Dumper(3) User Contributed Perl Documentation Dumper(3)NAME
PDL::IO::Dumper -- data dumping for structs with PDLs
DESCRIPTION
This package allows you cleanly to save and restore complex data
structures which include PDLs, as ASCII strings and/or transportable
ASCII files. It exports four functions into your namespace: sdump,
fdump, frestore, and deep_copy.
PDL::IO::Dumper traverses the same types of structure that Data::Dumper
knows about, because it uses a call to Data::Dumper. Unlike
Data::Dumper it doesn't crash when accessing PDLs.
The PDL::IO::Dumper routines have a slightly different syntax than
Data::Dumper does: you may only dump a single scalar perl expression
rather than an arbitrary one. Of course, the scalar may be a ref to
whatever humongous pile of spaghetti you want, so that's no big loss.
The output string is intended to be about as readable as Dumper's
output is for non-PDL expressions. To that end, small PDLs (up to 8
elements) are stored as inline perl expressions, midsized PDLs (up to
200 elements) are stored as perl expressions above the main data
structure, and large PDLs are stored as FITS files that are uuencoded
and included in the dump string. (You have to have access to either
uuencode(1) or the CPAN module Convert::UU for this to work).
No attempt is made to shrink the output string -- for example, inlined
PDL expressions all include explicit reshape() and typecast commands,
and uuencoding expands stuff by a factor of about 1.5. So your data
structures will grow when you dump them.
Bugs
It's still possible to break this code and cause it to dump core, for
the same reason that Data::Dumper crashes. In particular, other
external-hook variables aren't recognized (for that a more universal
Dumper would be needed) and will still exercise the Data::Dumper crash.
This is by choice: (A) it's difficult to recognize which objects are
actually external, and (B) most everyday objects are quite safe.
Another shortfall of Data::Dumper is that it doesn't recognize tied
objects. This might be a Good Thing or a Bad Thing depending on your
point of view, but it means that PDL::IO::Dumper includes a kludge to
handle the tied Astro::FITS::Header objects associated with FITS
headers (see the rfits documentation in PDL::IO::Misc for details).
There's currently no reference recursion detection, so a non-treelike
reference topology will cause Dumper to buzz forever. That will likely
be fixed in a future version. Meanwhile a warning message finds likely
cases.
Author, copyright, no warranty
Copyright 2002, Craig DeForest.
This code may be distributed under the same terms as Perl itself
(license available at http://ww.perl.org). Copying, reverse
engineering, distribution, and modification are explicitly allowed so
long as this notice is preserved intact and modified versions are
clearly marked as such.
This package comes with NO WARRANTY.
HISTORY
· 1.0: initial release
· 1.1 (26-Feb-2002): Shorter form for short PDLs; more readability
· 1.2 (28-Feb-2002): Added deep_copy()-- exported convenience
function
for "eval sdump"
· 1.3 (15-May-2002): Added checking for tied objects in gethdr()
[workaround for hole in Data::Dumper]
· 1.4 (15-Jan-2003): Added support for Convert::UU as well as
command-line uu{en|de}code
FUNCTIONS
sdump
Dump a data structure to a string.
use PDL::IO::Dumper;
$s = sdump(<VAR>);
...
<VAR> = eval $s;
sdump dumps a single complex data structure into a string. You restore
the data structure by eval-ing the string. Since eval is a builtin, no
convenience routine exists to use it.
fdump
Dump a data structure to a file
use PDL::IO::Dumper;
fdump(<VAR>,$filename);
...
<VAR> = frestore($filename);
fdump dumps a single complex data structure to a file. You restore the
data structure by eval-ing the perl code put in the file. A
convenience routine (frestore) exists to do it for you.
I suggest using the extension '.pld' or (for non-broken OS's) '.pdld'
to distinguish Dumper files. That way they are reminiscent of .pl
files for perl, while still looking a little different so you can pick
them out. You can certainly feed a dump file straight into perl (for
syntax checking) but it will not do much for you, just build your data
structure and exit.
frestore
Restore a dumped file
use PDL::IO::Dumper;
fdump(<VAR>,$filename);
...
<VAR> = frestore($filename);
frestore() is a convenience function that just reads in the named file
and executes it in an eval. It's paired with fdump().
deep_copy
Convenience function copies a complete perl data structure by the brute
force method of "eval sdump".
PDL::IO::Dumper::big_PDL
Identify whether a PDL is ``big'' [Internal routine]
Internal routine takes a PDL and returns a boolean indicating whether
it's small enough for direct insertion into the dump string. If 0, it
can be inserted. Larger numbers yield larger scopes of PDL. 1 implies
that it should be broken out but can be handled with a couple of perl
commands; 2 implies full uudecode treatment.
PDLs with Astro::FITS::Header objects as headers are taken to be FITS
files and are always treated as huge, regardless of size.
PDL::IO::Dumper::stringify_PDL
Turn a PDL into a 1-part perl expr [Internal routine]
Internal routine that takes a PDL and returns a perl string that evals
to the PDL. It should be used with care because it doesn't dump
headers and it doesn't check number of elements. The point here is
that numbers are dumped with the correct precision for their storage
class. Things we don't know about get stringified element-by-element
by their builtin class, which is probably not a bad guess.
PDL::IO::Dumper::uudecode_PDL
Recover a PDL from a uuencoded string [Internal routine]
This routine encapsulates uudecoding of the dumped string for large
piddles. It's separate to encapsulate the decision about which method
of uudecoding to try (both the built-in Convert::UU and the shell
command uudecode(1) are supported).
PDL::IO::Dumper::dump_PDL
Generate 1- or 2-part expr for a PDL [Internal routine]
Internal routine that produces commands defining a PDL. You supply
(<PDL>, <name>) and get back two strings: a prepended command string
and an expr that evaluates to the final PDL. PDL is the PDL you want
to dump. <inline> is a flag whether dump_PDL is being called inline or
before the inline dump string (0 for before; 1 for in). <name> is the
name of the variable to be assigned (for medium and large PDLs, which
are defined before the dump string and assigned unique IDs).
PDL::IO::Dumper::find_PDLs
Walk a data structure and dump PDLs [Internal routine]
Walks the original data structure and generates appropriate exprs for
each PDL. The exprs are inserted into the Data::Dumper output string.
You shouldn't call this unless you know what you're doing. (see sdump,
above).
perl v5.10.0 2006-03-14 Dumper(3)