[System.IO.Hashing] crc32 hash does not match

[onefreddy]

Hi I tried this library (Version 6.0.2 in net 6 project). And the result it gives is wrong. For comparison

1. HashTab result: B8FF80ED
   

2. php result: B8FF80ED

<?php

$data = file_get_contents("diary-now.json");
$hash = strtoupper(hash('crc32b', $data));
echo $hash;

3. c# result (wrong): ed80ffb8

        static async Task Main(string[] args)
        {
            var crc32 = new Crc32();

            using (var fs = File.OpenRead("diary-now.json"))
            {
                await crc32.AppendAsync(fs);
            }

            var checkSum = crc32.GetCurrentHash();
            var hash = BitConverter.ToString(checkSum).Replace("-", "").ToLower();

            Console.WriteLine(hash);
        }

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[vcsjones]

It looks like the endianness is backward. The bytes are backward.

B8-FF-80-ED
 
ED-80-FF-B8

According to the .NET docs:

This implementation emits the answer in the Little Endian byte order so that the CRC residue relationship

I suspect those other tools are showing the CRC32 value in big endian.

I think you just need to reverse the bytes:

var checkSum = crc32.GetCurrentHash();
Array.Reverse(checkSum);
var hash = BitConverter.ToString(checkSum).Replace("-", "").ToLower();

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Issue Details

---

Hi I tried this library (Version 6.0.2 in net 6 project). And the result it gives is wrong. For comparison

1. HashTab result: B8FF80ED
   

2. php result: B8FF80ED

<?php

$data = file_get_contents("diary-now.json");
$hash = strtoupper(hash('crc32b', $data));
echo $hash;

3. c# result (wrong): ed80ffb8

        static async Task Main(string[] args)
        {
            var crc32 = new Crc32();

            using (var fs = File.OpenRead("diary-now.json"))
            {
                await crc32.AppendAsync(fs);
            }

            var checkSum = crc32.GetCurrentHash();
            var hash = BitConverter.ToString(checkSum).Replace("-", "").ToLower();

            Console.WriteLine(hash);
        }

Author:	onefreddy
Assignees:	-
Labels:	area-System.IO, untriaged
Milestone:	-