Question

I’m writing a Perl script and I’ve come to a point where I need to parse a Java source file line by line checking for references to a fully qualified Java class name. I know the class I’m looking for up front; also the fully qualified name of the source file that is being searched (based on its path).

For example find all valid references to foo.bar.Baz inside the com/bob/is/YourUncle.java file.

At this moment the cases I can think of that it needs to account for are:

1. The file being parsed is in the same package as the search class.

   find foo.bar.Baz references in foo/bar/Boing.java

2. It should ignore comments.

   // this is a comment saying this method returns a foo.bar.Baz or Baz instance  // it shouldn't count  /*   a multiline comment as well  this shouldn't count  if I put foo.bar.Baz or Baz in here either */ 

3. In-line fully qualified references.

   foo.bar.Baz fb = new foo.bar.Baz(); 

4. References based off an import statement.

   import foo.bar.Baz; ... Baz b = new Baz(); 

What would be the most efficient way to do this in Perl 5.8? Some fancy regex perhaps?

open F, $File::Find::name or die; # these three things are already known # $classToFind    looking for references of this class # $pkgToFind      the package of the class you're finding references of # $currentPkg     package name of the file being parsed while(<F>){   # ... do work here    } close F; # the results are availble here in some form 

Answer 1

You also need to skip quoted strings (you can’t even skip comments correctly if you don’t also deal with quoted strings).

I’d probably write a fairly simple, efficient, and incomplete tokenizer very similar to the one I wrote in node 566467.

Based on that code I’d probably just dig through the non-comment/non-string chunks looking for \bimport\b and \b\Q$toFind\E\b matches. Perhaps similar to:

if( m[         \G         (?:             [^''/]+           | /(?![/*])         )+     ]xgc ) {     my $code = substr( $_, $-[0], $+[0] - $-[0] );     my $imported = 0;     while( $code =~ /\b(import\s+)?\Q$package\E\b/g ) {         if( $1 ) {             ... # Found importing of package             while( $code =~ /\b\Q$class\E\b/g ) {                 ... # Found mention of imported class             }             last;         }         ... # Found a package reference     } } elsif( m[ \G ' (?: [^'\\]+ | \\. )* ' ]xgc     ||   m[ \G ' (?: [^'\\]+ | \\. )* ' ]xgc ) {     # skip quoted strings } elsif(  m[\G//.*]g­c  ) {     # skip C++ comments