hx2dp_c |

Table of contents## Procedurehx2dp_c ( Hexadecimal string to d.p. number ) void hx2dp_c ( ConstSpiceChar * string, SpiceInt errmln, SpiceDouble * number, SpiceBoolean * error, SpiceChar errmsg [] ) ## AbstractConvert a string representing a double precision number in a base 16 "scientific notation" into its equivalent double precision number. ## Required_ReadingNone. ## KeywordsALPHANUMERIC CONVERSION ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- MAXMAN P Maximum number of digits in a hex mantissa. string I Hex form string to convert to double precision. errmln I Available space for output string `errmsg'. number O Double precision value to be returned. error O A logical flag which is SPICETRUE on error. errmsg O A descriptive error message. ## Detailed_Inputstring is a character string containing a base 16 "scientific notation" representation of a double precision number which is to be converted to a double precision number. Examples of such a string are: "2A^3" = ( 2/16 + 10/( 16^2 ) ) * 16^3 = 672.0 and "-B^1" = - ( 11/16 ) * 16^1 = -11.0 The following table describes the character set used to represent the hexadecimal digits and their corresponding values. Character Value Character Value --------- ------- --------- ------- "0" 0.0e0 "8" 8.0e0 "1" 1.0e0 "9" 9.0e0 "2" 2.0e0 "A","a" 10.0e0 "3" 3.0e0 "B","b" 11.0e0 "4" 4.0e0 "C","c" 12.0e0 "5" 5.0e0 "D","d" 13.0e0 "6" 6.0e0 "E","e" 14.0e0 "7" 7.0e0 "F","f" 15.0e0 The caret, or hat, character, "^", is used to distinguish the exponent. The plus sign, "+", and the minus sign, "-", are used, and they have their usual meanings. A base 16 "scientific notation" character string which is to be parsed by this routine should consist of a sign, "+" or "-" (the plus sign is optional for nonnegative numbers), followed immediately by a contiguous sequence of hexadecimal digits, the exponent character, and a signed hexadecimal exponent. The exponent is required, but the sign is optional for a nonnegative exponent. A number in base 16 "scientific notation" consists of a contiguous sequence of characters with one of the 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 (5) +h h h h ... h ^+H H ... H 1 2 3 4 n 1 2 m (6) -h h h h ... h ^+H H ... H 1 2 3 4 n 1 2 m (7) h h h h ... h ^-H H ... H 1 2 3 4 n 1 2 m (8) +h h h h ... h ^-H H ... H 1 2 3 4 n 1 2 m (9) -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; and + and - have their usual interpretations. `string' may have leading and trailing blanks, but blanks embedded within the significant portion of the input string are not allowed. errmln is the maximum length of the output `errmsg'. The value defined by `errmln' should be one plus the value large enough to hold any possible output. ## Detailed_Outputnumber is the double precision value to be returned. The value of this argument is not changed if an error occurs while parsing the input string. error is a logical flag which indicates whether an error occurred while attempting to parse `number' from the input character string `string'. `error' will have the value SPICETRUE if an error occurs. It will have the value SPICEFALSE otherwise. errmsg is a descriptive error message if an error occurs while attempting to parse the number `number' from the hexadecimal character string `string', blank otherwise. ## ParametersMAXMAN is the maximum number of digits in a hexadecimal mantissa. The value of MAXMAN is 31. The current value of MAXMAN is more than sufficient for most double precision implementations, providing almost twice as many digits as can actually be produced. This value may be changed when a greater precision is known to exist among all of the supported platforms. ## Exceptions1) If an unexpected character is encountered, an appropriate error message will be set, and the routine will exit. The value of `number' will be unchanged. 2) If the input string represents a number that is larger in absolute magnitude than the maximum representable double precision number an appropriate error message will be set, and the routine will exit. The value of `number' will be unchanged. 3) If the input string is blank, an appropriate error message will be set, and the routine will exit. The value of `number' will be unchanged. 4) If the string has too many digits in the mantissa, then an appropriate error message will be set, and the routine will exit. The value of `number' will be unchanged. 5) If the output error message string is not long enough to contain the entire error message, the error message will be truncated on the right. 6) This routine does NOT check for underflow errors when constructing a double precision number. 7) If the `string' input string pointer is null, the error SPICE(NULLPOINTER) is signaled. 8) If the `string' input string has zero length, the error SPICE(EMPTYSTRING) is signaled. 9) If the `errmsg' output string pointer is null, the error SPICE(NULLPOINTER) is signaled. 10) If the `errmsg' output string has length less than two characters, the error SPICE(STRINGTOOSHORT) is signaled, since the output string is too short to contain one character of output data plus a null terminator. ## FilesNone. ## ParticularsThis routine will convert a character string containing a number in base 16 "scientific notation" into its equivalent double precision number. 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_c -- Convert a double precision number into a base 16 "scientific notation" character string. ## ExamplesThe numerical results shown for this example may differ across platforms. The results depend on the SPICE kernels used as input, the compiler and supporting libraries, and the machine specific arithmetic implementation. 1) Convert a set of character strings containing a base 16 "scientific notation" representation of a double precision number, to their double precision values. Example code begins here. /. Program hx2dp_ex1 ./ #include <stdio.h> #include "SpiceUsr.h" int main() { /. Local constants. ./ #define ERRLEN 81 /. Local variables. ./ SpiceBoolean error; SpiceChar errmsg [ERRLEN]; SpiceDouble value; SpiceInt i; /. Assign an array of strings representing, in base 16 "scientific notation", double precision numbers. Not all of them are valid representations. ./ SpiceChar * number[] = { "89705F4136B4A6^-7", "12357898765X34", "1^1", "-1^1", "4^3", "-4^3", "7F5EB^5", "7F5eb^5", "1B^2", "+1B^2", "+1B^+2", "0^0", " ", "-AB238Z^2", "234ABC", "234ABC^" }; /. Loop over the `number' array, call ## Restrictions1) The current value of MAXMAN is more than sufficient for most double precision implementations, providing almost twice as many digits as can actually be produced. ## Literature_ReferencesNone. ## Author_and_InstitutionJ. Diaz del Rio (ODC Space) E.D. Wright (JPL) ## Version-CSPICE Version 1.1.0, 10-AUG-2021 (JDR) Changed the input argument name "lenout" to "errmln" for consistency with other routines. Updated wrapper code to remove unnecessary chkin_c/chkout_c calls and cast output `error' flag to SpiceBoolean. Edited the header to comply with NAIF standard. Added complete code example based on existing example. Added description of MAXMAN parameter to the -Brief_I/O and -Parameters sections. -CSPICE Version 1.0.0, 10-APR-2010 (EDW) ## Index_Entriesconvert signed normalized hexadecimal string to d.p. convert encoded d.p. number to d.p. number convert base 16 scientific notation d.p. number |

Fri Dec 31 18:41:08 2021