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module Immutable
# @private
class Trie
def self.[](pairs)
result = new(0)
pairs.each { |key, val| result.put!(key, val) }
result
end
# Returns the number of key-value pairs in the trie.
attr_reader :size
def initialize(bitshift, size = 0, entries = [], children = [])
@bitshift = bitshift
@entries = entries
@children = children
@size = size
end
# Returns <tt>true</tt> if the trie contains no key-value pairs.
def empty?
@size == 0
end
# Returns <tt>true</tt> if the given key is present in the trie.
def key?(key)
!!get(key)
end
# Calls <tt>block</tt> once for each entry in the trie, passing the key-value pair as parameters.
def each(&block)
@entries.each { |entry| yield entry if entry }
@children.each do |child|
child.each(&block) if child
end
nil
end
def reverse_each(&block)
@children.reverse_each do |child|
child.reverse_each(&block) if child
end
@entries.reverse_each { |entry| yield(entry) if entry }
nil
end
def reduce(memo)
each { |entry| memo = yield(memo, entry) }
memo
end
def select
keys_to_delete = []
each { |entry| keys_to_delete << entry[0] unless yield(entry) }
bulk_delete(keys_to_delete)
end
# @return [Trie] A copy of `self` with the given value associated with the
# key (or `self` if no modification was needed because an identical
# key-value pair was already stored
def put(key, value)
index = index_for(key)
entry = @entries[index]
if !entry
entries = @entries.dup
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
entries[index] = [key, value].freeze
Trie.new(@bitshift, @size + 1, entries, @children)
elsif entry[0].eql?(key)
if entry[1].equal?(value)
self
else
entries = @entries.dup
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
entries[index] = [key, value].freeze
Trie.new(@bitshift, @size, entries, @children)
end
else
child = @children[index]
if child
new_child = child.put(key, value)
if new_child.equal?(child)
self
else
children = @children.dup
children[index] = new_child
new_self_size = @size + (new_child.size - child.size)
Trie.new(@bitshift, new_self_size, @entries, children)
end
else
children = @children.dup
children[index] = Trie.new(@bitshift + 5).put!(key, value)
Trie.new(@bitshift, @size + 1, @entries, children)
end
end
end
# Put multiple elements into a Trie. This is more efficient than several
# calls to `#put`.
#
# @param key_value_pairs Enumerable of pairs (`[key, value]`)
# @return [Trie] A copy of `self` after associated the given keys and
# values (or `self` if no modifications where needed).
def bulk_put(key_value_pairs)
new_entries = nil
new_children = nil
new_size = @size
key_value_pairs.each do |key, value|
index = index_for(key)
entry = (new_entries || @entries)[index]
if !entry
new_entries ||= @entries.dup
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
new_entries[index] = [key, value].freeze
new_size += 1
elsif entry[0].eql?(key)
if !entry[1].equal?(value)
new_entries ||= @entries.dup
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
new_entries[index] = [key, value].freeze
end
else
child = (new_children || @children)[index]
if child
new_child = child.put(key, value)
if !new_child.equal?(child)
new_children ||= @children.dup
new_children[index] = new_child
new_size += new_child.size - child.size
end
else
new_children ||= @children.dup
new_children[index] = Trie.new(@bitshift + 5).put!(key, value)
new_size += 1
end
end
end
if new_entries || new_children
Trie.new(@bitshift, new_size, new_entries || @entries, new_children || @children)
else
self
end
end
# Returns <tt>self</tt> after overwriting the element associated with the specified key.
def put!(key, value)
index = index_for(key)
entry = @entries[index]
if !entry
@size += 1
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
@entries[index] = [key, value].freeze
elsif entry[0].eql?(key)
key = key.dup.freeze if key.is_a?(String) && !key.frozen?
@entries[index] = [key, value].freeze
else
child = @children[index]
if child
old_child_size = child.size
@children[index] = child.put!(key, value)
@size += child.size - old_child_size
else
@children[index] = Trie.new(@bitshift + 5).put!(key, value)
@size += 1
end
end
self
end
# Retrieves the entry corresponding to the given key. If not found, returns <tt>nil</tt>.
def get(key)
index = index_for(key)
entry = @entries[index]
if entry && entry[0].eql?(key)
entry
else
child = @children[index]
child.get(key) if child
end
end
# Returns a copy of <tt>self</tt> with the given key (and associated value) deleted. If not found, returns <tt>self</tt>.
def delete(key)
find_and_delete(key) || Trie.new(@bitshift)
end
# Delete multiple elements from a Trie. This is more efficient than
# several calls to `#delete`.
#
# @param keys [Enumerable] The keys to delete
# @return [Trie]
def bulk_delete(keys)
new_entries = nil
new_children = nil
new_size = @size
keys.each do |key|
index = index_for(key)
entry = (new_entries || @entries)[index]
if !entry
next
elsif entry[0].eql?(key)
new_entries ||= @entries.dup
child = (new_children || @children)[index]
if child
# Bring up the first entry from the child into entries
new_children ||= @children.dup
new_children[index] = child.delete_at do |entry|
new_entries[index] = entry
end
else
new_entries[index] = nil
end
new_size -= 1
else
child = (new_children || @children)[index]
if child
copy = child.find_and_delete(key)
unless copy.equal?(child)
new_children ||= @children.dup
new_children[index] = copy
new_size -= (child.size - copy_size(copy))
end
end
end
end
if new_entries || new_children
Trie.new(@bitshift, new_size, new_entries || @entries, new_children || @children)
else
self
end
end
def include?(key, value)
entry = get(key)
entry && value.eql?(entry[1])
end
def at(index)
@entries.each do |entry|
if entry
return entry if index == 0
index -= 1
end
end
@children.each do |child|
if child
if child.size >= index+1
return child.at(index)
else
index -= child.size
end
end
end
nil
end
# Returns <tt>true</tt> if . <tt>eql?</tt> is synonymous with <tt>==</tt>
def eql?(other)
return true if equal?(other)
return false unless instance_of?(other.class) && size == other.size
each do |entry|
return false unless other.include?(entry[0], entry[1])
end
true
end
alias == eql?
protected
# Returns a replacement instance after removing the specified key.
# If not found, returns <tt>self</tt>.
# If empty, returns <tt>nil</tt>.
def find_and_delete(key)
index = index_for(key)
entry = @entries[index]
if entry && entry[0].eql?(key)
return delete_at(index)
else
child = @children[index]
if child
copy = child.find_and_delete(key)
unless copy.equal?(child)
children = @children.dup
children[index] = copy
new_size = @size - (child.size - copy_size(copy))
return Trie.new(@bitshift, new_size, @entries, children)
end
end
end
self
end
# Returns a replacement instance after removing the specified entry. If empty, returns <tt>nil</tt>
def delete_at(index = @entries.index { |e| e })
yield(@entries[index]) if block_given?
if size > 1
entries = @entries.dup
child = @children[index]
if child
children = @children.dup
children[index] = child.delete_at do |entry|
entries[index] = entry
end
else
entries[index] = nil
end
Trie.new(@bitshift, @size - 1, entries, children || @children)
end
end
private
def index_for(key)
(key.hash.abs >> @bitshift) & 31
end
def copy_size(copy)
copy ? copy.size : 0
end
end
# @private
EmptyTrie = Trie.new(0).freeze
end
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