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https://github.com/SEPPDROID/Digital-Research-Source-Code.git
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107 lines
2.5 KiB
C
107 lines
2.5 KiB
C
/*
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Copyright 1982
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Alcyon Corporation
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8716 Production Ave.
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San Diego, Ca. 92121
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*/
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/*char *version "@(#) atof - dec 29, 1982"; */
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/*
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* Ascii String to FFP Floating Point Routine :
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* FFP Standard Single Precision Representation Floating Point
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*
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* float
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* atof(buf)
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* char *buf;
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*
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* No more than 9 significant digits are allowed in single precision.
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* Largest positive number is 3.4 * 10^18 and the smallest positive
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* number is 1.2 * 10^-20.
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* Rely's on the fact that a long and a float are both 32 bits.
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*/
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#define EXPSIZ 4
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#define FRACSIZ 20
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long fptoffp();
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float strbin();
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float power10();
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long
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atof(buf)
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char *buf;
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{
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char ibuf[FRACSIZ], ebuf[EXPSIZ];
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register char *ip, *ep;
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long ffp;
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int dp, esign, isign, ebin, places;
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float ibin, fp;
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ip = ibuf; ep = ebuf; dp = 0; places = 0L;
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while (*buf == ' ' || *buf == '\t') /* ignore white spaces */
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buf++;
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isign = (*buf == '-');
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if (*buf == '-' || *buf == '+')
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buf++;
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while (*buf && *buf != 'e' && *buf != 'E') {
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if (*buf == '.')
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dp++;
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else { /* digit seen */
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*ip++ = *buf;
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if (dp)
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places++;
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}
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buf++;
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}
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*ip = 0;
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if (*buf == 'e' || *buf == 'E') { /* exponent string */
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buf++;
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esign = (*buf == '-');
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if (*buf == '-' || *buf == '+')
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buf++;
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while (*buf) /* get exponent string */
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*ep++ = *buf++;
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}
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*ep = 0;
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ibin = strbin(ibuf);
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ebin = atoi(ebuf);
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places = (esign) ? -ebin - places : ebin - places;
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fp = ibin * power10(places);
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ffp = fptoffp(fp);
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if (isign) /* negative float */
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ffp |= 0x80;
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return( ffp );
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}
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float
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power10(pwr) /* 10^pwr */
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int pwr;
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{
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float f;
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if (pwr < 0) /* negative power */
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for (f = 1.0; pwr < 0; pwr++)
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f = f / 10.0;
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else /* positive power */
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for (f = 1.0; pwr > 0; pwr--)
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f = f * 10.0;
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return(f);
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}
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float
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strbin(p) /* decimal string => binary long */
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char *p;
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{
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float f;
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for (f = 0.0; *p >= '0' && *p <= '9'; p++) {
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f = f * 10.0;
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f = f + (*p - '0');
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}
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return(f);
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}
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