Class: Concurrent::Map
- Inherits:
-
Collection::MapImplementation
- Object
- Concurrent::Map
- Defined in:
- lib/concurrent-ruby/concurrent/map.rb
Overview
‘Concurrent::Map` is a hash-like object and should have much better performance characteristics, especially under high concurrency, than `Concurrent::Hash`. However, `Concurrent::Map `is not strictly semantically equivalent to a ruby `Hash` – for instance, it does not necessarily retain ordering by insertion time as `Hash` does. For most uses it should do fine though, and we recommend you consider `Concurrent::Map` instead of `Concurrent::Hash` for your concurrency-safe hash needs.
Instance Method Summary collapse
-
#[](key) ⇒ Object
(also: #get)
Get a value with key.
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#[]=(key, value) ⇒ Object
(also: #put)
Set a value with key.
-
#compute(key) {|old_value| ... } ⇒ Object?
Compute and store new value for key.
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#compute_if_absent(key) { ... } ⇒ Object
Compute and store new value for key if the key is absent.
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#compute_if_present(key) {|old_value| ... } ⇒ Object?
Compute and store new value for key if the key is present.
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#delete(key) ⇒ Object?
Delete key and its value.
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#delete_pair(key, value) ⇒ true, false
Delete pair and its value if current value equals the provided value.
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#each_key {|key| ... } ⇒ self
Iterates over each key.
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#each_pair {|key, value| ... } ⇒ self
(also: #each)
Iterates over each key value pair.
-
#each_value {|value| ... } ⇒ self
Iterates over each value.
-
#empty? ⇒ true, false
Is map empty?.
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#fetch(key, default_value = NULL) {|key| ... } ⇒ Object
Get a value with key, or default_value when key is absent, or fail when no default_value is given.
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#fetch_or_store(key, default_value = NULL) {|key| ... } ⇒ Object
Fetch value with key, or store default value when key is absent, or fail when no default_value is given.
-
#get_and_set(key, value) ⇒ Object?
Get the current value under key and set new value.
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#initialize(options = nil, &default_proc) ⇒ Map
constructor
A new instance of Map.
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#key(value) ⇒ Object?
Find key of a value.
-
#keys ⇒ ::Array<Object>
All keys.
-
#merge_pair(key, value) {|old_value| ... } ⇒ Object?
If the key is absent, the value is stored, otherwise new value is computed with a block.
-
#put_if_absent(key, value) ⇒ Object?
Insert value into map with key if key is absent in one atomic step.
-
#replace_if_exists(key, new_value) ⇒ Object?
Replaces current value with new_value if key exists This method is atomic.
-
#replace_pair(key, old_value, new_value) ⇒ true, false
Replaces old_value with new_value if key exists and current value matches old_value This method is atomic.
-
#size ⇒ Integer
The size of map.
-
#value?(value) ⇒ true, false
Is the value stored in the map.
-
#values ⇒ ::Array<Object>
All values.
Constructor Details
#initialize(options = nil, &default_proc) ⇒ Map
Returns a new instance of Map.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 133 def initialize( = nil, &default_proc) if .kind_of?(::Hash) () else = nil end super() @default_proc = default_proc end |
Instance Method Details
#[](key) ⇒ Object Also known as: get
Get a value with key
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 147 def [](key) if value = super # non-falsy value is an existing mapping, return it right away value # re-check is done with get_or_default(key, NULL) instead of a simple !key?(key) in order to avoid a race condition, whereby by the time the current thread gets to the key?(key) call # a key => value mapping might have already been created by a different thread (key?(key) would then return true, this elsif branch wouldn't be taken and an incorrent +nil+ value # would be returned) # note: nil == value check is not technically necessary elsif @default_proc && nil == value && NULL == (value = get_or_default(key, NULL)) @default_proc.call(self, key) else value end end |
#[]=(key, value) ⇒ Object Also known as: put
Set a value with key
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 49
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#compute(key) {|old_value| ... } ⇒ Object?
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Compute and store new value for key. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 72
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#compute_if_absent(key) { ... } ⇒ Object
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Compute and store new value for key if the key is absent. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 55
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#compute_if_present(key) {|old_value| ... } ⇒ Object?
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Compute and store new value for key if the key is present. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 63
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#delete(key) ⇒ Object?
Delete key and its value. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 115
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#delete_pair(key, value) ⇒ true, false
Delete pair and its value if current value equals the provided value. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 121
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#each_key {|key| ... } ⇒ self
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Iterates over each key. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 255 def each_key each_pair { |k, v| yield k } end |
#each_pair {|key, value| ... } ⇒ self Also known as: each
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Iterates over each key value pair. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 274 def each_pair return enum_for :each_pair unless block_given? super end |
#each_value {|value| ... } ⇒ self
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
Iterates over each value. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 264 def each_value each_pair { |k, v| yield v } end |
#empty? ⇒ true, false
Is map empty?
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 291 def empty? each_pair { |k, v| return false } true end |
#fetch(key, default_value = NULL) {|key| ... } ⇒ Object
The “fetch-then-act” methods of ‘Map` are not atomic. `Map` is intended to be use as a concurrency primitive with strong happens-before guarantees. It is not intended to be used as a high-level abstraction supporting complex operations. All read and write operations are thread safe, but no guarantees are made regarding race conditions between the fetch operation and yielding to the block. Additionally, this method does not support recursion. This is due to internal constraints that are very unlikely to change in the near future.
Get a value with key, or default_value when key is absent, or fail when no default_value is given.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 183 def fetch(key, default_value = NULL) if NULL != (value = get_or_default(key, NULL)) value elsif block_given? yield key elsif NULL != default_value default_value else raise_fetch_no_key end end |
#fetch_or_store(key, default_value = NULL) {|key| ... } ⇒ Object
Fetch value with key, or store default value when key is absent, or fail when no default_value is given. This is a two step operation, therefore not atomic. The store can overwrite other concurrently stored value.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 205 def fetch_or_store(key, default_value = NULL) fetch(key) do put(key, block_given? ? yield(key) : (NULL == default_value ? raise_fetch_no_key : default_value)) end end |
#get_and_set(key, value) ⇒ Object?
Get the current value under key and set new value. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 108
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#key(value) ⇒ Object?
Find key of a value.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 284 def key(value) each_pair { |k, v| return k if v == value } nil end |
#keys ⇒ ::Array<Object>
All keys
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 236 def keys arr = [] each_pair { |k, v| arr << k } arr end |
#merge_pair(key, value) {|old_value| ... } ⇒ Object?
Atomic methods taking a block do not allow the ‘self` instance to be used within the block. Doing so will cause a deadlock.
If the key is absent, the value is stored, otherwise new value is computed with a block. This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 81
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#put_if_absent(key, value) ⇒ Object?
Insert value into map with key if key is absent in one atomic step.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 215 def put_if_absent(key, value) computed = false result = compute_if_absent(key) do computed = true value end computed ? nil : result end |
#replace_if_exists(key, new_value) ⇒ Object?
Replaces current value with new_value if key exists This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 101
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#replace_pair(key, old_value, new_value) ⇒ true, false
Replaces old_value with new_value if key exists and current value matches old_value This method is atomic.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 92
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#size ⇒ Integer
The size of map.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 298 def size count = 0 each_pair { |k, v| count += 1 } count end |
#value?(value) ⇒ true, false
Is the value stored in the map. Iterates over all values.
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 227 def value?(value) each_value do |v| return true if value.equal?(v) end false end |
#values ⇒ ::Array<Object>
All values
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# File 'lib/concurrent-ruby/concurrent/map.rb', line 244 def values arr = [] each_pair { |k, v| arr << v } arr end |