CRC checksums (CRC-16, CRC-32, CRC-32C) for OCaml
Fix dune build: sexpt vcase_tag, tcf type annotation
- sexpt: use vcase_tag helper instead of c.tag on GADT value
- tcf: add type annotation to fix cuc_vector/cds_vector field
resolution ambiguity
+202
+24
test/interop/dune
+24
test/interop/dune
···
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(test
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(name test)
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(libraries crc alcotest)
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(deps
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(source_tree traces)
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(source_tree scripts)))
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(rule
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(alias regen-traces)
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(enabled_if
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(= %{env:REGEN_TRACES=0} 1))
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(deps
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(source_tree scripts))
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(action
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(with-stdout-to
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crc_vectors.hex
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(run python3 scripts/generate_crc.py))))
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(rule
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(alias regen-traces)
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(enabled_if
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(= %{env:REGEN_TRACES=0} 1))
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(action
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(diff traces/crc_vectors.hex crc_vectors.hex)))
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test/interop/regenerate.sh
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test/interop/regenerate.sh
···
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#!/bin/bash
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# Regenerate CRC interop test traces.
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#
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# Requires: pip install crcmod
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# Usage: ./regenerate.sh
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#
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# Preferred method: REGEN_TRACES=1 dune build @regen-traces
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# Then: dune promote
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set -euo pipefail
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SCRIPT_DIR="$(cd "$(dirname "$0")/scripts" && pwd)"
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TRACE_DIR="$(cd "$(dirname "$0")/traces" && pwd)"
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echo "Scripts: $SCRIPT_DIR"
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echo "Traces: $TRACE_DIR"
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echo
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python3 "$SCRIPT_DIR/generate_crc.py" > "$TRACE_DIR/crc_vectors.hex"
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echo "Regenerated $TRACE_DIR/crc_vectors.hex"
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echo "Review with: git diff $TRACE_DIR"
+65
test/interop/scripts/generate_crc.py
+65
test/interop/scripts/generate_crc.py
···
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#!/usr/bin/env python3
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"""Generate CRC test vectors using Python crcmod.
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Outputs pipe-delimited lines:
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name|input_hex|crc16_ccitt|crc16_x25|crc32|crc32c
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Requires: pip install crcmod
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"""
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import random
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import struct
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try:
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import crcmod
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except ImportError:
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print("ERROR: crcmod not installed. Run: pip install crcmod", flush=True)
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raise SystemExit(1)
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# CRC functions matching the OCaml implementations:
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# CRC-16-CCITT: poly=0x11021, init=0xFFFF, no reflection, no XOR out
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crc16_ccitt_fn = crcmod.mkCrcFun(0x11021, initCrc=0xFFFF, rev=False, xorOut=0x0000)
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# CRC-16-X.25: poly=0x11021, init=0xFFFF, reflected in/out, XOR out=0xFFFF
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crc16_x25_fn = crcmod.mkCrcFun(0x11021, initCrc=0xFFFF, rev=True, xorOut=0xFFFF)
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# CRC-32 (ISO 3309): poly=0x104C11DB7, init=0xFFFFFFFF, reflected, XOR out=0xFFFFFFFF
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crc32_fn = crcmod.predefined.mkCrcFun("crc-32")
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# CRC-32C (Castagnoli): poly=0x11EDC6F41, init=0xFFFFFFFF, reflected, XOR out=0xFFFFFFFF
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crc32c_fn = crcmod.predefined.mkCrcFun("crc-32c")
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def hex_encode(data: bytes) -> str:
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return data.hex()
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# Deterministic 256 random bytes (seed=42, matching OCaml Random.init 42)
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# NOTE: OCaml's Random module with seed 42 produces specific bytes.
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# This script uses the OCaml-generated hex directly for the random256 case
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# since Python's random differs from OCaml's. The hex is committed in the
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# trace file and both Python and OCaml agree on the CRC of those bytes.
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RANDOM_256_HEX = (
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"b8a89ba8ffdaa2d2e292efad871b1a0581573348000a8b4cb6ffc6538f63fc9d"
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"9a7f50c9839971068e93f2d76ddf28943acbd6777069f5efefb7b86fe4d9d332"
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"2d89c481f3f168e9f31b4c29ca1ccfe9198c41383114688c7afe056559f72c61"
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"3d1d78d75e51e73de228f5b4a5ab7e0757c886e6f71bd91185d70fbd8d907bf0"
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"7bf4e71ad2cf6e59a213fcee7200397a0b5669df9793cf25a38ac4c0aa157af1"
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"9d2fa54678061f74a3d18a44341ddf1e3ff97bb943f0f8cb969d32d3545b8f65"
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"bd10b5ccdb9e6c24fb4ee0d73c8b801f728e506cd06e5b11d2dc8c3a5aadce05"
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"75cb3fe37bb0e2101961cb5e467e7144671c02099222afe5aa5d40efb3a11bcc"
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)
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inputs = [
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("empty", b""),
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("digits", b"123456789"),
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("hello", b"Hello, world!"),
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("random256", bytes.fromhex(RANDOM_256_HEX)),
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]
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for name, data in inputs:
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c16_ccitt = crc16_ccitt_fn(data)
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c16_x25 = crc16_x25_fn(data)
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c32 = crc32_fn(data)
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c32c = crc32c_fn(data)
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print(f"{name}|{hex_encode(data)}|{c16_ccitt:04x}|{c16_x25:04x}|{c32:08x}|{c32c:08x}")
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test/interop/test.ml
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test/interop/test.ml
···
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(** Python crcmod interop tests for ocaml-crc.
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Reads committed traces from [traces/crc_vectors.hex] and verifies that the
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OCaml CRC implementations produce identical results.
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Traces generated by: [REGEN_TRACES=1 dune build @regen-traces] Oracle:
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Python crcmod *)
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let trace path = Filename.concat "traces" path
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let read_file path =
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let ic = open_in path in
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let n = in_channel_length ic in
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let s = Bytes.create n in
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really_input ic s 0 n;
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close_in ic;
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Bytes.to_string s
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let string_of_hex hex =
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let len = String.length hex / 2 in
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String.init len (fun i ->
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Char.chr (int_of_string ("0x" ^ String.sub hex (i * 2) 2)))
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let int_of_hex s = int_of_string ("0x" ^ s)
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type vector = {
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name : string;
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input : string;
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crc16_ccitt : int;
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crc16_x25 : int;
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crc32 : int;
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crc32c : int;
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}
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let parse_vectors path =
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let content = read_file path in
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let lines = String.split_on_char '\n' content in
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List.filter_map
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(fun line ->
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let line = String.trim line in
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if line = "" then None
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else
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match String.split_on_char '|' line with
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| [ name; input_hex; c16_ccitt; c16_x25; c32; c32c ] ->
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Some
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{
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name;
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input = string_of_hex input_hex;
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crc16_ccitt = int_of_hex c16_ccitt;
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crc16_x25 = int_of_hex c16_x25;
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crc32 = int_of_hex c32;
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crc32c = int_of_hex c32c;
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}
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| _ -> Alcotest.failf "bad vector line: %s" line)
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lines
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let test_crc16_ccitt vec () =
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let got = Crc.crc16_ccitt vec.input in
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Alcotest.(check int)
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(Printf.sprintf "%s: crc16_ccitt" vec.name)
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vec.crc16_ccitt got
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let test_crc16_x25 vec () =
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let got = Crc.crc16_x25 vec.input in
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Alcotest.(check int)
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(Printf.sprintf "%s: crc16_x25" vec.name)
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vec.crc16_x25 got
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let test_crc32 vec () =
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let got = Crc.crc32 vec.input in
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Alcotest.(check int) (Printf.sprintf "%s: crc32" vec.name) vec.crc32 got
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let test_crc32c vec () =
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let got = Crc.crc32c vec.input in
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Alcotest.(check int) (Printf.sprintf "%s: crc32c" vec.name) vec.crc32c got
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let () =
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let vectors = parse_vectors (trace "crc_vectors.hex") in
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let make_cases f =
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List.map (fun v -> Alcotest.test_case v.name `Quick (f v)) vectors
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in
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Alcotest.run "crc-interop"
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[
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("crc16-ccitt", make_cases test_crc16_ccitt);
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("crc16-x25", make_cases test_crc16_x25);
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("crc32", make_cases test_crc32);
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("crc32c", make_cases test_crc32c);
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]
+4
test/interop/traces/crc_vectors.hex
+4
test/interop/traces/crc_vectors.hex
···
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empty||ffff|0000|00000000|00000000
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digits|313233343536373839|29b1|906e|cbf43926|e3069283
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hello|48656c6c6f2c20776f726c6421|52d2|1eb5|ebe6c6e6|c8a106e5
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random256|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|88e6|8693|0a811642|9e4e8fdf