TAX was inspired by Stephen Uhler's HTML parser in 10 lines. In fact, the code is almost exactly the same. Just a couple of extra bells and whistles.
TAX, the Tiny API for XML, is vaguely similar to SAX in that for both TAX & SAX, XML is handled by defining a handler for tags. Otherwise, TAX & SAX have more differences than similarities. The most important difference is that with TAX, both the XML and the processed XML reside in memory, so TAX makes inefficient use of memory. For this reason, it's best for small XML files. In contrast, SAX is an event-driven parser that operates on a stream, so the XML doesn't have to all be loaded into memory. (Of course, another important difference is that SAX is a mature, full-featured, well-documented, and well-supported API.)
As with Stephen Uhler's gem, TAX takes an XML file and converts it into a Tcl script. Tags become procs. The XML is then executed by eval'ing the script.
Here's the essential code:
############################################################ # # Based heavily on Stephen Uhler's HTML parser in 10 lines # Modified by Eric Kemp-Benedict for XML # # Turn XML into TCL commands # xml A string containing an html document # cmd A command to run for each html tag found # start The name of the dummy html start/stop tags # # Namespace "tax" stands for "Tiny API for XML" # namespace eval tax {} proc tax::parse {cmd xml {start docstart}} { regsub -all \{ $xml {\&ob;} xml regsub -all \} $xml {\&cb;} xml set exp {<(/?)([^\s/>]+)\s*([^/>]*)(/?)>} set sub "\}\n$cmd {\\2} \[expr \{{\\1} ne \"\"\}\] \[expr \{{\\4} ne \"\"\}\] \ \[regsub -all -- \{\\s+|(\\s*=\\s*)\} {\\3} \" \"\] \{" regsub -all $exp $xml $sub xml eval "$cmd {$start} 0 0 {} \{ $xml \}" eval "$cmd {$start} 1 1 {} {}" }
To use it, create a parser command, cmd, that will handle any tag found in the string xml. The parser calls cmd in the following way:
cmd tag cl selfcl props body
where
Here's an example of use (that also uses snit to build the parser -- there's one snit method for each tag).
package require snit ############################################################ # # Based heavily on Stephen Uhler's HTML parser in 10 lines # Modified by Eric Kemp-Benedict for XML # # Turn XML into TCL commands # xml A string containing an html document # cmd A command to run for each html tag found # start The name of the dummy html start/stop tags # # Namespace "tax" stands for "Tiny API for XML" # namespace eval tax {} proc tax::parse {cmd xml {start docstart}} { regsub -all \{ $xml {\&ob;} xml regsub -all \} $xml {\&cb;} xml set exp {<(/?)([^\s/>]+)\s*([^/>]*)(/?)>} set sub "\}\n$cmd {\\2} \[expr \{{\\1} ne \"\"\}\] \[expr \{{\\4} ne \"\"\}\] \ \[regsub -all -- \{\\s+|(\\s*=\\s*)\} {\\3} \" \"\] \{" regsub -all $exp $xml $sub xml eval "$cmd {$start} 0 0 {} \{ $xml \}" eval "$cmd {$start} 1 0 {} {}" } snit::type parser { proc compactws {s} { return [regsub -all -- {\s+} [string trim $s] " "] } method docstart {cl args} { if $cl { puts "\n...End document" } else { puts "Start document...\n" } } method para {cl selfcl props body} { array set temp $props if {!$cl} { set outstring [compactws $body] if [info exists temp(indent)] { set outstring "[string repeat { } $temp(indent)]$outstring" } puts $outstring } } method meta {cl selfcl props body} { array set temp $props foreach item [array names temp] { puts "[string totitle $item]: $temp($item)" } if {!$selfcl} { puts [compactws $body] } else { puts "" } } } parser myparser tax::parse myparser { <meta author="Anne Onymous"/> <meta> Composed in haste for purposes of demonstration. </meta> <para indent="3"> This is an indented paragraph. Only the first line is indented, which you can tell if the paragraph goes on long enough. </para> <para> This is an ordinary paragraph. No line is indented. Not one. None at all, which you can tell if the paragraph goes on long enough. </para> }
It gives this output:
Start document... Author: Anne Onymous Composed in haste for purposes of demonstration. This is an indented paragraph. Only the first line is indented, which you can tell if the paragraph goes on long enough. This is an ordinary paragraph. No line is indented. Not one. None at all, which you can tell if the paragraph goes on long enough. ...End document
Category XML Category Word and Text Processing Category Internet