#! /usr/local/gnu/bin/perl
#
#-----------------------------------------------------------------------
#
# purpose : to provide incremental updates to the spooles.a library
#
# the spooles.a library is a global library and contains all spooles 
# methods. (this is in contrast to local libraries that contain 
# methods for only one object, e.g., A2/src/A2.a) 
#
# the spooles.a library is usually created once, by executing
# "make global" in the spooles directory, which compiles each
# and every source file in all the object/src directories.
# on many systems this can take quite a long time.
#
# there are times when we make a change to one method and want to
# update the spooles.a library. calling "make global" in the
# spooles directory would compile all the source once again.
#
# what is needed is a way to compile only those src files that
# need to be compiled. well, we haven't quite achieved this.
# what this perl script helps do is to create a makefile (written
# to stdout) that will compile all src files that are more recent 
# than spooles.a library. this perl script is called when
# executing "make updateLib" within the object's src directory.
#
# this works well in some cases. for example, let us say that we
# are working in the FrontMtx/drivers directory and we see that 
# the A2/src/QRreduce.c file needs a change. we open another window,
# move to the A2/src directory, and make the change in QRreduce.c.
# we then execute "make updateLib", which first calls this
# script to generate a makefile that will compile QRreduce.c
# and load into spooles.a. the makefile is then executed to perform
# that operation, and then removed. we have a good incremental
# change to the global spooles.a library.
#
# here is a second case where it doesn't work as well. assume again
# that we are working in the FrontMtx/drivers directory, and we
# see that changes need to be made to two different src files,
# the first A2/src/QRreduce.c and the second SubMtx/src/util.c.
# we edit the two source files and then need to update the spooles.a 
# library.
#
# we first go to the A2/src directory and execute "make updateLib"
# then the QRreduce.c file gets compiled and loaded into spooles.a. 
# we then go to the SubMtx/src directory and execute "make updateLib" 
# and the util.c file # is NOT compiled and loaded into the library. 
# this is because spooles.a is more recent the SubMtx/src/util.c, 
# because spooles.a was just modified when A2/src/QRreduce.c was 
# compiled and loaded.
#
# i presently don't know of a clean solution to this problem
# (and am open to suggestions). a decent workaround is this.
# (1) go to A2/src, modify QRreduce.c, then "make updateLib"
# (2) go to SubMtx/src, modify util.c, then "make updateLib"
# here the util.c file is more recent than spooles.a. in other words,
# update the library after each src file is changed.
#
# this is my first perl script, so don't laugh, 
# just send me comments and suggestions.
#
# created -- 98dec16, cca
#
#-----------------------------------------------------------------------
#
#  open the makefile to extract out the src file names
#
$makefile = "makefile" ;
open( MAKEFILE, $makefile ) or die "Cannot open $makefile" ;
#
#  get the last modification time for ../../spooles.a
#
if ( -e "../../spooles.a" ) {
   $lib_time = -M "../../spooles.a" ;
}
#
#  read in each line, look for $(OBJ).a(srcname.o)
#  put srcname into the @srcnames array
#
while ( $line = <MAKEFILE> ) {
   chop($line) ;
   if ( $line =~ /OBJ =/ ) {
      ($first, $objname) = split /OBJ = /, $line
   }
   if ( $line =~ /\$\(OBJ\)\.a\(/ ) {
      ($first, $second) = split /\$\(OBJ\)\.a\(/, $line ;
      ($srcname, $remainder) = split /\.o\)/, $second ;
      $srcname = $srcname . ".c" ;
#
#     get the last modification time for srcname.c
#
      $srcname_time = -M $srcname ;
      if ( (! -e "../../spooles.a") or ($srcname_time < $lib_time) ) {
         push @srcnames, $srcname
      }
   }
}
#
# now start printing the makefile to stdout
#
print "\ninclude ../../Make.inc" ;
print "\n" ;
print "\nOBJ = $objname" ;
print "\n\nSRC = " ;
foreach $src ( @srcnames ) {
   $srcname = " \\\n     " . $src ;
   print $srcname ;
}
print "\n\nOBJ_FILES = \$\{SRC:.c=.o\}" ;
print "\n\n" ;
print <<'EOF' ;
.c.o :
	$(PURIFY) $(CC) -c $(CFLAGS) $*.c -o $(OBJ)_$*.o

../../spooles.a : ${OBJ_FILES}
	$(AR) $(ARFLAGS) ../../spooles.a $(OBJ)_*.o
	rm -f $(OBJ)_*.o
	$(RANLIB) ../../spooles.a
EOF