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/***
*_fptostr.c - workhorse routine for converting floating point to string
*
* Copyright (c) 1985-1991, Microsoft Corporation. All rights reserved.
*
*Purpose:
* Workhorse routine for fcvt, ecvt.
*
*Revision History:
* 09-17-84 DFW created
* 03-05-90 GJF Fixed calling type, added #include <cruntime.h>,
* removed #include <register.h>, fixed copyright. Also,
* cleaned up the formatting a bit.
* 07-20-90 SBM Compiles cleanly with -W3 (added #include <string.h>)
* 08-01-90 SBM Renamed <struct.h> to <fltintrn.h>
* 09-27-90 GJF New-style function declarator.
* 06-11-92 GDP Bug fix: Shorten string if leadig (overflow) digit is 1
* 10-09-92 GDP Backed out last fix for ecvt (printf regressed)
*
*******************************************************************************/
#include <cruntime.h>
#include <string.h>
#include <fltintrn.h>
/***
*void _fptostr(buf, digits, pflt) - workhorse floating point conversion
*
*Purpose:
* This is the workhorse routine for fcvt, ecvt. Here is where
* all the digits are put into a buffer and the rounding is
* performed and indicators of the decimal point position are set. Note,
* this must not change the mantissa field of pflt since routines which
* use this routine rely on this being unchanged.
*
*Entry:
* char *buf - the buffer in which the digits are to be put
* int digits - the number of digits which are to go into the buffer
* STRFLT pflt - a pointer to a structure containing information on the
* floating point value, including a string containing the
* non-zero significant digits of the mantissa.
*
*Exit:
* Changes the contents of the buffer and also may increment the decpt
* field of the structure pointer to by the 'pflt' parameter if overflow
* occurs during rounding (e.g. 9.999999... gets rounded to 10.000...).
*
*Exceptions:
*
*******************************************************************************/
void _CALLTYPE1 _fptostr (
char *buf,
REG4 int digits,
REG3 STRFLT pflt
)
{
REG1 char *pbuf = buf;
REG2 char *mantissa = pflt->mantissa;
/* initialize the first digit in the buffer to '0' (NOTE - NOT '\0')
* and set the pointer to the second digit of the buffer. The first
* digit is used to handle overflow on rounding (e.g. 9.9999...
* becomes 10.000...) which requires a carry into the first digit.
*/
*pbuf++ = '0';
/* Copy the digits of the value into the buffer (with 0 padding)
* and insert the terminating null character.
*/
while (digits > 0) {
*pbuf++ = (*mantissa) ? *mantissa++ : (char)'0';
digits--;
}
*pbuf = '\0';
/* do any rounding which may be needed. Note - if digits < 0 don't
* do any rounding since in this case, the rounding occurs in a digit
* which will not be output beause of the precision requested
*/
if (digits >= 0 && *mantissa >= '5') {
pbuf--;
while (*pbuf == '9')
*pbuf-- = '0';
*pbuf += 1;
}
if (*buf == '1') {
/* the rounding caused overflow into the leading digit (e.g.
* 9.999.. went to 10.000...), so increment the decpt position
* by 1
*/
pflt->decpt++;
}
else {
/* move the entire string to the left one digit to remove the
* unused overflow digit.
*/
strcpy(buf, buf+1);
}
}
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