John Kirk > Text-TreeFile > Text::TreeFile::details


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Text::TreeFile::details - precise usage specifications


  use Text::TreeFile;

  my $filename='demodata/treetest.tre';

  # read in single-tree mode
  my $tf=Text::TreeFile->new($filename);

  my $treeref=$$tf{top};

  print "The string content of the top-level tree node is:\n\n";
  print "    $$treeref[0]\n\n";
  print "It has ",scalar @{$$treeref[1]}," second-level child nodes\n";


First, each public function is described. Then, a test script. After that, a few more details.

CONSTRUCTOR: new [ filename, [ endq ] ] ^

The constructor (function new()) for module Text::TreeFile can be invoked with zero, one or two parameters. The first is a filename to be read into an internal tree structure of strings; the second, a single/multiple tree flag. If no parameters are specified, an object (a blessed reference to a hash) will be returned with only the prototype entries present. In this case, one might create a tree by other external means and put it into the hash.

Parameter: filename

If at least one parameter is specified, the first will be taken to be the name of the tree file to be read. If it contains a slash ("/") character, the leading path up to the final file name will be remembered (under key, "idir") and used as a prefix for all include files named in the course of reading the tree(s). The filename is remembered under key, "iname" in the blessed hash created.

Parameter: endq

If two parameters are specified in the call to new(), the second will be interpreted as an indicator whether reading the file should stop at the end of the first full top-level tree. If present, the string specified in this parameter is copied into the blessed hash under the key, "endq". This will indicate multiple-tree mode, in which case the entire file will be read and interpreted as a tree of text strings. If unspecified, or specified as undef, the default of single-tree mode will be used for reading the file.

Single-tree Reading Mode

In the default file reading mode, only a single (the first, if there are more than one) top-level tree will be read from the file. The element of the module's blessed hash with key, "top", will have as value a reference to this tree (node). (To access file data following the first tree in the file, refer to the internals documentation file.)

Multiple-tree Reading Mode

If the endq parameter is specified to new(), the entire file must conform to proper tree file syntax, and will be read into a data structure consisting of an array of top-level trees (tree nodes). In this case the element of the blessed hash with key, "top", will have as its value a reference to this array instead of a reference to just a single top-level tree (node).

FUNCTION: showlines ^

showlines() is called with a reference to a tree data structure as its first parameter and, optionally, an initial (integer) level number as its second parameter. It recursively prints the contents of the tree.

FUNCTION: showglobals ^

showglobals() is called with no parameters, and shows the contents of the blessed hash which is taken to contain global variables.,


The script conducts some tests of the module.


Nothing is exported by default. Functions showlines() and showglobals() may be imported on request. The module's new() function returns a blessed reference to a hash containing a number of data items, notably one with key, "top" which is the (top node of) the resulting tree of text strings read from the file.

Key: "top"

The tree structure of text strings returned by this module is remembered under the key, "top", in the object hash whose blessed reference is returned by new().


Each node of the tree of text strings created by this module is an array of two elements, the first being a text string which is the content of this node, and the second being a reference to an array of references to the child nodes of the current node.


The new() function will return the undef value if _loadtree() returns false.

The _loadtree() function prints a warning to STDOUT and returns the undef value if an internal error allows it to be called with no input filename specified at the top file nesting level. The module should not allow this to occur.

As a separate case, the prior paragraph's description applies, with a slightly different warning message, below the top file nesting level.

If a filename is specified, but _loadtree() is unsuccessful in opening the file, a warning is printed to STDOUT and the undef value is returned.

If _readspec() finds a line without an indent of an exact multiple of two space characters, it issues a die() call with a warning message.


The module doesn't use the Carp(3pm) module for warnings, calls die() in some exceptional cases, uses "print STDOUT" for warnings, and returns special values in most exceptional cases. It should use Carp(3pm) to issue warnings and then return special values, for all exceptions.

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