CRC64 Interoperability Fixture

This directory contains interoperability tests for the V hash.crc64 module, cross-validating against reference implementations in C and Python.

Overview

The fixture verifies that hash.crc64 produces identical CRC-64-ECMA-182 checksums when:

• Computing the same data in V, C, and Python
• Operating on various input patterns (empty, binary, text, large payloads)This helps catch:
• Bit-ordering errors
• Polynomial table generation bugs
• Byte-order issues
• Implementation divergences

Files

• crc64_interop.vsh - Main V interop checker script
• crc64_ref.c - C reference implementation (auto-compiled)
• crc64_ref.py - Python reference implementation

Running the fixture

From the V repository root:

v run vlib/hash/crc64/interop/crc64_interop.vsh

Test vectors

The fixture tests 10 vector categories:

1. empty - Zero-length input
2. single_a - Single character 'a'
3. single_null - Single null byte
4. text_123456789 - Standard test vector
5. text_hello_world - Common greeting
6. all_zeros_16 - 16 zero bytes
7. all_ones_16 - 16 0xFF bytes
8. repeating_pattern - 150 bytes of "abc" repeated
9. all_bytes - All 256 byte values in sequence
10. large_payload - 10000 bytes of "test data " repeatedEach vector is checksummed by:

• V: hash.crc64.sum(data)
• C: compiled from crc64_ref.c
• Python: crc64_ref.py

Polynomial

All implementations use CRC-64-ECMA-182:

• Polynomial: 0x42F0E1EBA9EA3693
• Initial value: 0x0000000000000000
• Final XOR: 0x0000000000000000
• Check value for "123456789": 0x6c40df5f0b497347

Prerequisites

• V compiler (tested with current repo version)
• GCC (to compile C reference)
• Python 3 (for Python reference)

Expected output

Compiling C reference helper...
Running cross-validation tests...
OK: empty => 0x0000000000000000
OK: single_a => 0x926a79e87a919f5d
OK: single_null => 0xbd4a6ec89c7eaafb
...
=== Results ===
Passed: 10
Failed: 0
Total:  10

Troubleshooting

If the fixture fails:

1. Ensure gcc and python3 are in PATH
2. Check that hash.crc64 module can be imported (v -silent test vlib/hash/crc64/)
3. Manual check: python3 crc64_ref.py checksum 313233343536373839 (should match C)