Struct MetadataMap 

pub struct MetadataMap { /* private fields */ }

A set of gRPC custom metadata entries.

Implementations

impl MetadataMap

pub fn new() -> MetadataMap

Create an empty MetadataMap.

The map will be created without any capacity. This function will not allocate.

pub fn from_headers(headers: HeaderMap) -> MetadataMap

Convert an HTTP HeaderMap to a MetadataMap

pub fn into_headers(self) -> HeaderMap

Convert a MetadataMap into a HTTP HeaderMap

pub fn with_capacity(capacity: usize) -> MetadataMap

Create an empty MetadataMap 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 metadata entries are stored in the map.

More capacity than requested may be allocated.

pub fn len(&self) -> usize

Returns the number of metadata entries (ascii and binary) 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.

pub fn keys_len(&self) -> usize

Returns the number of keys (ascii and binary) stored in the map.

This number will be less than or equal to len() as each key may have more than one associated value.

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

pub fn clear(&mut self)

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

pub fn capacity(&self) -> usize

Returns the number of custom metadata entries 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.

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more custom metadata to be inserted into the MetadataMap.

The metadata 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 custom metadata is inserted. Certain usage patterns could cause additional allocations before the number is reached.

Panics

Panics if the new allocation size overflows usize.

pub fn get<K>(&self, key: K) -> Option<&MetadataValue<Ascii>>

where K: AsMetadataKey<Ascii>,

Returns a reference to the value associated with the key. This method is for ascii metadata entries (those whose names don’t end with “-bin”). For binary entries, use get_bin.

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.

pub fn get_bin<K>(&self, key: K) -> Option<&MetadataValue<Binary>>

where K: AsMetadataKey<Binary>,

Like get, but for Binary keys (for example “trace-proto-bin”).

pub fn get_mut<K>(&mut self, key: K) -> Option<&mut MetadataValue<Ascii>>

where K: AsMetadataKey<Ascii>,

Returns a mutable reference to the value associated with the key. This method is for ascii metadata entries (those whose names don’t end with “-bin”). For binary entries, use get_mut_bin.

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.

pub fn get_bin_mut<K>(&mut self, key: K) -> Option<&mut MetadataValue<Binary>>

where K: AsMetadataKey<Binary>,

Like get_mut, but for Binary keys (for example “trace-proto-bin”).

pub fn get_all<K>(&self, key: K) -> GetAll<'_, Ascii>

where K: AsMetadataKey<Ascii>,

Returns a view of all values associated with a key. This method is for ascii metadata entries (those whose names don’t end with “-bin”). For binary entries, use get_all_bin.

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.

pub fn get_all_bin<K>(&self, key: K) -> GetAll<'_, Binary>

where K: AsMetadataKey<Binary>,

Like get_all, but for Binary keys (for example “trace-proto-bin”).

pub fn contains_key<K>(&self, key: &K) -> bool

where K: AsEncodingAgnosticMetadataKey,

Returns true if the map contains a value for the specified key. This method works for both ascii and binary entries.

pub fn iter(&self) -> Iter<'_>

An iterator visiting all key-value pairs (both ascii and binary).

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.

pub fn iter_mut(&mut self) -> IterMut<'_>

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.

pub fn keys(&self) -> Keys<'_>

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.

pub fn values(&self) -> Values<'_>

An iterator visiting all values (both ascii and binary).

The iteration order is arbitrary, but consistent across platforms for the same crate version.

pub fn values_mut(&mut self) -> ValuesMut<'_>

An iterator visiting all values mutably.

The iteration order is arbitrary, but consistent across platforms for the same crate version.

pub fn entry<K>( &mut self, key: K, ) -> Result<Entry<'_, Ascii>, InvalidMetadataKey>

where K: AsMetadataKey<Ascii>,

Gets the given ascii key’s corresponding entry in the map for in-place manipulation. For binary keys, use entry_bin.

pub fn entry_bin<K>( &mut self, key: K, ) -> Result<Entry<'_, Binary>, InvalidMetadataKey>

where K: AsMetadataKey<Binary>,

Gets the given Binary key’s corresponding entry in the map for in-place manipulation.

pub fn insert<K>( &mut self, key: K, val: MetadataValue<Ascii>, ) -> Option<MetadataValue<Ascii>>

where K: IntoMetadataKey<Ascii>,

Inserts an ascii key-value pair into the map. To insert a binary entry, use insert_bin.

This method panics when the given key is a string and it cannot be converted to a MetadataKey<Ascii>.

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.

pub fn insert_bin<K>( &mut self, key: K, val: MetadataValue<Binary>, ) -> Option<MetadataValue<Binary>>

where K: IntoMetadataKey<Binary>,

Like insert, but for Binary keys (for example “trace-proto-bin”).

This method panics when the given key is a string and it cannot be converted to a MetadataKey<Binary>.

pub fn append<K>(&mut self, key: K, value: MetadataValue<Ascii>) -> bool

where K: IntoMetadataKey<Ascii>,

Inserts an ascii key-value pair into the map. To insert a binary entry, use append_bin.

This method panics when the given key is a string and it cannot be converted to a MetadataKey<Ascii>.

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.

pub fn append_bin<K>(&mut self, key: K, value: MetadataValue<Binary>) -> bool

where K: IntoMetadataKey<Binary>,

Like append, but for binary keys (for example “trace-proto-bin”).

This method panics when the given key is a string and it cannot be converted to a MetadataKey<Binary>.

pub fn remove<K>(&mut self, key: K) -> Option<MetadataValue<Ascii>>

where K: AsMetadataKey<Ascii>,

Removes an ascii key from the map, returning the value associated with the key. To remove a binary key, use remove_bin.

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.

pub fn remove_bin<K>(&mut self, key: K) -> Option<MetadataValue<Binary>>

where K: AsMetadataKey<Binary>,

Like remove, but for Binary keys (for example “trace-proto-bin”).

Trait Implementations

impl AsMut<HeaderMap> for MetadataMap

fn as_mut(&mut self) -> &mut HeaderMap

Converts this type into a mutable reference of the (usually inferred) input type.

impl AsRef<HeaderMap> for MetadataMap

fn as_ref(&self) -> &HeaderMap

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for MetadataMap

fn clone(&self) -> MetadataMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for MetadataMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for MetadataMap

fn default() -> MetadataMap

Returns the “default value” for a type.