1 /* ------------------------------------------------------------------ 2 * Copyright (C) 1998-2009 PacketVideo 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either 13 * express or implied. 14 * See the License for the specific language governing permissions 15 * and limitations under the License. 16 * ------------------------------------------------------------------- 17 */ 18 /* 19 20 Filename: pv_div.c 21 22 ------------------------------------------------------------------------------ 23 REVISION HISTORY 24 25 26 Who: Date: MM/DD/YYYY 27 Description: 28 29 ------------------------------------------------------------------------------ 30 INPUT AND OUTPUT DEFINITIONS 31 32 Int32 x 32-bit integer numerator 33 Int32 y 32-bit integer denominator 34 Quotient *result structure that hold result and shift factor 35 36 37 ------------------------------------------------------------------------------ 38 FUNCTION DESCRIPTION 39 40 Implement division of two Int32 numbers, provides back quotient and a 41 shift factor 42 ------------------------------------------------------------------------------ 43 REQUIREMENTS 44 45 46 ------------------------------------------------------------------------------ 47 REFERENCES 48 49 ------------------------------------------------------------------------------ 50 PSEUDO-CODE 51 52 ------------------------------------------------------------------------------ 53 */ 54 55 56 /*---------------------------------------------------------------------------- 57 ; INCLUDES 58 ----------------------------------------------------------------------------*/ 59 #ifdef AAC_PLUS 60 61 62 #include "pv_audio_type_defs.h" 63 #include "fxp_mul32.h" 64 #include "pv_div.h" 65 #include "pv_normalize.h" 66 67 /*---------------------------------------------------------------------------- 68 ; MACROS 69 ; Define module specific macros here 70 ----------------------------------------------------------------------------*/ 71 72 73 /*---------------------------------------------------------------------------- 74 ; DEFINES 75 ; Include all pre-processor statements here. Include conditional 76 ; compile variables also. 77 ----------------------------------------------------------------------------*/ 78 79 /*---------------------------------------------------------------------------- 80 ; LOCAL FUNCTION DEFINITIONS 81 ; Function Prototype declaration 82 ----------------------------------------------------------------------------*/ 83 84 /*---------------------------------------------------------------------------- 85 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS 86 ; Variable declaration - defined here and used outside this module 87 ----------------------------------------------------------------------------*/ 88 89 /*---------------------------------------------------------------------------- 90 ; EXTERNAL FUNCTION REFERENCES 91 ; Declare functions defined elsewhere and referenced in this module 92 ----------------------------------------------------------------------------*/ 93 94 /*---------------------------------------------------------------------------- 95 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES 96 ; Declare variables used in this module but defined elsewhere 97 ----------------------------------------------------------------------------*/ 98 99 /*---------------------------------------------------------------------------- 100 ; FUNCTION CODE 101 ----------------------------------------------------------------------------*/ 102 103 104 void pv_div(Int32 x, Int32 y, Quotient *result) 105 { 106 /*---------------------------------------------------------------------------- 107 ; Define all local variables 108 ----------------------------------------------------------------------------*/ 109 Int32 quotient; 110 Int32 i; 111 Int32 j; 112 Int32 y_ov_y_hi; 113 Int32 flag = 0; /* carries negative sign, if any */ 114 115 116 result->shift_factor = 0; /* default */ 117 118 if (y == 0) 119 { 120 x = 0; /* this will return 0 for any div/0 */ 121 } 122 /* 123 * make sure x and y are both positive 124 */ 125 126 if (y < 0) 127 { 128 y = -y; 129 flag ^= 1; 130 } 131 132 133 if (x < 0) 134 { 135 x = -x; 136 flag ^= 1; 137 } 138 139 if (x != 0) 140 { 141 /*---------------------------------------------------------------------------- 142 ; Scale the input to get maximum precision for x 143 ----------------------------------------------------------------------------*/ 144 145 i = pv_normalize(x); 146 147 x <<= i; 148 149 150 /*---------------------------------------------------------------------------- 151 ; Scale the input to get maximum precision for y 152 ----------------------------------------------------------------------------*/ 153 154 j = pv_normalize(y); 155 156 y <<= j; 157 158 result->shift_factor = i - j; 159 160 /*---------------------------------------------------------------------------- 161 ; Function body here 162 ----------------------------------------------------------------------------*/ 163 /*--------------------------------------------------------------- 164 ; take the inverse of the 16 MSB of y 165 ---------------------------------------------------------------*/ 166 167 quotient = (0x40000000 / (y >> 15)); 168 169 y_ov_y_hi = fxp_mul32_Q15(y, quotient); /* y*(1/y_hi) */ 170 171 y_ov_y_hi = 0x7FFFFFFF - y_ov_y_hi; /* 2 - y*(1/y_hi) */ 172 y_ov_y_hi = fxp_mul32_Q14(quotient, y_ov_y_hi); 173 i = fxp_mul32_Q31(y_ov_y_hi, x) << 1; 174 175 result->quotient = flag ? -i : i; 176 } 177 else 178 { 179 result->quotient = 0; 180 } 181 182 183 184 } 185 186 #endif 187 188 189
