this is on the todo list there are some internal discussions on interactions with sfreserve() and the possibilty of supporting multiple active sfreserve() buffers
the idea being that if sfreserve() is mmap()ing one could keep a chain of mmap() blocks large enough to cover a context-sized window scrolling through the file with data copies limited to lines that cross buffer boundaries there's even some thought about generalizing the lines-crossing-buffer-boundaries code (which is always a pain to get right and is duplicated too many places in ast code) for some of the contiguous string api's like regnexec() all in the hopes of doing it the right way On Fri, 19 Apr 2013 19:05:40 +0200 Wendy Lin wrote: > On 16 April 2013 15:04, Glenn Fowler <[email protected]> wrote: > > > > thanks for the report > > the work adding -C was apparently interrupted a while back > > its on the todo list > > > > this is not an easy fix for ast grep because the fast inner loop matches > > buffers containing multiple lines and does not parse line structure until > > a match is found > > > > the only time single lines are matched is when lines cross buffer boundaries > > > > mmap()ing the entire file (topic under discussion) would make it easy but > > would not help the very common input from pipe case > > > > On Tue, 16 Apr 2013 11:05:10 +0200 Wendy Lin wrote: > >> On 13 April 2013 16:05, Wendy Lin <[email protected]> wrote: > >> > Dear ast-devel, > >> > > >> > the grep -C from the latest ast-ksh (2013-04-09) does not work > >> > compared to GNU grep 2.14 > >> > > >> > In GNU grep 2.14 I get this for the context option: > >> > > >> > seq 200 >"²âÊÔÎļþ" > >> > ksh -c '/usr/bin/grep --context=2 51 <"²âÊÔÎļþ"' > >> > 49 > >> > 50 > >> > 51 > >> > 52 > >> > 53 > >> > -- > >> > 149 > >> > 150 > >> > 151 > >> > 152 > >> > 153 > >> > > >> > But I get this from grep from ast-ksh for the context option: > >> > > >> > ksh -c 'builtin grep ; grep --context=2 51 <"²âÊÔÎļþ"' > >> > 51 > >> > 151 > >> > > >> > Is this a bug or feature? > >> > > >> > AFAIK the -C option in ast-ksh grep should work like this: > >> > -C 2 gives 2 lines of context before and after the match > >> > -C ,2 gives only 2 lines of context after the match > >> > -C 2, gives only 2 lines of contetxt before the match > >> > > >> > optionally AST grep should support these two long options for GNU grep > >> > compatibility: > >> > > >> > --before-context=NUM print NUM lines of leading context > >> > --after-context=NUM print NUM lines of trailing context > >> > > >> > What do you think? > > > >> Was the bug report received? > >> > > >> > Wendy > Glenn, how long will it take to get grep -C implemented? > Wendy
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