[Python-Dev] Type of range object members (original) (raw)

James Y Knight foom at fuhm.net
Wed Aug 16 00:34:43 CEST 2006

On Aug 15, 2006, at 6:20 PM, Martin v. Löwis wrote:

Guido van Rossum schrieb:

From the Python user's perspective, yes, as much as possible. But I'm still playing with the thought of having two implementation types, since otherwise we'd have to devote 4 bytes (8 on a 64-bit platform) to the single bit telling the difference between the two internal representations. We had this discussion before; if you use obsize==0 to indicate that it's an int, this space isn't needed in a long int. On a 32-bit platform, the size of an int would go up from 12 to 16; if we stop using a special-cased allocator (which we should (*)), there isn't any space increase on such a platform. On a 64-bit platform, the size of an int would go up from 24 bytes to 32 bytes.

But it's the short int that you probably really want to make size
efficient. Which is of course also doable via something like:

typedef struct { PyObject_HEAD long ob_islong : 1; long ob_ival_or_size : LONG_BITS - 1; long ob_digit[0]; } PyIntObject;

There's no particular reason that a short int must be able to store
the entire range of C "long", so, as many bits can be stolen from it
as desired.

James

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