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25f64a11 AMS |
1 | # |
2 | # Copyright (c) 1995-2000, Raphael Manfredi | |
3 | # | |
4 | # You may redistribute only under the same terms as Perl 5, as specified | |
5 | # in the README file that comes with the distribution. | |
6 | # | |
7a6a85bf RG |
7 | |
8 | require DynaLoader; | |
9 | require Exporter; | |
10 | package Storable; @ISA = qw(Exporter DynaLoader); | |
11 | ||
12 | @EXPORT = qw(store retrieve); | |
13 | @EXPORT_OK = qw( | |
9e21b3d0 | 14 | nstore store_fd nstore_fd fd_retrieve |
7a6a85bf RG |
15 | freeze nfreeze thaw |
16 | dclone | |
9e21b3d0 | 17 | retrieve_fd |
dd19458b | 18 | lock_store lock_nstore lock_retrieve |
d4b9b6e4 | 19 | file_magic read_magic |
7a6a85bf RG |
20 | ); |
21 | ||
22 | use AutoLoader; | |
ab6f8ca1 | 23 | use FileHandle; |
01d7b99e | 24 | use vars qw($canonical $forgive_me $VERSION); |
7a6a85bf | 25 | |
afce0a13 | 26 | $VERSION = '2.22'; |
7a6a85bf RG |
27 | *AUTOLOAD = \&AutoLoader::AUTOLOAD; # Grrr... |
28 | ||
29 | # | |
30 | # Use of Log::Agent is optional | |
31 | # | |
32 | ||
bb65ef26 AMS |
33 | { |
34 | local $SIG{__DIE__}; | |
35 | eval "use Log::Agent"; | |
36 | } | |
7a6a85bf | 37 | |
530b72ba | 38 | require Carp; |
7a6a85bf | 39 | |
dd19458b JH |
40 | # |
41 | # They might miss :flock in Fcntl | |
42 | # | |
43 | ||
44 | BEGIN { | |
596596d5 | 45 | if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) { |
dd19458b JH |
46 | Fcntl->import(':flock'); |
47 | } else { | |
48 | eval q{ | |
49 | sub LOCK_SH () {1} | |
50 | sub LOCK_EX () {2} | |
51 | }; | |
52 | } | |
53 | } | |
54 | ||
a8b7ef86 AMS |
55 | sub CLONE { |
56 | # clone context under threads | |
57 | Storable::init_perinterp(); | |
58 | } | |
59 | ||
b8778c7c | 60 | # Can't Autoload cleanly as this clashes 8.3 with &retrieve |
9e21b3d0 | 61 | sub retrieve_fd { &fd_retrieve } # Backward compatibility |
cb3d9de5 | 62 | |
530b72ba NC |
63 | # By default restricted hashes are downgraded on earlier perls. |
64 | ||
65 | $Storable::downgrade_restricted = 1; | |
e8189732 | 66 | $Storable::accept_future_minor = 1; |
b8778c7c NC |
67 | bootstrap Storable; |
68 | 1; | |
69 | __END__ | |
530b72ba NC |
70 | # |
71 | # Use of Log::Agent is optional. If it hasn't imported these subs then | |
72 | # Autoloader will kindly supply our fallback implementation. | |
73 | # | |
74 | ||
75 | sub logcroak { | |
76 | Carp::croak(@_); | |
77 | } | |
78 | ||
79 | sub logcarp { | |
80 | Carp::carp(@_); | |
81 | } | |
b8778c7c | 82 | |
862382c7 JH |
83 | # |
84 | # Determine whether locking is possible, but only when needed. | |
85 | # | |
86 | ||
530b72ba | 87 | sub CAN_FLOCK; my $CAN_FLOCK; sub CAN_FLOCK { |
862382c7 JH |
88 | return $CAN_FLOCK if defined $CAN_FLOCK; |
89 | require Config; import Config; | |
90 | return $CAN_FLOCK = | |
91 | $Config{'d_flock'} || | |
92 | $Config{'d_fcntl_can_lock'} || | |
93 | $Config{'d_lockf'}; | |
94 | } | |
95 | ||
0a0da639 JH |
96 | sub show_file_magic { |
97 | print <<EOM; | |
98 | # | |
99 | # To recognize the data files of the Perl module Storable, | |
100 | # the following lines need to be added to the local magic(5) file, | |
101 | # usually either /usr/share/misc/magic or /etc/magic. | |
0a0da639 JH |
102 | # |
103 | 0 string perl-store perl Storable(v0.6) data | |
8b793558 JH |
104 | >4 byte >0 (net-order %d) |
105 | >>4 byte &01 (network-ordered) | |
106 | >>4 byte =3 (major 1) | |
107 | >>4 byte =2 (major 1) | |
108 | ||
0a0da639 | 109 | 0 string pst0 perl Storable(v0.7) data |
8b793558 JH |
110 | >4 byte >0 |
111 | >>4 byte &01 (network-ordered) | |
112 | >>4 byte =5 (major 2) | |
113 | >>4 byte =4 (major 2) | |
114 | >>5 byte >0 (minor %d) | |
0a0da639 JH |
115 | EOM |
116 | } | |
117 | ||
d4b9b6e4 GA |
118 | sub file_magic { |
119 | my $file = shift; | |
ab6f8ca1 AT |
120 | my $fh = new FileHandle; |
121 | open($fh, "<". $file) || die "Can't open '$file': $!"; | |
d4b9b6e4 GA |
122 | binmode($fh); |
123 | defined(sysread($fh, my $buf, 32)) || die "Can't read from '$file': $!"; | |
124 | close($fh); | |
125 | ||
126 | $file = "./$file" unless $file; # ensure TRUE value | |
127 | ||
128 | return read_magic($buf, $file); | |
129 | } | |
130 | ||
b8778c7c | 131 | sub read_magic { |
d4b9b6e4 GA |
132 | my($buf, $file) = @_; |
133 | my %info; | |
134 | ||
135 | my $buflen = length($buf); | |
136 | my $magic; | |
137 | if ($buf =~ s/^(pst0|perl-store)//) { | |
138 | $magic = $1; | |
139 | $info{file} = $file || 1; | |
140 | } | |
141 | else { | |
142 | return undef if $file; | |
143 | $magic = ""; | |
144 | } | |
145 | ||
146 | return undef unless length($buf); | |
147 | ||
148 | my $net_order; | |
149 | if ($magic eq "perl-store" && ord(substr($buf, 0, 1)) > 1) { | |
150 | $info{version} = -1; | |
151 | $net_order = 0; | |
152 | } | |
153 | else { | |
154 | $net_order = ord(substr($buf, 0, 1, "")); | |
155 | my $major = $net_order >> 1; | |
156 | return undef if $major > 4; # sanity (assuming we never go that high) | |
157 | $info{major} = $major; | |
158 | $net_order &= 0x01; | |
159 | if ($major > 1) { | |
160 | return undef unless length($buf); | |
161 | my $minor = ord(substr($buf, 0, 1, "")); | |
162 | $info{minor} = $minor; | |
163 | $info{version} = "$major.$minor"; | |
164 | $info{version_nv} = sprintf "%d.%03d", $major, $minor; | |
165 | } | |
166 | else { | |
167 | $info{version} = $major; | |
168 | } | |
169 | } | |
170 | $info{version_nv} ||= $info{version}; | |
171 | $info{netorder} = $net_order; | |
172 | ||
173 | unless ($net_order) { | |
174 | return undef unless length($buf); | |
175 | my $len = ord(substr($buf, 0, 1, "")); | |
176 | return undef unless length($buf) >= $len; | |
177 | return undef unless $len == 4 || $len == 8; # sanity | |
178 | $info{byteorder} = substr($buf, 0, $len, ""); | |
179 | $info{intsize} = ord(substr($buf, 0, 1, "")); | |
180 | $info{longsize} = ord(substr($buf, 0, 1, "")); | |
181 | $info{ptrsize} = ord(substr($buf, 0, 1, "")); | |
182 | if ($info{version_nv} >= 2.002) { | |
183 | return undef unless length($buf); | |
184 | $info{nvsize} = ord(substr($buf, 0, 1, "")); | |
185 | } | |
186 | } | |
187 | $info{hdrsize} = $buflen - length($buf); | |
188 | ||
189 | return \%info; | |
190 | } | |
191 | ||
192 | sub BIN_VERSION_NV { | |
193 | sprintf "%d.%03d", BIN_MAJOR(), BIN_MINOR(); | |
194 | } | |
195 | ||
196 | sub BIN_WRITE_VERSION_NV { | |
197 | sprintf "%d.%03d", BIN_MAJOR(), BIN_WRITE_MINOR(); | |
b8778c7c | 198 | } |
7a6a85bf RG |
199 | |
200 | # | |
201 | # store | |
202 | # | |
203 | # Store target object hierarchy, identified by a reference to its root. | |
204 | # The stored object tree may later be retrieved to memory via retrieve. | |
205 | # Returns undef if an I/O error occurred, in which case the file is | |
206 | # removed. | |
207 | # | |
208 | sub store { | |
dd19458b | 209 | return _store(\&pstore, @_, 0); |
7a6a85bf RG |
210 | } |
211 | ||
212 | # | |
213 | # nstore | |
214 | # | |
215 | # Same as store, but in network order. | |
216 | # | |
217 | sub nstore { | |
dd19458b JH |
218 | return _store(\&net_pstore, @_, 0); |
219 | } | |
220 | ||
221 | # | |
222 | # lock_store | |
223 | # | |
224 | # Same as store, but flock the file first (advisory locking). | |
225 | # | |
226 | sub lock_store { | |
227 | return _store(\&pstore, @_, 1); | |
228 | } | |
229 | ||
230 | # | |
231 | # lock_nstore | |
232 | # | |
233 | # Same as nstore, but flock the file first (advisory locking). | |
234 | # | |
235 | sub lock_nstore { | |
236 | return _store(\&net_pstore, @_, 1); | |
7a6a85bf RG |
237 | } |
238 | ||
239 | # Internal store to file routine | |
240 | sub _store { | |
241 | my $xsptr = shift; | |
242 | my $self = shift; | |
dd19458b | 243 | my ($file, $use_locking) = @_; |
7a6a85bf | 244 | logcroak "not a reference" unless ref($self); |
b12202d0 | 245 | logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist |
7a6a85bf | 246 | local *FILE; |
dd19458b | 247 | if ($use_locking) { |
6e0ac6f5 | 248 | open(FILE, ">>$file") || logcroak "can't write into $file: $!"; |
862382c7 | 249 | unless (&CAN_FLOCK) { |
b29b780f RM |
250 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
251 | return undef; | |
f567092b | 252 | } |
dd19458b JH |
253 | flock(FILE, LOCK_EX) || |
254 | logcroak "can't get exclusive lock on $file: $!"; | |
255 | truncate FILE, 0; | |
256 | # Unlocking will happen when FILE is closed | |
6e0ac6f5 JH |
257 | } else { |
258 | open(FILE, ">$file") || logcroak "can't create $file: $!"; | |
dd19458b | 259 | } |
6e0ac6f5 | 260 | binmode FILE; # Archaic systems... |
7a6a85bf RG |
261 | my $da = $@; # Don't mess if called from exception handler |
262 | my $ret; | |
263 | # Call C routine nstore or pstore, depending on network order | |
264 | eval { $ret = &$xsptr(*FILE, $self) }; | |
265 | close(FILE) or $ret = undef; | |
266 | unlink($file) or warn "Can't unlink $file: $!\n" if $@ || !defined $ret; | |
267 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
268 | $@ = $da; | |
269 | return $ret ? $ret : undef; | |
270 | } | |
271 | ||
272 | # | |
273 | # store_fd | |
274 | # | |
275 | # Same as store, but perform on an already opened file descriptor instead. | |
276 | # Returns undef if an I/O error occurred. | |
277 | # | |
278 | sub store_fd { | |
279 | return _store_fd(\&pstore, @_); | |
280 | } | |
281 | ||
282 | # | |
283 | # nstore_fd | |
284 | # | |
285 | # Same as store_fd, but in network order. | |
286 | # | |
287 | sub nstore_fd { | |
288 | my ($self, $file) = @_; | |
289 | return _store_fd(\&net_pstore, @_); | |
290 | } | |
291 | ||
292 | # Internal store routine on opened file descriptor | |
293 | sub _store_fd { | |
294 | my $xsptr = shift; | |
295 | my $self = shift; | |
296 | my ($file) = @_; | |
297 | logcroak "not a reference" unless ref($self); | |
298 | logcroak "too many arguments" unless @_ == 1; # No @foo in arglist | |
299 | my $fd = fileno($file); | |
300 | logcroak "not a valid file descriptor" unless defined $fd; | |
301 | my $da = $@; # Don't mess if called from exception handler | |
302 | my $ret; | |
303 | # Call C routine nstore or pstore, depending on network order | |
304 | eval { $ret = &$xsptr($file, $self) }; | |
305 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
596596d5 | 306 | local $\; print $file ''; # Autoflush the file if wanted |
7a6a85bf RG |
307 | $@ = $da; |
308 | return $ret ? $ret : undef; | |
309 | } | |
310 | ||
311 | # | |
312 | # freeze | |
313 | # | |
314 | # Store oject and its hierarchy in memory and return a scalar | |
315 | # containing the result. | |
316 | # | |
317 | sub freeze { | |
318 | _freeze(\&mstore, @_); | |
319 | } | |
320 | ||
321 | # | |
322 | # nfreeze | |
323 | # | |
324 | # Same as freeze but in network order. | |
325 | # | |
326 | sub nfreeze { | |
327 | _freeze(\&net_mstore, @_); | |
328 | } | |
329 | ||
330 | # Internal freeze routine | |
331 | sub _freeze { | |
332 | my $xsptr = shift; | |
333 | my $self = shift; | |
334 | logcroak "not a reference" unless ref($self); | |
335 | logcroak "too many arguments" unless @_ == 0; # No @foo in arglist | |
336 | my $da = $@; # Don't mess if called from exception handler | |
337 | my $ret; | |
338 | # Call C routine mstore or net_mstore, depending on network order | |
339 | eval { $ret = &$xsptr($self) }; | |
340 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
341 | $@ = $da; | |
342 | return $ret ? $ret : undef; | |
343 | } | |
344 | ||
345 | # | |
346 | # retrieve | |
347 | # | |
348 | # Retrieve object hierarchy from disk, returning a reference to the root | |
349 | # object of that tree. | |
350 | # | |
351 | sub retrieve { | |
dd19458b JH |
352 | _retrieve($_[0], 0); |
353 | } | |
354 | ||
355 | # | |
356 | # lock_retrieve | |
357 | # | |
358 | # Same as retrieve, but with advisory locking. | |
359 | # | |
360 | sub lock_retrieve { | |
361 | _retrieve($_[0], 1); | |
362 | } | |
363 | ||
364 | # Internal retrieve routine | |
365 | sub _retrieve { | |
366 | my ($file, $use_locking) = @_; | |
7a6a85bf | 367 | local *FILE; |
dd19458b | 368 | open(FILE, $file) || logcroak "can't open $file: $!"; |
7a6a85bf RG |
369 | binmode FILE; # Archaic systems... |
370 | my $self; | |
371 | my $da = $@; # Could be from exception handler | |
dd19458b | 372 | if ($use_locking) { |
862382c7 | 373 | unless (&CAN_FLOCK) { |
8be2b38b | 374 | logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O"; |
b29b780f RM |
375 | return undef; |
376 | } | |
8be2b38b | 377 | flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!"; |
dd19458b JH |
378 | # Unlocking will happen when FILE is closed |
379 | } | |
7a6a85bf RG |
380 | eval { $self = pretrieve(*FILE) }; # Call C routine |
381 | close(FILE); | |
382 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
383 | $@ = $da; | |
384 | return $self; | |
385 | } | |
386 | ||
387 | # | |
9e21b3d0 | 388 | # fd_retrieve |
7a6a85bf RG |
389 | # |
390 | # Same as retrieve, but perform from an already opened file descriptor instead. | |
391 | # | |
9e21b3d0 | 392 | sub fd_retrieve { |
7a6a85bf RG |
393 | my ($file) = @_; |
394 | my $fd = fileno($file); | |
395 | logcroak "not a valid file descriptor" unless defined $fd; | |
396 | my $self; | |
397 | my $da = $@; # Could be from exception handler | |
398 | eval { $self = pretrieve($file) }; # Call C routine | |
399 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
400 | $@ = $da; | |
401 | return $self; | |
402 | } | |
403 | ||
404 | # | |
405 | # thaw | |
406 | # | |
407 | # Recreate objects in memory from an existing frozen image created | |
408 | # by freeze. If the frozen image passed is undef, return undef. | |
409 | # | |
410 | sub thaw { | |
411 | my ($frozen) = @_; | |
412 | return undef unless defined $frozen; | |
413 | my $self; | |
414 | my $da = $@; # Could be from exception handler | |
415 | eval { $self = mretrieve($frozen) }; # Call C routine | |
416 | logcroak $@ if $@ =~ s/\.?\n$/,/; | |
417 | $@ = $da; | |
418 | return $self; | |
419 | } | |
420 | ||
a2307be4 NC |
421 | 1; |
422 | __END__ | |
423 | ||
7a6a85bf RG |
424 | =head1 NAME |
425 | ||
f062ea6c | 426 | Storable - persistence for Perl data structures |
7a6a85bf RG |
427 | |
428 | =head1 SYNOPSIS | |
429 | ||
430 | use Storable; | |
431 | store \%table, 'file'; | |
432 | $hashref = retrieve('file'); | |
433 | ||
434 | use Storable qw(nstore store_fd nstore_fd freeze thaw dclone); | |
435 | ||
436 | # Network order | |
437 | nstore \%table, 'file'; | |
438 | $hashref = retrieve('file'); # There is NO nretrieve() | |
439 | ||
440 | # Storing to and retrieving from an already opened file | |
441 | store_fd \@array, \*STDOUT; | |
442 | nstore_fd \%table, \*STDOUT; | |
9e21b3d0 JH |
443 | $aryref = fd_retrieve(\*SOCKET); |
444 | $hashref = fd_retrieve(\*SOCKET); | |
7a6a85bf RG |
445 | |
446 | # Serializing to memory | |
447 | $serialized = freeze \%table; | |
448 | %table_clone = %{ thaw($serialized) }; | |
449 | ||
450 | # Deep (recursive) cloning | |
451 | $cloneref = dclone($ref); | |
452 | ||
dd19458b JH |
453 | # Advisory locking |
454 | use Storable qw(lock_store lock_nstore lock_retrieve) | |
455 | lock_store \%table, 'file'; | |
456 | lock_nstore \%table, 'file'; | |
457 | $hashref = lock_retrieve('file'); | |
458 | ||
7a6a85bf RG |
459 | =head1 DESCRIPTION |
460 | ||
f062ea6c | 461 | The Storable package brings persistence to your Perl data structures |
7a6a85bf | 462 | containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be |
c261f00e | 463 | conveniently stored to disk and retrieved at a later time. |
7a6a85bf RG |
464 | |
465 | It can be used in the regular procedural way by calling C<store> with | |
466 | a reference to the object to be stored, along with the file name where | |
467 | the image should be written. | |
775ecd75 | 468 | |
7a6a85bf RG |
469 | The routine returns C<undef> for I/O problems or other internal error, |
470 | a true value otherwise. Serious errors are propagated as a C<die> exception. | |
471 | ||
f062ea6c PN |
472 | To retrieve data stored to disk, use C<retrieve> with a file name. |
473 | The objects stored into that file are recreated into memory for you, | |
474 | and a I<reference> to the root object is returned. In case an I/O error | |
7a6a85bf RG |
475 | occurs while reading, C<undef> is returned instead. Other serious |
476 | errors are propagated via C<die>. | |
477 | ||
478 | Since storage is performed recursively, you might want to stuff references | |
479 | to objects that share a lot of common data into a single array or hash | |
480 | table, and then store that object. That way, when you retrieve back the | |
481 | whole thing, the objects will continue to share what they originally shared. | |
482 | ||
483 | At the cost of a slight header overhead, you may store to an already | |
484 | opened file descriptor using the C<store_fd> routine, and retrieve | |
9e21b3d0 | 485 | from a file via C<fd_retrieve>. Those names aren't imported by default, |
c261f00e | 486 | so you will have to do that explicitly if you need those routines. |
7a6a85bf RG |
487 | The file descriptor you supply must be already opened, for read |
488 | if you're going to retrieve and for write if you wish to store. | |
489 | ||
490 | store_fd(\%table, *STDOUT) || die "can't store to stdout\n"; | |
9e21b3d0 | 491 | $hashref = fd_retrieve(*STDIN); |
7a6a85bf RG |
492 | |
493 | You can also store data in network order to allow easy sharing across | |
494 | multiple platforms, or when storing on a socket known to be remotely | |
495 | connected. The routines to call have an initial C<n> prefix for I<network>, | |
496 | as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be | |
497 | correctly restored so you don't have to know whether you're restoring | |
dd19458b JH |
498 | from native or network ordered data. Double values are stored stringified |
499 | to ensure portability as well, at the slight risk of loosing some precision | |
500 | in the last decimals. | |
7a6a85bf | 501 | |
9e21b3d0 | 502 | When using C<fd_retrieve>, objects are retrieved in sequence, one |
7a6a85bf RG |
503 | object (i.e. one recursive tree) per associated C<store_fd>. |
504 | ||
505 | If you're more from the object-oriented camp, you can inherit from | |
506 | Storable and directly store your objects by invoking C<store> as | |
507 | a method. The fact that the root of the to-be-stored tree is a | |
508 | blessed reference (i.e. an object) is special-cased so that the | |
509 | retrieve does not provide a reference to that object but rather the | |
510 | blessed object reference itself. (Otherwise, you'd get a reference | |
511 | to that blessed object). | |
512 | ||
513 | =head1 MEMORY STORE | |
514 | ||
515 | The Storable engine can also store data into a Perl scalar instead, to | |
516 | later retrieve them. This is mainly used to freeze a complex structure in | |
517 | some safe compact memory place (where it can possibly be sent to another | |
518 | process via some IPC, since freezing the structure also serializes it in | |
519 | effect). Later on, and maybe somewhere else, you can thaw the Perl scalar | |
520 | out and recreate the original complex structure in memory. | |
521 | ||
522 | Surprisingly, the routines to be called are named C<freeze> and C<thaw>. | |
523 | If you wish to send out the frozen scalar to another machine, use | |
524 | C<nfreeze> instead to get a portable image. | |
525 | ||
526 | Note that freezing an object structure and immediately thawing it | |
527 | actually achieves a deep cloning of that structure: | |
528 | ||
529 | dclone(.) = thaw(freeze(.)) | |
530 | ||
531 | Storable provides you with a C<dclone> interface which does not create | |
532 | that intermediary scalar but instead freezes the structure in some | |
c261f00e | 533 | internal memory space and then immediately thaws it out. |
7a6a85bf | 534 | |
dd19458b JH |
535 | =head1 ADVISORY LOCKING |
536 | ||
f062ea6c PN |
537 | The C<lock_store> and C<lock_nstore> routine are equivalent to |
538 | C<store> and C<nstore>, except that they get an exclusive lock on | |
539 | the file before writing. Likewise, C<lock_retrieve> does the same | |
540 | as C<retrieve>, but also gets a shared lock on the file before reading. | |
dd19458b | 541 | |
f062ea6c PN |
542 | As with any advisory locking scheme, the protection only works if you |
543 | systematically use C<lock_store> and C<lock_retrieve>. If one side of | |
544 | your application uses C<store> whilst the other uses C<lock_retrieve>, | |
dd19458b JH |
545 | you will get no protection at all. |
546 | ||
f062ea6c PN |
547 | The internal advisory locking is implemented using Perl's flock() |
548 | routine. If your system does not support any form of flock(), or if | |
549 | you share your files across NFS, you might wish to use other forms | |
550 | of locking by using modules such as LockFile::Simple which lock a | |
551 | file using a filesystem entry, instead of locking the file descriptor. | |
dd19458b | 552 | |
7a6a85bf RG |
553 | =head1 SPEED |
554 | ||
555 | The heart of Storable is written in C for decent speed. Extra low-level | |
4d3295e3 PN |
556 | optimizations have been made when manipulating perl internals, to |
557 | sacrifice encapsulation for the benefit of greater speed. | |
7a6a85bf RG |
558 | |
559 | =head1 CANONICAL REPRESENTATION | |
560 | ||
f062ea6c | 561 | Normally, Storable stores elements of hashes in the order they are |
7a6a85bf RG |
562 | stored internally by Perl, i.e. pseudo-randomly. If you set |
563 | C<$Storable::canonical> to some C<TRUE> value, Storable will store | |
564 | hashes with the elements sorted by their key. This allows you to | |
565 | compare data structures by comparing their frozen representations (or | |
566 | even the compressed frozen representations), which can be useful for | |
567 | creating lookup tables for complicated queries. | |
568 | ||
f062ea6c | 569 | Canonical order does not imply network order; those are two orthogonal |
7a6a85bf RG |
570 | settings. |
571 | ||
d2b96869 SR |
572 | =head1 CODE REFERENCES |
573 | ||
574 | Since Storable version 2.05, CODE references may be serialized with | |
575 | the help of L<B::Deparse>. To enable this feature, set | |
3c4b39be | 576 | C<$Storable::Deparse> to a true value. To enable deserialization, |
d2b96869 SR |
577 | C<$Storable::Eval> should be set to a true value. Be aware that |
578 | deserialization is done through C<eval>, which is dangerous if the | |
579 | Storable file contains malicious data. You can set C<$Storable::Eval> | |
580 | to a subroutine reference which would be used instead of C<eval>. See | |
581 | below for an example using a L<Safe> compartment for deserialization | |
582 | of CODE references. | |
583 | ||
197b90bc SR |
584 | If C<$Storable::Deparse> and/or C<$Storable::Eval> are set to false |
585 | values, then the value of C<$Storable::forgive_me> (see below) is | |
586 | respected while serializing and deserializing. | |
587 | ||
c261f00e NC |
588 | =head1 FORWARD COMPATIBILITY |
589 | ||
590 | This release of Storable can be used on a newer version of Perl to | |
f062ea6c | 591 | serialize data which is not supported by earlier Perls. By default, |
c261f00e | 592 | Storable will attempt to do the right thing, by C<croak()>ing if it |
775ecd75 | 593 | encounters data that it cannot deserialize. However, the defaults |
f062ea6c | 594 | can be changed as follows: |
c261f00e NC |
595 | |
596 | =over 4 | |
597 | ||
598 | =item utf8 data | |
599 | ||
600 | Perl 5.6 added support for Unicode characters with code points > 255, | |
601 | and Perl 5.8 has full support for Unicode characters in hash keys. | |
602 | Perl internally encodes strings with these characters using utf8, and | |
603 | Storable serializes them as utf8. By default, if an older version of | |
604 | Perl encounters a utf8 value it cannot represent, it will C<croak()>. | |
605 | To change this behaviour so that Storable deserializes utf8 encoded | |
606 | values as the string of bytes (effectively dropping the I<is_utf8> flag) | |
607 | set C<$Storable::drop_utf8> to some C<TRUE> value. This is a form of | |
608 | data loss, because with C<$drop_utf8> true, it becomes impossible to tell | |
609 | whether the original data was the Unicode string, or a series of bytes | |
610 | that happen to be valid utf8. | |
611 | ||
612 | =item restricted hashes | |
613 | ||
f062ea6c PN |
614 | Perl 5.8 adds support for restricted hashes, which have keys |
615 | restricted to a given set, and can have values locked to be read only. | |
616 | By default, when Storable encounters a restricted hash on a perl | |
617 | that doesn't support them, it will deserialize it as a normal hash, | |
618 | silently discarding any placeholder keys and leaving the keys and | |
619 | all values unlocked. To make Storable C<croak()> instead, set | |
620 | C<$Storable::downgrade_restricted> to a C<FALSE> value. To restore | |
621 | the default set it back to some C<TRUE> value. | |
c261f00e | 622 | |
e8189732 NC |
623 | =item files from future versions of Storable |
624 | ||
625 | Earlier versions of Storable would immediately croak if they encountered | |
626 | a file with a higher internal version number than the reading Storable | |
627 | knew about. Internal version numbers are increased each time new data | |
628 | types (such as restricted hashes) are added to the vocabulary of the file | |
629 | format. This meant that a newer Storable module had no way of writing a | |
f062ea6c | 630 | file readable by an older Storable, even if the writer didn't store newer |
e8189732 NC |
631 | data types. |
632 | ||
633 | This version of Storable will defer croaking until it encounters a data | |
634 | type in the file that it does not recognize. This means that it will | |
635 | continue to read files generated by newer Storable modules which are careful | |
636 | in what they write out, making it easier to upgrade Storable modules in a | |
637 | mixed environment. | |
638 | ||
639 | The old behaviour of immediate croaking can be re-instated by setting | |
f062ea6c | 640 | C<$Storable::accept_future_minor> to some C<FALSE> value. |
e8189732 | 641 | |
c261f00e NC |
642 | =back |
643 | ||
f062ea6c | 644 | All these variables have no effect on a newer Perl which supports the |
c261f00e NC |
645 | relevant feature. |
646 | ||
7a6a85bf RG |
647 | =head1 ERROR REPORTING |
648 | ||
649 | Storable uses the "exception" paradigm, in that it does not try to workaround | |
650 | failures: if something bad happens, an exception is generated from the | |
651 | caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap | |
652 | those exceptions. | |
653 | ||
654 | When Storable croaks, it tries to report the error via the C<logcroak()> | |
655 | routine from the C<Log::Agent> package, if it is available. | |
656 | ||
212e9bde JH |
657 | Normal errors are reported by having store() or retrieve() return C<undef>. |
658 | Such errors are usually I/O errors (or truncated stream errors at retrieval). | |
659 | ||
7a6a85bf RG |
660 | =head1 WIZARDS ONLY |
661 | ||
662 | =head2 Hooks | |
663 | ||
664 | Any class may define hooks that will be called during the serialization | |
665 | and deserialization process on objects that are instances of that class. | |
666 | Those hooks can redefine the way serialization is performed (and therefore, | |
c261f00e | 667 | how the symmetrical deserialization should be conducted). |
7a6a85bf RG |
668 | |
669 | Since we said earlier: | |
670 | ||
671 | dclone(.) = thaw(freeze(.)) | |
672 | ||
673 | everything we say about hooks should also hold for deep cloning. However, | |
674 | hooks get to know whether the operation is a mere serialization, or a cloning. | |
675 | ||
676 | Therefore, when serializing hooks are involved, | |
677 | ||
678 | dclone(.) <> thaw(freeze(.)) | |
679 | ||
680 | Well, you could keep them in sync, but there's no guarantee it will always | |
681 | hold on classes somebody else wrote. Besides, there is little to gain in | |
f062ea6c | 682 | doing so: a serializing hook could keep only one attribute of an object, |
7a6a85bf RG |
683 | which is probably not what should happen during a deep cloning of that |
684 | same object. | |
685 | ||
686 | Here is the hooking interface: | |
687 | ||
bbc7dcd2 | 688 | =over 4 |
7a6a85bf RG |
689 | |
690 | =item C<STORABLE_freeze> I<obj>, I<cloning> | |
691 | ||
692 | The serializing hook, called on the object during serialization. It can be | |
693 | inherited, or defined in the class itself, like any other method. | |
694 | ||
695 | Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating | |
696 | whether we're in a dclone() or a regular serialization via store() or freeze(). | |
697 | ||
698 | Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized | |
699 | is the serialized form to be used, and the optional $ref1, $ref2, etc... are | |
700 | extra references that you wish to let the Storable engine serialize. | |
701 | ||
702 | At deserialization time, you will be given back the same LIST, but all the | |
703 | extra references will be pointing into the deserialized structure. | |
704 | ||
705 | The B<first time> the hook is hit in a serialization flow, you may have it | |
706 | return an empty list. That will signal the Storable engine to further | |
707 | discard that hook for this class and to therefore revert to the default | |
708 | serialization of the underlying Perl data. The hook will again be normally | |
709 | processed in the next serialization. | |
710 | ||
711 | Unless you know better, serializing hook should always say: | |
712 | ||
713 | sub STORABLE_freeze { | |
714 | my ($self, $cloning) = @_; | |
715 | return if $cloning; # Regular default serialization | |
716 | .... | |
717 | } | |
718 | ||
719 | in order to keep reasonable dclone() semantics. | |
720 | ||
721 | =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ... | |
722 | ||
723 | The deserializing hook called on the object during deserialization. | |
f062ea6c | 724 | But wait: if we're deserializing, there's no object yet... right? |
7a6a85bf RG |
725 | |
726 | Wrong: the Storable engine creates an empty one for you. If you know Eiffel, | |
727 | you can view C<STORABLE_thaw> as an alternate creation routine. | |
728 | ||
729 | This means the hook can be inherited like any other method, and that | |
730 | I<obj> is your blessed reference for this particular instance. | |
731 | ||
732 | The other arguments should look familiar if you know C<STORABLE_freeze>: | |
733 | I<cloning> is true when we're part of a deep clone operation, I<serialized> | |
734 | is the serialized string you returned to the engine in C<STORABLE_freeze>, | |
735 | and there may be an optional list of references, in the same order you gave | |
736 | them at serialization time, pointing to the deserialized objects (which | |
737 | have been processed courtesy of the Storable engine). | |
738 | ||
212e9bde JH |
739 | When the Storable engine does not find any C<STORABLE_thaw> hook routine, |
740 | it tries to load the class by requiring the package dynamically (using | |
741 | the blessed package name), and then re-attempts the lookup. If at that | |
742 | time the hook cannot be located, the engine croaks. Note that this mechanism | |
c261f00e | 743 | will fail if you define several classes in the same file, but L<perlmod> |
212e9bde JH |
744 | warned you. |
745 | ||
f062ea6c | 746 | It is up to you to use this information to populate I<obj> the way you want. |
7a6a85bf RG |
747 | |
748 | Returned value: none. | |
749 | ||
2f796f32 AMS |
750 | =item C<STORABLE_attach> I<class>, I<cloning>, I<serialized> |
751 | ||
752 | While C<STORABLE_freeze> and C<STORABLE_thaw> are useful for classes where | |
3c4b39be | 753 | each instance is independent, this mechanism has difficulty (or is |
2f796f32 AMS |
754 | incompatible) with objects that exist as common process-level or |
755 | system-level resources, such as singleton objects, database pools, caches | |
756 | or memoized objects. | |
757 | ||
758 | The alternative C<STORABLE_attach> method provides a solution for these | |
1e2a0f0b RGS |
759 | shared objects. Instead of C<STORABLE_freeze> --E<gt> C<STORABLE_thaw>, |
760 | you implement C<STORABLE_freeze> --E<gt> C<STORABLE_attach> instead. | |
2f796f32 AMS |
761 | |
762 | Arguments: I<class> is the class we are attaching to, I<cloning> is a flag | |
763 | indicating whether we're in a dclone() or a regular de-serialization via | |
764 | thaw(), and I<serialized> is the stored string for the resource object. | |
765 | ||
766 | Because these resource objects are considered to be owned by the entire | |
767 | process/system, and not the "property" of whatever is being serialized, | |
768 | no references underneath the object should be included in the serialized | |
769 | string. Thus, in any class that implements C<STORABLE_attach>, the | |
770 | C<STORABLE_freeze> method cannot return any references, and C<Storable> | |
771 | will throw an error if C<STORABLE_freeze> tries to return references. | |
772 | ||
773 | All information required to "attach" back to the shared resource object | |
774 | B<must> be contained B<only> in the C<STORABLE_freeze> return string. | |
775 | Otherwise, C<STORABLE_freeze> behaves as normal for C<STORABLE_attach> | |
776 | classes. | |
777 | ||
778 | Because C<STORABLE_attach> is passed the class (rather than an object), | |
779 | it also returns the object directly, rather than modifying the passed | |
780 | object. | |
781 | ||
782 | Returned value: object of type C<class> | |
783 | ||
7a6a85bf RG |
784 | =back |
785 | ||
786 | =head2 Predicates | |
787 | ||
c261f00e | 788 | Predicates are not exportable. They must be called by explicitly prefixing |
7a6a85bf RG |
789 | them with the Storable package name. |
790 | ||
bbc7dcd2 | 791 | =over 4 |
7a6a85bf RG |
792 | |
793 | =item C<Storable::last_op_in_netorder> | |
794 | ||
795 | The C<Storable::last_op_in_netorder()> predicate will tell you whether | |
796 | network order was used in the last store or retrieve operation. If you | |
797 | don't know how to use this, just forget about it. | |
798 | ||
799 | =item C<Storable::is_storing> | |
800 | ||
801 | Returns true if within a store operation (via STORABLE_freeze hook). | |
802 | ||
803 | =item C<Storable::is_retrieving> | |
804 | ||
f062ea6c | 805 | Returns true if within a retrieve operation (via STORABLE_thaw hook). |
7a6a85bf RG |
806 | |
807 | =back | |
808 | ||
809 | =head2 Recursion | |
810 | ||
f062ea6c PN |
811 | With hooks comes the ability to recurse back to the Storable engine. |
812 | Indeed, hooks are regular Perl code, and Storable is convenient when | |
813 | it comes to serializing and deserializing things, so why not use it | |
814 | to handle the serialization string? | |
7a6a85bf | 815 | |
f062ea6c | 816 | There are a few things you need to know, however: |
7a6a85bf | 817 | |
bbc7dcd2 | 818 | =over 4 |
7a6a85bf RG |
819 | |
820 | =item * | |
821 | ||
822 | You can create endless loops if the things you serialize via freeze() | |
f062ea6c PN |
823 | (for instance) point back to the object we're trying to serialize in |
824 | the hook. | |
7a6a85bf RG |
825 | |
826 | =item * | |
827 | ||
828 | Shared references among objects will not stay shared: if we're serializing | |
829 | the list of object [A, C] where both object A and C refer to the SAME object | |
830 | B, and if there is a serializing hook in A that says freeze(B), then when | |
831 | deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D, | |
832 | a deep clone of B'. The topology was not preserved. | |
833 | ||
834 | =back | |
835 | ||
836 | That's why C<STORABLE_freeze> lets you provide a list of references | |
837 | to serialize. The engine guarantees that those will be serialized in the | |
838 | same context as the other objects, and therefore that shared objects will | |
839 | stay shared. | |
840 | ||
841 | In the above [A, C] example, the C<STORABLE_freeze> hook could return: | |
842 | ||
843 | ("something", $self->{B}) | |
844 | ||
845 | and the B part would be serialized by the engine. In C<STORABLE_thaw>, you | |
846 | would get back the reference to the B' object, deserialized for you. | |
847 | ||
848 | Therefore, recursion should normally be avoided, but is nonetheless supported. | |
849 | ||
850 | =head2 Deep Cloning | |
851 | ||
f062ea6c | 852 | There is a Clone module available on CPAN which implements deep cloning |
7a6a85bf RG |
853 | natively, i.e. without freezing to memory and thawing the result. It is |
854 | aimed to replace Storable's dclone() some day. However, it does not currently | |
855 | support Storable hooks to redefine the way deep cloning is performed. | |
856 | ||
0a0da639 JH |
857 | =head1 Storable magic |
858 | ||
859 | Yes, there's a lot of that :-) But more precisely, in UNIX systems | |
860 | there's a utility called C<file>, which recognizes data files based on | |
861 | their contents (usually their first few bytes). For this to work, | |
8b793558 | 862 | a certain file called F<magic> needs to taught about the I<signature> |
0a0da639 | 863 | of the data. Where that configuration file lives depends on the UNIX |
f062ea6c | 864 | flavour; often it's something like F</usr/share/misc/magic> or |
8b793558 JH |
865 | F</etc/magic>. Your system administrator needs to do the updating of |
866 | the F<magic> file. The necessary signature information is output to | |
f062ea6c PN |
867 | STDOUT by invoking Storable::show_file_magic(). Note that the GNU |
868 | implementation of the C<file> utility, version 3.38 or later, | |
869 | is expected to contain support for recognising Storable files | |
870 | out-of-the-box, in addition to other kinds of Perl files. | |
0a0da639 | 871 | |
d4b9b6e4 GA |
872 | You can also use the following functions to extract the file header |
873 | information from Storable images: | |
874 | ||
875 | =over | |
876 | ||
877 | =item $info = Storable::file_magic( $filename ) | |
878 | ||
879 | If the given file is a Storable image return a hash describing it. If | |
880 | the file is readable, but not a Storable image return C<undef>. If | |
881 | the file does not exist or is unreadable then croak. | |
882 | ||
883 | The hash returned has the following elements: | |
884 | ||
885 | =over | |
886 | ||
887 | =item C<version> | |
888 | ||
889 | This returns the file format version. It is a string like "2.7". | |
890 | ||
891 | Note that this version number is not the same as the version number of | |
892 | the Storable module itself. For instance Storable v0.7 create files | |
893 | in format v2.0 and Storable v2.15 create files in format v2.7. The | |
894 | file format version number only increment when additional features | |
895 | that would confuse older versions of the module are added. | |
896 | ||
897 | Files older than v2.0 will have the one of the version numbers "-1", | |
898 | "0" or "1". No minor number was used at that time. | |
899 | ||
900 | =item C<version_nv> | |
901 | ||
902 | This returns the file format version as number. It is a string like | |
903 | "2.007". This value is suitable for numeric comparisons. | |
904 | ||
905 | The constant function C<Storable::BIN_VERSION_NV> returns a comparable | |
906 | number that represent the highest file version number that this | |
907 | version of Storable fully support (but see discussion of | |
908 | C<$Storable::accept_future_minor> above). The constant | |
909 | C<Storable::BIN_WRITE_VERSION_NV> function returns what file version | |
910 | is written and might be less than C<Storable::BIN_VERSION_NV> in some | |
911 | configuations. | |
912 | ||
913 | =item C<major>, C<minor> | |
914 | ||
915 | This also returns the file format version. If the version is "2.7" | |
916 | then major would be 2 and minor would be 7. The minor element is | |
917 | missing for when major is less than 2. | |
918 | ||
919 | =item C<hdrsize> | |
920 | ||
921 | The is the number of bytes that the Storable header occupies. | |
922 | ||
923 | =item C<netorder> | |
924 | ||
925 | This is TRUE if the image store data in network order. This means | |
926 | that it was created with nstore() or similar. | |
927 | ||
928 | =item C<byteorder> | |
929 | ||
930 | This is only present when C<netorder> is FALSE. It is the | |
931 | $Config{byteorder} string of the perl that created this image. It is | |
932 | a string like "1234" (32 bit little endian) or "87654321" (64 bit big | |
933 | endian). This must match the current perl for the image to be | |
934 | readable by Storable. | |
935 | ||
936 | =item C<intsize>, C<longsize>, C<ptrsize>, C<nvsize> | |
937 | ||
938 | These are only present when C<netorder> is FALSE. These are the sizes of | |
939 | various C datatypes of the perl that created this image. These must | |
940 | match the current perl for the image to be readable by Storable. | |
941 | ||
942 | The C<nvsize> element is only present for file format v2.2 and | |
943 | higher. | |
944 | ||
945 | =item C<file> | |
946 | ||
947 | The name of the file. | |
948 | ||
949 | =back | |
950 | ||
951 | =item $info = Storable::read_magic( $buffer ) | |
952 | ||
953 | =item $info = Storable::read_magic( $buffer, $must_be_file ) | |
954 | ||
955 | The $buffer should be a Storable image or the first few bytes of it. | |
956 | If $buffer starts with a Storable header, then a hash describing the | |
957 | image is returned, otherwise C<undef> is returned. | |
958 | ||
959 | The hash has the same structure as the one returned by | |
960 | Storable::file_magic(). The C<file> element is true if the image is a | |
961 | file image. | |
962 | ||
963 | If the $must_be_file argument is provided and is TRUE, then return | |
964 | C<undef> unless the image looks like it belongs to a file dump. | |
965 | ||
966 | The maximum size of a Storable header is currently 21 bytes. If the | |
967 | provided $buffer is only the first part of a Storable image it should | |
968 | at least be this long to ensure that read_magic() will recognize it as | |
969 | such. | |
970 | ||
971 | =back | |
972 | ||
7a6a85bf RG |
973 | =head1 EXAMPLES |
974 | ||
975 | Here are some code samples showing a possible usage of Storable: | |
976 | ||
977 | use Storable qw(store retrieve freeze thaw dclone); | |
978 | ||
979 | %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1); | |
980 | ||
2359510d | 981 | store(\%color, 'mycolors') or die "Can't store %a in mycolors!\n"; |
7a6a85bf | 982 | |
2359510d SD |
983 | $colref = retrieve('mycolors'); |
984 | die "Unable to retrieve from mycolors!\n" unless defined $colref; | |
7a6a85bf RG |
985 | printf "Blue is still %lf\n", $colref->{'Blue'}; |
986 | ||
987 | $colref2 = dclone(\%color); | |
988 | ||
989 | $str = freeze(\%color); | |
990 | printf "Serialization of %%color is %d bytes long.\n", length($str); | |
991 | $colref3 = thaw($str); | |
992 | ||
993 | which prints (on my machine): | |
994 | ||
995 | Blue is still 0.100000 | |
996 | Serialization of %color is 102 bytes long. | |
997 | ||
d2b96869 SR |
998 | Serialization of CODE references and deserialization in a safe |
999 | compartment: | |
1000 | ||
197b90bc SR |
1001 | =for example begin |
1002 | ||
d2b96869 SR |
1003 | use Storable qw(freeze thaw); |
1004 | use Safe; | |
1005 | use strict; | |
1006 | my $safe = new Safe; | |
197b90bc | 1007 | # because of opcodes used in "use strict": |
d1e2299c | 1008 | $safe->permit(qw(:default require)); |
d2b96869 SR |
1009 | local $Storable::Deparse = 1; |
1010 | local $Storable::Eval = sub { $safe->reval($_[0]) }; | |
197b90bc | 1011 | my $serialized = freeze(sub { 42 }); |
d2b96869 | 1012 | my $code = thaw($serialized); |
197b90bc SR |
1013 | $code->() == 42; |
1014 | ||
1015 | =for example end | |
1016 | ||
1017 | =for example_testing | |
1018 | is( $code->(), 42 ); | |
d2b96869 | 1019 | |
7a6a85bf RG |
1020 | =head1 WARNING |
1021 | ||
1022 | If you're using references as keys within your hash tables, you're bound | |
f062ea6c | 1023 | to be disappointed when retrieving your data. Indeed, Perl stringifies |
7a6a85bf RG |
1024 | references used as hash table keys. If you later wish to access the |
1025 | items via another reference stringification (i.e. using the same | |
1026 | reference that was used for the key originally to record the value into | |
1027 | the hash table), it will work because both references stringify to the | |
1028 | same string. | |
1029 | ||
6fe6778b PN |
1030 | It won't work across a sequence of C<store> and C<retrieve> operations, |
1031 | however, because the addresses in the retrieved objects, which are | |
1032 | part of the stringified references, will probably differ from the | |
1033 | original addresses. The topology of your structure is preserved, | |
1034 | but not hidden semantics like those. | |
7a6a85bf RG |
1035 | |
1036 | On platforms where it matters, be sure to call C<binmode()> on the | |
1037 | descriptors that you pass to Storable functions. | |
1038 | ||
1039 | Storing data canonically that contains large hashes can be | |
1040 | significantly slower than storing the same data normally, as | |
c261f00e | 1041 | temporary arrays to hold the keys for each hash have to be allocated, |
7a6a85bf RG |
1042 | populated, sorted and freed. Some tests have shown a halving of the |
1043 | speed of storing -- the exact penalty will depend on the complexity of | |
1044 | your data. There is no slowdown on retrieval. | |
1045 | ||
1046 | =head1 BUGS | |
1047 | ||
eda690a0 | 1048 | You can't store GLOB, FORMLINE, REGEXP, etc.... If you can define semantics |
197b90bc SR |
1049 | for those operations, feel free to enhance Storable so that it can |
1050 | deal with them. | |
7a6a85bf RG |
1051 | |
1052 | The store functions will C<croak> if they run into such references | |
1053 | unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that | |
1054 | case, the fatal message is turned in a warning and some | |
1055 | meaningless string is stored instead. | |
1056 | ||
1057 | Setting C<$Storable::canonical> may not yield frozen strings that | |
1058 | compare equal due to possible stringification of numbers. When the | |
f062ea6c | 1059 | string version of a scalar exists, it is the form stored; therefore, |
7a6a85bf RG |
1060 | if you happen to use your numbers as strings between two freezing |
1061 | operations on the same data structures, you will get different | |
1062 | results. | |
1063 | ||
dd19458b JH |
1064 | When storing doubles in network order, their value is stored as text. |
1065 | However, you should also not expect non-numeric floating-point values | |
1066 | such as infinity and "not a number" to pass successfully through a | |
1067 | nstore()/retrieve() pair. | |
1068 | ||
1069 | As Storable neither knows nor cares about character sets (although it | |
1070 | does know that characters may be more than eight bits wide), any difference | |
1071 | in the interpretation of character codes between a host and a target | |
1072 | system is your problem. In particular, if host and target use different | |
1073 | code points to represent the characters used in the text representation | |
1074 | of floating-point numbers, you will not be able be able to exchange | |
1075 | floating-point data, even with nstore(). | |
1076 | ||
c261f00e NC |
1077 | C<Storable::drop_utf8> is a blunt tool. There is no facility either to |
1078 | return B<all> strings as utf8 sequences, or to attempt to convert utf8 | |
1079 | data back to 8 bit and C<croak()> if the conversion fails. | |
1080 | ||
ee0f7aac NC |
1081 | Prior to Storable 2.01, no distinction was made between signed and |
1082 | unsigned integers on storing. By default Storable prefers to store a | |
1083 | scalars string representation (if it has one) so this would only cause | |
3c4b39be | 1084 | problems when storing large unsigned integers that had never been converted |
ee0f7aac NC |
1085 | to string or floating point. In other words values that had been generated |
1086 | by integer operations such as logic ops and then not used in any string or | |
1087 | arithmetic context before storing. | |
1088 | ||
1089 | =head2 64 bit data in perl 5.6.0 and 5.6.1 | |
1090 | ||
1091 | This section only applies to you if you have existing data written out | |
1092 | by Storable 2.02 or earlier on perl 5.6.0 or 5.6.1 on Unix or Linux which | |
1093 | has been configured with 64 bit integer support (not the default) | |
1094 | If you got a precompiled perl, rather than running Configure to build | |
1095 | your own perl from source, then it almost certainly does not affect you, | |
1096 | and you can stop reading now (unless you're curious). If you're using perl | |
1097 | on Windows it does not affect you. | |
1098 | ||
1099 | Storable writes a file header which contains the sizes of various C | |
1100 | language types for the C compiler that built Storable (when not writing in | |
1101 | network order), and will refuse to load files written by a Storable not | |
1102 | on the same (or compatible) architecture. This check and a check on | |
1103 | machine byteorder is needed because the size of various fields in the file | |
1104 | are given by the sizes of the C language types, and so files written on | |
1105 | different architectures are incompatible. This is done for increased speed. | |
1106 | (When writing in network order, all fields are written out as standard | |
1107 | lengths, which allows full interworking, but takes longer to read and write) | |
1108 | ||
1109 | Perl 5.6.x introduced the ability to optional configure the perl interpreter | |
1110 | to use C's C<long long> type to allow scalars to store 64 bit integers on 32 | |
1111 | bit systems. However, due to the way the Perl configuration system | |
1112 | generated the C configuration files on non-Windows platforms, and the way | |
1113 | Storable generates its header, nothing in the Storable file header reflected | |
1114 | whether the perl writing was using 32 or 64 bit integers, despite the fact | |
1115 | that Storable was storing some data differently in the file. Hence Storable | |
1116 | running on perl with 64 bit integers will read the header from a file | |
1117 | written by a 32 bit perl, not realise that the data is actually in a subtly | |
1118 | incompatible format, and then go horribly wrong (possibly crashing) if it | |
1119 | encountered a stored integer. This is a design failure. | |
1120 | ||
1121 | Storable has now been changed to write out and read in a file header with | |
1122 | information about the size of integers. It's impossible to detect whether | |
1123 | an old file being read in was written with 32 or 64 bit integers (they have | |
1124 | the same header) so it's impossible to automatically switch to a correct | |
1125 | backwards compatibility mode. Hence this Storable defaults to the new, | |
1126 | correct behaviour. | |
1127 | ||
1128 | What this means is that if you have data written by Storable 1.x running | |
1129 | on perl 5.6.0 or 5.6.1 configured with 64 bit integers on Unix or Linux | |
1130 | then by default this Storable will refuse to read it, giving the error | |
1131 | I<Byte order is not compatible>. If you have such data then you you | |
1132 | should set C<$Storable::interwork_56_64bit> to a true value to make this | |
1133 | Storable read and write files with the old header. You should also | |
1134 | migrate your data, or any older perl you are communicating with, to this | |
1135 | current version of Storable. | |
1136 | ||
1137 | If you don't have data written with specific configuration of perl described | |
1138 | above, then you do not and should not do anything. Don't set the flag - | |
1139 | not only will Storable on an identically configured perl refuse to load them, | |
1140 | but Storable a differently configured perl will load them believing them | |
1141 | to be correct for it, and then may well fail or crash part way through | |
1142 | reading them. | |
1143 | ||
7a6a85bf RG |
1144 | =head1 CREDITS |
1145 | ||
1146 | Thank you to (in chronological order): | |
1147 | ||
1148 | Jarkko Hietaniemi <jhi@iki.fi> | |
1149 | Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de> | |
1150 | Benjamin A. Holzman <bah@ecnvantage.com> | |
1151 | Andrew Ford <A.Ford@ford-mason.co.uk> | |
1152 | Gisle Aas <gisle@aas.no> | |
1153 | Jeff Gresham <gresham_jeffrey@jpmorgan.com> | |
1154 | Murray Nesbitt <murray@activestate.com> | |
1155 | Marc Lehmann <pcg@opengroup.org> | |
9e21b3d0 JH |
1156 | Justin Banks <justinb@wamnet.com> |
1157 | Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!) | |
dd19458b JH |
1158 | Salvador Ortiz Garcia <sog@msg.com.mx> |
1159 | Dominic Dunlop <domo@computer.org> | |
1160 | Erik Haugan <erik@solbors.no> | |
7a6a85bf RG |
1161 | |
1162 | for their bug reports, suggestions and contributions. | |
1163 | ||
1164 | Benjamin Holzman contributed the tied variable support, Andrew Ford | |
1165 | contributed the canonical order for hashes, and Gisle Aas fixed | |
f062ea6c | 1166 | a few misunderstandings of mine regarding the perl internals, |
7a6a85bf RG |
1167 | and optimized the emission of "tags" in the output streams by |
1168 | simply counting the objects instead of tagging them (leading to | |
1169 | a binary incompatibility for the Storable image starting at version | |
f062ea6c | 1170 | 0.6--older images are, of course, still properly understood). |
7a6a85bf | 1171 | Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading |
f062ea6c | 1172 | and references to tied items support. |
7a6a85bf | 1173 | |
7a6a85bf RG |
1174 | =head1 AUTHOR |
1175 | ||
0ba8809e | 1176 | Storable was written by Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>> |
775ecd75 | 1177 | Maintenance is now done by the perl5-porters F<E<lt>perl5-porters@perl.orgE<gt>> |
0ba8809e NC |
1178 | |
1179 | Please e-mail us with problems, bug fixes, comments and complaints, | |
d119459b | 1180 | although if you have compliments you should send them to Raphael. |
0ba8809e NC |
1181 | Please don't e-mail Raphael with problems, as he no longer works on |
1182 | Storable, and your message will be delayed while he forwards it to us. | |
7a6a85bf RG |
1183 | |
1184 | =head1 SEE ALSO | |
1185 | ||
c261f00e | 1186 | L<Clone>. |
7a6a85bf RG |
1187 | |
1188 | =cut |