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/*
* Copyright 2003-2004, Franz-Josef Elmer, All rights reserved
*
* This library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details
* (http://www.gnu.org/copyleft/lesser.html).
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package jcckit.util;
/**
*
*
* @author Franz-Josef Elmer
*/
class FormatElement {
/** All descriptor characters. */
static final String DESCRIPTORS = "doxfeEgG";
private static final String INT_DESCRIPTORS = "dox";
private static final int INT_DESCRIPTOR = 0;
private static final int FLOAT_DESCRIPTOR = 1;
/**
* Calculate the integer power of a floating point number.
* @param n Exponent.
* @param x Number.
* @return x^n.
*/
private static final double power(double x, int n) {
return n < 0 ? 1.0 / power2(x, -n) : power2(x, n);
}
/** Calculate x^n recursively assuming n > 0. */
private static final double power2(double x, int n) {
switch (n) {
case 0: return 1;
case 1: return x;
default:
double p = power2(x, n / 2);
return p * p * power2(x, n % 2);
}
}
private final char _descriptor;
private final int _descriptorType;
private final double _tenToPrecision;
private boolean _decimalPoint;
private boolean _flushLeft;
private boolean _leadingZeros;
private boolean _alwaysSign;
private int _width;
private int _precision;
/** Creates an instance for the specified format string. */
FormatElement(String formatString) {
int len = formatString.length() - 1;
_descriptor = formatString.charAt(len);
if (DESCRIPTORS.indexOf(_descriptor) < 0) {
throw new IllegalArgumentException("Format element '" + formatString
+ "' does not ends with one of the following characters: "
+ DESCRIPTORS);
}
_descriptorType = INT_DESCRIPTORS.indexOf(_descriptor) >= 0
? INT_DESCRIPTOR : FLOAT_DESCRIPTOR;
if (formatString.length() > 1) {
switch (formatString.charAt(0)) {
case '-':
_flushLeft = true;
formatString = formatString.substring(1);
break;
case '0':
_leadingZeros = true;
formatString = formatString.substring(1);
break;
case '+':
_alwaysSign = true;
formatString = formatString.substring(1);
break;
}
len = formatString.length() - 1;
int index = formatString.indexOf('.');
_decimalPoint = index >= 0;
int last = _decimalPoint ? index : len;
if (last > 0) {
_width = Integer.parseInt(formatString.substring(0, last));
}
if (_decimalPoint) {
index++;
if (index < len) {
_precision = Integer.parseInt(formatString.substring(index, len));
}
}
}
_tenToPrecision = power(10, _precision);
}
/**
* Format a number in accordance of the format string
* given at the initialisation of this instance.
* @param buffer Buffer to which the formated output will be appended.
* @param number Number to be formated.
*/
public void form(StringBuffer buffer, long number) {
if (_descriptorType == FLOAT_DESCRIPTOR) {
form(buffer, (double) number);
} else {
// Format absolut value in the right base
buffer.append(form(number < 0,
Long.toString(Math.abs(number),
_descriptor == 'o' ? 8
: (_descriptor == 'x' ? 16 : 10)),
""));
}
}
/**
* Format a number in accordance of the format string
* given at the initialisation of this instance.
* @param buffer Buffer to which the formated output will be appended.
* @param number Number to be formated.
*/
public void form(StringBuffer buffer, double number) {
if (_descriptorType == INT_DESCRIPTOR) {
form(buffer, (long) Math.floor(number + 0.5));
} else if (_descriptor == 'f') {
buffer.append(formF(number));
} else if (_descriptor == 'e' || _descriptor == 'E') {
buffer.append(formE(number));
} else if (_descriptor == 'g' || _descriptor == 'G') {
String formF = formF(number);
String formE = formE(number);
buffer.append(formF.length() > formE.length() ? formE : formF);
}
}
private String form(boolean negativeValue, String intPart, String fracPart) {
int len = intPart.length() + fracPart.length();
// Buffer holding the result
StringBuffer result = new StringBuffer();
int count = 0;
// add sign if necessary
if (_alwaysSign || negativeValue) {
result.append(negativeValue ? '-' : '+');
count++;
}
// add zeros if necessary
if (_leadingZeros) {
for (int i = count + len; i < _width; i++) {
result.append('0');
count++;
}
}
// add number
result.append(intPart).append(fracPart);
count += len;
// add spaces if necessary
if (_flushLeft) {
for (; count < _width; count++) {
result.append(' ');
}
} else {
for (; count < _width; count++) {
result.insert(0, ' ');
}
}
return new String(result);
}
/** Format floating point number with exponent. */
private String formE(double number) {
// format absolute mantisse
int exponent = 0;
String zeros = "00000000000000000000000".substring(0, _precision + 1);
if (number != 0) {
exponent = (int) Math.floor(Math.log(Math.abs(number)) / Math.log(10));
double mantisse = Math.floor(Math.abs(number * power(10.0,
_precision - exponent)) + 0.5);
if (mantisse >= 10 * _tenToPrecision) {
exponent++;
mantisse = Math.floor(Math.abs(number * power(10.0,
_precision - exponent)) + 0.5);
}
zeros = Long.toString((long) mantisse);
}
// make fractional part
StringBuffer fracPart = new StringBuffer();
if (_decimalPoint) {
fracPart.append('.').append(zeros.substring(1));
}
// make exponent
fracPart.append(Character.isLowerCase(_descriptor) ? 'e': 'E')
.append(exponent < 0 ? '-' : '+');
exponent = Math.abs(exponent);
for (int i = 0, n = fracPart.length(); i < 3; i++) {
fracPart.insert(n, Character.forDigit(exponent % 10, 10));
exponent /= 10;
}
return form(number < 0, zeros.substring(0, 1), new String(fracPart));
}
/** Format floating point number. */
private String formF(double number) {
// Format absolut value
double multiplier = number < 0 ? - _tenToPrecision : _tenToPrecision;
String digits
= Long.toString((long) Math.floor(number * multiplier + 0.5));
String intPart = digits;
StringBuffer fracPart = new StringBuffer();
if (_decimalPoint) {
int len = digits.length() - _precision;
fracPart.append('.').append(digits.substring(Math.max(0, len)));
if (len > 0) {
intPart = digits.substring(0, len);
} else {
intPart = "0";
for (; len < 0; len++) {
fracPart.insert(1, '0');
}
}
}
return form(number < 0, intPart, new String(fracPart));
}
}
