/* This routine reads the main header record of a ELAS data file.  

Required input variables:
   name of file (passed as a calling argument)

The name of the input file must contain the fully qualified name of the ELAS file.  
______________

Doug Rickman  10/13/96
mod. June 21, 1997
mod. for ELAS  Oct 25, 1997
mod. for Comments and Color Table Nov 9, 1997
mod. June 19, 1998
_______________________________________________________________ */

input=arg(1)

rc=stream(input,'c','open read')
if rc<>'READY:' then do
   return 'File could not be made ready.'
   end

/* write out the header */
/* Bytes in header  - Bytes per line - Initial Line    - LastLine            */
/* Initial Element  - Last Element   - No. of Channels - ELAS ID flag        */
/* YCD              - YOF            - XCD             - XOF                 */
/* Ht               - Wid            - Tran1           - Tran2               */
/* Tran3            - Tran4          - Word 19         - blank               */
/* blank            - Eikonix flag   - Labl status     - Created by module   */
/* words 25-120 - comments                                          */
/*                                                                           */

/* Read header data from ELAS file                                           */
Header=c2x(charin(input,,4))
if Header='00000400' then nop
else Return 'is not an ELAS file.'

BperLine=x2d(c2x(charin(input,,4)))

InitialLine=x2d(c2x(charin(input,,4)))
LastLine=x2d(c2x(charin(input,,4)))
Nlines=LastLine-InitialLine+1

InitialElement=x2d(c2x(charin(input,,4)))
LastElement=x2d(c2x(charin(input,,4)))
Nelements=LastElement-InitialElement+1

NChannels=x2d(c2x(charin(input,,4)))
ELASflag=charin(input,,4)
YCD=charin(input,,4)
YOF=x2d(c2x(charin(input,,4)),8)
XCD=charin(input,,4)
XOF=x2d(c2x(charin(input,,4)),8)
HT=c2f(reverse(charin(input,,4)))
WID=c2f(reverse(charin(input,,4)))

tran1=c2f(reverse(charin(input,,4)))
tran2=c2f(reverse(charin(input,,4)))
tran3=c2f(reverse(charin(input,,4)))
tran4=c2f(reverse(charin(input,,4)))

/* word 19 */
Sentinal=x2d(c2x(charin(input,,2)))
Word19_16_31=x2b(c2x(charin(input,,2)))
ChannelHeaderFlag=left(Word19_16_31,1)
DataTypeCode=substr(Word19_16_31,2,5)
NBperElement=substr(Word19_16_31,9)

DataTypeCode = x2d(b2x(DataTypeCode))
NBperElement = x2d(b2x(NBperElement))

select
	when DataTypeCode=0  then do
		DataType='MIXED OR UNSPECIFIED DATA TYPE'
		PCIDataType='?'
		end
	when DataTypeCode=1  then do
		DataType='UNSIGNED INTEGER'
		PCIDataType='U'
		end
	when DataTypeCode=16 then do
		DataType='SINGLE PRECISION REAL'
		PCIDataType='R'
		end
	when DataTypeCode=17 then do
		DataType='DOUBLE PRECISION REAL'
		PCIDataType='R'
		end
	when DataTypeCode=18 then do
		DataType='SINGLE PRECISION COMPLEX'
		PCIDataType='Complex'
		end
	when DataTypeCode=19 then do
		DataType='DOUBLE PRECISION COMPLEX'
		PCIDataType='Complex'
		end
	when DataTypeCode=31 then do
		DataType='ASCII CHARACTERS'
		PCIDataType='ASCII'
		end
	otherwise say 'SOMETHING IS WRONG WITH THE DATA TYPE CODE!!!'
	end

/* Words 20-24 */
Undefined1=charin(input,,4)
Undefined2=charin(input,,4)
Eikonix=charin(input,,4)
LABLStatus=charin(input,,4)

CreatedBy=charin(input,,4)

/*  6 lines of comments,  Words 25 - 120 */
comments=''
do i = 1 to 6 
	Comment.i=charin(input,,64)
	comments=comments||comment.i
	end i

/* 256 color table entries, Words 121 - 248  */
do i = 0 to 255
	data=c2x(charin(input,,2))
	Blue.i=x2d(substr(data,2,1))
	Red.i=x2d(substr(data,3,1))
	Green.i=x2d(substr(data,4,1))
	end i

/* undefined block, words 249- 256 */
Undefined3=charin(input,,4)
Undefined4=charin(input,,4)
Undefined5=charin(input,,4)
Undefined6=charin(input,,4)
Undefined7=charin(input,,4)
Undefined8=charin(input,,4)
Undefined9=charin(input,,4)
Undefined10=charin(input,,4)



rc=lineout(in)

return 1