All three of the examples presented here follow the same model: The RPG IV procedures take one varying-length character parameter and return a varying-length character value. Within the procedure, there's a loop over each character of the input. The character is changed if necessary and is then appended to the result.
All three examples demonstrate modifying some text that will be used as input to some other program, an increasingly common programming technique these days. These filters are necessary to ensure that the text is valid input to the other program.
At the end of this tip, I've included two files (Figures 1 and 2). File FILTERS includes the procedures and instructions for use. File TESTFILTS demonstrates how to use the filters.
The first procedure, "QUOTE()", should be used when dynamically constructing SQL queries. For example, you might want to build a query where some value is included in the query as a character literal. Not only are apostrophes needed at the beginning and end, but since apostrophes delimit literals, something must be done with apostrophes within the value. To have a syntactically correct literal, apostrophes within the literal must be doubled. Procedure "QUOTE()" does just that.
The second procedure, "ESCAPE_HTML()", is needed for applications that create HTML documents. Like the apostrophe within SQL literals, certain characters have special meaning within HTML documents. In particular, the less-than and greater-than characters (< and >) bracket HTML tags. When an HTML browser encounters a <, it assumes it has reached an HTML tag. Any text between the < and the > is treated as an HTML tag and is not presented to the user. If you insert text from a database into an HTML document without escaping the special characters, some important text may be invisible to the client. Likewise, the ampersand (&) signals the start of an HTML character entity, so that character needs special treatment too. The solution is to convert the characters <, >, and & to the appropriate character entities:
< = <
> = >
& = &
The final example illustrates a common situation in CGI programming. CGI programs often dynamically build URLs. For example, "http://www.mysite.ca/req?userid=hans&pw=glorp." But notice again that some characters have special meanings within the URL. The question mark (?) identifies the beginning of the parameters. The ampersand (&) separates individual parameters. And the equals sign (=) separates the parameter name from the parameter value. In addition, spaces are not allowed within the string. If you construct a query string with one of the special characters within the text of a parameter, a CGI program may justifiably end up confused. So what do we do if we want one of these special characters within a URL parameter value?
The solution is to convert any "non-safe" character to a hex code prefixed by a percent sign (%), yet another character with special meaning! You've probably seen URLs containing lots of funny characters like %25 or %5E. Procedure ENCODE_QUERY() converts the "non-safe" characters to their appropriate hex value suitable for use in a CGI query string.
These days, when more and more programs construct text intended to be processed by some other program, it is vitally important to build that text in a form that's acceptable to the other program. At best, the program will just abend, and the bug will become obvious to the programmer before the application is made public. Worse, incorrect text could be displayed to clients. At the extreme, errors in constructing URLs could potentially open a server to hacking.
--Hans Boldt
Figure 1: The Procedures and Instructions for Use
Figure 2: How to Use the Filters
|
More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.
TRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now! Request Now.
Forms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.
Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:
Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.
IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn:
LATEST COMMENTS
MC Press Online