[apparmor] [PATCH 1/5] Add basic string matching to the hfa

[Seth Arnold]

Oh yes, I like that very much. :) thanks John!

------Original Message------
From: John Johansen
To: Seth Arnold
Cc: apparmor at lists.ubuntu.com
Subject: Re: [apparmor] [PATCH 1/5] Add basic string matching to the hfa
Sent: Jan 2, 2012 3:21 PM

On 12/27/2011 08:13 PM, Seth Arnold wrote:
> Yay! I love patches. :)
>
>

<< snip >>
  
> It seems unfortunate to me that this walks the string _twice_ -- once for
> strlen, once for the match_len call. Is this me prematurely optimizing? Or
> is this a potential performance problem?
>

And how do you find this for a solution

---

 From 8f391bbc7e522d798a69809f3d40b7a6d6cdb8a1 Mon Sep 17 00:00:00 2001
From: John Johansen <john.johansen at canonical.com>
Date: Fri, 30 Dec 2011 17:36:05 -0800
Subject: [PATCH] Make hfa::match not need to walk a string twice

Currently hfa::match calls hfa::match_len to do matching.  However this
requires walking the input string twice.  Instead provide a match routine for
input that is supposed to terminate at a given input character.

Signed-off-by: John Johansen <john.johansen at canonical.com>
---
  parser/libapparmor_re/hfa.cc |   10 +++++++++-
  parser/libapparmor_re/hfa.h  |    1 +
  2 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/parser/libapparmor_re/hfa.cc b/parser/libapparmor_re/hfa.cc
index 86e5bd5..dca9304 100644
--- a/parser/libapparmor_re/hfa.cc
+++ b/parser/libapparmor_re/hfa.cc
@@ -276,9 +276,17 @@ State *DFA::match_len(State *state, const char *str, size_t len)
  	return state;
  }
  
+State *DFA::match_until(State *state, const char *str, const char term)
+{
+	while (*str != term)
+		state = state->next(*str++);
+
+	return state;
+}
+
  State *DFA::match(const char *str)
  {
-	return match_len(start, str, strlen(str));
+	return match_until(start, str, 0);
  }
  
  void DFA::dump_uniq_perms(const char *s)
diff --git a/parser/libapparmor_re/hfa.h b/parser/libapparmor_re/hfa.h
index 3e8d99b..66f0a70 100644
--- a/parser/libapparmor_re/hfa.h
+++ b/parser/libapparmor_re/hfa.h
@@ -349,6 +349,7 @@ public:
  	virtual ~DFA();
  
  	State *match_len(State *state, const char *str, size_t len);
+	State *match_until(State *state, const char *str, const char term);
  	State *match(const char *str);
  
  	void remove_unreachable(dfaflags_t flags);
-- 
1.7.7.3