Re: matching tags in text

On 12/13/06, James Rich <james@xxxxxxxxxxx> wrote:

I've written some code which has some bugs.  I think I need to scrap the
whole thing and start over with a fresh approach.  I need to replace tags
in a string with another string.  So I'm looking for ideas on the best
ways to accomplish this.  Here's an example of what the original string
might look like:

This string is <tag 1>an example string</tag 1> that I made up.

My code needs to replace <tag 1> with some string (passed to it is
beginstring) and replace </tag 1> with some string (passed as endstring).
I need to catch errors like opening tags that don't have closing tags and
opening tags that occur before a previous opening tag's matching end tag.
I'm almost certain this is something that lots of RPG programmers have
done before.  My code sucks.  How do you do it?

Hi James,

I would start with a control struct that encapsulates a tag in a string:
  d  refTag    ds    qualified
  d  bx          10i 0
  d  Lx          10i 0
  d tagType     1a

constants that enumerate the tagType:
 d  conTagType_Begin   c    '1'
 d  conTagType_End     c   '2'
 d  conTagType_eof      c  '3'
 d  conTagType_bof      c  '4'

a proc that constructs a tag:
 d  tag_Construct     pr     likeds(refTag)
 d                                     extproc(''tag_Construct')
 d InTagType               1a  const

a procedure to scan for the next tag:
 d  tag_ScanNext    pr        likeds(refTag)
 d                                      extproc('tag_ScanNext')
 d InString             32000 a  varying options(*varsize) const
 d InCurTag                         const likeds(refTag)
 d                                       options(*omit)

this proc starts the scan from the current tag and returns the refTag
struct that represents the next tag.

here is that basic loop that steps from tag to tag in the string
 /free
     tag  = tags_Construct( conTagType_bof ) ;
     dow    conTrue ;
      curTag = tag ;
       tag = tag_ScanNext( sText: curTag ) ;
       select ;
       when    tag.TagType = conTagType_eof ;
          leave ;

       when    curTag.TagType = conTagType_begin
                  and tag.TagType <> conTagType_end ;
          // this is an error. begin tag not followed by end tag

       when    curTag.TagType = conTagType_bof
                  and  tag.TagType = conTagType_end ;
          // error. end tag not preceeded by begin tag

       when    tag.TagType = conTagType_begin
                  and curTag.TagType = conTagType_bof ;
           iter ;   // got the begin tag. now loop back and get the end tag.

        when   curTag.TagType = conTagType_begin
                   and tag.TagType = conTagType_end
           RenameTag( sText: curTag: tag ) ;

         endsl ;
       enddo ;

to rename the key in both the begin and end tag:
 d tag_RenameKey   pr
 d                                             extproc('tag_RenameKey')
 d  InString                    32000 a  varying options(*varsize)
 d  InBeginTag                            likeds(refTag)
 d InEndTag                              likeds(refTag)
 d InNewKey                     80a  const varying

this proc can rename the keys in the tags because it gets the string
the tags are contained in and the refTag structs of the begin and end
tag that identifiy the location of the tags in the string.

good luck! hope it helps.

-Steve