cds.c

/****************************************************************
Copyright 1990, 1993, 1994, 2000 by AT&T, Lucent Technologies and Bellcore.

Permission to use, copy, modify, and distribute this software
and its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appear in all
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permission notice and warranty disclaimer appear in supporting
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software without specific, written prior permission.

AT&T, Lucent and Bellcore disclaim all warranties with regard to
this software, including all implied warranties of
merchantability and fitness.  In no event shall AT&T, Lucent or
Bellcore be liable for any special, indirect or consequential
damages or any damages whatsoever resulting from loss of use,
data or profits, whether in an action of contract, negligence or
other tortious action, arising out of or in connection with the
use or performance of this software.
****************************************************************/

/* 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 "defs.h"

 char *
#ifdef KR_headers
cds(s, z0)
	char *s;
	char *z0;
#else
cds(char *s, char *z0)
#endif
{
	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;
		}
	switch(c) {
		case 0:
			break;
#ifndef VAX
		case 'i':
		case 'I':
			Fatal("Overflow evaluating constant expression.");
		case 'n':
		case 'N':
			Fatal("Constant expression yields NaN.");
#endif
		default:
			Fatal("unexpected character in cds.");
		}
	ex -= ea;
	if (!nd) {
		if (!z0)
			z0 = mem(4,0);
		strcpy(z0, "-0.");
		/* sign = 0; */ /* 20010820: preserve sign of 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 += (int)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;
	}