pub struct FinderRev<'n> { /* private fields */ }Expand description
A single substring reverse searcher fixed to a particular needle.
The purpose of this type is to permit callers to construct a substring
searcher that can be used to search haystacks without the overhead of
constructing the searcher in the first place. This is a somewhat niche
concern when it’s necessary to re-use the same needle to search multiple
different haystacks with as little overhead as possible. In general,
using rfind is good enough, but FinderRev is useful when you can
meaningfully observe searcher construction time in a profile.
When the std feature is enabled, then this type has an into_owned
version which permits building a FinderRev that is not connected to
the lifetime of its needle.
Implementations§
source§impl<'n> FinderRev<'n>
impl<'n> FinderRev<'n>
sourcepub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> FinderRev<'n>
pub fn new<B: ?Sized + AsRef<[u8]>>(needle: &'n B) -> FinderRev<'n>
Create a new reverse finder for the given needle.
sourcepub fn rfind<B: AsRef<[u8]>>(&self, haystack: B) -> Option<usize>
pub fn rfind<B: AsRef<[u8]>>(&self, haystack: B) -> Option<usize>
Returns the index of the last occurrence of this needle in the given haystack.
The haystack may be any type that can be cheaply converted into a
&[u8]. This includes, but is not limited to, &str and &[u8].
Complexity
This routine is guaranteed to have worst case linear time complexity
with respect to both the needle and the haystack. That is, this runs
in O(needle.len() + haystack.len()) time.
This routine is also guaranteed to have worst case constant space complexity.
Examples
Basic usage:
use memchr::memmem::FinderRev;
let haystack = b"foo bar baz";
assert_eq!(Some(0), FinderRev::new("foo").rfind(haystack));
assert_eq!(Some(4), FinderRev::new("bar").rfind(haystack));
assert_eq!(None, FinderRev::new("quux").rfind(haystack));sourcepub fn rfind_iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> FindRevIter<'h, 'a> ⓘ
pub fn rfind_iter<'a, 'h>(&'a self, haystack: &'h [u8]) -> FindRevIter<'h, 'a> ⓘ
Returns a reverse iterator over all occurrences of a substring in a haystack.
Complexity
This routine is guaranteed to have worst case linear time complexity
with respect to both the needle and the haystack. That is, this runs
in O(needle.len() + haystack.len()) time.
This routine is also guaranteed to have worst case constant space complexity.
Examples
Basic usage:
use memchr::memmem::FinderRev;
let haystack = b"foo bar foo baz foo";
let finder = FinderRev::new(b"foo");
let mut it = finder.rfind_iter(haystack);
assert_eq!(Some(16), it.next());
assert_eq!(Some(8), it.next());
assert_eq!(Some(0), it.next());
assert_eq!(None, it.next());sourcepub fn as_ref(&self) -> FinderRev<'_>
pub fn as_ref(&self) -> FinderRev<'_>
Convert this finder into its borrowed variant.
This is primarily useful if your finder is owned and you’d like to store its borrowed variant in some intermediate data structure.
Note that the lifetime parameter of the returned finder is tied to the
lifetime of self, and may be shorter than the 'n lifetime of the
needle itself. Namely, a finder’s needle can be either borrowed or
owned, so the lifetime of the needle returned must necessarily be the
shorter of the two.
sourcepub fn needle(&self) -> &[u8]
pub fn needle(&self) -> &[u8]
Returns the needle that this finder searches for.
Note that the lifetime of the needle returned is tied to the lifetime
of the finder, and may be shorter than the 'n lifetime. Namely, a
finder’s needle can be either borrowed or owned, so the lifetime of the
needle returned must necessarily be the shorter of the two.