class StringPool
inherits Reference
¶
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.
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
Class methods¶
.new(initial_capacity = 8)
¶
(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.
pool = StringPool.new(256)
pool.size # => 0
Methods¶
#empty?
¶
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
#get(str : Pointer(UInt8), len)
¶
(str : Pointer(UInt8), len)
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
#get(slice : Bytes)
¶
(slice : Bytes)
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
#get(str : IO::Memory)
¶
(str : IO::Memory)
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
#get(str : String)
¶
(str : 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
#rehash
¶
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.
#size : Int32
¶
: Int32
Returns the size
require "string_pool"
pool = StringPool.new
pool.size # => 0