class StringPool

Overview

A string pool is a collection of strings. It allows a runtime to save memory by preserving strings in a pool, allowing to reuse an instance of a common string instead of creating a new one.

NOTE To use StringPool, you must explicitly import it with require "string_pool"

require "string_pool"

pool = StringPool.new
a = "foo" + "bar"
b = "foo" + "bar"
a.object_id # => 136294360
b.object_id # => 136294336
a = pool.get(a)
b = pool.get(b)
a.object_id # => 136294312
b.object_id # => 136294312

Defined in:

string_pool.cr

Constructors

Instance Method Summary

Instance methods inherited from class Reference

==(other : self)
==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup, hash(hasher) hash, initialize initialize, inspect(io : IO) : Nil inspect, object_id : UInt64 object_id, pretty_print(pp) : Nil pretty_print, same?(other : Reference) : Bool
same?(other : Nil) same?, to_s(io : IO) : Nil to_s

Constructor methods inherited from class Reference

new new

Instance methods inherited from class Object

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

Class methods inherited from class Object

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

Constructor Detail

def self.new(initial_capacity = 8) #

Creates a new empty string pool.

The initial_capacity is useful to avoid unnecessary reallocations of the internal buffers in case of growth. If you have an estimate of the maximum number of elements the pool will hold it should be initialized with that capacity for improved performance. Inputs lower than 8 are ignored.

pool = StringPool.new(256)
pool.size # => 0

[View source]

Instance Method Detail

def empty? : Bool #

Returns true if the StringPool has no element otherwise returns false.

require "string_pool"

pool = StringPool.new
pool.empty? # => true
pool.get("crystal")
pool.empty? # => false

[View source]
def get(str : Pointer(UInt8), len) : String #

Returns a String with the contents given by the pointer str of size len.

If a string with those contents was already present in the pool, that one is returned. Otherwise a new string is created, put in the pool and returned.

require "string_pool"

pool = StringPool.new
pool.get("hey".to_unsafe, 3)
pool.size # => 1

[View source]
def get(slice : Bytes) : String #

Returns a String with the contents of the given slice.

If a string with those contents was already present in the pool, that one is returned. Otherwise a new string is created, put in the pool and returned.

require "string_pool"

pool = StringPool.new
ptr = Pointer.malloc(9) { |i| ('a'.ord + i).to_u8 }
slice = Slice.new(ptr, 3)
pool.empty? # => true
pool.get(slice)
pool.empty? # => false

[View source]
def get(str : IO::Memory) : String #

Returns a String with the contents of the given IO::Memory.

If a string with those contents was already present in the pool, that one is returned. Otherwise a new string is created, put in the pool and returned.

require "string_pool"

pool = StringPool.new
io = IO::Memory.new "crystal"
pool.empty? # => true
pool.get(io)
pool.empty? # => false

[View source]
def get(str : String) : String #

Returns a String with the contents of the given string.

If a string with those contents was already present in the pool, that one is returned. Otherwise a new string is created, put in the pool and returned.

require "string_pool"

pool = StringPool.new
string = "crystal"
pool.empty? # => true
pool.get(string)
pool.empty? # => false

[View source]
def rehash : Nil #

Rebuilds the hash based on the current hash values for each key, if values of key objects have changed since they were inserted.

Call this method if you modified a string submitted to the pool.


[View source]
def size : Int32 #

Returns the size

require "string_pool"

pool = StringPool.new
pool.size # => 0

[View source]