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require 'yaml'
require 'dbm'
module YAML
# YAML + DBM = YDBM
#
# YAML::DBM provides the same interface as ::DBM.
#
# However, while DBM only allows strings for both keys and values,
# this library allows one to use most Ruby objects for values
# by first converting them to YAML. Keys must be strings.
#
# Conversion to and from YAML is performed automatically.
#
# See the documentation for ::DBM and ::YAML for more information.
class DBM < ::DBM
VERSION = "0.1"
# Return value associated with +key+ from database.
#
# Returns +nil+ if there is no such +key+.
def []( key )
fetch( key )
end
# :call-seq:
# []=( key, value )
#
# Set +key+ to +value+ in database.
#
# +value+ will be converted to YAML before storage.
def []=( key, val )
store( key, val )
end
# :call-seq:
# fetch( key, ifnone = nil )
# fetch( key, &block )
#
# Return value associated with +key+.
#
# If there is no value for +key+ and no block is given, returns +ifnone+.
#
# Otherwise, calls block passing in the given +key+.
def fetch( keystr, ifnone = nil )
begin
val = super( keystr )
return YAML.load( val ) if String === val
rescue IndexError
end
if block_given?
yield keystr
else
ifnone
end
end
# Deprecated, used YAML::DBM#key instead.
# ----
# Note:
# YAML::DBM#index makes warning from internal of ::DBM#index.
# It says 'DBM#index is deprecated; use DBM#key', but DBM#key
# behaves not same as DBM#index.
#
def index( keystr )
super( keystr.to_yaml )
end
def key( keystr )
invert[keystr]
end
# Returns an array containing the values associated with the given keys.
def values_at( *keys )
keys.collect { |k| fetch( k ) }
end
# Deletes value from database associated with +key+.
#
# Returns value or +nil+.
def delete( key )
v = super( key )
if String === v
v = YAML.load( v )
end
v
end
# Calls the given block once for each +key+, +value+ pair in the database.
# Deletes all entries for which the block returns true.
#
# Returns +self+.
def delete_if # :yields: [key, value]
del_keys = keys.dup
del_keys.delete_if { |k| yield( k, fetch( k ) ) == false }
del_keys.each { |k| delete( k ) }
self
end
# Converts the contents of the database to an in-memory Hash, then calls
# Hash#reject with the specified code block, returning a new Hash.
def reject
hsh = self.to_hash
hsh.reject { |k,v| yield k, v }
end
# Calls the given block once for each +key+, +value+ pair in the database.
#
# Returns +self+.
def each_pair # :yields: [key, value]
keys.each { |k| yield k, fetch( k ) }
self
end
# Calls the given block for each value in database.
#
# Returns +self+.
def each_value # :yields: value
super { |v| yield YAML.load( v ) }
self
end
# Returns an array of values from the database.
def values
super.collect { |v| YAML.load( v ) }
end
# Returns true if specified value is found in the database.
def has_value?( val )
each_value { |v| return true if v == val }
return false
end
# Returns a Hash (not a DBM database) created by using each value in the
# database as a key, with the corresponding key as its value.
#
# Note that all values in the hash will be Strings, but the keys will be
# actual objects.
def invert
h = {}
keys.each { |k| h[ self.fetch( k ) ] = k }
h
end
# Replaces the contents of the database with the contents of the specified
# object. Takes any object which implements the each_pair method, including
# Hash and DBM objects.
def replace( hsh )
clear
update( hsh )
end
# Removes a [key, value] pair from the database, and returns it.
# If the database is empty, returns +nil+.
#
# The order in which values are removed/returned is not guaranteed.
def shift
a = super
a[1] = YAML.load( a[1] ) if a
a
end
# :call-seq:
# select( &block )
# select( *keys )
#
# If a block is provided, returns a new array containing [key, value] pairs
# for which the block returns true.
#
# Otherwise, same as #values_at
def select( *keys )
if block_given?
self.keys.collect { |k| v = self[k]; [k, v] if yield k, v }.compact
else
values_at( *keys )
end
end
# :call-seq:
# store( key, value )
#
#Stores +value+ in database with +key+ as the index. +value+ is converted
#to YAML before being stored.
#
#Returns +value+
def store( key, val )
super( key, val.to_yaml )
val
end
# Updates the database with multiple values from the specified object.
# Takes any object which implements the each_pair method, including
# Hash and DBM objects.
#
# Returns +self+.
def update( hsh )
hsh.each_pair do |k,v|
self.store( k, v )
end
self
end
# Converts the contents of the database to an array of [key, value] arrays,
# and returns it.
def to_a
a = []
keys.each { |k| a.push [ k, self.fetch( k ) ] }
a
end
# Converts the contents of the database to an in-memory Hash object, and
# returns it.
def to_hash
h = {}
keys.each { |k| h[ k ] = self.fetch( k ) }
h
end
alias :each :each_pair
end
end
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