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1: /* Fixed.java -- Utility methods for fixed point arithmetics 2: Copyright (C) 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.java.math; 40: 41: /** 42: * Utility methods for fixed point arithmetics. 43: */ 44: public final class Fixed 45: { 46: 47: /** 48: * Private constructor to avoid instantiation. 49: */ 50: private Fixed() 51: { 52: // Forbidden constructor. 53: } 54: 55: /** 56: * Divides two fixed point values with <code>n</code> digits. 57: * 58: * @param n the number of digits 59: * @param a the first operand as fixed point value 60: * @param b the second operand as fixed point value 61: * 62: * @return <code>a / b</code> as fixed point value 63: */ 64: public static int div(int n, int a, int b) 65: { 66: return (int) ((((long) a) << n) / b); 67: } 68: 69: /** 70: * Multiplies two fixed point values with <code>n</code> digits. 71: * 72: * @param n the number of digits 73: * @param a the first operand as fixed point value 74: * @param b the second operand as fixed point value 75: * 76: * @return <code>a * b</code> as fixed point value 77: */ 78: public static int mul(int n, int a, int b) 79: { 80: return (int) ((((long) a) * b) >> n); 81: } 82: 83: /** 84: * Returns the ceiling value of a fixed point value <code>a</code> with 85: * the <code>n</code> digits. 86: * 87: * @param n the number of digits 88: * @param a the fixed point value 89: * 90: * @return <code>ceil(a)</code> as fixed point value 91: */ 92: public static int ceil(int n, int a) 93: { 94: return (a + (1 << n - 1)) & -(1 << n); 95: } 96: 97: /** 98: * Returns the floor value of a fixed point value <code>a</code> with 99: * <code>n</code> digits. 100: * 101: * @param n the number of digits 102: * @param a the fixed point value 103: * 104: * @return <code>floor(a)</code> as fixed point value 105: */ 106: public static int floor(int n, int a) 107: { 108: return a & -(1 << n); 109: } 110: 111: /** 112: * Truncates the number so that only the digits after the point are left. 113: * 114: * @param n the number of digits 115: * @param a the fixed point value 116: * 117: * @return the truncated value 118: */ 119: public static int trunc(int n, int a) 120: { 121: return a & (0xFFFFFFFF >>> 32 - n); 122: } 123: 124: /** 125: * Returns the round value of a fixed point value <code>a</code> with 126: * the <code>n</code> digits. 127: * 128: * @param n the number of digits 129: * @param a the fixed point value 130: * 131: * @return <code>round(a)</code> as fixed point value 132: */ 133: public static int round(int n, int a) 134: { 135: return (a + (1 << (n - 1))) & -(1 << n); 136: } 137: 138: /** 139: * Returns the fixed point value <code>a</code> with <code>n</code> digits 140: * as float. 141: * 142: * @param n the number of digits 143: * @param a the fixed point value 144: * 145: * @return the float value of <code>a</code> 146: */ 147: public static float floatValue(int n, int a) 148: { 149: return ((float) a) / (1 << n); 150: } 151: 152: /** 153: * Returns the fixed point value <code>a</code> with <code>n</code> digits 154: * as double. 155: * 156: * @param n the number of digits 157: * @param a the fixed point value 158: * 159: * @return the double value of <code>a</code> 160: */ 161: public static double doubleValue(int n, int a) 162: { 163: return ((double) a) / (1 << n); 164: } 165: 166: /** 167: * Returns the fixed point value that corresponds to the specified float 168: * value <code>a</code> with <code>n</code> digits. 169: * 170: * @param n the number of digits 171: * @param a the float value 172: * 173: * @return the fixed point value 174: */ 175: public static int fixedValue(int n, float a) 176: { 177: return (int) (a * (1 << n)); 178: } 179: 180: /** 181: * Returns the fixed point value that corresponds to the specified double 182: * value <code>a</code> with <code>n</code> digits. 183: * 184: * @param n the number of digits 185: * @param a the double value 186: * 187: * @return the fixed point value 188: */ 189: public static int fixedValue(int n, double a) 190: { 191: return (int) (a * (1 << n)); 192: } 193: 194: /** 195: * Returns the integer value of the specified fixed point value 196: * <code>a</code>. This simply cuts of the digits (== floor(a)). 197: * 198: * @param n the number of digits 199: * @param a the fixed point value 200: * 201: * @return the integer value 202: */ 203: public static int intValue(int n, int a) 204: { 205: return a >> n; 206: } 207: 208: /** 209: * Returns a fixed point decimal as rounded integer value. 210: * 211: * @param n the number of digits 212: * @param a the fixed point number 213: * 214: * @return the fixed point decimal as rounded integer value 215: */ 216: public static int roundIntValue(int n, int a) 217: { 218: return (a + (1 << (n - 1))) >> n; 219: } 220: }