1Dumper(3) User Contributed Perl Documentation Dumper(3)
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6 PDL::IO::Dumper -- data dumping for structs with PDLs
7
9 This package allows you cleanly to save and restore complex data struc‐
10 tures which include PDLs, as ASCII strings and/or transportable ASCII
11 files. It exports four functions into your namespace: sdump, fdump,
12 frestore, and deep_copy.
13 PDL::IO::Dumper traverses the same types of structure that Data::Dumper
15 knows about, because it uses a call to Data::Dumper. Unlike
16 Data::Dumper it doesn't crash when accessing PDLs.
17 The PDL::IO::Dumper routines have a slightly different syntax than
19 Data::Dumper does: you may only dump a single scalar perl expression
20 rather than an arbitrary one. Of course, the scalar may be a ref to
21 whatever humongous pile of spaghetti you want, so that's no big loss.
22 The output string is intended to be about as readable as Dumper's out‐
24 put is for non-PDL expressions. To that end, small PDLs (up to 8 ele‐
25 ments) are stored as inline perl expressions, midsized PDLs (up to 200
26 elements) are stored as perl expressions above the main data structure,
27 and large PDLs are stored as FITS files that are uuencoded and included
28 in the dump string. (You have to have access to either uuencode(1) or
29 the CPAN module Convert::UU for this to work).
30 No attempt is made to shrink the output string -- for example, inlined
32 PDL expressions all include explicit reshape() and typecast commands,
33 and uuencoding expands stuff by a factor of about 1.5. So your data
34 structures will grow when you dump them.
35
37 It's still possible to break this code and cause it to dump core, for
38 the same reason that Data::Dumper crashes. In particular, other exter‐
39 nal-hook variables aren't recognized (for that a more universal Dumper
40 would be needed) and will still exercise the Data::Dumper crash. This
41 is by choice: (A) it's difficult to recognize which objects are actu‐
42 ally external, and (B) most everyday objects are quite safe.
43 Another shortfall of Data::Dumper is that it doesn't recognize tied
45 objects. This might be a Good Thing or a Bad Thing depending on your
46 point of view, but it means that PDL::IO::Dumper includes a kludge to
47 handle the tied Astro::FITS::Header objects associated with FITS head‐
48 ers (see the rfits documentation in PDL::IO::Misc for details).
49 There's currently no reference recursion detection, so a non-treelike
51 reference topology will cause Dumper to buzz forever. That will likely
52 be fixed in a future version. Meanwhile a warning message finds likely
53 cases.
54
56 Copyright 2002, Craig DeForest.
57 This code may be distributed under the same terms as Perl itself
59 (license available at http://ww.perl.org). Copying, reverse engineer‐
60 ing, distribution, and modification are explicitly allowed so long as
61 this notice is preserved intact and modified versions are clearly
62 marked as such.
63 This package comes with NO WARRANTY.
65
67 * 1.0: initial release
68 * 1.1 (26-Feb-2002): Shorter form for short PDLs; more readability
69 * 1.2 (28-Feb-2002): Added deep_copy() -- exported convenience function
70 for "eval sdump"
71 * 1.3 (15-May-2002): Added checking for tied objects in gethdr() [work‐
72 around for hole in Data::Dumper]
73 * 1.4 (15-Jan-2003): Added support for Convert::UU as well as command-
74 line uu{en⎪de}code
75
77 sdump
78 Dump a data structure to a string.
80 use PDL::IO::Dumper;
82 $s = sdump(<VAR>);
83 ...
84 <VAR> = eval $s;
85 sdump dumps a single complex data structure into a string. You restore
87 the data structure by eval-ing the string. Since eval is a builtin, no
88 convenience routine exists to use it.
89 fdump
91 Dump a data structure to a file
93 use PDL::IO::Dumper;
95 fdump(<VAR>,$filename);
96 ...
97 <VAR> = frestore($filename);
98 fdump dumps a single complex data structure to a file. You restore the
100 data structure by eval-ing the perl code put in the file. A conve‐
101 nience routine (frestore) exists to do it for you.
102 I suggest using the extension '.pld' or (for non-broken OS's) '.pdld'
104 to distinguish Dumper files. That way they are reminiscent of .pl
105 files for perl, while still looking a little different so you can pick
106 them out. You can certainly feed a dump file straight into perl (for
107 syntax checking) but it will not do much for you, just build your data
108 structure and exit.
109 frestore
111 Restore a dumped file
113 use PDL::IO::Dumper;
115 fdump(<VAR>,$filename);
116 ...
117 <VAR> = frestore($filename);
118 frestore() is a convenience function that just reads in the named file
120 and executes it in an eval. It's paired with fdump().
121 deep_copy
123 Convenience function copies a complete perl data structure by the brute
125 force method of "eval sdump".
126 PDL::IO::Dumper::big_PDL
128 Identify whether a PDL is ``big'' [Internal routine]
130 Internal routine takes a PDL and returns a boolean indicating whether
132 it's small enough for direct insertion into the dump string. If 0, it
133 can be inserted. Larger numbers yield larger scopes of PDL. 1 implies
134 that it should be broken out but can be handled with a couple of perl
135 commands; 2 implies full uudecode treatment.
136 PDLs with Astro::FITS::Header objects as headers are taken to be FITS
138 files and are always treated as huge, regardless of size.
139 PDL::IO::Dumper::stringify_PDL
141 Turn a PDL into a 1-part perl expr [Internal routine]
143 Internal routine that takes a PDL and returns a perl string that evals
145 to the PDL. It should be used with care because it doesn't dump head‐
146 ers and it doesn't check number of elements. The point here is that
147 numbers are dumped with the correct precision for their storage class.
148 Things we don't know about get stringified element-by-element by their
149 builtin class, which is probably not a bad guess.
150 PDL::IO::Dumper::uudecode_PDL
152 Recover a PDL from a uuencoded string [Internal routine]
154 This routine encapsulates uudecoding of the dumped string for large
156 piddles. It's separate to encapsulate the decision about which method
157 of uudecoding to try (both the built-in Convert::UU and the shell com‐
158 mand uudecode(1) are supported).
159 PDL::IO::Dumper::dump_PDL
161 Generate 1- or 2-part expr for a PDL [Internal routine]
163 Internal routine that produces commands defining a PDL. You supply
165 (<PDL>, <name>) and get back two strings: a prepended command string
166 and an expr that evaluates to the final PDL. PDL is the PDL you want
167 to dump. <inline> is a flag whether dump_PDL is being called inline or
168 before the inline dump string (0 for before; 1 for in). <name> is the
169 name of the variable to be assigned (for medium and large PDLs, which
170 are defined before the dump string and assigned unique IDs).
171 PDL::IO::Dumper::find_PDLs
173 Walk a data structure and dump PDLs [Internal routine]
175 Walks the original data structure and generates appropriate exprs for
177 each PDL. The exprs are inserted into the Data::Dumper output string.
178 You shouldn't call this unless you know what you're doing. (see sdump,
179 above).
180perl v5.8.8 2006-12-02 Dumper(3)