249 lines
7 KiB
C
249 lines
7 KiB
C
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/***
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*fcvt.c - convert floating point value to string
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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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* Converts a floating point value to a string.
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*
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*Revision History:
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* 09-09-83 RKW written
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* 09-14-84 DFW fixed problems with buffer overflow and
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* streamlined the code
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* 11-09-87 BCM different interface under ifdef MTHREAD
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* 11-19-87 WAJ fcvt now uses emulator data area for buffer
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* 12-11-87 JCR Added "_LOAD_DS" to declaration
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* 05-24-88 PHG Merged DLL and normal versions
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* 10-04-88 JCR 386: Removed 'far' keyword
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* 10-20-88 JCR Changed 'DOUBLE' to 'double' for 386
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* 03-02-90 GJF Added #include <cruntime.h>. Removed some (now) useless
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* preprocessor directives. Also, fixed copyright.
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* 03-06-90 GJF Fixed calling type, removed some leftover 16-bit
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* support.
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* 03-23-90 GJF Made _fpcvt() _CALLTYPE4 and removed prototype for
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* _fptostr() (now in struct.h).
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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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* 01-21-91 GJF ANSI naming.
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* 10-03-91 JCR Fixed mthread buffer allocation
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* 02-16-93 GJF Changed for new _getptd().
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* 04-06-93 SKS Replace _CRTAPI* with _cdecl
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* 08-05-94 JWM Insure that _ecvt returns no more than ndigits.
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* 09-06-94 CFW Remove Cruiser support.
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 01-10-95 CFW Debug CRT allocs.
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* 09-05-00 GB Changed the defination of fltout functions. Use DOUBLE
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* instead of double
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <fltintrn.h>
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#include <cvt.h>
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#include <mtdll.h>
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#include <stdlib.h>
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#include <dbgint.h>
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/*
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* The static character array buf[CVTBUFSIZE] is used by the _fpcvt routine
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* (the workhorse for _ecvt and _fcvt) for storage of its output. The routine
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* gcvt expects the user to have set up their own storage. CVTBUFSIZE is set
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* large enough to accomodate the largest double precision number plus 40
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* decimal places (even though you only have 16 digits of accuracy in a
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* double precision IEEE number, the user may ask for more to effect 0
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* padding; but there has to be a limit somewhere).
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*/
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/*
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* define a maximum size for the conversion buffer. It should be at least
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* as long as the number of digits in the largest double precision value
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* (?.?e308 in IEEE arithmetic). We will use the same size buffer as is
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* used in the printf support routine (_output)
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*/
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#ifdef _MT
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char * __cdecl _fpcvt(STRFLT, int, int *, int *);
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#else
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static char * __cdecl _fpcvt(STRFLT, int, int *, int *);
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static char buf[CVTBUFSIZE];
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#endif
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/***
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*char *_fcvt(value, ndec, decpr, sign) - convert floating point to char string
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*
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*Purpose:
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* _fcvt like _ecvt converts the value to a null terminated
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* string of ASCII digits, and returns a pointer to the
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* result. The routine prepares data for Fortran F-format
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* output with the number of digits following the decimal
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* point specified by ndec. The position of the decimal
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* point relative to the beginning of the string is returned
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* indirectly through decpt. The correct digit for Fortran
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* F-format is rounded.
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* NOTE - to avoid the possibility of generating floating
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* point instructions in this code we fool the compiler
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* about the type of the 'value' parameter using a struct.
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* This is OK since all we do is pass it off as a
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* parameter.
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*
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*Entry:
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* double value - number to be converted
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* int ndec - number of digits after decimal point
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*
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*Exit:
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* returns pointer to the character string representation of value.
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* also, the output is written into the static char array buf.
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* int *decpt - pointer to int with pos. of dec. point
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* int *sign - pointer to int with sign (0 = pos, non-0 = neg)
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*
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*Exceptions:
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*
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*******************************************************************************/
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char * __cdecl _fcvt (
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double value,
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int ndec,
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int *decpt,
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int *sign
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)
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{
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REG1 STRFLT pflt;
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DOUBLE *pdvalue = (DOUBLE *)&value;
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#ifdef _MT
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struct _strflt strfltstruct;
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char resultstring[21];
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/* ok to take address of stack struct here; fltout2 knows to use ss */
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pflt = _fltout2( *pdvalue, &strfltstruct, resultstring );
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#else
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pflt = _fltout( *pdvalue );
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#endif
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return( _fpcvt( pflt, pflt->decpt + ndec, decpt, sign ) );
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}
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/***
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*char *_ecvt( value, ndigit, decpt, sign ) - convert floating point to string
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*
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*Purpose:
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* _ecvt converts value to a null terminated string of
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* ASCII digits, and returns a pointer to the result.
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* The position of the decimal point relative to the
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* begining of the string is stored indirectly through
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* decpt, where negative means to the left of the returned
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* digits. If the sign of the result is negative, the
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* word pointed to by sign is non zero, otherwise it is
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* zero. The low order digit is rounded.
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*
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*Entry:
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* double value - number to be converted
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* int ndigit - number of digits after decimal point
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*
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*Exit:
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* returns pointer to the character representation of value.
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* also the output is written into the statuc char array buf.
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* int *decpt - pointer to int with position of decimal point
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* int *sign - pointer to int with sign in it (0 = pos, non-0 = neg)
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*
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*Exceptions:
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*
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*******************************************************************************/
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char * __cdecl _ecvt (
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double value,
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int ndigit,
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int *decpt,
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int *sign
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)
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{
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char *retbuf;
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DOUBLE *pdvalue = (DOUBLE *)&value;
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#ifdef _MT
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REG1 STRFLT pflt;
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struct _strflt strfltstruct; /* temporary buffers */
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char resultstring[21];
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/* ok to take address of stack struct here; fltout2 knows to use ss */
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pflt = _fltout2( *pdvalue, &strfltstruct, resultstring );
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retbuf = _fpcvt( pflt, ndigit, decpt, sign );
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#else
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retbuf = _fpcvt( _fltout(*pdvalue), ndigit, decpt, sign );
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#endif
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/* _fptostr() occasionally returns an extra character in the buffer ... */
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if (retbuf[ndigit])
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retbuf[ndigit] = '\0';
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return( retbuf );
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}
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/***
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*char *_fpcvt() - gets final string and sets decpt and sign [STATIC]
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*
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*Purpose:
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* This is a small common routine used by [ef]cvt. It calls fptostr
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* to get the final string and sets the decpt and sign indicators.
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*
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*Entry:
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*
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*Exit:
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*
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*Exceptions:
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*
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*******************************************************************************/
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#ifdef _MT
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char * __cdecl _fpcvt (
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#else
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static char * __cdecl _fpcvt (
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#endif
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REG2 STRFLT pflt,
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REG3 int digits,
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int *decpt,
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int *sign
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)
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{
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#ifdef _MT
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/* use a per-thread buffer */
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char *buf;
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_ptiddata ptd;
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ptd = _getptd();
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if ( ptd->_cvtbuf == NULL )
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if ( (ptd->_cvtbuf = _malloc_crt(CVTBUFSIZE)) == NULL )
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return(NULL);
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buf = ptd->_cvtbuf;
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#endif /* _MT */
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/* make sure we don't overflow the buffer size. If the user asks for
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* more digits than the buffer can handle, truncate it to the maximum
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* size allowed in the buffer. The maximum size is CVTBUFSIZE - 2
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* since we useone character for overflow and one for the terminating
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* null character.
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*/
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_fptostr(buf, (digits > CVTBUFSIZE - 2) ? CVTBUFSIZE - 2 : digits, pflt);
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/* set the sign flag and decimal point position */
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*sign = (pflt->sign == '-') ? 1 : 0;
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*decpt = pflt->decpt;
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return(buf);
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}
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