STRING_TO_DECIMAL(3C) Standard C Library Functions STRING_TO_DECIMAL(3C)

NAME


string_to_decimal, file_to_decimal, func_to_decimal - parse characters
into decimal record

SYNOPSIS


#include <floatingpoint.h>

void string_to_decimal(char **pc, int nmax,
int fortran_conventions, decimal_record *pd,
enum decimal_string_form *pform, char **pechar);


void func_to_decimal(char **pc, int nmax,
int fortran_conventions, decimal_record *pd,
enum decimal_string_form *pform, char **pechar,
int (*pget)(void), int *pnread, int (*punget)(int c));


#include <stdio.h>

void file_to_decimal(char **pc, int nmax,
int fortran_conventions, decimal_record *pd,
enum decimal_string_form *pform, char **pechar,
FILE *pf, int *pnread);


DESCRIPTION


These functions attempt to parse a numeric token from at most nmax
characters read from a string **pc, a file *pf, or function (*pget). They
set the decimal record *pd to reflect the value of the numeric token
recognized and set *pform and *pechar to indicate its form.


The accepted forms for the numeric token consist of an initial, possibly
empty, sequence of white-space characters, as defined by isspace(3C),
followed by a subject sequence representing a numeric value, infinity, or
NaN. The subject sequence consists of an optional plus or minus sign
followed by one of the following:

o a non-empty sequence of decimal digits optionally containing a
decimal point character, then an optional exponent part

o one of INF or INFINITY, ignoring case

o one of NAN or NAN(string), ignoring case in the NAN part;
string can be any sequence of characters not containing ')'
(right parenthesis) or '\0' (null).


The fortran_conventions argument provides additional control over the set
of accepted forms. It must be one of the following values:

0
no Fortran conventions


1
Fortran list-directed input conventions


2
Fortran formatted input conventions, blanks are ignored


3
Fortran formatted input conventions, blanks are interpreted as
zeroes


When fortran_conventions is zero, the decimal point character is the
current locale's decimal point character, and the exponent part consists
of the letter E or e followed by an optional sign and a non-empty string
of decimal digits.


When fortran_conventions is non-zero, the decimal point character is "."
(period), and the exponent part consists of either a sign or one of the
letters E, e, D, d, Q, or q followed by an optional sign, then a non-
empty string of decimal digits.


When fortran_conventions is 2 or 3, blanks can appear in the digit
strings for the integer, fraction, and exponent parts, between the
exponent delimiter and optional exponent sign, and after an INF,
INFINITY, NAN, or NAN(string). When fortran_conventions is 2, all blanks
are ignored. When fortran_conventions is 3, blanks in digit strings are
interpreted as zeros and other blanks are ignored.


The following table summarizes the accepted forms and shows the
corresponding values to which *pform and pd->fpclass are set. Here digits
represents any string of decimal digits, "." (period) stands for the
decimal point character, and exponent represents the exponent part as
defined above. Numbers in brackets refer to the notes following the
table.


form *pform pd->fpclass
------------------------------------------------------------------
all white space [1] whitespace_form fp_zero
digits fixed_int_form fp_normal [2]
digits. fixed_intdot_form fp_normal [2]
.digits fixed_dotfrac_form fp_normal [2]
digits.digits fixed_intdotfrac_form fp_normal [2]
digits exponent floating_int_form fp_normal [2]
digits. exponent floating_intdot_form fp_normal [2]
.digits exponent floating_dotfrac_form fp_normal [2]
digits.digits exponent floating_intdotfrac_form fp_normal [2]
INF inf_form fp_infinity
INFINITY infinity_form fp_infinity
NAN nan_form fp_quiet
NAN(string) nanstring_form fp_quiet
none of the above invalid_form fp_signaling


Notes:

1. The whitespace_form is accepted only when fortran_conventions
is 2 or 3 and is interpreted as zero.

2. For all numeric forms, pd->fpclass is set to fp_normal if any
non-zero digits appear in the integer or fraction parts, and
otherwise pd->fpclass is set to fp_zero.


If the accepted token has one of the numeric forms and represents a non-
zero number x, its significant digits are stored in pd->ds. Leading and
trailing zeroes and the radix point are omitted. pd->sign and
pd->exponent are set so that if m is the integer represented by pd->ds,

-1**(pd->sign) * m * 10**(pd->exponent)


approximates x to at least 511 significant digits. pd->more is set to 1
if this approximation is not exact (that is, the accepted token contains
additional non-zero digits beyond those copied to pd->ds) and to 0
otherwise.


If the accepted token has the NAN(string) form, up to 511 characters from
the string part are copied to pd->ds.


pd->ds is always terminated by a null byte, and pd->ndigits is set to the
length of the string stored in pd->ds.


On entry, *pc points to the beginning of a character string buffer. The
string_to_decimal() function reads characters from this buffer until
either enough characters are read to delimit the accepted token (for
example, a null character marking the end of the string is found) or the
limit of nmax characters is reached. The file_to_decimal() function reads
characters from the file *pf and stores them in the buffer. The
func_to_decimal() function reads characters one at a time by calling the
function (*pget)() and stores them in the buffer; (*pget)() must return
integer values in the range -1 to 255, where -1 is interpreted as EOF and
0, ..., 255 are interpreted as unsigned char values. Both
file_to_decimal() and func_to_decimal() read characters until either
enough characters are read to delimit the accepted token, EOF is
encountered, or the limit of nmax characters is reached. These functions,
therefore, typically read one or more additional characters beyond the
end of the accepted token and attempt to push back any excess characters
read. Provided that the punget argument is not NULL, func_to_decimal()
pushes back characters one at a time by calling (*punget)(c), where c is
an integer in the range 0 to 255 corresponding to a value previously read
via (*pget)(). After pushing back as many excess characters as possible,
file_to_decimal() and func_to_decimal() store a null byte in the buffer
following the last character read and not pushed back and set *pnread to
the number of characters stored in the buffer prior to this null byte.
Since these functions can read up to nmax characters, the buffer must be
large enough to hold nmax + 1.


On exit, *pc points to the next character in the buffer past the last one
that was accepted as part of the numeric token. If no valid token is
found, *pc is unchanged. If file_to_decimal() and func_to_decimal()
successfully push back all unused characters, *pc points to the null byte
stored in the buffer following the last character read and not pushed
back.


If the accepted token contains an exponent part, *pechar is set to point
to the position in the buffer where the first character of the exponent
field is stored. If the accepted token does not contain an exponent
part, *pechar is set to NULL.

USAGE


If the _IOWRT flag is set in *pf, file_to_decimal() reads characters
directly from the file buffer until a null character is found. (The
_IOWRT flag should only be set when file_to_decimal() is called from
sscanf(3C).) Otherwise, file_to_decimal() uses getc_unlocked(3C), so it
is not MT-safe unless the caller holds the stream lock.

ATTRIBUTES


See attributes(7) for descriptions of the following attributes:


+---------------+-------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-------------------------+
|MT-Level | MT-Safe with exceptions |
+---------------+-------------------------+

SEE ALSO


ctype(3C), decimal_to_floating(3C), getc_unlocked(3C), isspace(3C),
localeconv(3C), scanf(3C), setlocale(3C), strtod(3C), ungetc(3C),
attributes(7)

illumos October 1, 2003 STRING_TO_DECIMAL(3C)