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include <mach.h>
include "idsmtn.h"
define RED_FLAG_OFFSET 3 # Byte offset (starts at bit 17)
define DF_ORD_OFFSET 9 # Byte offset to df order value (bit 65)
define DFB 4 # Number of bytes per DF coefficient
define FIRST_BYTE 13
# REDUCTION_FLAGS -- Extract and interpret the reduction flags found in
# the IDS header. 9 flags are used: DF, SM, QF, DC, QD, EX, BS, CA, CO.
# Each flag is represented by a single bit in a varian 16-bit integer.
# If a flag is set, it's value = 0; unset flags = -1. If the QF flag is
# set, the order of the fitting polynomial must be unpacked. If the DF
# flag is set, the order of the fitting polynomial as well as the
# coefficients must be unpacked from the header. The location of the
# coefficients depends on the order of the fit.
procedure reduction_flags (vn, ids)
int vn[ARB] # Input buffer of IDS record - one byte per int
pointer ids # Pointer to ids header structure
int flag_word, offset, byte_offset, op
real rtemp, tmp[MAX_NCOEFF]
errchk vn_rred
begin
# Initialize flags to -1
DF_FLAG(ids) = -1
SM_FLAG(ids) = -1
QF_FLAG(ids) = -1
DC_FLAG(ids) = -1
QD_FLAG(ids) = -1
EX_FLAG(ids) = -1
BS_FLAG(ids) = -1
CA_FLAG(ids) = -1
CO_FLAG(ids) = -1
# Unpack the flag_word from the header and determine flags. If a
# flag_bit is set, the corresponding flag is true and set = 0.
flag_word = vn[RED_FLAG_OFFSET] * (2 ** 8) + vn[RED_FLAG_OFFSET+1]
if (and (flag_word, 40B) != 0)
CO_FLAG(ids) = 0
if (and (flag_word, 100B) != 0)
CA_FLAG(ids) = 0
if (and (flag_word, 200B) != 0)
BS_FLAG(ids) = 0
if (and (flag_word, 400B) != 0)
EX_FLAG(ids) = 0
if (and (flag_word, 1000B) != 0)
QD_FLAG(ids) = 0
if (and (flag_word, 2000B) != 0)
DC_FLAG(ids) = 0
if (and (flag_word, 4000B) != 0)
# The qf_flag is set equal to the degree of the fitting polynomial.
# This value is stored in the lowest 5-bits of the flag word.
QF_FLAG(ids) = and (flag_word, 37B)
if (and (flag_word, 10000B) != 0)
SM_FLAG(ids) = 0
# The df_flag is interpreted next:
if (and (flag_word, 20000B) != 0) {
# The degree of the fitting polynomial is written in 2wrd_vn_fp at
# the location of the first data pixel. The df_flag is set equal
# to the integer value of the polynomial degree.
call vn_rred (vn, DF_ORD_OFFSET, rtemp, 1)
DF_FLAG(ids) = int (rtemp)
# Now to unpack the coefficients. The coefficients have been
# written over pixels at the beginning and end of the IDS scan.
# The number and location of the overwritten pixels depends on
# the order of fit and values of NP1 and NP2.
do op = 1, DF_FLAG(ids) {
offset = op
if (offset >= NP1(ids))
# This coefficient must be stored at the end of scan
offset = offset + NP2(ids) - NP1(ids)
byte_offset = FIRST_BYTE + ((offset - 1) * DFB)
call vn_rred (vn, byte_offset, tmp[op], 1)
}
# Copy decoded coefficients into structure
call amovr (tmp, Memr[COEFF(ids)], DF_FLAG(ids))
}
end
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