make-dissectors-reg: optimize by factoring out the loops

Instead of calling the grep/sed pipelines for each file, build the
list of files in the beginning and call each pipeline only once,
passing the list to the first grep.

This results in a massive speedup in Cygwin; in my test, the time
it takes to run make-dissector-reg . dissectors packet-*.c in dissectors/epan
is reduced from ~116 to ~3 seconds. I also tried it on NetBSD, where
the time do to the same goes from ~6 to ~0.5 seconds.

Amend makefile comments to elide mentions of invoking multiple processes
per file.

Change-Id: Iad441e7d2b6cc3669dada57646e2f8f6b987fd34
Reviewed-on: https://code.wireshark.org/review/2826
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/plugins/wimax/Makefile.nmake b/plugins/wimax/Makefile.nmake
index 52c4ea0604..981cf8f1d1 100644
--- a/plugins/wimax/Makefile.nmake
+++ b/plugins/wimax/Makefile.nmake
@@ -64,11 +64,11 @@ $(PLUGIN_NAME).dll $(PLUGIN_NAME).exp $(PLUGIN_NAME).lib : $(OBJECTS) $(LINK_PLU
 # pass only the first few names in the list to the shell, for some
 # reason.
 #
-# Therefore, we have a script to generate the plugin.c file.
-# The shell script runs slowly, as multiple greps and seds are run
-# for each input file; this is especially slow on Windows.  Therefore,
-# if Python is present (as indicated by PYTHON being defined), we run
-# a faster Python script to do that work instead.
+# Therefore, we use a script to generate the register.c file.
+# There are two versions of the script, a shell and a Python version.
+# The Python script runs faster, since it uses caching to speed up
+# repeated runs and doesn't invoke external processes, so we prefer
+# that if Python is available.
 #
 # The first argument is the directory in which the source files live.
 # The second argument is "plugin", to indicate that we should build