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If we already have stat() data, we might be able to

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determine if this is a physical dir without an lstat().
While I'm in here, try to clarify the comments around
the _is_dir() and _is_physical_dir() tests.
This commit is contained in:
Tim Kientzle 2007-02-21 05:07:43 +00:00
parent 9bf1500921
commit 671d7d80a4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=166859
1 changed files with 29 additions and 21 deletions
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50
usr.bin/tar/tree.c
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@ -393,45 +393,58 @@ tree_current_lstat(struct tree *t)
}
/*
* Test whether current entry is a dir or dir link.
* Test whether current entry is a dir or link to a dir.
*/
int
tree_current_is_dir(struct tree *t)
{
/* If we've already pulled stat(), just use that. */
if (t->flags & hasStat)
return (S_ISDIR(tree_current_stat(t)->st_mode));
/* If we've already pulled lstat(), we may be able to use that. */
/*
* If we already have lstat() info, then try some
* cheap tests to determine if this is a dir.
*/
if (t->flags & hasLstat) {
/* If lstat() says it's a dir, it must be a dir. */
if (S_ISDIR(tree_current_lstat(t)->st_mode))
return 1;
/* If it's not a dir and not a link, we're done. */
/* Not a dir; might be a link to a dir. */
/* If it's not a link, then it's not a link to a dir. */
if (!S_ISLNK(tree_current_lstat(t)->st_mode))
return 0;
/*
* If the above two tests fail, then it's a link, but
* we don't know whether it's a link to a dir or a
* non-dir.
* It's a link, but we don't know what it's a link to,
* so we'll have to use stat().
*/
}
/* TODO: Use a more efficient mechanism when available. */
/* Use the definitive test. Hopefully this is cached. */
return (S_ISDIR(tree_current_stat(t)->st_mode));
}
/*
* Test whether current entry is a physical directory.
* Test whether current entry is a physical directory. Usually, we
* already have at least one of stat() or lstat() in memory, so we
* use tricks to try to avoid an extra trip to the disk.
*/
int
tree_current_is_physical_dir(struct tree *t)
{
/* If we've already pulled lstat(), just use that. */
if (t->flags & hasLstat)
return (S_ISDIR(tree_current_lstat(t)->st_mode));
/* TODO: Use a more efficient mechanism when available. */
/*
* If stat() says it isn't a dir, then it's not a dir.
* If stat() data is cached, this check is free, so do it first.
*/
if ((t->flags & hasStat)
&& (!S_ISDIR(tree_current_stat(t)->st_mode)))
return 0;
/*
* Either stat() said it was a dir (in which case, we have
* to determine whether it's really a link to a dir) or
* stat() info wasn't available. So we use lstat(), which
* hopefully is already cached.
*/
/* Use the definitive test. Hopefully this is cached. */
return (S_ISDIR(tree_current_lstat(t)->st_mode));
}
@ -441,11 +454,6 @@ tree_current_is_physical_dir(struct tree *t)
int
tree_current_is_physical_link(struct tree *t)
{
/* If we've already pulled lstat(), just use that. */
if (t->flags & hasLstat)
return (S_ISLNK(tree_current_lstat(t)->st_mode));
/* TODO: Use a more efficient mechanism when available. */
return (S_ISLNK(tree_current_lstat(t)->st_mode));
}