TextSearch

Class Overview

TextSearch searches through a PDF document for a user-given search pattern. The current implementation supports both verbatim search and the search using regular expressions, whose detailed syntax can be found at:

• http://www.boost.org/doc/libs/release/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html

TextSearch also provides users with several useful search modes and extra information besides the found string that matches the pattern. TextSearch can either keep running until a matched string is found or be set to return periodically in order for the caller to perform any necessary updates (e.g., UI updates). It is also worth mentioning that the search modes can be changed on the fly while searching through a document.

Possible use case scenarios for TextSearch include:

• Guide users of a PDF viewer (e.g. implemented by PDFViewCtrl) to places where they are intersted in;
• Find interested PDF documents which contain certain patterns;
• Extract interested information (e.g., credit card numbers) from a set of files;
• Extract Highlight information (refer to the Highlights class for details) from files for external use.

Note: Since hyphens ('-') are frequently used in PDF documents to concatenate the two broken pieces of a word at the end of a line, for example

"TextSearch is powerful for finding patterns in PDF files; yes, it is really pow- erful."

a search for "powerful" should return both instances. However, not all end-of-line hyphens are hyphens added to connect a broken word; some of them could be "real" hyphens. In addition, an input search pattern may also contain hyphens that complicate the situation. To tackle this problem, the following conventions are adopted:

1. When in the verbatim search mode and the pattern contains no hyphen, a matching string is returned if it is exactly the same or it contains end-of-line or start-of-line hyphens. For example, as mentioned above, a search for "powerful" would return both instances.
2. When in verbatim search mode and the pattern contains one or multiple hyphens, a matching string is returned only if the string matches the pattern exactly. For example, a search for "pow-erful" will only return the second instance, and a search for "power-ful" will return nothing.
3. When searching using regular expressions, hyphens are not taken care implicitly. Users should take care of it themselves. For example, in order to find both the "powerful" instances, the input pattern can be "pow-{0,1}erful".

A sample use case is coded below: (for a full sample, please take a look at the TextSearch sample project):

 // ... Initialize PDFNet ... 
 PDFDoc doc = new PDFDoc(filein);
 doc.initSecurityHandler(); 
 int mode = TextSearch.e_whole_word | TextSearch.e_page_stop; 
 UString pattern( "joHn sMiTh" ); 
 TextSearch txt_search = new TextSearch(); 

 //PDFDoc doesn't allow simultaneous access from different threads. If this
 //document could be used from other threads (e.g., the rendering thread inside
 //PDFView/PDFViewCtrl, if used), it is good practice to lock it.
 //Notice: don't forget to call doc.Unlock() to avoid deadlock.
 doc.lock(); 

 txt_search.begin( doc, pattern, mode, -1, -1 ); 
 while ( true ) { 
     TextSearchResult result = txt_search.run();
     if ( result.getCode() == TextSearchResult.e_found ) {
         System.out.println("found one instance: " + result.getResultStr()); 
     
     else { 
        break; 
     } 
 }

 //unlock the document to avoid deadlock.
 doc.unLock();
 }
 

Summary

[Expand] Inherited Methods
From class java.lang.Object boolean equals(Object arg0) final Class<?> getClass() int hashCode() final void notify() final void notifyAll() String toString() final void wait(long arg0, int arg1) final void wait(long arg0) final void wait()
From interface java.lang.AutoCloseable abstract void close()