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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v103/libf/atof.c

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