Initial commit

.gitignore

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+*~

README.md

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+# compressIPv4
+
+IPv4 addresses are typically written down as octets, e.g. `127.0.0.1`.
+However the addresses seem to be actually interpreted as one large number (after conversion into binary).
+This allows for funny things, like to call `http://0x7f000001:9000` to open a HTTP service on your local host, listenting on port 9000.
+
+This repo holds a shiny tool to do the converstion for you.
+It's inspired by [a blog post from 2021](https://daniel.haxx.se/blog/2021/04/19/curl-those-funny-ipv4-addresses) by the [curl CEO](https://mastodon.social/@bagder/113979166039412014).
+<!--
+vim:syntax=markdown:fileencoding=utf-8:ts=4:expandtab:linebreak:wrap
+-->

compressIPv4.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# SPDX-License-Identifier: MIT
+# Nils Freydank <nils.freydan@datenschutz-ist-voll-doof.de>, 2025
+
+import traceback
+from typing import Union
+
+__version__: str = "1.0.0"
+__author__: str = "Nils Freydank <nils.freydank@datenschutz-ist-voll-doof.de>"
+__copyright__: str = "MIT"
+
+
+def get_compressed_v4(addr_v4: str, hex_out: bool = False) -> Union[int, str]:
+    """
+    Read the canonical IPv4 address and compress it into a single number.
+
+    :param addr_v4: String containing the IPv4 address in dotted notation.
+    :param hex_out: Opt. control if the output should be hex instead of int.
+    :return: Integer with the compressed, decimal "IPv4 addr" - or hex string.
+             Return -1 or "-0x1" for invalid addresses.
+
+    Note: Function may explode in funny ways due to missed input checks.
+    """
+    LEN_BIN_BLOCK_MAX: int = 8  # i.e. len(str(bin(255)).replace("0b", ""))
+    MAX_ADDR_POSSIBLE: int = 2**32 - 1  # full 32bit, i.e. 255.255.255.255
+    compressed_addr: str = ""
+    try:
+        blocks: list[str] = addr_v4.split(".")
+        bin_addr: str = ""
+        for block in blocks:
+            bin_block: str = str(bin(int(block))).replace("0b", "")
+            # Make sure to align each block properly to 8 bit.
+            len_delta: int = LEN_BIN_BLOCK_MAX - len(bin_block)
+            bin_addr = bin_addr + len_delta * "0" + bin_block
+        # Nice try. Put a valid IPv4 address inside, next time.
+        if (compressed_addr := int(bin_addr, 2)) > MAX_ADDR_POSSIBLE:
+            compressed_addr = -1
+
+    except ValueError:
+        print("Something broke, maybe an invalid address?")
+        traceback.print_exc()
+
+    return hex(compressed_addr) if hex_out else compressed_addr
+
+
+if __name__ == "__main__":
+    # First, run some checks.
+    assert get_compressed_v4("0.0.0.1") == 1
+    assert get_compressed_v4("0.0.0.1", False) == 1
+    assert get_compressed_v4("0.0.0.1", True) == "0x1"
+
+    assert get_compressed_v4("0") == 0
+    assert get_compressed_v4("0", False) == 0
+    assert get_compressed_v4("0", True) == "0x0"
+
+    assert get_compressed_v4("256.0.0.0") == -1
+    assert get_compressed_v4("256.0.0.0", False) == -1
+    assert get_compressed_v4("256.0.0.0", True) == "-0x1"
+
+    assert get_compressed_v4("255.255.255.255") == 2**32 - 1
+    assert get_compressed_v4("255.255.255.255", False) == 2**32 - 1
+    assert get_compressed_v4("255.255.255.255", True) == hex(2**32 - 1)
+
+    from argparse import ArgumentParser
+
+    parser = ArgumentParser()
+    parser.add_argument("ip_v4_address", help="IPv4 address that shall be compressed")
+    parser.add_argument(
+        "--hex", dest="hex", help="convert into hexadecimal", action="store_true"
+    )
+    parser.add_argument(
+        "--quiet",
+        dest="quiet",
+        help="be quiet do not print the greeter",
+        action="store_true",
+    )
+    args = parser.parse_args()
+    out_hex: bool = True if args.hex else False
+
+    if not args.quiet:
+        # Greet the user.
+        print("~" * 65)
+        print(f" v4 address fun, v{__version__}.")
+        print(f" by {__author__}")
+        print(f" use according to {__copyright__} license instructions")
+        print("~" * 65)
+
+    if args.ip_v4_address:
+        print(get_compressed_v4(args.ip_v4_address, out_hex))
+
+# vim:syntax=python:fileencoding=utf-8:ts=4:expandtab:linebreak:wrap