ack/lang/fortran/comp/cds.c

/****************************************************************
Copyright 1990 by AT&T Bell Laboratories and Bellcore.

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/* Put strings representing decimal floating-point numbers
 * into canonical form: always have a decimal point or
 * exponent field; if using an exponent field, have the
 * number before it start with a digit and decimal point
 * (if the number has more than one digit); only have an
 * exponent field if it saves space.
 *
 * Arrange that the return value, rv, satisfies rv[0] == '-' || rv[-1] == '-' .
 */

#include "sysdep.h"

 char *
cds(s, z0)
 char *s, *z0;
{
	int ea, esign, et, i, k, nd = 0, sign = 0, tz;
	char c, *z;
	char ebuf[24];
	long ex = 0;
	static char etype[Table_size], *db;
	static int dblen = 64;

	if (!db) {
		etype['E'] = 1;
		etype['e'] = 1;
		etype['D'] = 1;
		etype['d'] = 1;
		etype['+'] = 2;
		etype['-'] = 3;
		db = Alloc(dblen);
		}

	while((c = *s++) == '0');
	if (c == '-')
		{ sign = 1; c = *s++; }
	else if (c == '+')
		c = *s++;
	k = strlen(s) + 2;
	if (k >= dblen) {
		do dblen <<= 1;
			while(k >= dblen);
		free(db);
		db = Alloc(dblen);
		}
	if (etype[(unsigned char)c] >= 2)
		while(c == '0') c = *s++;
	tz = 0;
	while(c >= '0' && c <= '9') {
		if (c == '0')
			tz++;
		else {
			if (nd)
				for(; tz; --tz)
					db[nd++] = '0';
			else
				tz = 0;
			db[nd++] = c;
			}
		c = *s++;
		}
	ea = -tz;
	if (c == '.') {
		while((c = *s++) >= '0' && c <= '9') {
			if (c == '0')
				tz++;
			else {
				if (tz) {
					ea += tz;
					if (nd)
						for(; tz; --tz)
							db[nd++] = '0';
					else
						tz = 0;
					}
				db[nd++] = c;
				ea++;
				}
			}
		}
	if (et = etype[(unsigned char)c]) {
		esign = et == 3;
		c = *s++;
		if (et == 1) {
			if(etype[(unsigned char)c] > 1) {
				if (c == '-')
					esign = 1;
				c = *s++;
				}
			}
		while(c >= '0' && c <= '9') {
			ex = 10*ex + (c - '0');
			c = *s++;
			}
		if (esign)
			ex = -ex;
		}
	/* debug */ if (c)
	/* debug*/	Fatal("unexpected character in cds");
	ex -= ea;
	if (!nd) {
		if (!z0)
			z0 = mem(4,0);
		strcpy(z0, "-0.");
		sign = 0;
		}
	else if (ex > 2 || ex + nd < -2) {
		sprintf(ebuf, "%ld", ex + nd - 1);
		k = strlen(ebuf) + nd + 3;
		if (nd > 1)
			k++;
		if (!z0)
			z0 = mem(k,0);
		z = z0;
		*z++ = '-';
		*z++ = *db;
		if (nd > 1) {
			*z++ = '.';
			for(k = 1; k < nd; k++)
				*z++ = db[k];
			}
		*z++ = 'e';
		strcpy(z, ebuf);
		}
	else {
		k = (int)(ex + nd);
		i = nd + 3;
		if (k < 0)
			i -= k;
		else if (ex > 0)
			i += ex;
		if (!z0)
			z0 = mem(i,0);
		z = z0;
		*z++ = '-';
		if (ex >= 0) {
			for(k = 0; k < nd; k++)
				*z++ = db[k];
			while(--ex >= 0)
				*z++ = '0';
			*z++ = '.';
			}
		else {
			for(i = 0; i < k;)
				*z++ = db[i++];
			*z++ = '.';
			while(++k <= 0)
				*z++ = '0';
			while(i < nd)
				*z++ = db[i++];
			}
		*z = 0;
		}
	return sign ? z0 : z0+1;
	}