DP2HX ( D.p. number to hexadecimal string )
SUBROUTINE DP2HX ( NUMBER, STRING, LENGTH )
Convert a double precision number to an equivalent character
string using a base 16 ``scientific notation.''
None.
ALPHANUMERIC
CONVERSION
DOUBLE PRECISION NUMBER
CHARACTER*(*) STRING
INTEGER LENGTH
VARIABLE I/O DESCRIPTION
-------- --- --------------------------------------------------
NUMBER I D.p. number to be converted.
STRING O Equivalent character string, left justified.
LENGTH O Length of the character string produced.
NUMBER The double precision number to be converted to a
character string representation.
STRING The character string produced by this routine which
represents NUMBER in a base 16 ``scientific notation,''
e.g.:
672.0 = '2A^3' = ( 2/16 + 10/( 16**2 ) ) * 16**3
and
-11.0 = '-B^1' = - ( 11/16 ) * 16**1.
The following table describes the character set used to
represent the hexadecimal digits and their corresponding
values.
Character Value Character Value
--------- ------ --------- ------
'0' 0.0D0 '8' 8.0D0
'1' 1.0D0 '9' 9.0D0
'2' 2.0D0 'A' 10.0D0
'3' 3.0D0 'B' 11.0D0
'4' 4.0D0 'C' 12.0D0
'5' 5.0D0 'D' 13.0D0
'6' 6.0D0 'E' 14.0D0
'7' 7.0D0 'F' 15.0D0
The carat, or hat, character, '^', is used to
distinguish the exponent.
The plus sign, '+', and the minus sign, '-', are used,
and they have their usual meanings.
In order to obtain the entire character string produced
by this routine, the output character string should be
at least N characters long, where
# of bits per double precision mantissa + 3
N = 3 + ----------------------------------------------
4
# of bits per double precision exponent + 3
+ ---------------------------------------------- .
4
There should be one character position for the sign of
the mantissa, one for the sign of the exponent, one for
the exponentiation character, and one for each
hexadecimal digit that could be produced from a mantissa
and an exponent.
The following table contains minimum output string
lengths necessary to obtain the complete character
string produced by this routine for some typical
implementations of double precision numbers.
Double precision number
Size Mantissa Exponent Minimum output string length
bits bits bits
---- -------- -------- ----------------------------
64 48 15 3 + 12 + 4 = 19
64 55+1 8 3 + 14 + 2 = 19 (VAX)
64 52 11 3 + 13 + 3 = 19 (IEEE)
The base 16 ``scientific notation'' character string
produced by this routine will be left justified and
consist of a contiguous sequence of characters with one
of following formats:
(1) h h h h ... h ^H H ... H
1 2 3 4 n 1 2 m
(2) -h h h h ... h ^H H ... H
1 2 3 4 n 1 2 m
(3) h h h h ... h ^-H H ... H
1 2 3 4 n 1 2 m
(4) -h h h h ... h ^-H H ... H
1 2 3 4 n 1 2 m
where
h and H denote hexadecimal digits
i j
'^' denotes exponentiation ( base 16 )
and
'+' and '-' have their usual interpretations.
The character string produced will be blank padded on
the right if LENGTH < LEN( STRING ).
LENGTH Length of the base 16 ``scientific notation'' character
string produced by this routine.
None.
Error free.
1) If the output character string is not long enough to
contain the entire character string that was produced,
the string will be truncated on the right.
2) If LEN( STRING ) > LENGTH, the output character string will
be blank padded on the right.
None.
This routine converts a double precision number into an equivalent
character string using a base 16 ``scientific notation.'' This
representation allows the full precision of a number to be placed
in a format that is suitable for porting or archival storage.
This routine is one of a pair of routines which are used to
perform conversions between double precision numbers and
an equivalent base 16 ``scientific notation'' character string
representation:
DP2HX -- Convert a double precision number into a base 16
``scientific notation'' character string.
HX2DP -- Convert a base 16 ``scientific notation''
character string into a double precision number.
The following input and output argument values illustrate the
action of DP2HX for various input values of NUMBER.
Note: The hat or carat, '^', signals an exponent.
NUMBER STRING LENGTH
----------------- ----------------------------- ------
2.0D-9 89705F4136B4A6^-7 17
1.0D0 1^1 3
-1.0D0 -1^1 4
1024.0D0 4^3 3
-1024.0D0 -4^3 4
521707.0D0 7F5EB^5 7
27.0D0 1B^2 4
0.0D0 0^0 3
The maximum number of characters permitted in the output string
is specified by the local parameter STRLEN.
None.
K.R. Gehringer (JPL)
SPICELIB Version 1.0.1, 10-MAR-1994 (KRG)
Fixed a typo in the description of the input argument STRING.
The example showing the expansion of 160 into hexadecimal
was incorrect. 160 was replaced with 672 which makes the
example correct.
SPICELIB Version 1.0.0, 26-OCT-1992 (KRG)
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