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Date: Wed, 17 Mar 2010 16:59:00 +0900
From: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
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To: Arnaldo Carvalho de Melo <acme@infradead.org>
CC: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       h.mitake@gmail.com, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Paul Mackerras <paulus@samba.org>,
       Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH] perf: Make printing table easily
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On 03/17/10 16:50, Hitoshi Mitake wrote:
 > On 03/11/10 23:06, Arnaldo Carvalho de Melo wrote:
 >  > Em Thu, Mar 11, 2010 at 01:51:26PM +0100, Ingo Molnar escreveu:
 >  >>
 >  >> * Hitoshi Mitake<mitake@dcl.info.waseda.ac.jp> wrote:
 >  >>
 >  >>> Hi,
 >  >>>
 >  >>> Making table of matrix by printf is painful work,
 >  >>> but it can be found in perf here and there.
 >  >>> So I'd like to propose semi-automation of making table.
 >  >>> New files util/table.c provides stuffs for easy table printing.
 >  >>
 >  >> Looks quite reasonable in theory. I suspect it would be useful to
 > see a few
 >  >> table printing places converted to this facility, to see the
 > simplification
 >  >> factor in practice.
 >  >
 >  > I'm going thru the printing routines now to get them usable by 
TUI/GUIs,
 >  > starting with a libnewt based browser integrating initially report and
 >  > annotate, after I get the first patch in shape for merging I'll 
revisit
 >  > this table class of yours :-)
 >
 > Thanks Arnaldo!
 >
 > But I noticed fatal weak point of table.c.
 >
 > User of table.c can reduce the cost of specifying
 > format specifier for printf, but like this case:
 >
 > table_add_fixed(t, "%p", SIZE_OF_ADDR);
 > if (some_cond1)
 > table_add_fixed(t, "%10d", sizeof(int));
 > if (some_cond2)
 > table_add_string(t, "%30s", 30);
 >
 > table_printf() may produces a lot of if-branch like this:
 >
 > if (some_cond1 && some_cond2)
 > table_printf(t, table_test, 2501, "one");
 > else if (!some_cond1 && some_cond2)
 > table_printf(t, table_test, "one");
 > else if (some_cond1 && !some_cond2)
 > table_printf(t, table_test, 2501);
 >
 > It is not so good, as Ingo told, at least table of this style
 > is not useful in real world...
 >
 > But, how about this style?
 >
 > First, user declare column with name like this:
 > table_add_column(t, "num1", "%10d", sizeof(int));
 >
 > Then, user can add values with name,
 > table_add_field(t, "num1", 2501);
 >
 > Finally, flush stored column
 > table_flush_line(t);
 >

Another suggestion:
If table_add_column() returns "column ID",
table_add_field() can specify tha column with it
and duplication of string can be reduced.