ACE_Message_Queue
X X

SHAR_EOF $shar_touch -am 0124160599 'hdr' && chmod 0664 'hdr' || $echo 'restore of' 'hdr' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'hdr:' 'MD5 check failed' 1acf94beccfa9e953b2f55e02a0bb2e6 hdr SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'hdr'`" test 430 -eq "$shar_count" || $echo 'hdr:' 'original size' '430,' 'current size' "$shar_count!" fi fi # ============= bodies ============== if test -f 'bodies' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'bodies' '(file already exists)' else $echo 'x -' extracting 'bodies' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'bodies' && PAGE=2 work.h block.h message_queue.cpp task.h task.cpp SHAR_EOF $shar_touch -am 0124160199 'bodies' && chmod 0664 'bodies' || $echo 'restore of' 'bodies' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'bodies:' 'MD5 check failed' 3ad29f0a25bfe156b37630c9ee9f715c bodies SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'bodies'`" test 56 -eq "$shar_count" || $echo 'bodies:' 'original size' '56,' 'current size' "$shar_count!" fi fi # ============= page01.pre ============== if test -f 'page01.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page01.pre' '(file already exists)' else $echo 'x -' extracting 'page01.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page01.pre' &&

Last time around we put an object into a message queue by using the copy() method to create a duplicate of the object. That's probably OK for simple objects that aren't very large. However, if you have an object that contains pointers or tons of data then that approach is going to cause problems.

What we'll do in this tutorial is specialize the ACE_Message_Block object so that it can carry our data more efficiently. As you'll see, this isn't very difficult at all.

Kirthika's abstract:

SHAR_EOF $shar_touch -am 0126201599 'page01.pre' && chmod 0664 'page01.pre' || $echo 'restore of' 'page01.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page01.pre:' 'MD5 check failed' 5e7f58b50e75c303325b71866a2a4a4a page01.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page01.pre'`" test 1093 -eq "$shar_count" || $echo 'page01.pre:' 'original size' '1093,' 'current size' "$shar_count!" fi fi # ============= page02.pre ============== if test -f 'page02.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page02.pre' '(file already exists)' else $echo 'x -' extracting 'page02.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page02.pre' && We normally start by looking at main() and work our way out from there. This time, I want to start by showing you the ACE_Message_Block derivative but before that, I have to introduce you to the Work object and it's baseclass Unit_Of_Work

SHAR_EOF $shar_touch -am 0124160599 'page02.pre' && chmod 0664 'page02.pre' || $echo 'restore of' 'page02.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page02.pre:' 'MD5 check failed' 67c405a8085b9ad581912c2aec135ed4 page02.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page02.pre'`" test 263 -eq "$shar_count" || $echo 'page02.pre:' 'original size' '263,' 'current size' "$shar_count!" fi fi # ============= page03.pre ============== if test -f 'page03.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page03.pre' '(file already exists)' else $echo 'x -' extracting 'page03.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page03.pre' &&

In the previous tutorial we moved our complex data into the queue by copy()ing it directly into the message block's data area. I hope that most readers got a queasy feeling when I did that. It just isn't a good idea...

A better idea would be to teach the message queue about our data types (or at least a baseclass) so that it can more efficiently handle things:

SHAR_EOF $shar_touch -am 0124160599 'page03.pre' && chmod 0664 'page03.pre' || $echo 'restore of' 'page03.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page03.pre:' 'MD5 check failed' d8f77e8098d5086c71c164de8a78c29c page03.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page03.pre'`" test 397 -eq "$shar_count" || $echo 'page03.pre:' 'original size' '397,' 'current size' "$shar_count!" fi fi # ============= page04.pre ============== if test -f 'page04.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page04.pre' '(file already exists)' else $echo 'x -' extracting 'page04.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page04.pre' &&

Ok, finally we get to main(). Sorry for the diversion but it was important to lay some of that groundwork before getting here.

SHAR_EOF $shar_touch -am 0124160599 'page04.pre' && chmod 0664 'page04.pre' || $echo 'restore of' 'page04.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page04.pre:' 'MD5 check failed' 8989e75934f20e9b74d38a2d3687613a page04.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page04.pre'`" test 154 -eq "$shar_count" || $echo 'page04.pre:' 'original size' '154,' 'current size' "$shar_count!" fi fi # ============= page05.pre ============== if test -f 'page05.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page05.pre' '(file already exists)' else $echo 'x -' extracting 'page05.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page05.pre' &&

The Task is the only object we've not been through yet. I'll go ahead and show both the header and cpp on this one page since the header isn't very large.

SHAR_EOF $shar_touch -am 0124160599 'page05.pre' && chmod 0664 'page05.pre' || $echo 'restore of' 'page05.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page05.pre:' 'MD5 check failed' 499934db529597846d10ca45610bc52e page05.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page05.pre'`" test 183 -eq "$shar_count" || $echo 'page05.pre:' 'original size' '183,' 'current size' "$shar_count!" fi fi # ============= page06.pre ============== if test -f 'page06.pre' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page06.pre' '(file already exists)' else $echo 'x -' extracting 'page06.pre' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page06.pre' &&

Once again, we come to the end of a tutorial. By creating a simple specialization of ACE_Message_Block, we've been able to remove a lot of complexity and erorr potential from our previous implementation.

SHAR_EOF $shar_touch -am 0124160599 'page06.pre' && chmod 0664 'page06.pre' || $echo 'restore of' 'page06.pre' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page06.pre:' 'MD5 check failed' 64afabb236ea02927914d03f258e620b page06.pre SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page06.pre'`" test 448 -eq "$shar_count" || $echo 'page06.pre:' 'original size' '448,' 'current size' "$shar_count!" fi fi # ============= page02.pst ============== if test -f 'page02.pst' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page02.pst' '(file already exists)' else $echo 'x -' extracting 'page02.pst' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page02.pst' &&

This is basically the same as the DataBase in the previous tutorial but I've changed the name to be more generic. The feeling is that a Data object would be a C struct but an Work object would be a class with methods.

Now that you know what we'll be putting into the queue, lets go to the next page where I specialize the ACE_Message_Block.

SHAR_EOF $shar_touch -am 0124160599 'page02.pst' && chmod 0664 'page02.pst' || $echo 'restore of' 'page02.pst' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page02.pst:' 'MD5 check failed' 961a6ad181e25a24b2500abe013b5379 page02.pst SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page02.pst'`" test 395 -eq "$shar_count" || $echo 'page02.pst:' 'original size' '395,' 'current size' "$shar_count!" fi fi # ============= page03.pst ============== if test -f 'page03.pst' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page03.pst' '(file already exists)' else $echo 'x -' extracting 'page03.pst' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page03.pst' &&

Ok, this looks pretty good. We just construct our specialized Message_Block instead of the generic ACE_Message_Block and let it carry our data along. When our application is done with the message block and release()es it, we know that our work object will also be taken care of.

Let's now go to main() and see what we had to change there to use this specialization.

SHAR_EOF $shar_touch -am 0124160599 'page03.pst' && chmod 0664 'page03.pst' || $echo 'restore of' 'page03.pst' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page03.pst:' 'MD5 check failed' 282e52e360c416f48db0dc454354bfda page03.pst SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page03.pst'`" test 399 -eq "$shar_count" || $echo 'page03.pst:' 'original size' '399,' 'current size' "$shar_count!" fi fi # ============= page04.pst ============== if test -f 'page04.pst' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page04.pst' '(file already exists)' else $echo 'x -' extracting 'page04.pst' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page04.pst' &&

That certainly looks cleaner than the previous approach! If you blink, you'll miss the part where the Work object goes into the Queue.

SHAR_EOF $shar_touch -am 0124160599 'page04.pst' && chmod 0664 'page04.pst' || $echo 'restore of' 'page04.pst' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page04.pst:' 'MD5 check failed' 245db1d5e74203bf085369bb47d646db page04.pst SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page04.pst'`" test 162 -eq "$shar_count" || $echo 'page04.pst:' 'original size' '162,' 'current size' "$shar_count!" fi fi # ============= page05.pst ============== if test -f 'page05.pst' && test "$first_param" != -c; then $echo 'x -' SKIPPING 'page05.pst' '(file already exists)' else $echo 'x -' extracting 'page05.pst' '(text)' sed 's/^X//' << 'SHAR_EOF' > 'page05.pst' &&

Like main() this is actually simpler than the previous tutorial. It's much cleaner to carry around a pointer to the object we're working with than to try copying data.

The only complication is the new ACE_Barrier. It's a pretty simple object that makes it easy for you to synch threads in this way. You could do some fancy tricks with mutexes, counters & semaphores but why bother when the Barrier already exists.

SHAR_EOF $shar_touch -am 0124160599 'page05.pst' && chmod 0664 'page05.pst' || $echo 'restore of' 'page05.pst' 'failed' if ( md5sum --help 2>&1 | grep 'sage: md5sum \[' ) >/dev/null 2>&1 \ && ( md5sum --version 2>&1 | grep -v 'textutils 1.12' ) >/dev/null; then md5sum -c << SHAR_EOF >/dev/null 2>&1 \ || $echo 'page05.pst:' 'MD5 check failed' 1db9b33059c7da0ee0b30f0d077bd443 page05.pst SHAR_EOF else shar_count="`LC_ALL= LC_CTYPE= LANG= wc -c < 'page05.pst'`" test 449 -eq "$shar_count" || $echo 'page05.pst:' 'original size' '449,' 'current size' "$shar_count!" fi fi rm -fr _sh31139 exit 0