Re: [PATCH] base64: provide a fast path for encoding well sized buffers

[Pádraig Brady]

On 11/11/2013 06:37 PM, Paul Eggert wrote:
> Pádraig Brady wrote:
>> +  static const char b64c[64] =
>> +    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> ...
>> +  static const char b64c[64] =
>>      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> 
> There only needs to be one copy of b64c.

Moved to module scope.

>> +  if ((inlen % 3 == 0) && BASE64_LENGTH (inlen) == outlen)
> 
> This divides by 3 twice, once for % and once for BASE64_LENGTH,
> and if we want to be truly paranoid it can mess up due to overflow,
> e.g., on a 32-bit host if inlen == 2**32 - 1 && outlen == 0.
> 
> How about this instead?
> 
>   if (outlen % 4 == 0 && inlen == outlen / 4 * 3)
> 
> where any decent compiler should do the right thing and
> generate only shifts, masks, and adds; and there's no
> problem with overflow.

Ah right, reduce outlen to match inlen.

thanks!
Pádraig.