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122 lines
3.2 KiB
122 lines
3.2 KiB
/***
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*gcvt.c - convert floating point number to character string
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*
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* Copyright (c) 1985-1991, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* Converts floating point number into character string representation.
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*
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*Revision History:
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* 09-09-93 RKW written
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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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* 05-24-88 PHG Merged DLL and normal versions
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* 10-20-88 JCR Changed 'DOUBLE' to 'double' for 386
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* 06-27-89 PHG Changed "ndec" to "ndec-1" to correct significant
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* digits in exponential format (C6 bug #2124)
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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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* 07-20-90 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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* 01-21-91 GJF ANSI naming.
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* 08-13-92 SKS An old bug that was fixed in C 6.0 but that did not
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* make it into C 7.0, an off by 1 error when switching
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* from fixed point to scientific notation
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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 <internal.h>
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/***
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*double _gcvt(value, ndec, buffer) - convert floating point value to char
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* string
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*
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*Purpose:
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* _gcvt converts the value to a null terminated ASCII string
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* buf. It attempts to produce ndigit significant digits
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* in Fortran F format if possible, ortherwise E format,
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* ready for printing. Trailing zeros may be suppressed.
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* No error checking or overflow protection is provided.
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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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* value - double - number to be converted
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* ndec - int - number of significant digits
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* buf - char * - buffer to place result
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*
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*Exit:
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* result is written into buffer; it will be overwritten if it has
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* not been made big enough.
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*
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*Exceptions:
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*
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*******************************************************************************/
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char * _CALLTYPE1 _gcvt (
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double value,
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int ndec,
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char *buf
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)
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{
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#ifdef MTHREAD
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struct _strflt strfltstruct; /* temporary buffers */
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char resultstring[21];
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#endif
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STRFLT string;
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int magnitude;
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char *rc;
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REG1 char *str;
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REG2 char *stop;
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/* get the magnitude of the number */
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#ifdef MTHREAD
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string = _fltout2( value, &strfltstruct, resultstring );
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#else
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string = _fltout( value );
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#endif
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magnitude = string->decpt - 1;
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/* output the result according to the Fortran G format as outlined in
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Fortran language specification */
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if ( magnitude < -1 || magnitude > ndec-1 )
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/* then Ew.d d = ndec */
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rc = str = _cftoe( &value, buf, ndec-1, 0);
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else
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/* Fw.d where d = ndec-string->decpt */
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rc = str = _cftof( &value, buf, ndec-string->decpt );
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while (*str && *str != '.')
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str++;
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if (*str++) {
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while (*str && *str != 'e')
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str++;
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stop = str--;
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while (*str == '0')
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str--;
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while (*++str = *stop++)
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;
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}
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return(rc);
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}
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