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Re: Flexible string representation, unicode, typography, ...

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Fri, 31 Aug 2012 09:13:40 -0600
Subject Re: Flexible string representation, unicode, typography, ...
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On Fri, Aug 31, 2012 at 6:32 AM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> That's one thing that I'm unclear about -- under what circumstances will
> a string be in compact versus non-compact form?

I understand it to be entirely dependent on which API is used to
construct.  The legacy API generates legacy strings, and the new API
generates compact strings.  From the comments in unicodeobject.h:

    /* ASCII-only strings created through PyUnicode_New use the PyASCIIObject
    structure. state.ascii and state.compact are set, and the data
    immediately follow the structure. utf8_length and wstr_length can be found
    in the length field; the utf8 pointer is equal to the data pointer. */

...

    Legacy strings are created by PyUnicode_FromUnicode() and
    PyUnicode_FromStringAndSize(NULL, size) functions. They become ready
    when PyUnicode_READY() is called.

...

    /* Non-ASCII strings allocated through PyUnicode_New use the
    PyCompactUnicodeObject structure. state.compact is set, and the data
    immediately follow the structure. */


Since I'm not sure that this is clear, note that compact vs. legacy
does not describe which character width is used (except that
PyASCIIObject strings are always 1 byte wide).  Legacy and compact
strings can each use the 1, 2, or 4 byte representations.  "Compact"
merely denotes that the character data is stored inline with the
struct (as opposed to being stored somewhere else and pointed at by
the struct), not the relative size of the string data.  Again from the
comments:

    Compact strings use only one memory block (structure + characters),
    whereas legacy strings use one block for the structure and one block
    for characters.

Cheers,
Ian

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Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-23 05:47 -0700
  Re: Flexible string representation, unicode, typography, ... Neil Hodgson <nhodgson@iinet.net.au> - 2012-08-23 23:57 +1000
    Re: Flexible string representation, unicode, typography, ... MRAB <python@mrabarnett.plus.com> - 2012-08-23 16:11 +0100
    Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-23 09:19 -0600
    Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-23 11:33 -0700
      Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-23 13:22 -0600
        Re: Flexible string representation, unicode, typography, ... rusi <rustompmody@gmail.com> - 2012-08-24 09:06 -0700
          Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-24 17:47 +0100
          Re: Flexible string representation, unicode, typography, ... Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-24 14:34 -0400
      Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-23 20:34 +0100
  Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-23 15:18 +0100
  Re: Flexible string representation, unicode, typography, ... Ramchandra Apte <maniandram01@gmail.com> - 2012-08-24 07:38 -0700
    Re: Flexible string representation, unicode, typography, ... Antoine Pitrou <solipsis@pitrou.net> - 2012-08-25 00:24 +0000
      Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 00:27 -0700
        Re: Flexible string representation, unicode, typography, ... Ben Finney <ben+python@benfinney.id.au> - 2012-08-25 17:54 +1000
      Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 00:27 -0700
        Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-25 09:58 +0100
        Re: Flexible string representation, unicode, typography, ... Frank Millman <frank@chagford.com> - 2012-08-25 11:46 +0200
          Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 08:47 -0700
          Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 08:47 -0700
            Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-25 16:26 -0600
              Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 23:59 -0700
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-26 09:50 -0600
              Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-25 23:59 -0700
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 11:49 +0000
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-26 09:40 -0600
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 20:13 +0000
                Re: Flexible string representation, unicode, typography, ... Dan Sommers <dan@tombstonezero.net> - 2012-08-26 13:45 -0700
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-27 12:16 -0700
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-27 14:14 -0600
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-27 13:37 -0700
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-29 04:38 -0700
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-29 04:38 -0700
                Re: Flexible string representation, unicode, typography, ... Neil Hodgson <nhodgson@iinet.net.au> - 2012-08-28 09:54 +1000
                Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-29 13:59 +1000
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-28 22:15 -0600
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-29 08:05 +0000
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-29 04:40 -0700
                Re: Flexible string representation, unicode, typography, ... Dave Angel <d@davea.name> - 2012-08-29 08:01 -0400
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-29 08:43 -0700
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-30 06:55 +0000
                Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-30 18:59 +1000
                Re: Flexible string representation, unicode, typography, ... Roy Smith <roy@panix.com> - 2012-08-30 07:02 -0400
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-30 16:00 +0000
                Re: Flexible string representation, unicode, typography, ... Terry Reedy <tjreedy@udel.edu> - 2012-08-30 16:44 -0400
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-31 12:32 +0000
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-31 09:13 -0600
                Re: Flexible string representation, unicode, typography, ... Roy Smith <roy@panix.com> - 2012-08-31 08:43 -0400
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-31 14:54 +0000
                Re: Flexible string representation, unicode, typography, ... Antoine Pitrou <solipsis@pitrou.net> - 2012-08-30 15:01 +0000
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 00:36 -0700
                Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-02 09:58 +0100
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-02 03:06 -0600
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 11:58 -0700
                Re: Flexible string representation, unicode, typography, ... Michael Torrie <torriem@gmail.com> - 2012-09-02 13:45 -0600
                Re: Flexible string representation, unicode, typography, ... Dave Angel <d@davea.name> - 2012-09-02 16:07 -0400
                Re: Flexible string representation, unicode, typography, ... Terry Reedy <tjreedy@udel.edu> - 2012-09-02 16:38 -0400
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-03 01:42 +0000
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-03 18:26 +0300
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-04 00:53 +0000
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 11:58 -0700
                Re: Flexible string representation, unicode, typography, ... Peter Otten <__peter__@web.de> - 2012-09-02 11:52 +0200
                Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-02 11:36 +0100
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-02 15:00 +0300
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 22:39 -0700
                Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-03 07:11 +0100
                Re: Flexible string representation, unicode, typography, ... Peter Otten <__peter__@web.de> - 2012-09-03 08:15 +0200
                Re: Flexible string representation, unicode, typography, ... Terry Reedy <tjreedy@udel.edu> - 2012-09-03 04:38 -0400
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-03 18:56 +0300
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 22:39 -0700
                Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-02 13:23 +0100
                Re: Flexible string representation, unicode, typography, ... Roy Smith <roy@panix.com> - 2012-09-02 08:35 -0400
                Re: Flexible string representation, unicode, typography, ... Ramchandra Apte <maniandram01@gmail.com> - 2012-09-02 06:48 -0700
                Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-09-02 15:46 +0100
                Re: Flexible string representation, unicode, typography, ... Ramchandra Apte <maniandram01@gmail.com> - 2012-09-02 06:48 -0700
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-09-03 12:33 -0600
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-09-02 00:36 -0700
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-30 10:27 -0600
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-02 23:38 +0300
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-09-03 01:54 +0000
                Re: Flexible string representation, unicode, typography, ... Terry Reedy <tjreedy@udel.edu> - 2012-09-02 22:33 -0400
                Re: Flexible string representation, unicode, typography, ... Roy Smith <roy@panix.com> - 2012-09-03 11:24 -0400
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-03 18:41 +0300
                Re: Flexible string representation, unicode, typography, ... Serhiy Storchaka <storchaka@gmail.com> - 2012-09-03 00:45 +0300
                Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-30 01:54 +1000
                Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-29 22:34 +1000
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-29 04:40 -0700
                Re: Flexible string representation, unicode, typography, ... wxjmfauth@gmail.com - 2012-08-27 12:16 -0700
                Re: Flexible string representation, unicode, typography, ... Ian Kelly <ian.g.kelly@gmail.com> - 2012-08-26 15:42 -0600
                Re: Flexible string representation, unicode, typography, ... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-26 23:31 +0000
                Re: Flexible string representation, unicode, typography, ... Paul Rubin <no.email@nospam.invalid> - 2012-08-26 17:47 -0700
        Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-25 21:04 +1000
        Re: Flexible string representation, unicode, typography, ... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-25 12:05 +0100
        Re: Flexible string representation, unicode, typography, ... Chris Angelico <rosuav@gmail.com> - 2012-08-25 21:19 +1000
        Re: Flexible string representation, unicode, typography, ... Terry Reedy <tjreedy@udel.edu> - 2012-08-25 07:23 -0400

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