linux-kernel - Re: [PATCH] fscrypt: optimize fscrypt_base64url

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Message-Id: <20250831142531.16756-1-409411716@gms.tku.edu.tw>
Date: Sun, 31 Aug 2025 22:25:31 +0800
From: Guan-Chun Wu <409411716@....tku.edu.tw>
To: linux@...ssschuh.net
Cc: 409411716@....tku.edu.tw,
	ebiggers@...nel.org,
	jaegeuk@...nel.org,
	linux-fscrypt@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	tytso@....edu
Subject: Re: [PATCH] fscrypt: optimize fscrypt_base64url_encode() with block processing

Hi Thomas,

>On 2025-08-30 21:28:32+0800, Guan-Chun Wu wrote:
>> Previously, fscrypt_base64url_encode() processed input one byte at a
>> time, using a bitstream, accumulating bits and emitting characters when
>> 6 bits were available. This was correct but added extra computation.
>
>Can't the custom base64 implementations in fs/ not pass a custom table
>and padding to the generic algorithm in lib/? Then we only need to maintain
>this code once.
>
>
>Thomas

Thanks, that makes sense.

For v2, I’m considering extending the lib/base64 API to support a custom
encoding table and optional padding. That way, the fs/ code can just use
the generic implementation directly, and we only need to maintain the
logic in one place.