From 0621370cec890c43f71cbf5d971f8ee4f69110fa Mon Sep 17 00:00:00 2001
From: Denis Knauf <Denis.Knauf@gmail.com>
Date: Fri, 15 Jul 2011 10:03:38 +0200
Subject: [PATCH] --

---
 lib/aodbm.rb | 103 +++++++++++++++++++++++++++
 lib/plain.rb | 192 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 295 insertions(+)
 create mode 100644 lib/aodbm.rb
 create mode 100644 lib/plain.rb

diff --git a/lib/aodbm.rb b/lib/aodbm.rb
new file mode 100644
index 0000000..cf98858
--- /dev/null
+++ b/lib/aodbm.rb
@@ -0,0 +1,103 @@
+require 'ffi'
+
+module AODBM
+	class DB
+		attr_reader :c
+
+		def initialize name, flags = nil
+			flags ||= 0
+			@c = Lib::open name, flags
+		end
+
+		def open name, flags = nil
+			db = new name, flags
+			block_given? ? yield( db) : db
+		end
+
+		def close
+			Lib::close @c
+		end
+
+		def current
+			Version.new @c, Lib::current( @c)
+		end
+
+		def commit version
+			Lib::commit @c, version
+		end
+	end
+
+	class Version
+		attr_reader :db, :c
+
+		def initialize db, c
+			@db, @c = db, c
+		end
+
+		def previous
+			Version.new @db, Lib::previous( @db.c, @c)
+		end
+
+		def has? data
+			Lib::has @db.c, @c, Lib::Data.new( data)
+		end
+
+		def set key, val
+			Lib::set @db.c, @c, Lib::Data.new( key), Lib::Data.new( val)
+		end
+	end
+
+	module Lib
+		extend FFI::Library
+		ffi_lib "libaodbm.so"
+
+		typedef :pointer, :aodbm
+		typedef :uint64, :version
+
+		class Data < FFI::Struct
+			def initialilze data
+
+			end
+
+			layout :dat, :buffer,  :sz, :size_t
+		end
+		typedef :pointer, :data
+
+		attach_function :open, :aodbm_open, [:string, :int], :aodbm
+		attach_function :close, :aodbm_close, [:aodbm], :void
+
+		attach_function :current, :aodbm_current, [:aodbm], :version
+		attach_function :commit, :aodbm_commit, [:aodbm, :version], :bool
+
+		attach_function :has, :aodbm_has, [:aodbm, :version, :data], :bool
+		attach_function :set, :aodbm_set, [:aodbm, :version, :data, :data], :version
+		attach_function :get, :aodbm_get, [:aodbm, :version, :data], :data
+		attach_function :del, :aodbm_del, [:aodbm, :version, :data], :version
+
+		attach_function :is_based_on, :aodbm_is_based_on, [:aodbm, :version, :data], :bool
+		attach_function :previous, :aodbm_previous_version, [:aodbm, :version], :version
+		attach_function :common_ancestor, :aodbm_common_ancestor, [:aodbm, :version, :version], :version
+
+		#typedef :changeset, :pointer
+		#attach_function :aodbm_diff_prev, [:aodbm, :version], :changeset
+		#attach_function :aodbm_diff_prev_rev, [:aodbm, :version], :changeset
+		#attach_function :aodbm_diff, [:aodbm, :version, :version], :changeset
+		#attach_function :aodbm_apply, [:aodbm, :version, :changeset], :version
+		#attach_function :aodbm_apply_di, [:aodbm, :version, :changeset], :version
+		#attach_function :aodbm_merge, [:aodbm, :version, :version], :version
+
+		typedef :pointer, :iterator
+		class Record < FFI::Struct
+			layout :key, :data,  :val, :data
+		end
+		typedef :pointer, :record
+
+		attach_function :new_iterator, :aodbm_new_iterator, [:aodbm, :version], :iterator
+		attach_function :iterator_from, :aodbm_iterate_from, [:aodbm, :version, :data], :iterator
+		attach_function :iterate_next, :aodbm_iterator_next, [:aodbm, :iterator], :record
+		attach_function :iterate_goto, :aodbm_iterator_goto, [:aodbm, :iterator, :data], :void
+		attach_function :free_iterator, :aodbm_free_iterator, [:iterator], :void
+
+		attach_function :free_data, :aodbm_free_data, [:data], :void
+	end
+end
diff --git a/lib/plain.rb b/lib/plain.rb
new file mode 100644
index 0000000..edb4229
--- /dev/null
+++ b/lib/plain.rb
@@ -0,0 +1,192 @@
+require 'zlib'  # Zlib::crc32
+require 'uuidtools'
+
+# Maximum Filesize: 4GB because #pack("N")
+
+class Plain < File
+	UUID_SIZE   = 16        # Size of an key (UUID as raw 16byte string)
+	INT_SIZE    = 4
+	CRCR32_SIZE = INT_SIZE  # Size of CRC32 (32Bit)
+
+	KEY_SIZE    = UUID_SIZE
+	IDX_SIZE    = INT_SIZE  # Size of an index (big-endian 32bit integer)
+	SIZE_SIZE   = INT_SIZE  # Size of size_t
+	CHK_SIZE    = CRCR32_SIZE
+	IDXE_SIZE   = KEY_SIZE + IDX_SIZE # Size of an entry in index-file
+	DBP_SIZE    = KEY_SIZE + SIZE_SIZE + CHK_SIZE
+
+	UUID_PACK   = "a16"
+	INT_PACK    = "N"
+	STR_PACK    = "a*"
+	CRC32_PACK  = INT_PACK
+
+	KEY_PACK    = UUID_PACK
+	IDX_PACK    = INT_PACK
+	SIZE_PACK   = INT_PACK
+	CHK_PACK    = CRC32_PACK
+	IDXE_PACK   = KEY_PACK + IDX_PACK
+	DBP_PACK    = KEY_PACK + SIZE_PACK + CHK_PACK
+	VAL_PACK    = STR_PACK
+	ENTRY_PACK  = DBP_PACK + VAL_PACK
+
+	class Corrupt < Exception
+	end
+
+	module UUIDConv
+		class <<self
+			# Converts a UUIDTools::UUID to raw-String: UUIDTools::UUID#raw
+			def cto_s x
+				x.raw
+			end
+
+			# Converts a String to UUIDTools::UUID: UUIDTools::UUID.parse_raw
+			def cto_key x
+				UUIDTools::UUID.parse_raw x
+			end
+		end
+	end
+
+	# Converting-helper.
+	# To methods are required:
+	# #cto_str # obj => 16-byte-String
+	# #cto_key # 16-byte-String => obj
+	attr_accessor :conv
+	attr_reader :idx
+
+	def initialize *a
+		super *a
+		@conv = @@conv
+		@idx = File.open "#{path}.idx", a[1]
+	end
+
+	class <<self
+		# Default we use UUIDTool for keys.
+		@@conv = UUIDConv
+
+		def new *a
+			a[1] ||= 'a'
+			r = super *a
+			block_given? ? yield(r) : r
+		end
+
+		def open *a, &e
+			a[1] ||= 'r'
+			new *a, &e
+		end
+	end
+
+	def sync
+		super
+		@idx.sync
+	end
+
+	def close
+		super
+		@idx.close
+	end
+
+	def gen_entry key, val
+		[key, val.length, Zlib::crc32( val), val].pack( ENTRY_PACK)
+	end
+
+	def gen_idx key, pos = self.pos
+		[key, pos].pack IDXE_PACK
+	end
+
+	# Store an entry in DB
+	def push key, val
+		key = @conv.cto_s key
+		idx = gen_idx key
+		print gen_entry( key, val)
+		@idx.print idx
+		sync
+		@idx.sync
+		true
+	end
+
+	def put val
+		push UUIDTools::UUID.timestamp_create, val
+	end
+
+	# Read the entry.
+	# First you should seek, if you won't read sequential
+	def get
+		if m = read( DBP_SIZE)
+			key, length, chk = m.unpack DBP_PACK
+			val = read length
+			valchk = Zlib::crc32 val
+			raise Corrupt, "#{path} is corrupt: #{pos-length-CHK_SIZE-DBP_SIZE} #{chk} -- #{valchk}"  unless chk == valchk
+			[@conv.cto_key( key), length, val, chk]
+		end
+	end
+	alias next get
+
+	# yield(idx): must return:
+	#    -1:   to small
+	#    0:    found!  return true
+	#    1:    to big
+	# else:    like you use break nil
+	# yield is allowed to use break
+	def self.binary_search size
+		idx = 1
+		begin
+			i = size
+			while 0 < i
+				idx <<= 1
+				i >>= 1
+			end
+		end
+		idx >>= 1
+		t = idx
+		p idx
+
+		while t > 0
+			t >>= 1
+			i = yield idx
+			case i
+			when -1 then idx -= t
+			when 1  then idx += t
+			when 0  then return true
+			else return nil
+			end
+		end
+	end
+
+	# Get the value.
+	# key must provide: #<=> uuid
+	def search_ key
+		idx = self.length
+		position = nil
+		self.class.binary_search( idx) do |idx|
+			p idx
+			idx *= IDXE_SIZE
+			if idx > size
+				size = @idx.size
+				break  if idx > size
+			end
+			# Read entry i. p is position and k is key
+			@idx.seek idx
+			k, position = @idx.read( IDXE_SIZE).unpack IDXE_PACK
+			p pos: position, key: k
+			key <=> @conv.cto_key( k)
+		end ? position : nil
+	end
+
+	def [] key
+		if position = search_( key)
+			self.pos = position+KEY_SIZE
+			length,_ = read( SIZE_SIZE).unpack( SIZE_PACK)
+			read( length)[2]
+		end
+	end
+
+	def each
+		return Enumerator.new( self)  unless block_given?
+		yield *get  while !eof?
+	end
+
+	# counts entries (size of the idx): O(1)
+	def length
+		@idx.size/IDXE_SIZE
+	end
+end