While I strongly recommend a robust and tested pretty printer solution here is an example of how you could do it in a few lines of Perl. Not really very robust but you could do:

Update. Opps, wrong lang. Changed from trailing \ to \t indent continuation

my $wrap = 76;
my $tab  = 4;   # spaces occupied by tab
while(<DATA>) {
    do{ print; next } if length($_) < $wrap;
    do{ print "\n"; next } if m/^\s*$/;
    s/^(\s*)(?=\S)// or die "Choked on $_\n";
    my $indent = $1;
    my $l_wrap = $wrap - length($indent) - $tab;
    my @bits = $_ =~ m/\G(.{1,$l_wrap})\s+/gc;
    for ( my $i = 0; $i <@bits; $i++ ) {
        print $i == 0 ? "$indent$bits[$i]\n" : "$indent\t$bits[$i]\n";
    }
}


__DATA__
class ClassMyClassNameNoMatterHowLongItIsName:public BaseClass
{
    blah blah blah blah blah blah blah blah blah blah blah blah blah b
+lah blah blah blah blah blah blah blah blah blah blah blah blah blah 
+blah blah blah blah blah blah blah blah blah blah blah blah blah blah
+ blah
public:
    blah blah blah blah blah blah blah blah blah blah blah blah blah b
+lah blah blah blah blah blah blah blah
}

__END__
class ClassMyClassNameNoMatterHowLongItIsName:public BaseClass
{
    blah blah blah blah blah blah blah blah blah blah blah blah blah
        blah blah blah blah blah blah blah blah blah blah blah blah bl
+ah
        blah blah blah blah blah blah blah blah blah blah blah blah bl
+ah
        blah blah blah
public:
    blah blah blah blah blah blah blah blah blah blah blah blah blah
        blah blah blah blah blah blah blah blah
}
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