1Dumper(3)             User Contributed Perl Documentation            Dumper(3)
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NAME

6       PDL::IO::Dumper -- data dumping for structs with PDLs
7

DESCRIPTION

9       This package allows you cleanly to save and restore complex data
10       structures which include PDLs, as ASCII strings and/or transportable
11       ASCII files.  It exports four functions into your namespace: sdump,
12       fdump, frestore, and deep_copy.
13
14       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
18       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
23       The output string is intended to be about as readable as Dumper's
24       output is for non-PDL expressions. To that end, small PDLs (up to 8
25       elements) are stored as inline perl expressions, midsized PDLs (up to
26       200 elements) are stored as perl expressions above the main data
27       structure, and large PDLs are stored as FITS files that are uuencoded
28       and included in the dump string. (You have to have access to either
29       uuencode(1) or the CPAN module Convert::UU for this to work).
30
31       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

Bugs

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
39       external-hook variables aren't recognized (for that a more universal
40       Dumper would be needed) and will still exercise the Data::Dumper crash.
41       This is by choice:  (A) it's difficult to recognize which objects are
42       actually external, and (B) most everyday objects are quite safe.
43
44       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
48       headers (see the rfits documentation in PDL::IO::Misc for details).
49
50       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

Author, copyright, no warranty

56       Copyright 2002, Craig DeForest.
57
58       This code may be distributed under the same terms as Perl itself
59       (license available at <http://ww.perl.org>).  Copying, reverse
60       engineering, distribution, and modification are explicitly allowed so
61       long as this notice is preserved intact and modified versions are
62       clearly marked as such.
63
64       This package comes with NO WARRANTY.
65

HISTORY

67       ·  1.0: initial release
68
69       ·  1.1 (26-Feb-2002): Shorter form for short PDLs; more readability
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71       ·  1.2 (28-Feb-2002): Added deep_copy() -- exported convenience
72          function
73            for "eval sdump"
74
75       ·  1.3 (15-May-2002): Added checking for tied objects in gethdr()
76            [workaround for hole in Data::Dumper]
77
78       ·  1.4 (15-Jan-2003): Added support for Convert::UU as well as
79            command-line uu{en|de}code
80

FUNCTIONS

82   sdump
83       Dump a data structure to a string.
84
85         use PDL::IO::Dumper;
86         $s = sdump(<VAR>);
87         ...
88         <VAR> = eval $s;
89
90       sdump dumps a single complex data structure into a string.  You restore
91       the data structure by eval-ing the string.  Since eval is a builtin, no
92       convenience routine exists to use it.
93
94   fdump
95       Dump a data structure to a file
96
97         use PDL::IO::Dumper;
98         fdump(<VAR>,$filename);
99         ...
100         <VAR> = frestore($filename);
101
102       fdump dumps a single complex data structure to a file.  You restore the
103       data structure by eval-ing the perl code put in the file.  A
104       convenience routine (frestore) exists to do it for you.
105
106       I suggest using the extension '.pld' or (for non-broken OS's) '.pdld'
107       to distinguish Dumper files.  That way they are reminiscent of .pl
108       files for perl, while still looking a little different so you can pick
109       them out.  You can certainly feed a dump file straight into perl (for
110       syntax checking) but it will not do much for you, just build your data
111       structure and exit.
112
113   frestore
114       Restore a dumped file
115
116         use PDL::IO::Dumper;
117         fdump(<VAR>,$filename);
118         ...
119         <VAR> = frestore($filename);
120
121       frestore() is a convenience function that just reads in the named file
122       and executes it in an eval.  It's paired with fdump().
123
124   deep_copy
125       Convenience function copies a complete perl data structure by the brute
126       force method of "eval sdump".
127
128   PDL::IO::Dumper::big_PDL
129       Identify whether a PDL is ``big'' [Internal routine]
130
131       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
137       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
140   PDL::IO::Dumper::stringify_PDL
141       Turn a PDL into a 1-part perl expr [Internal routine]
142
143       Internal routine that takes a PDL and returns a perl string that evals
144       to the PDL.  It should be used with care because it doesn't dump
145       headers and it doesn't check number of elements.  The point here is
146       that numbers are dumped with the correct precision for their storage
147       class.  Things we don't know about get stringified element-by-element
148       by their builtin class, which is probably not a bad guess.
149
150   PDL::IO::Dumper::uudecode_PDL
151       Recover a PDL from a uuencoded string [Internal routine]
152
153       This routine encapsulates uudecoding of the dumped string for large
154       piddles.  It's separate to encapsulate the decision about which method
155       of uudecoding to try (both the built-in Convert::UU and the shell
156       command uudecode(1) are supported).
157
158   PDL::IO::Dumper::dump_PDL
159       Generate 1- or 2-part expr for a PDL [Internal routine]
160
161       Internal routine that produces commands defining a PDL.  You supply
162       (<PDL>, <name>) and get back two strings: a prepended command string
163       and an expr that evaluates to the final PDL.  PDL is the PDL you want
164       to dump.  <inline> is a flag whether dump_PDL is being called inline or
165       before the inline dump string (0 for before; 1 for in).  <name> is the
166       name of the variable to be assigned (for medium and large PDLs, which
167       are defined before the dump string and assigned unique IDs).
168
169   PDL::IO::Dumper::find_PDLs
170       Walk a data structure and dump PDLs [Internal routine]
171
172       Walks the original data structure and generates appropriate exprs for
173       each PDL.  The exprs are inserted into the Data::Dumper output string.
174       You shouldn't call this unless you know what you're doing.  (see sdump,
175       above).
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179perl v5.30.0                      2019-09-05                         Dumper(3)
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