tags/lttv-0.11.3-23102008/doc/developer/developer_guide/html/x50.html

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  77 >2.3. Using the reading context</A
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  79 ><P
  80 >&#13;If you have read the tutorials about writing a text and a graphic module, you
  81 should be fairly ready to use the information provided to your hook by the
  82 reading API.
  83 </P
  84 ><P
  85 >&#13;The data structures of the reading context are based on the gobject, a
  86 object-oriented library from the glib. Some evolved types that are found in the
  87 context also comes from the "glib" (GArray, GHashTable and so on). For detailed
  88 information about "gobjects" and the "glib", see the <A
  89 HREF="http://www.gtk.org"
  90 TARGET="_top"
  91 >www.gtk.org</A
  92 > website. They provide a complete
  93 API reference about the data types they provide.
  94 </P
  95 ><P
  96 >&#13;The reading context is object oriented. It is described by the lttv/tracecontext.h
  97 header. Is can be illustrated with this UML class diagram :
  98 </P
  99 ><P
 100 >&#13;<DIV
 101 CLASS="mediaobject"
 102 ><P
 103 ><IMG
 104 SRC="lttv-context.png"
 105 ALIGN="center"><DIV
 106 CLASS="caption"
 107 ><P
 108 >Linux Trace Toolkit Viewer Reading Context Class Diagram</P
 109 ></DIV
 110 ></P
 111 ></DIV
 112 >
 113 </P
 114 ><P
 115 >&#13;Though, for performance's sake, navigating through it is not as encapsulated as
 116 it could. Consider the class attributes to be all public (no get/set functions).
 117 Sometimes, iteration upon a specific element can be uneasy. For example, you may
 118 have to get the number of tracefiles in a trace from the "vt" field of the trace
 119 context to be able to iterate over all the tracefiles contained by the trace.
 120 </P
 121 ><P
 122 >&#13;To facilitate the common operations on the reading context, LTTV now provides a
 123 header that consists of simple macros : lttv/contextmacros.h. It gives an object
 124 look-and-feel to the context classes. Simple "GET" macros can be used to easily
 125 access the different fields are iterate over the elements (and get the total
 126 number of elements too).
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