concise.pm

source of perl for linux application,

Private flags, if any are set for an opcode, are displayed after a '/'

    8  <@> leave[1 ref] vKP/REFC ->(end)
    7     <2> sassign vKS/2 ->8

They're opcode specific, and occur less often than the public ones, so
they're represented by short mnemonics instead of single-chars; see
F<op.h> for gory details, or try this quick 2-liner:

  $> perl -MB::Concise -de 1
  DB<1> |x \%B::Concise::priv

=head1 FORMATTING SPECIFICATIONS

For each line-style ('concise', 'terse', 'linenoise', etc.) there are
3 format-specs which control how OPs are rendered.

The first is the 'default' format, which is used in both basic and exec
modes to print all opcodes.  The 2nd, goto-format, is used in exec
mode when branches are encountered.  They're not real opcodes, and are
inserted to look like a closing curly brace.  The tree-format is tree
specific.

When a line is rendered, the correct format-spec is copied and scanned
for the following items; data is substituted in, and other
manipulations like basic indenting are done, for each opcode rendered.

There are 3 kinds of items that may be populated; special patterns,
#vars, and literal text, which is copied verbatim.  (Yes, it's a set
of s///g steps.)

=head2 Special Patterns

These items are the primitives used to perform indenting, and to
select text from amongst alternatives.

=over 4

=item B<(x(>I<exec_text>B<;>I<basic_text>B<)x)>

Generates I<exec_text> in exec mode, or I<basic_text> in basic mode.

=item B<(*(>I<text>B<)*)>

Generates one copy of I<text> for each indentation level.

=item B<(*(>I<text1>B<;>I<text2>B<)*)>

Generates one fewer copies of I<text1> than the indentation level, followed
by one copy of I<text2> if the indentation level is more than 0.

=item B<(?(>I<text1>B<#>I<var>I<Text2>B<)?)>

If the value of I<var> is true (not empty or zero), generates the
value of I<var> surrounded by I<text1> and I<Text2>, otherwise
nothing.

=item B<~>

Any number of tildes and surrounding whitespace will be collapsed to
a single space.

=back

=head2 # Variables

These #vars represent opcode properties that you may want as part of
your rendering.  The '#' is intended as a private sigil; a #var's
value is interpolated into the style-line, much like "read $this".

These vars take 3 forms:

=over 4

=item B<#>I<var>

A property named 'var' is assumed to exist for the opcodes, and is
interpolated into the rendering.

=item B<#>I<var>I<N>

Generates the value of I<var>, left justified to fill I<N> spaces.
Note that this means while you can have properties 'foo' and 'foo2',
you cannot render 'foo2', but you could with 'foo2a'.  You would be
wise not to rely on this behavior going forward ;-)

=item B<#>I<Var>

This ucfirst form of #var generates a tag-value form of itself for
display; it converts '#Var' into a 'Var => #var' style, which is then
handled as described above.  (Imp-note: #Vars cannot be used for
conditional-fills, because the => #var transform is done after the check
for #Var's value).

=back

The following variables are 'defined' by B::Concise; when they are
used in a style, their respective values are plugged into the
rendering of each opcode.

Only some of these are used by the standard styles, the others are
provided for you to delve into optree mechanics, should you wish to
add a new style (see L</add_style> below) that uses them.  You can
also add new ones using L</add_callback>.

=over 4

=item B<#addr>

The address of the OP, in hexadecimal.

=item B<#arg>

The OP-specific information of the OP (such as the SV for an SVOP, the
non-local exit pointers for a LOOP, etc.) enclosed in parentheses.

=item B<#class>

The B-determined class of the OP, in all caps.

=item B<#classsym>

A single symbol abbreviating the class of the OP.

=item B<#coplabel>

The label of the statement or block the OP is the start of, if any.

=item B<#exname>

The name of the OP, or 'ex-foo' if the OP is a null that used to be a foo.

=item B<#extarg>

The target of the OP, or nothing for a nulled OP.

=item B<#firstaddr>

The address of the OP's first child, in hexadecimal.

=item B<#flags>

The OP's flags, abbreviated as a series of symbols.

=item B<#flagval>

The numeric value of the OP's flags.

=item B<#hints>

The COP's hint flags, rendered with abbreviated names if possible. An empty
string if this is not a COP. Here are the symbols used:

    $ strict refs
    & strict subs
    * strict vars
    i integers
    l locale
    b bytes
    [ arybase
    { block scope
    % localise %^H
    < open in
    > open out
    I overload int
    F overload float
    B overload binary
    S overload string
    R overload re
    T taint
    E eval
    X filetest access
    U utf-8

=item B<#hintsval>

The numeric value of the COP's hint flags, or an empty string if this is not
a COP.

=item B<#hyphseq>

The sequence number of the OP, or a hyphen if it doesn't have one.

=item B<#label>

'NEXT', 'LAST', or 'REDO' if the OP is a target of one of those in exec
mode, or empty otherwise.

=item B<#lastaddr>

The address of the OP's last child, in hexadecimal.

=item B<#name>

The OP's name.

=item B<#NAME>

The OP's name, in all caps.

=item B<#next>

The sequence number of the OP's next OP.

=item B<#nextaddr>

The address of the OP's next OP, in hexadecimal.

=item B<#noise>

A one- or two-character abbreviation for the OP's name.

=item B<#private>

The OP's private flags, rendered with abbreviated names if possible.

=item B<#privval>

The numeric value of the OP's private flags.

=item B<#seq>

The sequence number of the OP. Note that this is a sequence number
generated by B::Concise.

=item B<#seqnum>

5.8.x and earlier only. 5.9 and later do not provide this.

The real sequence number of the OP, as a regular number and not adjusted
to be relative to the start of the real program. (This will generally be
a fairly large number because all of B<B::Concise> is compiled before
your program is).

=item B<#opt>

Whether or not the op has been optimised by the peephole optimiser.

Only available in 5.9 and later.

=item B<#sibaddr>

The address of the OP's next youngest sibling, in hexadecimal.

=item B<#svaddr>

The address of the OP's SV, if it has an SV, in hexadecimal.

=item B<#svclass>

The class of the OP's SV, if it has one, in all caps (e.g., 'IV').

=item B<#svval>

The value of the OP's SV, if it has one, in a short human-readable format.

=item B<#targ>

The numeric value of the OP's targ.

=item B<#targarg>

The name of the variable the OP's targ refers to, if any, otherwise the
letter t followed by the OP's targ in decimal.

=item B<#targarglife>

Same as B<#targarg>, but followed by the COP sequence numbers that delimit
the variable's lifetime (or 'end' for a variable in an open scope) for a
variable.

=item B<#typenum>

The numeric value of the OP's type, in decimal.

=back

=head1 One-Liner Command tips

=over 4

=item perl -MO=Concise,bar foo.pl

Renders only bar() from foo.pl.  To see main, drop the ',bar'.  To see
both, add ',-main'

=item perl -MDigest::MD5=md5 -MO=Concise,md5 -e1

Identifies md5 as an XS function.  The export is needed so that BC can
find it in main.

=item perl -MPOSIX -MO=Concise,_POSIX_ARG_MAX -e1

Identifies _POSIX_ARG_MAX as a constant sub, optimized to an IV.
Although POSIX isn't entirely consistent across platforms, this is
likely to be present in virtually all of them.

=item perl -MPOSIX -MO=Concise,a -e 'print _POSIX_SAVED_IDS'

This renders a print statement, which includes a call to the function.
It's identical to rendering a file with a use call and that single
statement, except for the filename which appears in the nextstate ops.

=item perl -MPOSIX -MO=Concise,a -e 'sub a{_POSIX_SAVED_IDS}'

This is B<very> similar to previous, only the first two ops differ.  This
subroutine rendering is more representative, insofar as a single main
program will have many subs.

=item perl -MB::Concise -e 'B::Concise::compile("-exec","-src", \%B::Concise::)->()'

This renders all functions in the B::Concise package with the source
lines.  It eschews the O framework so that the stashref can be passed
directly to B::Concise::compile().  See -stash option for a more
convenient way to render a package.

=back

=head1 Using B::Concise outside of the O framework

The common (and original) usage of B::Concise was for command-line
renderings of simple code, as given in EXAMPLE.  But you can also use
B<B::Concise> from your code, and call compile() directly, and
repeatedly.  By doing so, you can avoid the compile-time only
operation of O.pm, and even use the debugger to step through
B::Concise::compile() itself.

Once you're doing this, you may alter Concise output by adding new
rendering styles, and by optionally adding callback routines which
populate new variables, if such were referenced from those (just
added) styles.  

=head2 Example: Altering Concise Renderings

    use B::Concise qw(set_style add_callback);
    add_style($yourStyleName => $defaultfmt, $gotofmt, $treefmt);
    add_callback
      ( sub {
            my ($h, $op, $format, $level, $stylename) = @_;
            $h->{variable} = some_func($op);
        });
    $walker = B::Concise::compile(@options,@subnames,@subrefs);
    $walker->();

=head2 set_style()

B<set_style> accepts 3 arguments, and updates the three format-specs
comprising a line-style (basic-exec, goto, tree).  It has one minor
drawback though; it doesn't register the style under a new name.  This
can become an issue if you render more than once and switch styles.
Thus you may prefer to use add_style() and/or set_style_standard()
instead.

=head2 set_style_standard($name)

This restores one of the standard line-styles: C<terse>, C<concise>,
C<linenoise>, C<debug>, C<env>, into effect.  It also accepts style
names previously defined with add_style().

=head2 add_style()

This subroutine accepts a new style name and three style arguments as
above, and creates, registers, and selects the newly named style.  It is
an error to re-add a style; call set_style_standard() to switch between
several styles.

=head2 add_callback()

If your newly minted styles refer to any new #variables, you'll need
to define a callback subroutine that will populate (or modify) those
variables.  They are then available for use in the style you've
chosen.

The callbacks are called for each opcode visited by Concise, in the
same order as they are added.  Each subroutine is passed five
parameters.

  1. A hashref, containing the variable names and values which are
     populated into the report-line for the op
  2. the op, as a B<B::OP> object
  3. a reference to the format string
  4. the formatting (indent) level
  5. the selected stylename

To define your own variables, simply add them to the hash, or change
existing values if you need to.  The level and format are passed in as
references to scalars, but it is unlikely that they will need to be
changed or even used.

=head2 Running B::Concise::compile()

B<compile> accepts options as described above in L</OPTIONS>, and
arguments, which are either coderefs, or subroutine names.

It constructs and returns a $treewalker coderef, which when invoked,
traverses, or walks, and renders the optrees of the given arguments to
STDOUT.  You can reuse this, and can change the rendering style used
each time; thereafter the coderef renders in the new style.

B<walk_output> lets you change the print destination from STDOUT to
another open filehandle, or into a string passed as a ref (unless
you've built perl with -Uuseperlio).

    my $walker = B::Concise::compile('-terse','aFuncName', \&aSubRef);  # 1
    walk_output(\my $buf);
    $walker->();			# 1 renders -terse
    set_style_standard('concise');	# 2
    $walker->();			# 2 renders -concise
    $walker->(@new);			# 3 renders whatever
    print "3 different renderings: terse, concise, and @new: $buf\n";

When $walker is called, it traverses the subroutines supplied when it
was created, and renders them using the current style.  You can change
the style afterwards in several different ways:

  1. call C<compile>, altering style or mode/order
  2. call C<set_style_standard>
  3. call $walker, passing @new options

Passing new options to the $walker is the easiest way to change
amongst any pre-defined styles (the ones you add are automatically
recognized as options), and is the only way to alter rendering order
without calling compile again.  Note however that rendering state is
still shared amongst multiple $walker objects, so they must still be
used in a coordinated manner.

=head2 B::Concise::reset_sequence()

This function (not exported) lets you reset the sequence numbers (note
that they're numbered arbitrarily, their goal being to be human
readable).  Its purpose is mostly to support testing, i.e. to compare
the concise output from two identical anonymous subroutines (but
different instances).  Without the reset, B::Concise, seeing that
they're separate optrees, generates different sequence numbers in
the output.

=head2 Errors

Errors in rendering (non-existent function-name, non-existent coderef)
are written to the STDOUT, or wherever you've set it via
walk_output().

Errors using the various *style* calls, and bad args to walk_output(),
result in die().  Use an eval if you wish to catch these errors and
continue processing.

=head1 AUTHOR

Stephen McCamant, E<lt>[e-mail]<gt>.

=cut