1 files changed, 91 insertions, 0 deletions
diff --git a/noao/imred/vtel/readsubswath.x b/noao/imred/vtel/readsubswath.x
new file mode 100644
index 00000000..9c15bb44
--- /dev/null
+++ b/noao/imred/vtel/readsubswath.x
@@ -0,0 +1,91 @@
+include <mach.h>
+include <fset.h>
+include	"vt.h"
+
+define	SZ_VTRECFD	5120		# length, in chars, of full disk recs
+
+# READSUBSWATH -- Read data from file whose logical unit is inputfd.
+# Swap the bytes in each data word.
+
+procedure readsubswath (inputfd, selfbuf, databuf, buflength, bp)
+
+int	inputfd			# input file discriptor
+int	buflength		# length of data buffer
+bool	selfbuf			# self buffering flag
+short	databuf[buflength]	# data buffer
+pointer	bp			# buffer pointer structure pointer
+
+int	num, bleft, last_recsize
+int	read()
+errchk	read
+
+begin
+	# If we are doing our own buffering, keep track of the number
+	# of records in each file, else let mtio do it.
+
+	last_recsize = 0
+	if (selfbuf) {		# do our own buffering
+
+	    # If there is enough data still in the buffer, just copy data
+	    # to the output buffer and move the pointer, otherwise, read
+	    # the next tape record.
+
+	    if ((VT_BUFBOT(bp) - VT_BP(bp)) >= buflength) {
+		# Copy the data into the data buffer, move the pointer.
+		call amovs (Mems[VT_BP(bp)], databuf, buflength)
+		VT_BP(bp) = VT_BP(bp) + buflength
+
+	    } else {
+		# Copy leftover data from the bottom of the input buffer
+		# into the top of the input buffer, reset the flags.
+
+		bleft = VT_BUFBOT(bp) - VT_BP(bp)
+		call amovs (Mems[VT_BP(bp)], Mems[VT_BUFP(bp)], bleft)
+		VT_BP(bp) = VT_BUFP(bp) + bleft
+
+		# Read in another tape record.
+		# Check the number of chars read.  If this number is EOF or
+		# too short, error.  If it is too long, truncate to correct
+		# length.  This is done because some data tapes are written
+		# in a weird way and have some noise chars tacked on the end
+		# of each tape record.
+
+	        iferr (num = read (inputfd, Mems[VT_BP(bp)],
+		    10000*SZB_SHORT/SZB_CHAR)) {
+		    call fseti (inputfd, F_VALIDATE,
+			SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
+		    call printf ("Error reading subswath.\n")
+		    num = read (inputfd, Mems[VT_BP(bp)],
+		        SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
+	        }
+		if (num == EOF)
+		    call error (0, "EOF encountered on tape read")
+	        else if (num < SZ_VTRECFD*SZB_SHORT/SZB_CHAR)
+	            call error (0, "error on tape read, record too short")
+		else if (num >= SZ_VTRECFD*SZB_SHORT/SZB_CHAR &&
+		    num < (SZ_VTRECFD+300)*SZB_SHORT/SZB_CHAR)
+		    num = SZ_VTRECFD*SZB_SHORT/SZB_CHAR 
+		else
+	            call error (0, "error on tape read, record too long")
+
+		# Update the pointers, move data into the data buffer.
+		VT_BUFBOT(bp) = VT_BP(bp) + num
+		call amovs (Mems[VT_BP(bp)], databuf, buflength)
+		VT_BP(bp) = VT_BP(bp) + buflength
+	    }
+	} else {		# Let the mtio do the buffering.
+	    iferr (num = read (inputfd, databuf,
+		buflength*SZB_SHORT/SZB_CHAR)) {
+		call fseti (inputfd, F_VALIDATE,
+		    last_recsize*SZB_SHORT/SZB_CHAR)
+		call printf ("Error on tape read.\n")
+		num = read (inputfd, databuf, buflength*SZB_SHORT/SZB_CHAR)
+	    }
+	    last_recsize = num
+	    if (num < buflength*SZB_SHORT/SZB_CHAR)
+	        call error (0, "eof encountered when reading subswath")
+	}
+
+	if (BYTE_SWAP2 == YES)
+	    call bswap2 (databuf, 1, databuf, 1, buflength * SZB_SHORT)
+end