diff options
author | Jim Meyering <jim@meyering.net> | 2003-01-03 19:30:29 +0000 |
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committer | Jim Meyering <jim@meyering.net> | 2003-01-03 19:30:29 +0000 |
commit | fab52f550d008951a2c8b78a9fe3f2dd4e30c3ea (patch) | |
tree | c2b3f0f7e8c7217318f0817d52d809b1bef43486 /lib | |
parent | 5ed7d34ed841aa0a04d5f5d721aab0c53b3ef5f8 (diff) | |
download | coreutils-fab52f550d008951a2c8b78a9fe3f2dd4e30c3ea.tar.xz |
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Diffstat (limited to 'lib')
-rw-r--r-- | lib/cycle-check.c | 63 | ||||
-rw-r--r-- | lib/cycle-check.h | 33 | ||||
-rw-r--r-- | lib/dev-ino.h | 10 |
3 files changed, 106 insertions, 0 deletions
diff --git a/lib/cycle-check.c b/lib/cycle-check.c new file mode 100644 index 000000000..403dc1615 --- /dev/null +++ b/lib/cycle-check.c @@ -0,0 +1,63 @@ +#include <sys/types.h> +#include <sys/stat.h> +#include <stdio.h> +#include <assert.h> +#include <stdlib.h> + +#if HAVE_STDBOOL_H +# include <stdbool.h> +#else +typedef enum {false = 0, true = 1} bool; +#endif + +#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 + +static inline bool +is_power_of_two (unsigned int 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_power_of_two (++(state->chdir_counter))) + { + 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..6f8c55d5d --- /dev/null +++ b/lib/cycle-check.h @@ -0,0 +1,33 @@ +#ifndef CYCLE_CHECK_H +# define CYCLE_CHECK_H 1 + +/* Before including this file, you need something like the following: + + #if HAVE_CONFIG_H + # include <config.h> + #endif + + #include <sys/types.h> + #include <sys/stat.h> + + #if HAVE_STDBOOL_H + # include <stdbool.h> + #else + typedef enum {false = 0, true = 1} bool; + #endif + + so that the proper identifiers are all declared. */ + +# include "dev-ino.h" + +struct cycle_check_state +{ + struct dev_ino dev_ino; + size_t chdir_counter; + long unsigned 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..79cc5203f --- /dev/null +++ b/lib/dev-ino.h @@ -0,0 +1,10 @@ +#ifndef DEV_INO_H +# define DEV_INO_H 1 + +struct dev_ino +{ + ino_t st_ino; + dev_t st_dev; +}; + +#endif |