-
- // Position the file position indicator at first tag (i.e.
- // after the file preamble and the "DICM" string).
- rewind(fp);
- fseek (fp, 132L, SEEK_SET);
- return;
- } // End of DicomV3
-
- // Alas, this is not a DicomV3 file and whatever happens there is no file
- // preamble. We can reset the file position indicator to where the data
- // is (i.e. the beginning of the file).
- dbg.Verbose(1, "gdcmHeader::CheckSwap:", "not a DICOM Version3 file");
- rewind(fp);
-
- // Our next best chance would be to be considering a 'clean' ACR/NEMA file.
- // By clean we mean that the length of the first tag is written down.
- // If this is the case and since the length of the first group HAS to be
- // four (bytes), then determining the proper swap code is straightforward.
-
- entCur = deb + 4;
- // We assume the array of char we are considering contains the binary
- // representation of a 32 bits integer. Hence the following dirty
- // trick :
- s = *((guint32 *)(entCur));
-
- switch (s) {
- case 0x00040000 :
- sw = 3412;
- filetype = ACR;
- return;
- case 0x04000000 :
- sw = 4321;
- filetype = ACR;
- return;
- case 0x00000400 :
- sw = 2143;
- filetype = ACR;
- return;
- case 0x00000004 :
- sw = 0;
- filetype = ACR;
- return;
- default :
- dbg.Verbose(0, "gdcmHeader::CheckSwap:",
- "ACR/NEMA unfound swap info (time to raise bets)");
- }
-
- // We are out of luck. It is not a DicomV3 nor a 'clean' ACR/NEMA file.
- // It is time for despaired wild guesses. So, let's assume this file
- // happens to be 'dirty' ACR/NEMA, i.e. the length of the group is
- // not present. Then the only info we have is the net2host one.
- filetype = Unknown;
- if (! net2host )
- sw = 0;
- else
- sw = 4321;
- return;
-}
-
-/**
- * \ingroup gdcmHeader
- * \brief
- * @param
- * @return
- */
- void gdcmHeader::SwitchSwapToBigEndian(void) {
- dbg.Verbose(1, "gdcmHeader::SwitchSwapToBigEndian",
- "Switching to BigEndian mode.");
- if ( sw == 0 ) {
- sw = 4321;
- return;
- }
- if ( sw == 4321 ) {
- sw = 0;
- return;
- }
- if ( sw == 3412 ) {
- sw = 2143;
- return;
- }
- if ( sw == 2143 )
- sw = 3412;
-}
-
-/**
- * \ingroup gdcmHeader
- * \brief Find the value representation of the current tag.
- */
-void gdcmHeader::FindVR( gdcmElValue *ElVal) {
- if (filetype != ExplicitVR)
- return;
-
- char VR[3];
- string vr;
- int lgrLue;
- char msg[100]; // for sprintf. Sorry
-
- long PositionOnEntry = ftell(fp);
- // Warning: we believe this is explicit VR (Value Representation) because
- // we used a heuristic that found "UL" in the first tag. Alas this
- // doesn't guarantee that all the tags will be in explicit VR. In some
- // cases (see e-film filtered files) one finds implicit VR tags mixed
- // within an explicit VR file. Hence we make sure the present tag
- // is in explicit VR and try to fix things if it happens not to be
- // the case.
- bool RealExplicit = true;
-
- lgrLue=fread (&VR, (size_t)2,(size_t)1, fp);
- VR[2]=0;
- vr = string(VR);
-
- // Assume we are reading a falsely explicit VR file i.e. we reached
- // a tag where we expect reading a VR but are in fact we read the
- // first to bytes of the length. Then we will interogate (through find)
- // the dicom_vr dictionary with oddities like "\004\0" which crashes
- // both GCC and VC++ implementations of the STL map. Hence when the
- // expected VR read happens to be non-ascii characters we consider
- // we hit falsely explicit VR tag.
-
- if ( (!isalpha(VR[0])) && (!isalpha(VR[1])) )
- RealExplicit = false;
-
- // CLEANME searching the dicom_vr at each occurence is expensive.
- // PostPone this test in an optional integrity check at the end
- // of parsing or only in debug mode.
- if ( RealExplicit && !dicom_vr->Count(vr) )
- RealExplicit= false;
-
- if ( RealExplicit ) {
- if ( ElVal->IsVrUnknown() ) {
- // When not a dictionary entry, we can safely overwrite the vr.
- ElVal->SetVR(vr);
- return;