1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
#
# How to use:
#
# db = PStore.new("/tmp/foo")
# db.transaction do
# p db.roots
# ary = db["root"] = [1,2,3,4]
# ary[0] = [1,1.5]
# end
# db.transaction do
# p db["root"]
# end
require "ftools"
require "digest/md5"
class PStore
class Error < StandardError
end
def initialize(file)
dir = File::dirname(file)
unless File::directory? dir
raise PStore::Error, format("directory %s does not exist", dir)
end
if File::exist? file and not File::readable? file
raise PStore::Error, format("file %s not readable", file)
end
@transaction = false
@filename = file
@abort = false
end
def in_transaction
raise PStore::Error, "not in transaction" unless @transaction
end
private :in_transaction
def [](name)
in_transaction
@table[name]
end
def fetch(name, default=PStore::Error)
unless @table.key? name
if default==PStore::Error
raise PStore::Error, format("undefined root name `%s'", name)
else
default
end
end
self[name]
end
def []=(name, value)
in_transaction
@table[name] = value
end
def delete(name)
in_transaction
@table.delete name
end
def roots
in_transaction
@table.keys
end
def root?(name)
in_transaction
@table.key? name
end
def path
@filename
end
def commit
in_transaction
@abort = false
throw :pstore_abort_transaction
end
def abort
in_transaction
@abort = true
throw :pstore_abort_transaction
end
def transaction(read_only=false)
raise PStore::Error, "nested transaction" if @transaction
begin
@transaction = true
value = nil
backup = @filename+"~"
begin
file = File::open(@filename, read_only ? "rb" : "rb+")
orig = true
rescue Errno::ENOENT
raise if read_only
file = File::open(@filename, "wb+")
end
file.flock(read_only ? File::LOCK_SH : File::LOCK_EX)
if read_only
@table = Marshal::load(file)
elsif orig and (content = file.read) != ""
@table = Marshal::load(content)
size = content.size
md5 = Digest::MD5.digest(content)
content = nil # unreference huge data
else
@table = {}
end
begin
catch(:pstore_abort_transaction) do
value = yield(self)
end
rescue Exception
@abort = true
raise
ensure
if !read_only and !@abort
file.rewind
content = Marshal::dump(@table)
if !md5 || size != content.size || md5 != Digest::MD5.digest(content)
File::copy @filename, backup
begin
file.write(content)
file.truncate(file.pos)
content = nil # unreference huge data
rescue
File::rename backup, @filename if File::exist?(backup)
raise
end
end
end
if @abort and !orig
File.unlink(@filename)
end
@abort = false
end
ensure
@table = nil
@transaction = false
file.close if file
end
value
end
end
if __FILE__ == $0
db = PStore.new("/tmp/foo")
db.transaction do
p db.roots
ary = db["root"] = [1,2,3,4]
ary[1] = [1,1.5]
end
1000.times do
db.transaction do
db["root"][0] += 1
p db["root"][0]
end
end
db.transaction(true) do
p db["root"]
end
end
|
