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| 991 | cejka | 1 | /* |
| 2 | * Copyright (C) 2006 Josef Cejka |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * |
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| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | * - Redistributions in binary form must reproduce the above copyright |
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| 12 | * notice, this list of conditions and the following disclaimer in the |
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| 13 | * documentation and/or other materials provided with the distribution. |
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| 14 | * - The name of the author may not be used to endorse or promote products |
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| 15 | * derived from this software without specific prior written permission. |
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| 16 | * |
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 27 | */ |
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| 28 | |||
| 1653 | cejka | 29 | /** @addtogroup softint SoftInt |
| 30 | * @brief Software implementation of basic arithmetic operations. |
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| 31 | * @{ |
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| 32 | */ |
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| 33 | /** |
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| 34 | * @file |
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| 35 | * SW implementation of 32 and 64 bit division and modulo. |
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| 36 | */ |
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| 37 | |||
| 991 | cejka | 38 | #include <division.h> |
| 39 | |||
| 40 | #define ABSVAL(x) ( (x) > 0 ? (x) : -(x)) |
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| 41 | #define SGN(x) ( (x) >= 0 ? 1 : 0 ) |
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| 42 | |||
| 43 | static unsigned int divandmod32(unsigned int a, unsigned int b, unsigned int *remainder) |
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| 44 | { |
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| 45 | unsigned int result; |
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| 46 | int steps = sizeof(unsigned int) * 8; |
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| 47 | |||
| 48 | *remainder = 0; |
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| 49 | result = 0; |
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| 50 | |||
| 51 | if (b == 0) { |
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| 52 | /* FIXME: division by zero */ |
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| 53 | return 0; |
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| 54 | } |
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| 55 | |||
| 56 | if ( a < b) { |
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| 57 | *remainder = a; |
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| 58 | return 0; |
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| 59 | } |
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| 60 | |||
| 61 | for ( ; steps > 0; steps--) { |
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| 62 | /* shift one bit to remainder */ |
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| 63 | *remainder = ( (*remainder) << 1) | (( a >> 31) & 0x1); |
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| 64 | result <<= 1; |
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| 65 | |||
| 66 | if (*remainder >= b) { |
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| 67 | *remainder -= b; |
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| 68 | result |= 0x1; |
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| 69 | } |
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| 70 | a <<= 1; |
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| 71 | } |
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| 72 | |||
| 73 | return result; |
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| 74 | } |
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| 75 | |||
| 76 | |||
| 77 | static unsigned long long divandmod64(unsigned long long a, unsigned long long b, unsigned long long *remainder) |
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| 78 | { |
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| 79 | unsigned long long result; |
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| 80 | int steps = sizeof(unsigned long long) * 8; |
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| 81 | |||
| 82 | *remainder = 0; |
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| 83 | result = 0; |
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| 84 | |||
| 85 | if (b == 0) { |
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| 86 | /* FIXME: division by zero */ |
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| 87 | return 0; |
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| 88 | } |
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| 89 | |||
| 90 | if ( a < b) { |
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| 91 | *remainder = a; |
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| 92 | return 0; |
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| 93 | } |
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| 94 | |||
| 95 | for ( ; steps > 0; steps--) { |
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| 96 | /* shift one bit to remainder */ |
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| 97 | *remainder = ( (*remainder) << 1) | ((a >> 63) & 0x1); |
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| 98 | result <<= 1; |
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| 99 | |||
| 100 | if (*remainder >= b) { |
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| 101 | *remainder -= b; |
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| 102 | result |= 0x1; |
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| 103 | } |
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| 104 | a <<= 1; |
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| 105 | } |
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| 106 | |||
| 107 | return result; |
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| 108 | } |
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| 109 | |||
| 110 | /* 32bit integer division */ |
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| 111 | int __divsi3(int a, int b) |
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| 112 | { |
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| 113 | unsigned int rem; |
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| 114 | int result; |
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| 115 | |||
| 116 | result = (int)divandmod32(ABSVAL(a), ABSVAL(b), &rem); |
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| 117 | |||
| 118 | if ( SGN(a) == SGN(b)) return result; |
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| 119 | return -result; |
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| 120 | } |
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| 121 | |||
| 122 | /* 64bit integer division */ |
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| 123 | long long __divdi3(long long a, long long b) |
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| 124 | { |
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| 125 | unsigned long long rem; |
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| 126 | long long result; |
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| 127 | |||
| 128 | result = (long long)divandmod64(ABSVAL(a), ABSVAL(b), &rem); |
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| 129 | |||
| 130 | if ( SGN(a) == SGN(b)) return result; |
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| 131 | return -result; |
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| 132 | } |
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| 133 | |||
| 134 | /* 32bit unsigned integer division */ |
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| 135 | unsigned int __udivsi3(unsigned int a, unsigned int b) |
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| 136 | { |
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| 137 | unsigned int rem; |
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| 138 | return divandmod32(a, b, &rem); |
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| 139 | } |
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| 140 | |||
| 141 | /* 64bit unsigned integer division */ |
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| 142 | unsigned long long __udivdi3(unsigned long long a, unsigned long long b) |
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| 143 | { |
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| 144 | unsigned long long rem; |
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| 145 | return divandmod64(a, b, &rem); |
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| 146 | } |
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| 147 | |||
| 148 | /* 32bit remainder of the signed division */ |
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| 149 | int __modsi3(int a, int b) |
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| 150 | { |
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| 151 | unsigned int rem; |
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| 152 | divandmod32(a, b, &rem); |
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| 153 | |||
| 154 | /* if divident is negative, remainder must be too */ |
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| 155 | if (!(SGN(a))) { |
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| 156 | return -((int)rem); |
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| 157 | } |
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| 158 | |||
| 159 | return (int)rem; |
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| 160 | } |
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| 161 | |||
| 162 | /* 64bit remainder of the signed division */ |
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| 163 | long long __moddi3(long long a,long long b) |
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| 164 | { |
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| 165 | unsigned long long rem; |
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| 166 | divandmod64(a, b, &rem); |
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| 167 | |||
| 168 | /* if divident is negative, remainder must be too */ |
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| 169 | if (!(SGN(a))) { |
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| 170 | return -((long long)rem); |
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| 171 | } |
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| 172 | |||
| 173 | return (long long)rem; |
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| 174 | } |
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| 175 | |||
| 176 | /* 32bit remainder of the unsigned division */ |
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| 177 | unsigned int __umodsi3(unsigned int a, unsigned int b) |
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| 178 | { |
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| 179 | unsigned int rem; |
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| 180 | divandmod32(a, b, &rem); |
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| 181 | return rem; |
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| 182 | } |
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| 183 | |||
| 184 | /* 64bit remainder of the unsigned division */ |
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| 185 | unsigned long long __umoddi3(unsigned long long a, unsigned long long b) |
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| 186 | { |
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| 187 | unsigned long long rem; |
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| 188 | divandmod64(a, b, &rem); |
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| 189 | return rem; |
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| 190 | } |
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| 191 | |||
| 192 | unsigned long long __udivmoddi3(unsigned long long a, unsigned long long b, unsigned long long *c) |
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| 193 | { |
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| 194 | return divandmod64(a, b, c); |
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| 195 | } |
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| 196 | |||
| 1653 | cejka | 197 | /** @} |
| 198 | */ |