windows-nt-4.0/private/crt32/convert/strtod.c

/***
*strtod.c - convert string to floating point number
*
*	Copyright (c) 1985-1992, Microsoft Corporation. All rights reserved.
*
*Purpose:
*	Convert character string to floating point number
*
*Revision History:
*	09-09-83  RKW	Module created
*	08-19-85  TDC	changed to strtod
*	04-13-87  JCR	Added "const" to declaration
*	04-20-87  BCM	Added checks for negative overflow and for underflow
*	11-09-87  BCM	different interface under ifdef MTHREAD
*	12-11-87  JCR	Added "_LOAD_DS" to declaration
*	02-22-88  JCR	Added cast to nptr to get rid of cl const warning
*	05-24-88  PHG	Merged DLL and normal versions
*	08-24-88  PHG	No digits found => *endptr = nptr [ANSI]
*			Revised test order so invalid detection works always
*	10-20-88  JCR	Changed 'DOUBLE' to 'double' for 386
*	11-20-89  JCR	atof() is always _cdecl in 386 (not pascal)
*	03-05-90  GJF	Fixed calling type, added #include <cruntime.h>,
*			removed #include <register.h>, removed redundant
*			prototypes, removed some leftover 16-bit support and
*			fixed the copyright. Also, cleaned up the formatting
*			a bit.
*	07-23-90  SBM	Compiles cleanly with -W3 (added/removed appropriate
*			#includes)
*	08-01-90  SBM	Renamed <struct.h> to <fltintrn.h>
*	09-27-90  GJF	New-style function declarators.
*	10-21-92  GJF	Made char-to-int conversion unsigned.
*
*******************************************************************************/

#include <cruntime.h>
#include <stdlib.h>
#include <fltintrn.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>
#include <math.h>

/***
*double strtod(nptr, endptr) - convert string to double
*
*Purpose:
*	strtod recognizes an optional string of tabs and spaces,
*	then an optional sign, then a string of digits optionally
*	containing a decimal point, then an optional e or E followed
*	by an optionally signed integer, and converts all this to
*	to a floating point number.  The first unrecognized
*	character ends the string, and is pointed to by endptr.
*
*Entry:
*	nptr - pointer to string to convert
*
*Exit:
*	returns value of character string
*	char **endptr - if not NULL, points to character which stopped
*			the scan
*
*Exceptions:
*
*******************************************************************************/

double _CRTAPI1 strtod (
	const char *nptr,
	REG2 char **endptr
	)
{

#ifdef	MTHREAD
	struct _flt answerstruct;
#endif

	FLT	 answer;
	double	     tmp;
	unsigned int flags;
	REG1 char *ptr = (char *) nptr;

	/* scan past leading space/tab characters */

	while ( isspace((int)(unsigned char)*ptr) )
		ptr++;

	/* let _fltin routine do the rest of the work */

#ifdef	MTHREAD
	/* ok to take address of stack variable here; fltin2 knows to use ss */
	answer = _fltin2( &answerstruct, ptr, strlen(ptr), 0, 0);
#else
	answer = _fltin(ptr, strlen(ptr), 0, 0);
#endif

	if ( endptr != NULL )
		*endptr = (char *) ptr + answer->nbytes;

	flags = answer->flags;
	if ( flags & (512 | 64)) {
		/* no digits found or invalid format:
		   ANSI says return 0.0, and *endptr = nptr */
		tmp = 0.0;
		if ( endptr != NULL )
			*endptr = (char *) nptr;
	}
	else if ( flags & (128 | 1) ) {
		if ( *ptr == '-' )
			tmp = -HUGE_VAL;	/* negative overflow */
		else
			tmp = HUGE_VAL; 	/* positive overflow */
		errno = ERANGE;
	}
	else if ( flags & 256 ) {
		tmp = 0.0;			/* underflow */
		errno = ERANGE;
	}
	else
		tmp = answer->dval;

	return(tmp);
}