Re: Unsigned 64 bit integer to numeric - Mailing list pgsql-hackers

From Andrew Gierth
Subject Re: Unsigned 64 bit integer to numeric
Date
Msg-id 87k17cb9ho.fsf@news-spur.riddles.org.uk
Whole thread Raw
In response to Unsigned 64 bit integer to numeric  (Dmitry Dolgov <9erthalion6@gmail.com>)
Responses Re: Unsigned 64 bit integer to numeric  (Dmitry Dolgov <9erthalion6@gmail.com>)
List pgsql-hackers
>>>>> "Dmitry" == Dmitry Dolgov <9erthalion6@gmail.com> writes:

 Dmitry> Hi,

 Dmitry> Probably a simple question, but I don't see a simple answer so
 Dmitry> far. In one extension I want to convert uint64 into a numeric
 Dmitry> to put it eventually into a jsonb object. As far as I see in
 Dmitry> numeric.c there are functions only for signed int64. Is there a
 Dmitry> way to achive this with uint64 (without duplicating significant
 Dmitry> part of numeric implementation in the extension)?

Sure. Flip the top bit; convert the value as if signed; then subtract
-(2^63) from the result. (Easier to subtract -(2^63) than to add 2^63,
since the former can itself be represented in a signed int64 for easy
conversion to numeric.)

-- 
Andrew (irc:RhodiumToad)



pgsql-hackers by date:

Previous
From: didier
Date:
Subject: Re: Unsigned 64 bit integer to numeric
Next
From: Amit Kapila
Date:
Subject: Re: [HACKERS] Block level parallel vacuum