First cut at toolkit to do package inspection.

README.md has all the info.

Author: tonyaiuto

tools/BUILD

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+# Copyright 2026 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""rules_pkg internal code.
+
+All interfaces are subject to change at any time.
+"""
+
+load("@rules_python//python:py_binary.bzl", "py_binary")
+
+package(
+    default_package_metadata = ["//:license"],
+    default_visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "standard_package",
+    srcs = [
+        "BUILD",
+    ] + glob([
+        "*.py",
+    ]),
+    visibility = [
+        "//distro:__pkg__",
+        "//doc_build:__pkg__",
+    ],
+)
+
+py_binary(
+    name = "cpio-ls",
+    srcs = [
+        "cpio-ls.py",
+    ],
+    deps = [
+        "//tools/lib:cpio",
+    ],
+)
+
+py_binary(
+    name = "rpm2cpio",
+    srcs = [
+        "rpm2cpio.py",
+    ],
+    deps = [
+        "//tools/lib:rpm_file",
+    ],
+)
+
+py_binary(
+    name = "tree_size_compare",
+    srcs = [
+        "tree_size_compare.py",
+    ],
+    deps = [
+        "//tools/lib:deb_reader",
+        "//tools/lib:fs_reader",
+        "//tools/lib:rpm_reader",
+        "//tools/lib:saved_tree",
+        "//tools/lib:tar_reader",
+        "//tools/lib:tree_reader",
+    ],
+)

tools/README.md

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+# package inspection and analysis tools
+
+This is toolkit for building need specific tools.  It consists of:
+
+- A collection of readers for various kinds of packages.
+- Some reference implementation tools to show how the readers work.
+
+Much of the code here is AI generated. The ar, deb, rpm and cpio readers
+were hand crafted by a human.  
+
+## Tools
+
+### rpm2cpio - portable rpm2cpio utility
+- runs anywhere with python 3.12 or higher
+- extracts and steams out the cpio archive
+- can also dump rpm headers
+
+### cpio-ls - read a cpio archive stream and list the files
+- this is just a demonstration of how you could write `cpio -i`
+
+### tree_size_compare
+- compare 2 archives and look for differences in sizes of files.

tools/cpio-ls.py

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+"""cpio file lister.
+
+This is mini-tool to ilst the paths in a cpio archive.
+"""
+
+import sys
+
+from tools.lib.cpio import CpioReader
+
+
+def lscpio(cpio):
+    while True:
+        info = cpio.next()
+        if not info:
+            break
+        if info.is_symlink:
+            print(f"{info.path}: {info.uid}/{info.gid}, mode:{info.mode}, {info.size} -> {info.symlink_target}")
+        else:
+         
+            print(f"{info.path}: {info.uid}/{info.gid}, mode:{info.mode}, {info.size}")
+
+
+def main(args):
+    if len(args) > 1:
+        with open(args[1], "rb") as inp:
+            cpio = CpioReader(inp)
+            lscpio(cpio)
+    else:
+        cpio = CpioReader(sys.stdin.buffer)
+        lscpio(cpio)
+
+
+if __name__ == "__main__":
+    main(sys.argv)

tools/lib/BUILD

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+# Copyright 2026 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""rules_pkg internal code.
+
+All interfaces are subject to change at any time.
+"""
+
+load("@rules_python//python:py_binary.bzl", "py_binary")
+load("@rules_python//python:py_library.bzl", "py_library")
+
+package(
+    default_package_metadata = ["//:license"],
+    default_visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "standard_package",
+    srcs = [
+        "BUILD",
+    ] + glob([
+        "*.py",
+    ]),
+    visibility = [
+        "//distro:__pkg__",
+        "//doc_build:__pkg__",
+    ],
+)
+
+py_library(
+    name = "cpio",
+    srcs = [
+        "cpio.py",
+    ],
+    deps = [":tree_reader"],
+)
+
+py_library(
+    name = "deb_reader",
+    srcs = [
+        "deb_reader.py",
+    ],
+    deps = [":tree_reader"],
+)
+
+py_library(
+    name = "fs_reader",
+    srcs = [
+        "fs_reader.py",
+    ],
+    deps = [":tree_reader"],
+)
+
+py_library(
+    name = "rpm_file",
+    srcs = [
+        "rpm_file.py",
+    ],
+)
+
+py_library(
+    name = "rpm_reader",
+    srcs = [
+        "rpm_reader.py",
+    ],
+    deps = [
+        ":cpio",
+        ":rpm_file",
+        ":tree_reader",
+    ],
+)
+
+py_library(
+    name = "saved_tree",
+    srcs = [
+        "saved_tree.py",
+    ],
+    deps = [":tree_reader"],
+)
+
+py_library(
+    name = "tar_reader",
+    srcs = [
+        "tar_reader.py",
+    ],
+    deps = [":tree_reader"],
+)
+
+py_library(
+    name = "tree_reader",
+    srcs = [
+        "tree_reader.py",
+    ],
+)