pub struct HeaderMap<T = HeaderValue> { /* private fields */ }
Expand description
A set of HTTP headers
HeaderMap
is an multimap of HeaderName
to values.
§Examples
Basic usage
let mut headers = HeaderMap::new();
headers.insert(HOST, "example.com".parse().unwrap());
headers.insert(CONTENT_LENGTH, "123".parse().unwrap());
assert!(headers.contains_key(HOST));
assert!(!headers.contains_key(LOCATION));
assert_eq!(headers[HOST], "example.com");
headers.remove(HOST);
assert!(!headers.contains_key(HOST));
Implementations§
source§impl<T> HeaderMap<T>
impl<T> HeaderMap<T>
sourcepub fn with_capacity(capacity: usize) -> HeaderMap<T>
pub fn with_capacity(capacity: usize) -> HeaderMap<T>
Create an empty HeaderMap
with the specified capacity.
The returned map will allocate internal storage in order to hold about
capacity
elements without reallocating. However, this is a “best
effort” as there are usage patterns that could cause additional
allocations before capacity
headers are stored in the map.
More capacity than requested may be allocated.
§Panics
This method panics if capacity exceeds max HeaderMap
capacity.
§Examples
let map: HeaderMap<u32> = HeaderMap::with_capacity(10);
assert!(map.is_empty());
assert_eq!(12, map.capacity());
sourcepub fn try_with_capacity(
capacity: usize,
) -> Result<HeaderMap<T>, MaxSizeReached>
pub fn try_with_capacity( capacity: usize, ) -> Result<HeaderMap<T>, MaxSizeReached>
Create an empty HeaderMap
with the specified capacity.
The returned map will allocate internal storage in order to hold about
capacity
elements without reallocating. However, this is a “best
effort” as there are usage patterns that could cause additional
allocations before capacity
headers are stored in the map.
More capacity than requested may be allocated.
§Errors
This function may return an error if HeaderMap
exceeds max capacity
§Examples
let map: HeaderMap<u32> = HeaderMap::try_with_capacity(10).unwrap();
assert!(map.is_empty());
assert_eq!(12, map.capacity());
sourcepub fn len(&self) -> usize
pub fn len(&self) -> usize
Returns the number of headers stored in the map.
This number represents the total number of values stored in the map. This number can be greater than or equal to the number of keys stored given that a single key may have more than one associated value.
§Examples
let mut map = HeaderMap::new();
assert_eq!(0, map.len());
map.insert(ACCEPT, "text/plain".parse().unwrap());
map.insert(HOST, "localhost".parse().unwrap());
assert_eq!(2, map.len());
map.append(ACCEPT, "text/html".parse().unwrap());
assert_eq!(3, map.len());
sourcepub fn keys_len(&self) -> usize
pub fn keys_len(&self) -> usize
Returns the number of keys stored in the map.
This number will be less than or equal to len()
as each key may have
more than one associated value.
§Examples
let mut map = HeaderMap::new();
assert_eq!(0, map.keys_len());
map.insert(ACCEPT, "text/plain".parse().unwrap());
map.insert(HOST, "localhost".parse().unwrap());
assert_eq!(2, map.keys_len());
map.insert(ACCEPT, "text/html".parse().unwrap());
assert_eq!(2, map.keys_len());
sourcepub fn is_empty(&self) -> bool
pub fn is_empty(&self) -> bool
Returns true if the map contains no elements.
§Examples
let mut map = HeaderMap::new();
assert!(map.is_empty());
map.insert(HOST, "hello.world".parse().unwrap());
assert!(!map.is_empty());
sourcepub fn clear(&mut self)
pub fn clear(&mut self)
Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello.world".parse().unwrap());
map.clear();
assert!(map.is_empty());
assert!(map.capacity() > 0);
sourcepub fn capacity(&self) -> usize
pub fn capacity(&self) -> usize
Returns the number of headers the map can hold without reallocating.
This number is an approximation as certain usage patterns could cause additional allocations before the returned capacity is filled.
§Examples
let mut map = HeaderMap::new();
assert_eq!(0, map.capacity());
map.insert(HOST, "hello.world".parse().unwrap());
assert_eq!(6, map.capacity());
sourcepub fn reserve(&mut self, additional: usize)
pub fn reserve(&mut self, additional: usize)
Reserves capacity for at least additional
more headers to be inserted
into the HeaderMap
.
The header map may reserve more space to avoid frequent reallocations.
Like with with_capacity
, this will be a “best effort” to avoid
allocations until additional
more headers are inserted. Certain usage
patterns could cause additional allocations before the number is
reached.
§Panics
Panics if the new allocation size overflows HeaderMap
MAX_SIZE
.
§Examples
let mut map = HeaderMap::new();
map.reserve(10);
sourcepub fn try_reserve(&mut self, additional: usize) -> Result<(), MaxSizeReached>
pub fn try_reserve(&mut self, additional: usize) -> Result<(), MaxSizeReached>
Reserves capacity for at least additional
more headers to be inserted
into the HeaderMap
.
The header map may reserve more space to avoid frequent reallocations.
Like with with_capacity
, this will be a “best effort” to avoid
allocations until additional
more headers are inserted. Certain usage
patterns could cause additional allocations before the number is
reached.
§Errors
This method differs from reserve
by returning an error instead of
panicking if the value is too large.
§Examples
let mut map = HeaderMap::new();
map.try_reserve(10).unwrap();
sourcepub fn get<K>(&self, key: K) -> Option<&T>where
K: AsHeaderName,
pub fn get<K>(&self, key: K) -> Option<&T>where
K: AsHeaderName,
Returns a reference to the value associated with the key.
If there are multiple values associated with the key, then the first one
is returned. Use get_all
to get all values associated with a given
key. Returns None
if there are no values associated with the key.
§Examples
let mut map = HeaderMap::new();
assert!(map.get("host").is_none());
map.insert(HOST, "hello".parse().unwrap());
assert_eq!(map.get(HOST).unwrap(), &"hello");
assert_eq!(map.get("host").unwrap(), &"hello");
map.append(HOST, "world".parse().unwrap());
assert_eq!(map.get("host").unwrap(), &"hello");
sourcepub fn get_mut<K>(&mut self, key: K) -> Option<&mut T>where
K: AsHeaderName,
pub fn get_mut<K>(&mut self, key: K) -> Option<&mut T>where
K: AsHeaderName,
Returns a mutable reference to the value associated with the key.
If there are multiple values associated with the key, then the first one
is returned. Use entry
to get all values associated with a given
key. Returns None
if there are no values associated with the key.
§Examples
let mut map = HeaderMap::default();
map.insert(HOST, "hello".to_string());
map.get_mut("host").unwrap().push_str("-world");
assert_eq!(map.get(HOST).unwrap(), &"hello-world");
sourcepub fn get_all<K>(&self, key: K) -> GetAll<'_, T>where
K: AsHeaderName,
pub fn get_all<K>(&self, key: K) -> GetAll<'_, T>where
K: AsHeaderName,
Returns a view of all values associated with a key.
The returned view does not incur any allocations and allows iterating
the values associated with the key. See GetAll
for more details.
Returns None
if there are no values associated with the key.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello".parse().unwrap());
map.append(HOST, "goodbye".parse().unwrap());
let view = map.get_all("host");
let mut iter = view.iter();
assert_eq!(&"hello", iter.next().unwrap());
assert_eq!(&"goodbye", iter.next().unwrap());
assert!(iter.next().is_none());
sourcepub fn contains_key<K>(&self, key: K) -> boolwhere
K: AsHeaderName,
pub fn contains_key<K>(&self, key: K) -> boolwhere
K: AsHeaderName,
Returns true if the map contains a value for the specified key.
§Examples
let mut map = HeaderMap::new();
assert!(!map.contains_key(HOST));
map.insert(HOST, "world".parse().unwrap());
assert!(map.contains_key("host"));
sourcepub fn iter(&self) -> Iter<'_, T> ⓘ
pub fn iter(&self) -> Iter<'_, T> ⓘ
An iterator visiting all key-value pairs.
The iteration order is arbitrary, but consistent across platforms for the same crate version. Each key will be yielded once per associated value. So, if a key has 3 associated values, it will be yielded 3 times.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello".parse().unwrap());
map.append(HOST, "goodbye".parse().unwrap());
map.insert(CONTENT_LENGTH, "123".parse().unwrap());
for (key, value) in map.iter() {
println!("{:?}: {:?}", key, value);
}
sourcepub fn iter_mut(&mut self) -> IterMut<'_, T> ⓘ
pub fn iter_mut(&mut self) -> IterMut<'_, T> ⓘ
An iterator visiting all key-value pairs, with mutable value references.
The iterator order is arbitrary, but consistent across platforms for the same crate version. Each key will be yielded once per associated value, so if a key has 3 associated values, it will be yielded 3 times.
§Examples
let mut map = HeaderMap::default();
map.insert(HOST, "hello".to_string());
map.append(HOST, "goodbye".to_string());
map.insert(CONTENT_LENGTH, "123".to_string());
for (key, value) in map.iter_mut() {
value.push_str("-boop");
}
sourcepub fn keys(&self) -> Keys<'_, T> ⓘ
pub fn keys(&self) -> Keys<'_, T> ⓘ
An iterator visiting all keys.
The iteration order is arbitrary, but consistent across platforms for the same crate version. Each key will be yielded only once even if it has multiple associated values.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello".parse().unwrap());
map.append(HOST, "goodbye".parse().unwrap());
map.insert(CONTENT_LENGTH, "123".parse().unwrap());
for key in map.keys() {
println!("{:?}", key);
}
sourcepub fn values(&self) -> Values<'_, T> ⓘ
pub fn values(&self) -> Values<'_, T> ⓘ
An iterator visiting all values.
The iteration order is arbitrary, but consistent across platforms for the same crate version.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello".parse().unwrap());
map.append(HOST, "goodbye".parse().unwrap());
map.insert(CONTENT_LENGTH, "123".parse().unwrap());
for value in map.values() {
println!("{:?}", value);
}
sourcepub fn values_mut(&mut self) -> ValuesMut<'_, T> ⓘ
pub fn values_mut(&mut self) -> ValuesMut<'_, T> ⓘ
An iterator visiting all values mutably.
The iteration order is arbitrary, but consistent across platforms for the same crate version.
§Examples
let mut map = HeaderMap::default();
map.insert(HOST, "hello".to_string());
map.append(HOST, "goodbye".to_string());
map.insert(CONTENT_LENGTH, "123".to_string());
for value in map.values_mut() {
value.push_str("-boop");
}
sourcepub fn drain(&mut self) -> Drain<'_, T> ⓘ
pub fn drain(&mut self) -> Drain<'_, T> ⓘ
Clears the map, returning all entries as an iterator.
The internal memory is kept for reuse.
For each yielded item that has None
provided for the HeaderName
,
then the associated header name is the same as that of the previously
yielded item. The first yielded item will have HeaderName
set.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello".parse().unwrap());
map.append(HOST, "goodbye".parse().unwrap());
map.insert(CONTENT_LENGTH, "123".parse().unwrap());
let mut drain = map.drain();
assert_eq!(drain.next(), Some((Some(HOST), "hello".parse().unwrap())));
assert_eq!(drain.next(), Some((None, "goodbye".parse().unwrap())));
assert_eq!(drain.next(), Some((Some(CONTENT_LENGTH), "123".parse().unwrap())));
assert_eq!(drain.next(), None);
sourcepub fn entry<K>(&mut self, key: K) -> Entry<'_, T>where
K: IntoHeaderName,
pub fn entry<K>(&mut self, key: K) -> Entry<'_, T>where
K: IntoHeaderName,
Gets the given key’s corresponding entry in the map for in-place manipulation.
§Panics
This method panics if capacity exceeds max HeaderMap
capacity
§Examples
let mut map: HeaderMap<u32> = HeaderMap::default();
let headers = &[
"content-length",
"x-hello",
"Content-Length",
"x-world",
];
for &header in headers {
let counter = map.entry(header).or_insert(0);
*counter += 1;
}
assert_eq!(map["content-length"], 2);
assert_eq!(map["x-hello"], 1);
sourcepub fn try_entry<K>(
&mut self,
key: K,
) -> Result<Entry<'_, T>, InvalidHeaderName>where
K: AsHeaderName,
pub fn try_entry<K>(
&mut self,
key: K,
) -> Result<Entry<'_, T>, InvalidHeaderName>where
K: AsHeaderName,
Gets the given key’s corresponding entry in the map for in-place manipulation.
§Errors
This method differs from entry
by allowing types that may not be
valid HeaderName
s to passed as the key (such as String
). If they
do not parse as a valid HeaderName
, this returns an
InvalidHeaderName
error.
If reserving space goes over the maximum, this will also return an
error. However, to prevent breaking changes to the return type, the
error will still say InvalidHeaderName
, unlike other try_*
methods
which return a MaxSizeReached
error.
sourcepub fn insert<K>(&mut self, key: K, val: T) -> Option<T>where
K: IntoHeaderName,
pub fn insert<K>(&mut self, key: K, val: T) -> Option<T>where
K: IntoHeaderName,
Inserts a key-value pair into the map.
If the map did not previously have this key present, then None
is
returned.
If the map did have this key present, the new value is associated with
the key and all previous values are removed. Note that only a single
one of the previous values is returned. If there are multiple values
that have been previously associated with the key, then the first one is
returned. See insert_mult
on OccupiedEntry
for an API that returns
all values.
The key is not updated, though; this matters for types that can be ==
without being identical.
§Panics
This method panics if capacity exceeds max HeaderMap
capacity
§Examples
let mut map = HeaderMap::new();
assert!(map.insert(HOST, "world".parse().unwrap()).is_none());
assert!(!map.is_empty());
let mut prev = map.insert(HOST, "earth".parse().unwrap()).unwrap();
assert_eq!("world", prev);
sourcepub fn try_insert<K>(
&mut self,
key: K,
val: T,
) -> Result<Option<T>, MaxSizeReached>where
K: IntoHeaderName,
pub fn try_insert<K>(
&mut self,
key: K,
val: T,
) -> Result<Option<T>, MaxSizeReached>where
K: IntoHeaderName,
Inserts a key-value pair into the map.
If the map did not previously have this key present, then None
is
returned.
If the map did have this key present, the new value is associated with
the key and all previous values are removed. Note that only a single
one of the previous values is returned. If there are multiple values
that have been previously associated with the key, then the first one is
returned. See insert_mult
on OccupiedEntry
for an API that returns
all values.
The key is not updated, though; this matters for types that can be ==
without being identical.
§Errors
This function may return an error if HeaderMap
exceeds max capacity
§Examples
let mut map = HeaderMap::new();
assert!(map.try_insert(HOST, "world".parse().unwrap()).unwrap().is_none());
assert!(!map.is_empty());
let mut prev = map.try_insert(HOST, "earth".parse().unwrap()).unwrap().unwrap();
assert_eq!("world", prev);
sourcepub fn append<K>(&mut self, key: K, value: T) -> boolwhere
K: IntoHeaderName,
pub fn append<K>(&mut self, key: K, value: T) -> boolwhere
K: IntoHeaderName,
Inserts a key-value pair into the map.
If the map did not previously have this key present, then false
is
returned.
If the map did have this key present, the new value is pushed to the end
of the list of values currently associated with the key. The key is not
updated, though; this matters for types that can be ==
without being
identical.
§Panics
This method panics if capacity exceeds max HeaderMap
capacity
§Examples
let mut map = HeaderMap::new();
assert!(map.insert(HOST, "world".parse().unwrap()).is_none());
assert!(!map.is_empty());
map.append(HOST, "earth".parse().unwrap());
let values = map.get_all("host");
let mut i = values.iter();
assert_eq!("world", *i.next().unwrap());
assert_eq!("earth", *i.next().unwrap());
sourcepub fn try_append<K>(
&mut self,
key: K,
value: T,
) -> Result<bool, MaxSizeReached>where
K: IntoHeaderName,
pub fn try_append<K>(
&mut self,
key: K,
value: T,
) -> Result<bool, MaxSizeReached>where
K: IntoHeaderName,
Inserts a key-value pair into the map.
If the map did not previously have this key present, then false
is
returned.
If the map did have this key present, the new value is pushed to the end
of the list of values currently associated with the key. The key is not
updated, though; this matters for types that can be ==
without being
identical.
§Errors
This function may return an error if HeaderMap
exceeds max capacity
§Examples
let mut map = HeaderMap::new();
assert!(map.try_insert(HOST, "world".parse().unwrap()).unwrap().is_none());
assert!(!map.is_empty());
map.try_append(HOST, "earth".parse().unwrap()).unwrap();
let values = map.get_all("host");
let mut i = values.iter();
assert_eq!("world", *i.next().unwrap());
assert_eq!("earth", *i.next().unwrap());
sourcepub fn remove<K>(&mut self, key: K) -> Option<T>where
K: AsHeaderName,
pub fn remove<K>(&mut self, key: K) -> Option<T>where
K: AsHeaderName,
Removes a key from the map, returning the value associated with the key.
Returns None
if the map does not contain the key. If there are
multiple values associated with the key, then the first one is returned.
See remove_entry_mult
on OccupiedEntry
for an API that yields all
values.
§Examples
let mut map = HeaderMap::new();
map.insert(HOST, "hello.world".parse().unwrap());
let prev = map.remove(HOST).unwrap();
assert_eq!("hello.world", prev);
assert!(map.remove(HOST).is_none());
Trait Implementations§
source§impl<T> Extend<(HeaderName, T)> for HeaderMap<T>
impl<T> Extend<(HeaderName, T)> for HeaderMap<T>
source§fn extend<I: IntoIterator<Item = (HeaderName, T)>>(&mut self, iter: I)
fn extend<I: IntoIterator<Item = (HeaderName, T)>>(&mut self, iter: I)
source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)source§impl<T> Extend<(Option<HeaderName>, T)> for HeaderMap<T>
impl<T> Extend<(Option<HeaderName>, T)> for HeaderMap<T>
source§fn extend<I: IntoIterator<Item = (Option<HeaderName>, T)>>(&mut self, iter: I)
fn extend<I: IntoIterator<Item = (Option<HeaderName>, T)>>(&mut self, iter: I)
Extend a HeaderMap
with the contents of another HeaderMap
.
This function expects the yielded items to follow the same structure as
IntoIter
.
§Panics
This panics if the first yielded item does not have a HeaderName
.
§Examples
let mut map = HeaderMap::new();
map.insert(ACCEPT, "text/plain".parse().unwrap());
map.insert(HOST, "hello.world".parse().unwrap());
let mut extra = HeaderMap::new();
extra.insert(HOST, "foo.bar".parse().unwrap());
extra.insert(COOKIE, "hello".parse().unwrap());
extra.append(COOKIE, "world".parse().unwrap());
map.extend(extra);
assert_eq!(map["host"], "foo.bar");
assert_eq!(map["accept"], "text/plain");
assert_eq!(map["cookie"], "hello");
let v = map.get_all("host");
assert_eq!(1, v.iter().count());
let v = map.get_all("cookie");
assert_eq!(2, v.iter().count());
source§fn extend_one(&mut self, item: A)
fn extend_one(&mut self, item: A)
extend_one
)source§fn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
extend_one
)source§impl<T> FromIterator<(HeaderName, T)> for HeaderMap<T>
impl<T> FromIterator<(HeaderName, T)> for HeaderMap<T>
source§fn from_iter<I>(iter: I) -> Selfwhere
I: IntoIterator<Item = (HeaderName, T)>,
fn from_iter<I>(iter: I) -> Selfwhere
I: IntoIterator<Item = (HeaderName, T)>,
source§impl<'a, K, T> Index<K> for HeaderMap<T>where
K: AsHeaderName,
impl<'a, K, T> Index<K> for HeaderMap<T>where
K: AsHeaderName,
source§impl<'a, T> IntoIterator for &'a HeaderMap<T>
impl<'a, T> IntoIterator for &'a HeaderMap<T>
source§impl<'a, T> IntoIterator for &'a mut HeaderMap<T>
impl<'a, T> IntoIterator for &'a mut HeaderMap<T>
source§impl<T> IntoIterator for HeaderMap<T>
impl<T> IntoIterator for HeaderMap<T>
source§fn into_iter(self) -> IntoIter<T> ⓘ
fn into_iter(self) -> IntoIter<T> ⓘ
Creates a consuming iterator, that is, one that moves keys and values out of the map in arbitrary order. The map cannot be used after calling this.
For each yielded item that has None
provided for the HeaderName
,
then the associated header name is the same as that of the previously
yielded item. The first yielded item will have HeaderName
set.
§Examples
Basic usage.
let mut map = HeaderMap::new();
map.insert(header::CONTENT_LENGTH, "123".parse().unwrap());
map.insert(header::CONTENT_TYPE, "json".parse().unwrap());
let mut iter = map.into_iter();
assert_eq!(iter.next(), Some((Some(header::CONTENT_LENGTH), "123".parse().unwrap())));
assert_eq!(iter.next(), Some((Some(header::CONTENT_TYPE), "json".parse().unwrap())));
assert!(iter.next().is_none());
Multiple values per key.
let mut map = HeaderMap::new();
map.append(header::CONTENT_LENGTH, "123".parse().unwrap());
map.append(header::CONTENT_LENGTH, "456".parse().unwrap());
map.append(header::CONTENT_TYPE, "json".parse().unwrap());
map.append(header::CONTENT_TYPE, "html".parse().unwrap());
map.append(header::CONTENT_TYPE, "xml".parse().unwrap());
let mut iter = map.into_iter();
assert_eq!(iter.next(), Some((Some(header::CONTENT_LENGTH), "123".parse().unwrap())));
assert_eq!(iter.next(), Some((None, "456".parse().unwrap())));
assert_eq!(iter.next(), Some((Some(header::CONTENT_TYPE), "json".parse().unwrap())));
assert_eq!(iter.next(), Some((None, "html".parse().unwrap())));
assert_eq!(iter.next(), Some((None, "xml".parse().unwrap())));
assert!(iter.next().is_none());
§type Item = (Option<HeaderName>, T)
type Item = (Option<HeaderName>, T)
source§impl<T: PartialEq> PartialEq for HeaderMap<T>
impl<T: PartialEq> PartialEq for HeaderMap<T>
source§impl<'a, K, V, T> TryFrom<&'a HashMap<K, V>> for HeaderMap<T>
impl<'a, K, V, T> TryFrom<&'a HashMap<K, V>> for HeaderMap<T>
Try to convert a HashMap
into a HeaderMap
.
§Examples
use std::collections::HashMap;
use std::convert::TryInto;
use http::HeaderMap;
let mut map = HashMap::new();
map.insert("X-Custom-Header".to_string(), "my value".to_string());
let headers: HeaderMap = (&map).try_into().expect("valid headers");
assert_eq!(headers["X-Custom-Header"], "my value");
impl<T: Eq> Eq for HeaderMap<T>
Auto Trait Implementations§
impl<T> Freeze for HeaderMap<T>
impl<T> RefUnwindSafe for HeaderMap<T>where
T: RefUnwindSafe,
impl<T> Send for HeaderMap<T>where
T: Send,
impl<T> Sync for HeaderMap<T>where
T: Sync,
impl<T> Unpin for HeaderMap<T>where
T: Unpin,
impl<T> UnwindSafe for HeaderMap<T>where
T: UnwindSafe,
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
source§default unsafe fn clone_to_uninit(&self, dst: *mut T)
default unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)