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 Portions of this file are derived from the following 3GPP standard: 20 21 3GPP TS 26.073 22 ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec 23 Available from http://www.3gpp.org 24 25 (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) 26 Permission to distribute, modify and use this file under the standard license 27 terms listed above has been obtained from the copyright holder. 28 ****************************************************************************************/ 29 /* 30 31 Pathname: ./gsm-amr/c/src/shr_r.c 32 33 ------------------------------------------------------------------------------ 34 REVISION HISTORY 35 36 Description: Created separate file for the shr_r function. Sync'ed up 37 with the current template and fixed tabs. 38 39 Description: Passing around pOverflow as per EPOC changes. 40 41 Who: Date: 42 Description: 43 44 ------------------------------------------------------------------------------ 45 INPUT AND OUTPUT DEFINITIONS 46 47 Inputs: 48 var1 = 16 bit short signed integer (Word16) whose value falls in 49 the range : 0xffff 8000 <= var1 <= 0x0000 7fff. 50 var2 = 16 bit short signed integer (Word16) whose value falls in 51 the range : 0xffff 8000 <= var2 <= 0x0000 7fff. 52 53 Local Stores/Buffers/Pointers Needed: 54 None 55 56 Global Stores/Buffers/Pointers Needed: 57 None 58 59 Outputs: 60 var_out = shifted input w/ rounding (Word16) 61 62 Pointers and Buffers Modified: 63 None 64 65 Local Stores Modified: 66 None 67 68 Global Stores Modified: 69 None 70 71 ------------------------------------------------------------------------------ 72 FUNCTION DESCRIPTION 73 74 This function arithmetically shifts the 16 bit input var1 right var2 positions 75 with rounding. If var2 is negative, arithmetically shift var1 left by 76 -var2 with rounding. Saturate the result in case of underflows or 77 overflows. 78 79 - If var2 is greater than zero : 80 if (sub(shl(shr(var1,var2),1),shr(var1,sub(var2,1)))) 81 is equal to zero 82 then 83 shr_r(var1,var2) = shr(var1,var2) 84 else 85 shr_r(var1,var2) = add(shr(var1,var2),1) 86 - If var2 is less than or equal to zero : 87 shr_r(var1,var2) = shr(var1,var2). 88 89 ------------------------------------------------------------------------------ 90 REQUIREMENTS 91 92 None 93 94 ------------------------------------------------------------------------------ 95 REFERENCES 96 97 [1] basicop2.c, ETS Version 2.0.0, February 8, 1999 98 99 ------------------------------------------------------------------------------ 100 PSEUDO-CODE 101 102 Word16 shr_r (Word16 var1, Word16 var2) 103 { 104 Word16 var_out; 105 106 if (var2 > 15) 107 { 108 var_out = 0; 109 } 110 else 111 { 112 var_out = shr (var1, var2); 113 #if (WMOPS) 114 multiCounter[currCounter].shr--; 115 #endif 116 117 if (var2 > 0) 118 { 119 if ((var1 & ((Word16) 1 << (var2 - 1))) != 0) 120 { 121 var_out++; 122 } 123 } 124 } 125 #if (WMOPS) 126 multiCounter[currCounter].shr_r++; 127 #endif 128 return (var_out); 129 } 130 131 ------------------------------------------------------------------------------ 132 RESOURCES USED 133 When the code is written for a specific target processor the 134 the resources used should be documented below. 135 136 STACK USAGE: [stack count for this module] + [variable to represent 137 stack usage for each subroutine called] 138 139 where: [stack usage variable] = stack usage for [subroutine 140 name] (see [filename].ext) 141 142 DATA MEMORY USED: x words 143 144 PROGRAM MEMORY USED: x words 145 146 CLOCK CYCLES: [cycle count equation for this module] + [variable 147 used to represent cycle count for each subroutine 148 called] 149 150 where: [cycle count variable] = cycle count for [subroutine 151 name] (see [filename].ext) 152 153 ------------------------------------------------------------------------------ 154 */ 155 156 157 /*---------------------------------------------------------------------------- 158 ; INCLUDES 159 ----------------------------------------------------------------------------*/ 160 #include "basic_op.h" 161 162 /*---------------------------------------------------------------------------- 163 ; MACROS 164 ; Define module specific macros here 165 ----------------------------------------------------------------------------*/ 166 167 /*---------------------------------------------------------------------------- 168 ; DEFINES 169 ; Include all pre-processor statements here. Include conditional 170 ; compile variables also. 171 ----------------------------------------------------------------------------*/ 172 173 /*---------------------------------------------------------------------------- 174 ; LOCAL FUNCTION DEFINITIONS 175 ; Function Prototype declaration 176 ----------------------------------------------------------------------------*/ 177 178 /*---------------------------------------------------------------------------- 179 ; LOCAL STORE/BUFFER/POINTER DEFINITIONS 180 ; Variable declaration - defined here and used outside this module 181 ----------------------------------------------------------------------------*/ 182 183 /*---------------------------------------------------------------------------- 184 ; EXTERNAL FUNCTION REFERENCES 185 ; Declare functions defined elsewhere and referenced in this module 186 ----------------------------------------------------------------------------*/ 187 188 /*---------------------------------------------------------------------------- 189 ; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES 190 ; Declare variables used in this module but defined elsewhere 191 ----------------------------------------------------------------------------*/ 192 193 /*---------------------------------------------------------------------------- 194 ; FUNCTION CODE 195 ----------------------------------------------------------------------------*/ 196 Word16 shr_r(register Word16 var1, register Word16 var2, Flag *pOverflow) 197 { 198 /*---------------------------------------------------------------------------- 199 ; Define all local variables 200 ----------------------------------------------------------------------------*/ 201 Word16 var_out; 202 203 /*---------------------------------------------------------------------------- 204 ; Function body here 205 ----------------------------------------------------------------------------*/ 206 if (var2 > 15) 207 { 208 var_out = 0; 209 } 210 else 211 { 212 var_out = shr(var1, var2, pOverflow); 213 if (var2 > 0) 214 { 215 if ((var1 & ((Word16) 1 << (var2 - 1))) != 0) 216 { 217 var_out++; 218 } 219 } 220 } 221 222 /*---------------------------------------------------------------------------- 223 ; Return nothing or data or data pointer 224 ----------------------------------------------------------------------------*/ 225 return (var_out); 226 } 227
