class PG::BasicTypeRegistry

conn.type_map_for_results = PG::BasicTypeMapForResults.new(conn, registry: regi)
regi.register_type(0, ‘inet’, InetEncoder, InetDecoder)
regi = PG::BasicTypeRegistry.new.register_default_types
conn = PG.connect
end
end
ip_addr.to_s
def encode(ip_addr)
class InetEncoder < PG::SimpleEncoder
end
end
IPAddr.new(string)
def decode(string, tuple=nil, field=nil)
class InetDecoder < PG::SimpleDecoder
require ‘ipaddr’
require ‘pg’
Additional types can be added like so:
This class defines the mapping between PostgreSQL types and encoder/decoder classes for PG::BasicTypeMapForResults, PG::BasicTypeMapForQueries and PG::BasicTypeMapBasedOnResult.

def alias_type(format, new, old)

Alias the +old+ type to the +new+ type. 
def alias_type(format, new, old)
	[:encoder, :decoder].each do |ende|
		enc = @coders_by_name[format][ende][old]
		if enc
			@coders_by_name[format][ende][new] = enc
		else
			@coders_by_name[format][ende].delete(new)
		end
	end
	self
end

def coders_for(format, direction)

The hash value is the registered coder object.
The hash key is the name as defined in table +pg_type+.
Retrieve a Hash of all en- or decoders for a given wire format. 
def coders_for(format, direction)
	check_format_and_direction(format, direction)
	@coders_by_name[format]&.[](direction)
end

def initialize 

def initialize
	# The key of these hashs maps to the `typname` column from the table pg_type.
	@coders_by_name = []
end

def register_coder(coder)

Coder#format can be 0 for text format and 1 for binary.
Coder#name must correspond to the +typname+ column in the +pg_type+ table.

Register an encoder or decoder instance for casting a PostgreSQL type. 
def register_coder(coder)
	h = @coders_by_name[coder.format] ||= { encoder: {}, decoder: {} }
	name = coder.name || raise(ArgumentError, "name of #{coder.inspect} must be defined")
	h[:encoder][name] = coder if coder.respond_to?(:encode)
	h[:decoder][name] = coder if coder.respond_to?(:decode)
	self
end

def register_default_types

Populate the registry with all builtin types of ruby-pg 
def register_default_types
	register_type 0, 'int2', PG::TextEncoder::Integer, PG::TextDecoder::Integer
	alias_type    0, 'int4', 'int2'
	alias_type    0, 'int8', 'int2'
	alias_type    0, 'oid',  'int2'
	register_type 0, 'numeric', PG::TextEncoder::Numeric, PG::TextDecoder::Numeric
	register_type 0, 'text', PG::TextEncoder::String, PG::TextDecoder::String
	alias_type 0, 'varchar', 'text'
	alias_type 0, 'char', 'text'
	alias_type 0, 'bpchar', 'text'
	alias_type 0, 'xml', 'text'
	alias_type 0, 'name', 'text'
	# FIXME: why are we keeping these types as strings?
	# alias_type 'tsvector', 'text'
	# alias_type 'interval', 'text'
	# alias_type 'macaddr',  'text'
	# alias_type 'uuid',     'text'
	#
	# register_type 'money', OID::Money.new
	register_type 0, 'bytea', PG::TextEncoder::Bytea, PG::TextDecoder::Bytea
	register_type 0, 'bool', PG::TextEncoder::Boolean, PG::TextDecoder::Boolean
	# register_type 'bit', OID::Bit.new
	# register_type 'varbit', OID::Bit.new
	register_type 0, 'float4', PG::TextEncoder::Float, PG::TextDecoder::Float
	alias_type 0, 'float8', 'float4'
	# For compatibility reason the timestamp in text format is encoded as local time (TimestampWithoutTimeZone) instead of UTC
	register_type 0, 'timestamp', PG::TextEncoder::TimestampWithoutTimeZone, PG::TextDecoder::TimestampWithoutTimeZone
	register_type 0, 'timestamptz', PG::TextEncoder::TimestampWithTimeZone, PG::TextDecoder::TimestampWithTimeZone
	register_type 0, 'date', PG::TextEncoder::Date, PG::TextDecoder::Date
	# register_type 'time', OID::Time.new
	#
	# register_type 'path', OID::Text.new
	# register_type 'point', OID::Point.new
	# register_type 'polygon', OID::Text.new
	# register_type 'circle', OID::Text.new
	# register_type 'hstore', OID::Hstore.new
	register_type 0, 'json', PG::TextEncoder::JSON, PG::TextDecoder::JSON
	alias_type    0, 'jsonb',  'json'
	# register_type 'citext', OID::Text.new
	# register_type 'ltree', OID::Text.new
	#
	register_type 0, 'inet', PG::TextEncoder::Inet, PG::TextDecoder::Inet
	alias_type 0, 'cidr', 'inet'
	register_type 1, 'int2', PG::BinaryEncoder::Int2, PG::BinaryDecoder::Integer
	register_type 1, 'int4', PG::BinaryEncoder::Int4, PG::BinaryDecoder::Integer
	register_type 1, 'int8', PG::BinaryEncoder::Int8, PG::BinaryDecoder::Integer
	alias_type    1, 'oid',  'int2'
	register_type 1, 'text', PG::BinaryEncoder::String, PG::BinaryDecoder::String
	alias_type 1, 'varchar', 'text'
	alias_type 1, 'char', 'text'
	alias_type 1, 'bpchar', 'text'
	alias_type 1, 'xml', 'text'
	alias_type 1, 'name', 'text'
	register_type 1, 'bytea', PG::BinaryEncoder::Bytea, PG::BinaryDecoder::Bytea
	register_type 1, 'bool', PG::BinaryEncoder::Boolean, PG::BinaryDecoder::Boolean
	register_type 1, 'float4', PG::BinaryEncoder::Float4, PG::BinaryDecoder::Float
	register_type 1, 'float8', PG::BinaryEncoder::Float8, PG::BinaryDecoder::Float
	register_type 1, 'timestamp', PG::BinaryEncoder::TimestampUtc, PG::BinaryDecoder::TimestampUtc
	register_type 1, 'timestamptz', PG::BinaryEncoder::TimestampUtc, PG::BinaryDecoder::TimestampUtcToLocal
	register_type 1, 'date', PG::BinaryEncoder::Date, PG::BinaryDecoder::Date
	self
end

def register_type(format, name, encoder_class, decoder_class)

+format+ can be 0 for text format and 1 for binary.
+name+ must correspond to the +typname+ column in the +pg_type+ table.

Register the given +encoder_class+ and/or +decoder_class+ for casting a PostgreSQL type. 
def register_type(format, name, encoder_class, decoder_class)
	register_coder(encoder_class.new(name: name, format: format).freeze) if encoder_class
	register_coder(decoder_class.new(name: name, format: format).freeze) if decoder_class
	self
end