535 lines
18 KiB
C++
535 lines
18 KiB
C++
/*
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********************************************************************************
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* *
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* COPYRIGHT: *
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* (C) Copyright Taligent, Inc., 1997 *
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* (C) Copyright International Business Machines Corporation, 1997-1998 *
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* Licensed Material - Program-Property of IBM - All Rights Reserved. *
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* US Government Users Restricted Rights - Use, duplication, or disclosure *
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* restricted by GSA ADP Schedule Contract with IBM Corp. *
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* *
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********************************************************************************
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*
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* File DIGITLST.CPP
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*
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* Modification History:
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*
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* Date Name Description
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* 03/21/97 clhuang Converted from java.
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* 03/21/97 clhuang Implemented with new APIs.
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* 03/27/97 helena Updated to pass the simple test after code review.
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* 03/31/97 aliu Moved isLONG_MIN to here, and fixed it.
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* 04/15/97 aliu Changed MAX_COUNT to DBL_DIG. Changed Digit to char.
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* Reworked representation by replacing fDecimalAt with
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* fExponent.
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* 04/16/97 aliu Rewrote set() and getDouble() to use sprintf/atof
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* to do digit conversion.
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* 09/09/97 aliu Modified for exponential notation support.
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* 08/02/98 stephen Added nearest/even rounding
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* Fixed bug in fitsIntoLong
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********************************************************************************
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*/
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#include "digitlst.h"
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#include <stdlib.h>
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#include <limits.h>
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#include <string.h>
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#include <stdio.h>
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// *****************************************************************************
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// class DigitList
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// This class handles the transcoding between numeric values and strings of
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// characters. Only handles as non-negative numbers.
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// *****************************************************************************
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const char DigitList::kZero = '0';
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char DigitList::LONG_MIN_REP[LONG_DIGITS];
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int32_t DigitList::LONG_MIN_REP_LENGTH = 0;
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// -------------------------------------
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// default constructor
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DigitList::DigitList()
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{
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clear();
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}
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// -------------------------------------
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DigitList::~DigitList()
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{
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}
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// -------------------------------------
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// copy constructor
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DigitList::DigitList(const DigitList &other)
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{
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*this = other;
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}
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// -------------------------------------
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// assignment operator
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DigitList&
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DigitList::operator=(const DigitList& other)
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{
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if (this != &other)
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{
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fDecimalAt = other.fDecimalAt;
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fCount = other.fCount;
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strncpy(fDigits, other.fDigits, MAX_DIGITS);
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}
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return *this;
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}
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// -------------------------------------
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bool_t
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DigitList::operator==(const DigitList& that) const
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{
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return ((this == &that) ||
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(fDecimalAt == that.fDecimalAt &&
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fCount == that.fCount &&
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0 == strncmp(fDigits, that.fDigits, fCount)));
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}
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// -------------------------------------
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// Resets the digit list; sets all the digits to zero.
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void
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DigitList::clear()
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{
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fDecimalAt = 0;
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fCount = 0;
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for (int32_t i=0; i<MAX_DIGITS; ++i) fDigits[i] = kZero;
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}
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// -------------------------------------
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// Appends the digit to the digit list if it's not out of scope.
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// Ignores the digit, otherwise.
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void
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DigitList::append(char digit)
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{
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// Ignore digits which exceed the precision we can represent
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if (fCount < MAX_DIGITS) fDigits[fCount++] = digit;
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}
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// -------------------------------------
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/**
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* Currently, getDouble() depends on atof() to do its conversion.
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*/
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double
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DigitList::getDouble() const
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{
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if (fCount == 0) return 0.0;
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// For the string "." + fDigits + "e" + fDecimalAt.
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char buffer[MAX_DIGITS+32];
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*buffer = '.';
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strncpy(buffer+1, fDigits, fCount);
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sprintf(buffer+fCount+1, "e%d", fDecimalAt);
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return atof(buffer);
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}
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// -------------------------------------
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int32_t DigitList::getLong() const
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{
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// This is 100% accurate in c++ because if we are representing
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// an integral value, we suffer nothing in the conversion to
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// double. If we are to support 64-bit longs later, this method
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// must be rewritten. [LIU]
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return (int32_t)getDouble();
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}
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/**
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* Return true if the number represented by this object can fit into
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* a long.
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*/
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bool_t
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DigitList::fitsIntoLong(bool_t isPositive, bool_t ignoreNegativeZero)
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{
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// Figure out if the result will fit in a long. We have to
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// first look for nonzero digits after the decimal point;
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// then check the size. If the digit count is 18 or less, then
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// the value can definitely be represented as a long. If it is 19
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// then it may be too large.
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// Trim trailing zeros. This does not change the represented value.
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while (fCount > 0 && fDigits[fCount - 1] == '0') --fCount;
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if (fCount == 0) {
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// Positive zero fits into a long, but negative zero can only
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// be represented as a double. - bug 4162852
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return isPositive || ignoreNegativeZero;
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}
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initializeLONG_MIN_REP();
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// If the digit list represents a double or this number is too
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// big for a long.
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if (fDecimalAt < fCount || fDecimalAt > LONG_MIN_REP_LENGTH) return FALSE;
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// If number is small enough to fit in a long
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if (fDecimalAt < LONG_MIN_REP_LENGTH) return TRUE;
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// At this point we have fDecimalAt == fCount, and fCount == LONG_MIN_REP_LENGTH.
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// The number will overflow if it is larger than LONG_MAX
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// or smaller than LONG_MIN.
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for (int32_t i=0; i<fCount; ++i)
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{
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char dig = fDigits[i], max = LONG_MIN_REP[i];
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if (dig > max) return FALSE;
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if (dig < max) return TRUE;
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}
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// At this point the first count digits match. If fDecimalAt is less
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// than count, then the remaining digits are zero, and we return true.
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if (fCount < fDecimalAt) return TRUE;
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// Now we have a representation of Long.MIN_VALUE, without the leading
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// negative sign. If this represents a positive value, then it does
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// not fit; otherwise it fits.
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return !isPositive;
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}
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// -------------------------------------
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/**
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* @param maximumDigits The maximum digits to be generated. If zero,
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* there is no maximum -- generate all digits.
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*/
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void
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DigitList::set(int32_t source, int32_t maximumDigits)
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{
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// for now, simple implementation; later, do proper IEEE stuff
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//String stringDigits = Long.toString(source);
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char string [10 + 1]; // maximum digits for a 32-bit signed number is 10 + 1 for sign
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sprintf(string, "%d", source);
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char *stringDigits = string;
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// This method does not expect a negative number. However,
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// "source" can be a Long.MIN_VALUE (-9223372036854775808),
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// if the number being formatted is a Long.MIN_VALUE. In that
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// case, it will be formatted as -Long.MIN_VALUE, a number
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// which is outside the legal range of a long, but which can
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// be represented by DigitList.
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if (stringDigits[0] == '-')
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stringDigits++;
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fCount = fDecimalAt = strlen(stringDigits);
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// Don't copy trailing zeros
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while (fCount > 1 && stringDigits[fCount - 1] == '0')
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--fCount;
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//for (int32_t i = 0; i < fCount; ++i)
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// fDigits[i] = (char) stringDigits[i];
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strncpy(fDigits, stringDigits, fCount);
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if(maximumDigits > 0)
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round(maximumDigits);
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#if(0)
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// {sfb} old implementation, keep around for now
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// Handle the case in which source == LONG_MIN
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set((source >= 0 ? (double)source : -((double)source)),
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maximumDigits > 0 ? maximumDigits : MAX_DIGITS,
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maximumDigits == 0);
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#endif
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}
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/**
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* Set the digit list to a representation of the given double value.
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* This method supports both fixed-point and exponential notation.
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* @param source Value to be converted; must not be Inf, -Inf, Nan,
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* or a value <= 0.
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* @param maximumDigits The most fractional or total digits which should
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* be converted. If total digits, and the value is zero, then
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* there is no maximum -- generate all digits.
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* @param fixedPoint If true, then maximumDigits is the maximum
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* fractional digits to be converted. If false, total digits.
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*/
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void
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DigitList::set(double source, int32_t maximumDigits, bool_t fixedPoint)
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{
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if(source == 0) source = 0;
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// Generate a representation of the form DDDDD, DDDDD.DDDDD, or
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// DDDDDE+/-DDDDD.
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//String rep = Double.toString(source);
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char rep[MAX_DIGITS + 7]; // Extra space for '.', e+NNN, and '\0' (actually +7 is enough)
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sprintf(rep, "%1.*e", MAX_DIGITS - 1, source);
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fDecimalAt = -1;
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fCount = 0;
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int32_t exponent = 0;
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// Number of zeros between decimal point and first non-zero digit after
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// decimal point, for numbers < 1.
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int32_t leadingZerosAfterDecimal = 0;
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bool_t nonZeroDigitSeen = FALSE;
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for (int32_t i=0; i < MAX_DIGITS + 7; ++i) {
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char c = rep[i];
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if (c == '.') {
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fDecimalAt = fCount;
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}
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else if (c == 'e' || c == 'E') {
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// Parse an exponent of the form /[eE][+-]?[0-9]*/
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//exponent = Integer.valueOf(rep.substring(i+1)).intValue();
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i += 1; // adjust for 'e'
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bool_t negExp = rep[i] == '-';
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if (negExp || rep[i] == '+') {
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++i;
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}
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while ((c = rep[i++]) >= '0' && c <= '9') {
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exponent = 10*exponent + c - '0';
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}
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if (negExp) {
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exponent = -exponent;
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}
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break;
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}
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else if (fCount < MAX_DIGITS) {
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if ( ! nonZeroDigitSeen) {
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nonZeroDigitSeen = (c != '0');
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if ( ! nonZeroDigitSeen && fDecimalAt != -1)
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++leadingZerosAfterDecimal;
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}
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if (nonZeroDigitSeen)
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fDigits[fCount++] = (char)c;
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}
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}
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if (fDecimalAt == -1)
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fDecimalAt = fCount;
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fDecimalAt += exponent - leadingZerosAfterDecimal;
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if (fixedPoint)
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{
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// The negative of the exponent represents the number of leading
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// zeros between the decimal and the first non-zero digit, for
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// a value < 0.1 (e.g., for 0.00123, -decimalAt == 2). If this
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// is more than the maximum fraction digits, then we have an underflow
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// for the printed representation.
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if (-fDecimalAt > maximumDigits) {
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// Handle an underflow to zero when we round something like
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// 0.0009 to 2 fractional digits.
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fCount = 0;
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return;
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} else if (-fDecimalAt == maximumDigits) {
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// If we round 0.0009 to 3 fractional digits, then we have to
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// create a new one digit in the least significant location.
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if (shouldRoundUp(0)) {
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fCount = 1;
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++fDecimalAt;
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fDigits[0] = (char)'1';
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} else {
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fCount = 0;
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}
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return;
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}
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}
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// Eliminate trailing zeros.
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while (fCount > 1 && fDigits[fCount - 1] == '0')
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--fCount;
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/*if (DEBUG)
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{
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System.out.print("Before rounding 0.");
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for (int i=0; i<fCount; ++i) System.out.print((char)digits[i]);
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System.out.println("x10^" + fDecimalAt);
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}*/
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// Eliminate digits beyond maximum digits to be displayed.
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// Round up if appropriate. Do NOT round in the special
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// case where maximumDigits == 0 and fixedPoint is FALSE.
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if (fixedPoint || maximumDigits > 0) {
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round(fixedPoint ? (maximumDigits + fDecimalAt) : maximumDigits);
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}
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/*if (DEBUG)
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{
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System.out.print("After rounding 0.");
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for (int i=0; i<fCount; ++i) System.out.print((char)digits[i]);
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System.out.println("x10^" + fDecimalAt);
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}*/
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}
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// -------------------------------------
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/**
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* Round the representation to the given number of digits.
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* @param maximumDigits The maximum number of digits to be shown.
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* Upon return, count will be less than or equal to maximumDigits.
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*/
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void
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DigitList::round(int32_t maximumDigits)
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{
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// Eliminate digits beyond maximum digits to be displayed.
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// Round up if appropriate.
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if (maximumDigits >= 0 && maximumDigits < fCount)
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{
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if (shouldRoundUp(maximumDigits)) {
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// Rounding up involved incrementing digits from LSD to MSD.
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// In most cases this is simple, but in a worst case situation
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// (9999..99) we have to adjust the decimalAt value.
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for (;;)
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{
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--maximumDigits;
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if (maximumDigits < 0)
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{
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// We have all 9's, so we increment to a single digit
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// of one and adjust the exponent.
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fDigits[0] = (char) '1';
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++fDecimalAt;
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maximumDigits = 0; // Adjust the count
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break;
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}
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++fDigits[maximumDigits];
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if (fDigits[maximumDigits] <= '9') break;
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// fDigits[maximumDigits] = '0'; // Unnecessary since we'll truncate this
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}
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++maximumDigits; // Increment for use as count
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}
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fCount = maximumDigits;
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// Eliminate trailing zeros.
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while (fCount > 1 && fDigits[fCount-1] == '0') {
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--fCount;
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}
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}
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}
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/**
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* Return true if truncating the representation to the given number
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* of digits will result in an increment to the last digit. This
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* method implements half-even rounding, the default rounding mode.
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* [bnf]
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* @param maximumDigits the number of digits to keep, from 0 to
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* <code>count-1</code>. If 0, then all digits are rounded away, and
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* this method returns true if a one should be generated (e.g., formatting
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* 0.09 with "#.#").
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* @return true if digit <code>maximumDigits-1</code> should be
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* incremented
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*/
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bool_t DigitList::shouldRoundUp(int32_t maximumDigits) {
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bool_t increment = FALSE;
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// Implement IEEE half-even rounding
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if (fDigits[maximumDigits] > '5') {
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return TRUE;
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} else if (fDigits[maximumDigits] == '5' ) {
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for (int i=maximumDigits+1; i<fCount; ++i) {
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if (fDigits[i] != '0') {
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return TRUE;
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}
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}
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return maximumDigits > 0 && (fDigits[maximumDigits-1] % 2 != 0);
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}
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return FALSE;
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}
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// -------------------------------------
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// In the Java implementation, we need a separate set(long) because 64-bit longs
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// have too much precision to fit into a 64-bit double. In C++, longs can just
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// be passed to set(double) as long as they are 32 bits in size. We currently
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// don't implement 64-bit longs in C++, although the code below would work for
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// that with slight modifications. [LIU]
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// void
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// DigitList::set(long source)
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// {
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// // handle the special case of zero using a standard exponent of 0.
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// // mathematically, the exponent can be any value.
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// if (source == 0)
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// {
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// fcount = 0;
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// fDecimalAt = 0;
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// return;
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// }
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// // we don't accept negative numbers, with the exception of long_min.
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// // long_min is treated specially by being represented as long_max+1,
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// // which is actually an impossible signed long value, so there is no
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// // ambiguity. we do this for convenience, so digitlist can easily
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// // represent the digits of a long.
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// bool islongmin = (source == long_min);
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// if (islongmin)
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// {
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// source = -(source + 1); // that is, long_max
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// islongmin = true;
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// }
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// sprintf(fdigits, "%d", source);
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// // now we need to compute the exponent. it's easy in this case; it's
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// // just the same as the count. e.g., 0.123 * 10^3 = 123.
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// fcount = strlen(fdigits);
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// fDecimalAt = fcount;
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// // here's how we represent long_max + 1. note that we always know
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// // that the last digit of long_max will not be 9, because long_max
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// // is of the form (2^n)-1.
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// if (islongmin) ++fdigits[fcount-1];
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// // finally, we trim off trailing zeros. we don't alter fDecimalAt,
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// // so this has no effect on the represented value. we know the first
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// // digit is non-zero (see code above), so we only have to check down
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// // to fdigits[1].
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// while (fcount > 1 && fdigits[fcount-1] == kzero) --fcount;
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// }
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/**
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* Return true if this object represents the value zero. Anything with
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* no digits, or all zero digits, is zero, regardless of fDecimalAt.
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*/
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bool_t
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DigitList::isZero() const
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{
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for (int32_t i=0; i<fCount; ++i) if (fDigits[i] != kZero) return FALSE;
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return TRUE;
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}
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/**
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* We represent LONG_MIN internally as LONG_MAX + 1. This is actually an impossible
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* value, for positive long integers, so we are safe in doing so.
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*/
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bool_t
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DigitList::isLONG_MIN() const
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{
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initializeLONG_MIN_REP();
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if (fCount != LONG_MIN_REP_LENGTH) return FALSE;
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for (int32_t i = 0; i < LONG_MIN_REP_LENGTH; ++i)
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{
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if (fDigits[i] != LONG_MIN_REP[i+1]) return FALSE;
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}
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return TRUE;
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}
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// Initialize the LONG_MIN representation buffer. Note that LONG_MIN
|
|
// is stored as LONG_MAX+1 (LONG_MIN without the negative sign).
|
|
|
|
void
|
|
DigitList::initializeLONG_MIN_REP()
|
|
{
|
|
if (LONG_MIN_REP_LENGTH == 0)
|
|
{
|
|
// THIS ASSUMES A 32-BIT LONG_MIN VALUE
|
|
char buf[LONG_DIGITS];
|
|
sprintf(buf, "%d", LONG_MIN);
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|
LONG_MIN_REP_LENGTH = strlen(buf) - 1;
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|
// assert(LONG_MIN_REP_LENGTH == LONG_DIGITS);
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|
for (int32_t i=1; i<=LONG_MIN_REP_LENGTH; ++i) LONG_MIN_REP[i-1] = buf[i];
|
|
}
|
|
}
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|
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//eof
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