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tricsnex.tex

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+\subsection{TRICS NeXus Data Files}
+This section describes the data file handling for the four circle
+diffractometer TRICS at SinQ. TRICS collects a lot of detector frames in
+time intervalls of days or weeks. The data writing scheme has to adress the
+issue, that the HDF routines  cannot ensure that there is no data corruption
+when writing data files. 
+
+Thus the following scheme is implemented: With a special command, the user
+enforces a new file. At that time header information is written. After that
+the file is closed. With another command, the file is reopened and a frame
+is added to it. Each frame data group will hold a flag which decides if the
+frame is valid or not. After writing the frame, the file is closed again.
+This scheme minimises the danger of data corruption.
+
+The current frame number is kept in a non NeXus standard field in the data file
+itself. This allows to reopen files and append data to it. 
+
+The interface to this object looks like this:
+
+\begin{flushleft} \small
+\begin{minipage}{\linewidth} \label{scrap1}
+$\langle$nxtrics {\footnotesize ?}$\rangle\equiv$
+\vspace{-1ex}
+\begin{list}{}{} \item
+\mbox{}\verb@@\\
+\mbox{}\verb@    typedef struct __NexTrics *pNexTrics;@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@/*----------------------------- live & death -----------------------------*/@\\
+\mbox{}\verb@  pNexTrics CreateNexTrics(pDataNumber pNum, char *pRoot, char *pDict,@\\
+\mbox{}\verb@                           SicsInterp *pSics);@\\
+\mbox{}\verb@  void      DeleteNexTrics(void *pData);@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  int NexTricsFactory(SConnection *pCon, SicsInterp *pSics, void *pData,@\\
+\mbox{}\verb@                      int argc, char *argv[]);@\\
+\mbox{}\verb@/*----------------------------- interaction ------------------------------*/@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  int StartFile(pNexTrics self, SConnection *pCon);@\\
+\mbox{}\verb@ @\\
+\mbox{}\verb@  int ReopenFile(pNexTrics self, char *filename);@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  int DumpFrame(pNexTrics self, SConnection *pCon);@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  int NexTricsAction(SConnection *pCon, SicsInterp *pSics, void *pData,@\\
+\mbox{}\verb@                      int argc, char *argv[]);@\\
+\mbox{}\verb@ @\\
+\mbox{}\verb@@$\diamond$
+\end{list}
+\vspace{-1ex}
+\footnotesize\addtolength{\baselineskip}{-1ex}
+\begin{list}{}{\setlength{\itemsep}{-\parsep}\setlength{\itemindent}{-\leftmargin}}
+\item Macro referenced in scrap ?.
+\end{list}
+\end{minipage}\\[4ex]
+\end{flushleft}
+\begin{description}
+\item[CreateNexTrics] creates a new TRICS NeXus data file writing object.
+Parameters are a data number object for the automatic creation of file names
+and the directory name where the data files ought to live. The next
+parameter is the name of the NeXus dictionary file to use for writing.
+\item[DeleteNexTrics] deletes a NexTrics object. The last parameter is the
+name of the SICS interpreter to search for objects. NexTrics will maintain a
+cache of frequently used SICS objects for writing. 
+\item[NexTricsFactory] is the interpreter wrapper function for the command
+to install the nexus data writing object for Trics into the system.
+\item[StartFile] will automatically create a new file and write the header
+information to it.
+\item[DumpFrame] will dump a frame worth of data to the file. Thereby
+reopening and closing it. This will be called for each detector shot, i.e.
+in the end three frames will be written when all three detectors have been
+installed at TRICS.
+\item[NexTricsAction] is the command interface to the TRICS NeXus data file
+writing object.
+\end{description}
+
+\begin{flushleft} \small
+\begin{minipage}{\linewidth} \label{scrap2}
+\verb@"nextrics.h"@ {\footnotesize ? }$\equiv$
+\vspace{-1ex}
+\begin{list}{}{} \item
+\mbox{}\verb@@\\
+\mbox{}\verb@/*----------------------------------------------------------------------------@\\
+\mbox{}\verb@                           N E X T R I C S@\\
+\mbox{}\verb@ @\\
+\mbox{}\verb@  An object for writing NeXus data files for the four ciclre diffractometer@\\
+\mbox{}\verb@  TRICS at PSI. Can be used as basis for writing files for other four@\\
+\mbox{}\verb@  circles equiped with a PSD as well.@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  copyright: see copyright.h@\\
+\mbox{}\verb@@\\
+\mbox{}\verb@  Mark Koennecke, April 1998@\\
+\mbox{}\verb@------------------------------------------------------------------------------*/@\\
+\mbox{}\verb@#ifndef NEXTRICS@\\
+\mbox{}\verb@#define NEXTRICS@\\
+\mbox{}\verb@@$\langle$nxtrics {\footnotesize ?}$\rangle$\verb@@\\
+\mbox{}\verb@#endif@\\
+\mbox{}\verb@@$\diamond$
+\end{list}
+\vspace{-2ex}
+\end{minipage}\\[4ex]
+\end{flushleft}