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* lib/pstore.rb: replaced by Hongli Lai's faster version.

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git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@15948 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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matz 2008-04-10 07:12:41 +00:00
parent db4a767d25
commit 1d63f4eead
3 changed files with 284 additions and 80 deletions
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2
ChangeLog
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@ -2,6 +2,8 @@ Thu Apr 10 15:03:47 2008 Yukihiro Matsumoto <matz@ruby-lang.org>
* lib/generator.rb: removed obsolete library. [ruby-core:16233]
* lib/pstore.rb: replaced by Hongli Lai's faster version.
Thu Apr 10 10:27:24 2008 Nobuyoshi Nakada <nobu@ruby-lang.org>
* thread_pthread.c (native_sleep): sleep_cond is initialized at

288
lib/pstore.rb
View file

@ -3,12 +3,14 @@
# pstore.rb -
# originally by matz
# documentation by Kev Jackson and James Edward Gray II
# improved by Hongli Lai
#
# See PStore for documentation.
require "fileutils"
require "digest/md5"
require "thread"
#
# PStore implements a file based persistance mechanism based on a Hash. User
@ -77,6 +79,20 @@ require "digest/md5"
# end
# end
#
# == Transaction modes
#
# By default, file integrity is only ensured as long as the operating system
# (and the underlying hardware) doesn't raise any unexpected I/O errors. If an
# I/O error occurs while PStore is writing to its file, then the file will
# become corrupted.
#
# You can prevent this by setting <em>pstore.ultra_safe = true</em>.
# However, this results in a minor performance loss, and only works on platforms
# that support atomic file renames. Please consult the documentation for
# +ultra_safe+ for details.
#
# Needless to say, if you're storing valuable data with PStore, then you should
# backup the PStore files from time to time.
class PStore
binmode = defined?(File::BINARY) ? File::BINARY : 0
RDWR_ACCESS = File::RDWR | File::CREAT | binmode
@ -86,12 +102,24 @@ class PStore
# The error type thrown by all PStore methods.
class Error < StandardError
end
# Whether PStore should do its best to prevent file corruptions, even when under
# unlikely-to-occur error conditions such as out-of-space conditions and other
# unusual OS filesystem errors. Setting this flag comes at the price in the form
# of a performance loss.
#
# This flag only has effect on platforms on which file renames are atomic (e.g.
# all POSIX platforms: Linux, MacOS X, FreeBSD, etc). The default value is false.
attr_accessor :ultra_safe
#
# To construct a PStore object, pass in the _file_ path where you would like
# the data to be stored.
#
# PStore objects are always reentrant. But if _thread_safe_ is set to true,
# then it will become thread-safe at the cost of a minor performance hit.
#
def initialize(file)
def initialize(file, thread_safe = false)
dir = File::dirname(file)
unless File::directory? dir
raise PStore::Error, format("directory %s does not exist", dir)
@ -102,6 +130,12 @@ class PStore
@transaction = false
@filename = file
@abort = false
@ultra_safe = false
if @thread_safe
@lock = Mutex.new
else
@lock = DummyMutex.new
end
end
# Raises PStore::Error if the calling code is not in a PStore#transaction.
@ -142,10 +176,10 @@ class PStore
def fetch(name, default=PStore::Error)
in_transaction
unless @table.key? name
if default==PStore::Error
raise PStore::Error, format("undefined root name `%s'", name)
if default == PStore::Error
raise PStore::Error, format("undefined root name `%s'", name)
else
return default
return default
end
end
@table[name]
@ -281,94 +315,188 @@ class PStore
#
# Note that PStore does not support nested transactions.
#
def transaction(read_only=false) # :yields: pstore
def transaction(read_only = false, &block) # :yields: pstore
value = nil
raise PStore::Error, "nested transaction" if @transaction
begin
@lock.synchronize do
@rdonly = read_only
@abort = false
@transaction = true
value = nil
new_file = @filename + ".new"
content = nil
unless read_only
file = File.open(@filename, RDWR_ACCESS)
file.flock(File::LOCK_EX)
commit_new(file) if FileTest.exist?(new_file)
content = file.read()
else
@abort = false
file = open_and_lock_file(@filename, read_only)
if file
begin
file = File.open(@filename, RD_ACCESS)
file.flock(File::LOCK_SH)
content = (File.open(new_file, RD_ACCESS) {|n| n.read} rescue file.read())
rescue Errno::ENOENT
content = ""
end
end
if content != ""
@table = load(content)
if !read_only
size = content.size
md5 = Digest::MD5.digest(content)
@table, checksum, original_data_size = load_data(file, read_only)
catch(:pstore_abort_transaction) do
value = yield(self)
end
if !@abort && !read_only
save_data(checksum, original_data_size, file)
end
ensure
file.close if !file.closed?
end
else
@table = {}
# This can only occur if read_only == true.
@table = {}
catch(:pstore_abort_transaction) do
value = yield(self)
end
end
content = nil # unreference huge data
begin
catch(:pstore_abort_transaction) do
value = yield(self)
end
rescue Exception
@abort = true
raise
ensure
if !read_only and !@abort
tmp_file = @filename + ".tmp"
content = dump(@table)
if !md5 || size != content.size || md5 != Digest::MD5.digest(content)
File.open(tmp_file, WR_ACCESS) {|t| t.write(content)}
File.rename(tmp_file, new_file)
commit_new(file)
end
content = nil # unreference huge data
end
end
ensure
@table = nil
@transaction = false
file.close if file
end
ensure
@transaction = false
value
end
# This method is just a wrapped around Marshal.dump.
def dump(table) # :nodoc:
Marshal::dump(table)
end
# This method is just a wrapped around Marshal.load.
def load(content) # :nodoc:
Marshal::load(content)
end
# This method is just a wrapped around Marshal.load.
def load_file(file) # :nodoc:
Marshal::load(file)
end
private
# Commits changes to the data store file.
def commit_new(f)
f.truncate(0)
f.rewind
new_file = @filename + ".new"
File.open(new_file, RD_ACCESS) do |nf|
FileUtils.copy_stream(nf, f)
# Constant for relieving Ruby's garbage collector.
EMPTY_STRING = ""
EMPTY_MARSHAL_DATA = Marshal.dump({})
EMPTY_MARSHAL_CHECKSUM = Digest::MD5.digest(EMPTY_MARSHAL_DATA)
class DummyMutex
def synchronize
yield
end
File.unlink(new_file)
end
#
# Open the specified filename (either in read-only mode or in
# read-write mode) and lock it for reading or writing.
#
# The opened File object will be returned. If _read_only_ is true,
# and the file does not exist, then nil will be returned.
#
# All exceptions are propagated.
#
def open_and_lock_file(filename, read_only)
if read_only
begin
file = File.new(filename, RD_ACCESS)
begin
file.flock(File::LOCK_SH)
return file
rescue
file.close
raise
end
rescue Errno::ENOENT
return nil
end
else
file = File.new(filename, RDWR_ACCESS)
file.flock(File::LOCK_EX)
return file
end
end
# Load the given PStore file.
# If +read_only+ is true, the unmarshalled Hash will be returned.
# If +read_only+ is false, a 3-tuple will be returned: the unmarshalled
# Hash, an MD5 checksum of the data, and the size of the data.
def load_data(file, read_only)
if read_only
begin
table = Marshal.load(file)
if !table.is_a?(Hash)
raise Error, "PStore file seems to be corrupted."
end
rescue EOFError
# This seems to be a newly-created file.
table = {}
end
table
else
data = file.read
if data.empty?
# This seems to be a newly-created file.
table = {}
checksum = EMPTY_MARSHAL_CHECKSUM
size = EMPTY_MARSHAL_DATA.size
else
table = Marshal.load(data)
checksum = Digest::MD5.digest(data)
size = data.size
if !table.is_a?(Hash)
raise Error, "PStore file seems to be corrupted."
end
end
data.replace(EMPTY_STRING)
[table, checksum, size]
end
end
def on_windows?
is_windows = RUBY_PLATFORM =~ /mswin/ ||
RUBY_PLATFORM =~ /mingw/ ||
RUBY_PLATFORM =~ /bbcwin/ ||
RUBY_PLATFORM =~ /wince/
self.class.__send__(:define_method, :on_windows?) do
is_windows
end
is_windows
end
# Check whether Marshal.dump supports the 'canonical' option. This option
# makes sure that Marshal.dump always dumps data structures in the same order.
# This is important because otherwise, the checksums that we generate may differ.
def marshal_dump_supports_canonical_option?
begin
Marshal.dump(nil, -1, true)
result = true
rescue
result = false
end
self.class.__send__(:define_method, :marshal_dump_supports_canonical_option?) do
result
end
result
end
def save_data(original_checksum, original_file_size, file)
# We only want to save the new data if the size or checksum has changed.
# This results in less filesystem calls, which is good for performance.
if marshal_dump_supports_canonical_option?
new_data = Marshal.dump(@table, -1, true)
else
new_data = Marshal.dump(@table)
end
new_checksum = Digest::MD5.digest(new_data)
if new_data.size != original_file_size || new_checksum != original_checksum
if @ultra_safe && !on_windows?
# Windows doesn't support atomic file renames.
save_data_with_atomic_file_rename_strategy(new_data, file)
else
save_data_with_fast_strategy(new_data, file)
end
end
new_data.replace(EMPTY_STRING)
end
def save_data_with_atomic_file_rename_strategy(data, file)
temp_filename = "#{@filename}.tmp.#{Process.pid}.#{rand 1000000}"
temp_file = File.new(temp_filename, WR_ACCESS)
begin
temp_file.flock(File::LOCK_EX)
temp_file.write(data)
temp_file.flush
File.rename(temp_filename, @filename)
rescue
File.unlink(temp_file) rescue nil
raise
ensure
temp_file.close
end
end
def save_data_with_fast_strategy(data, file)
file.rewind
file.truncate(0)
file.write(data)
end
end

74
test/test_pstore.rb Normal file
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@ -0,0 +1,74 @@
require 'test/unit'
require 'pstore'
class PStoreTest < Test::Unit::TestCase
def setup
@pstore_file = "pstore.tmp.#{Process.pid}"
@pstore = PStore.new(@pstore_file)
end
def teardown
File.unlink(@pstore_file) rescue nil
end
def test_opening_new_file_in_readonly_mode_should_result_in_empty_values
@pstore.transaction(true) do
assert_nil @pstore[:foo]
assert_nil @pstore[:bar]
end
end
def test_opening_new_file_in_readwrite_mode_should_result_in_empty_values
@pstore.transaction do
assert_nil @pstore[:foo]
assert_nil @pstore[:bar]
end
end
def test_data_should_be_loaded_correctly_when_in_readonly_mode
@pstore.transaction do
@pstore[:foo] = "bar"
end
@pstore.transaction(true) do
assert_equal "bar", @pstore[:foo]
end
end
def test_data_should_be_loaded_correctly_when_in_readwrite_mode
@pstore.transaction do
@pstore[:foo] = "bar"
end
@pstore.transaction do
assert_equal "bar", @pstore[:foo]
end
end
def test_changes_after_commit_are_discarded
@pstore.transaction do
@pstore[:foo] = "bar"
@pstore.commit
@pstore[:foo] = "baz"
end
@pstore.transaction(true) do
assert_equal "bar", @pstore[:foo]
end
end
def test_changes_are_not_written_on_abort
@pstore.transaction do
@pstore[:foo] = "bar"
@pstore.abort
end
@pstore.transaction(true) do
assert_nil @pstore[:foo]
end
end
def test_writing_inside_readonly_transaction_raises_error
assert_raise(PStore::Error) do
@pstore.transaction(true) do
@pstore[:foo] = "bar"
end
end
end
end