Horton

Re: encode/decode support for base64url

Chao Li <li.evan.chao@gmail.com>

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From: Chao Li <li.evan.chao@gmail.com>
To: Florents Tselai <florents.tselai@gmail.com>
Cc: Daniel Gustafsson <daniel@yesql.se>, Masahiko Sawada <sawada.mshk@gmail.com>, "David E. Wheeler" <david@justatheory.com>, Aleksander Alekseev <aleksander@tigerdata.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Cary Huang <cary.huang@highgo.ca>, Przemysław Sztoch <przemyslaw@sztoch.pl>
Date: 2025-09-19T06:56:27Z
Lists: pgsql-hackers

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Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add support for base64url encoding and decoding


> On Sep 19, 2025, at 14:45, Florents Tselai <florents.tselai@gmail.com> wrote:
>> 
>> I reviewed and tested this patch. Overall looks good to me. Actually, I think this patched fixed a bug of current implementation of base64 encoding by moving the logic of handling newline into “if (pos<0)”.
> 
> IIUC what you mean, I can’t confirm that.
> 
> Both existing and new implementation handle new lines the same 
> 
> SELECT decode(E'QUFB\nQUFB', 'base64url');
>      decode     
> ----------------
>  \x414141414141
> (1 row)
> 

The current implementation isn’t actually wrong, but at least not optimized as your version. Because we don’t need to check “if (p >= lend)” after p is bumped, and only when “if (pos <0)”, p is bumped.

> 
>> 
>> 3.
>> ```
>>  					ereport(ERROR,
>>  							(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
>> -							 errmsg("unexpected \"=\" while decoding base64 sequence")));
>> +							 errmsg("unexpected \"=\" while decoding %s sequence", url ? "base64url" : "base64")));
>> ```
>> 
>> This is a normal usage that injects sub-strings based on condition. However, PG doesn’t like that, see here: https://www.postgresql.org/docs/devel/nls-programmer.html#NLS-GUIDELINES 
> 
> Well, that’s a very interesting catch. 
> I’ll let a comitter confirm & advise. 


I got to know this because once I reviewed a Tom Lane’s patch, it had the similarly situation, but Tom wrote code like:

```
If (something)
    Ereport(“function xxx”)
Else
    Ereport(“procedure xxx”)
```

I raised a comment to suggest avoid duplicate code in the way like your code do, and I got a response with “no” and the link.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/