125 lines
4.2 KiB
C
125 lines
4.2 KiB
C
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/***
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*strtod.c - convert string to floating point number
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*
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* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* Convert character string to floating point number
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*
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*Revision History:
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* 09-09-83 RKW Module created
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* 08-19-85 TDC changed to strtod
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* 04-13-87 JCR Added "const" to declaration
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* 04-20-87 BCM Added checks for negative overflow and for underflow
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* 11-09-87 BCM different interface under ifdef MTHREAD
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* 12-11-87 JCR Added "_LOAD_DS" to declaration
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* 02-22-88 JCR Added cast to nptr to get rid of cl const warning
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* 05-24-88 PHG Merged DLL and normal versions
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* 08-24-88 PHG No digits found => *endptr = nptr [ANSI]
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* Revised test order so invalid detection works always
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* 10-20-88 JCR Changed 'DOUBLE' to 'double' for 386
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* 11-20-89 JCR atof() is always _cdecl in 386 (not pascal)
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* 03-05-90 GJF Fixed calling type, added #include <cruntime.h>,
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* removed #include <register.h>, removed redundant
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* prototypes, removed some leftover 16-bit support and
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* fixed the copyright. Also, cleaned up the formatting
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* a bit.
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* 07-23-90 SBM Compiles cleanly with -W3 (added/removed appropriate
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* #includes)
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* 08-01-90 SBM Renamed <struct.h> to <fltintrn.h>
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* 09-27-90 GJF New-style function declarators.
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* 10-21-92 GJF Made char-to-int conversion unsigned.
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* 04-06-93 SKS Replace _CRTAPI* with _cdecl
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 12-15-98 GJF Changes for 64-bit size_t.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <stdlib.h>
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#include <fltintrn.h>
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#include <string.h>
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#include <ctype.h>
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#include <errno.h>
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#include <math.h>
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/***
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*double strtod(nptr, endptr) - convert string to double
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*
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*Purpose:
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* strtod recognizes an optional string of tabs and spaces,
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* then an optional sign, then a string of digits optionally
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* containing a decimal point, then an optional e or E followed
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* by an optionally signed integer, and converts all this to
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* to a floating point number. The first unrecognized
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* character ends the string, and is pointed to by endptr.
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*
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*Entry:
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* nptr - pointer to string to convert
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*
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*Exit:
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* returns value of character string
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* char **endptr - if not NULL, points to character which stopped
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* the scan
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*
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*Exceptions:
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*
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*******************************************************************************/
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double __cdecl strtod (
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const char *nptr,
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REG2 char **endptr
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)
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{
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#ifdef _MT
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struct _flt answerstruct;
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#endif
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FLT answer;
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double tmp;
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unsigned int flags;
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REG1 char *ptr = (char *) nptr;
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/* scan past leading space/tab characters */
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while ( isspace((int)(unsigned char)*ptr) )
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ptr++;
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/* let _fltin routine do the rest of the work */
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#ifdef _MT
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/* ok to take address of stack variable here; fltin2 knows to use ss */
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answer = _fltin2( &answerstruct, ptr, (int)strlen(ptr), 0, 0);
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#else
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answer = _fltin(ptr, (int)strlen(ptr), 0, 0);
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#endif
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if ( endptr != NULL )
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*endptr = (char *) ptr + answer->nbytes;
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flags = answer->flags;
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if ( flags & (512 | 64)) {
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/* no digits found or invalid format:
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ANSI says return 0.0, and *endptr = nptr */
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tmp = 0.0;
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if ( endptr != NULL )
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*endptr = (char *) nptr;
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}
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else if ( flags & (128 | 1) ) {
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if ( *ptr == '-' )
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tmp = -HUGE_VAL; /* negative overflow */
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else
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tmp = HUGE_VAL; /* positive overflow */
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errno = ERANGE;
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}
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else if ( flags & 256 ) {
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tmp = 0.0; /* underflow */
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errno = ERANGE;
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}
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else
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tmp = answer->dval;
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return(tmp);
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}
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