tools: add automatic C skeleton dissector generator.

Generate a dissector based on doc/packet-PROTOABBREV.c.

Change-Id: I9233c1212acb30f7166ba91e39d98bc3fb123731
Reviewed-on: https://code.wireshark.org/review/35062
Reviewed-by: Graham Bloice <graham.bloice@trihedral.com>
Reviewed-by: Dario Lombardo <lomato@gmail.com>

3 files changed, 147 insertions, 2 deletions

diff --git a/doc/README.dissector b/doc/README.dissector
index b885ee5827..16bbba6cde 100644
--- a/doc/README.dissector
+++ b/doc/README.dissector
@@ -97,6 +97,9 @@ PROTOSHORTNAME  An abbreviated name for the protocol; this is displayed
 PROTOABBREV     A name for the protocol for use in filter expressions;
                 it may contain only lower-case letters, digits, and hyphens,
                 underscores, and periods.
+LICENSE         The license this dissector is under. Please use a SPDX License
+                identifier.
+YEARS           The years the above license is valid for.
 FIELDNAME       The displayed name for the header field.
 FIELDABBREV     The abbreviated name for the header field; it may contain
                 only letters, digits, hyphens, underscores, and periods.
@@ -195,6 +198,16 @@ If, for example, PROTONAME is "Internet Bogosity Discovery Protocol",
 PROTOSHORTNAME would be "IBDP", and PROTOABBREV would be "ibdp". Try to
 conform with IANA names.
 
+1.2.1 Automatic substitution in code skeleton
+
+Instead of manual substitutions in the code skeleton, a tool to automate it can
+be found under the tools directory. The script is called tools/generate-dissector.py
+and takes all the needed options to generate a compilable dissector. Look at the
+above fields to know how to set them. Some assumptions have been made in the
+generation to shorten the list of required options. The script patches the
+CMakeLists.txt file adding the new dissector in the proper list, alphabetically
+sorted.
+
 1.3 The dissector and the data it receives.
 
 
diff --git a/doc/packet-PROTOABBREV.c b/doc/packet-PROTOABBREV.c
index 69262e8acc..f8625e8bb8 100644
--- a/doc/packet-PROTOABBREV.c
+++ b/doc/packet-PROTOABBREV.c
@@ -1,12 +1,12 @@
 /* packet-PROTOABBREV.c
  * Routines for PROTONAME dissection
- * Copyright 201x, YOUR_NAME <YOUR_EMAIL_ADDRESS>
+ * Copyright YEARS, YOUR_NAME <YOUR_EMAIL_ADDRESS>
  *
  * Wireshark - Network traffic analyzer
  * By Gerald Combs <gerald@wireshark.org>
  * Copyright 1998 Gerald Combs
  *
- * SPDX-License-Identifier: GPL-2.0-or-later
+ * SPDX-License-Identifier: LICENSE
  */
 
 /*
diff --git a/tools/generate-dissector.py b/tools/generate-dissector.py
new file mode 100755
index 0000000000..9f5103fdec
--- /dev/null
+++ b/tools/generate-dissector.py
@@ -0,0 +1,132 @@
+#!/usr/bin/env python
+#
+# Copyright 2019-2020, Dario Lombardo <lomato@gmail.com>
+#
+# Wireshark - Network traffic analyzer
+# By Gerald Combs <gerald@wireshark.org>
+# Copyright 1998 Gerald Combs
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# This script generates a Wireshark skeleton dissector, based on the example in the doc/ directory.
+#
+# Example usage:
+#
+# generate-dissector.py --name "My Self" --email "myself@example.com" --protoname "The dumb protocol"
+#   --protoshortname DUMB --protoabbrev dumb --license GPL-2.0-or-later --years "2019-2020"
+#
+
+import os
+import argparse
+from datetime import datetime
+
+parser = argparse.ArgumentParser(description='The Wireshark Dissector Generator')
+parser.add_argument("--name", help="The author of the dissector", required=True)
+parser.add_argument("--email", help="The email address of the author", required=True)
+parser.add_argument("--protoname", help="The name of the protocol", required=True)
+parser.add_argument("--protoshortname", help="The protocol short name", required=True)
+parser.add_argument("--protoabbrev", help="The protocol abbreviation", required=True)
+parser.add_argument("--license", help="The license for this dissector (please use a SPDX-License-Identifier). If omitted, GPL-2.0-or-later will be used")
+parser.add_argument("--years", help="Years of validity for the license. If omitted, the current year will be used")
+parser.add_argument("-f", "--force", action='store_true', help="Force overwriting the dissector file if it already exists")
+
+def wsdir():
+    return os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
+
+def output_file(args):
+    return os.path.join(wsdir(), "epan/dissectors/packet-" + args.protoabbrev + ".c")
+
+def read_skeleton():
+    skeletonfile = os.path.join(wsdir(), "doc/packet-PROTOABBREV.c")
+    print("Reding skeleton file: " + skeletonfile)
+    return open(skeletonfile).read()
+
+def replace_fields(buffer, args):
+    print("Replacing fields in skeleton")
+    output = buffer\
+        .replace("YOUR_NAME", args.name)\
+        .replace("YOUR_EMAIL_ADDRESS", args.email)\
+        .replace("PROTONAME", args.protoname)\
+        .replace("PROTOSHORTNAME", args.protoshortname)\
+        .replace("PROTOABBREV", args.protoabbrev)\
+        .replace("FIELDNAME", "Sample Field")\
+        .replace("FIELDABBREV", "sample_field")\
+        .replace("FT_FIELDTYPE", "FT_STRING")\
+        .replace("FIELDDISPLAY", "BASE_NONE")\
+        .replace("FIELDCONVERT", "NULL")\
+        .replace("BITMASK", "0x0")\
+        .replace("FIELDDESCR", "NULL")\
+        .replace("MAX_NEEDED_FOR_HEURISTICS", "1")\
+        .replace("TEST_HEURISTICS_FAIL", "0")\
+        .replace("ENC_xxx", "ENC_NA")\
+        .replace("EXPERTABBREV", "expert")\
+        .replace("PI_GROUP", "PI_PROTOCOL")\
+        .replace("PI_SEVERITY", "PI_ERROR")\
+        .replace("TEST_EXPERT_condition", "0")\
+        .replace("const char *subtree", "\"\"")
+
+    if args.license:
+        output = output.replace("LICENSE", args.license)
+    else:
+        output = output.replace("LICENSE", "GPL-2.0-or-later")
+
+    if args.years:
+        output = output.replace("YEARS", args.years)
+    else:
+        output = output.replace("YEARS", str(datetime.now().year))
+
+    return output
+
+def write_dissector(buffer, args):
+    ofile = output_file(args)
+    if os.path.isfile(ofile) and not args.force:
+        raise Exception("The file " + ofile + " already exists. You're likely overwriting an existing dissector.")
+    print("Writing output file: " + ofile)
+    return open(ofile, "w").write(buffer)
+
+def patch_makefile(args):
+    cmakefile = os.path.join(wsdir(), "epan/dissectors/CMakeLists.txt")
+    print("Patching makefile: " + cmakefile)
+    output = ""
+    patchline = "${CMAKE_CURRENT_SOURCE_DIR}/packet-" + args.protoabbrev + ".c"
+    in_group = False
+    patched = False
+    for line in open(cmakefile):
+        line_strip = line.strip()
+        if in_group and line_strip == ")":
+            in_group = False
+        if in_group and not patched and line_strip > patchline:
+            output += "\t" + patchline + "\n"
+            patched = True
+        if line_strip == "set(DISSECTOR_SRC":
+            in_group = True
+        if line_strip != patchline:
+            output += line
+    open(cmakefile, "w").write(output)
+
+def print_header():
+    print("")
+    print("**************************************************")
+    print("*   Wireshark skeleton dissector generator       *")
+    print("*                                                *")
+    print("*   Generate a new dissector for your protocol   *")
+    print("*   starting from the skeleton provided in the   *")
+    print("*   doc directory.                               *")
+    print("*                                                *")
+    print("*   Copyright 2019 Dario Lombardo                *")
+    print("**************************************************")
+    print("")
+
+def print_trailer(args):
+    print("")
+    print("The skeleton for the dissector of the " + args.protoshortname + " protocol has been generated.")
+    print("Please review/extend it to match your specific criterias.")
+    print("")
+
+if __name__ == '__main__':
+    print_header()
+    args = parser.parse_args()
+    buffer = replace_fields(read_skeleton(), args)
+    write_dissector(buffer, args)
+    patch_makefile(args)
+    print_trailer(args)