From 53115a537a914f32506050c056d4e327621ac9a7 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 5 Aug 2004 23:52:18 +0000 Subject: [PATCH] New cycle-check module imported from coreutils. --- lib/cycle-check.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++ lib/cycle-check.h | 44 +++++++++++++++++++++++++ lib/dev-ino.h | 13 ++++++++ modules/cycle-check | 21 ++++++++++++ 4 files changed, 172 insertions(+) create mode 100644 lib/cycle-check.c create mode 100644 lib/cycle-check.h create mode 100644 lib/dev-ino.h create mode 100644 modules/cycle-check diff --git a/lib/cycle-check.c b/lib/cycle-check.c new file mode 100644 index 000000000..99a88c35e --- /dev/null +++ b/lib/cycle-check.c @@ -0,0 +1,94 @@ +/* help detect directory cycles efficiently + + Copyright (C) 2003, 2004 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; see the file COPYING. + If not, write to the Free Software Foundation, + 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ + +/* Written by Jim Meyering */ + +#if HAVE_CONFIG_H +# include +#endif + +#include +#include +#include +#include +#include + +#include + +#include "cycle-check.h" +#include "xalloc.h" + +#define SAME_INODE(Stat_buf_1, Stat_buf_2) \ + ((Stat_buf_1).st_ino == (Stat_buf_2).st_ino \ + && (Stat_buf_1).st_dev == (Stat_buf_2).st_dev) + +#define CC_MAGIC 9827862 + +/* Return true if I is a power of 2, or is zero. */ + +static inline bool +is_zero_or_power_of_two (uintmax_t i) +{ + return (i & (i - 1)) == 0; +} + +void +cycle_check_init (struct cycle_check_state *state) +{ + state->chdir_counter = 0; + state->magic = CC_MAGIC; +} + +/* In traversing a directory hierarchy, call this function once for each + descending chdir call, with SB corresponding to the chdir operand. + If SB corresponds to a directory that has already been seen, + return true to indicate that there is a directory cycle. + Note that this is done `lazily', which means that some of + the directories in the cycle may be processed twice before + the cycle is detected. */ + +bool +cycle_check (struct cycle_check_state *state, struct stat const *sb) +{ + assert (state->magic == CC_MAGIC); + + /* If the current directory ever happens to be the same + as the one we last recorded for the cycle detection, + then it's obviously part of a cycle. */ + if (state->chdir_counter && SAME_INODE (*sb, state->dev_ino)) + return true; + + /* If the number of `descending' chdir calls is a power of two, + record the dev/ino of the current directory. */ + if (is_zero_or_power_of_two (++(state->chdir_counter))) + { + /* On all architectures that we know about, if the counter + overflows then there is a directory cycle here somewhere, + even if we haven't detected it yet. Typically this happens + only after the counter is incremented 2**64 times, so it's a + fairly theoretical point. */ + if (state->chdir_counter == 0) + return true; + + state->dev_ino.st_dev = sb->st_dev; + state->dev_ino.st_ino = sb->st_ino; + } + + return false; +} diff --git a/lib/cycle-check.h b/lib/cycle-check.h new file mode 100644 index 000000000..7b7f54d14 --- /dev/null +++ b/lib/cycle-check.h @@ -0,0 +1,44 @@ +/* help detect directory cycles efficiently + + Copyright (C) 2003, 2004 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2, or (at your option) + any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; see the file COPYING. + If not, write to the Free Software Foundation, + 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ + +/* Written by Jim Meyering */ + +#ifndef CYCLE_CHECK_H +# define CYCLE_CHECK_H 1 + +# if HAVE_INTTYPES_H +# include +# endif +# if HAVE_STDINT_H +# include +# endif +# include +# include "dev-ino.h" + +struct cycle_check_state +{ + struct dev_ino dev_ino; + uintmax_t chdir_counter; + int magic; +}; + +void cycle_check_init (struct cycle_check_state *state); +bool cycle_check (struct cycle_check_state *state, struct stat const *sb); + +#endif diff --git a/lib/dev-ino.h b/lib/dev-ino.h new file mode 100644 index 000000000..695d38c7b --- /dev/null +++ b/lib/dev-ino.h @@ -0,0 +1,13 @@ +#ifndef DEV_INO_H +# define DEV_INO_H 1 + +# include +# include + +struct dev_ino +{ + ino_t st_ino; + dev_t st_dev; +}; + +#endif diff --git a/modules/cycle-check b/modules/cycle-check new file mode 100644 index 000000000..91c4e3166 --- /dev/null +++ b/modules/cycle-check @@ -0,0 +1,21 @@ +Description: +help detect directory cycles efficiently + +Files: +lib/cycle-check.c +lib/cycle-check.h +lib/dev-ino.h + +Depends-on: + +configure.ac: + +Makefile.am: +lib_SOURCES += cycle-check.c cycle-check.h dev-ino.h + +Include: +"cycle-check.h" + +Maintainer: +Jim Meyering + -- 2.11.0