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 Filename: /audio/gsm_amr/c/src/l_shr_r.c 31 32 ------------------------------------------------------------------------------ 33 REVISION HISTORY 34 35 Description: Created separate file for the L_shr_r function. Sync'ed up 36 with the current template and fixed tabs. 37 38 Description: Updated template. Changed function interface to pass in a 39 pointer to overflow flag into the function instead of using a 40 global flag. Removed code that updates MOPS counter. Changed 41 function return value name from "L_var_out" to "result". 42 43 Who: Date: 44 Description: 45 46 ------------------------------------------------------------------------------ 47 */ 48 49 50 /*---------------------------------------------------------------------------- 51 ; INCLUDES 52 ----------------------------------------------------------------------------*/ 53 #include "basic_op.h" 54 55 /*---------------------------------------------------------------------------- 56 ; MACROS 57 ; [Define module specific macros here] 58 ----------------------------------------------------------------------------*/ 59 60 /*---------------------------------------------------------------------------- 61 ; DEFINES 62 ; [Include all pre-processor statements here. Include conditional 63 ; compile variables also.] 64 ----------------------------------------------------------------------------*/ 65 66 /*---------------------------------------------------------------------------- 67 ; LOCAL FUNCTION DEFINITIONS 68 ; [List function prototypes here] 69 ----------------------------------------------------------------------------*/ 70 71 /*---------------------------------------------------------------------------- 72 ; LOCAL VARIABLE DEFINITIONS 73 ; [Variable declaration - defined here and used outside this module] 74 ----------------------------------------------------------------------------*/ 75 76 77 /* 78 ------------------------------------------------------------------------------ 79 FUNCTION NAME: L_shr_r 80 ------------------------------------------------------------------------------ 81 INPUT AND OUTPUT DEFINITIONS 82 83 Inputs: 84 L_var1 = 32 bit long signed integer (Word32 ) whose value falls 85 in the range : 0x8000 0000 <= L_var1 <= 0x7fff ffff. 86 var2 = 16 bit short signed integer (Word16) whose value falls in 87 the range : 0xffff 8000 <= var2 <= 0x0000 7fff. 88 89 pOverflow = pointer to overflow (Flag) 90 91 Outputs: 92 pOverflow -> 1 if the 32 bit shift operation resulted in overflow 93 94 Returns: 95 result = Shifted result w/ rounding (Word32) 96 97 Global Variables Used: 98 None 99 100 Local Variables Needed: 101 None 102 103 ------------------------------------------------------------------------------ 104 FUNCTION DESCRIPTION 105 106 This function arithmetically shifts the 32 bit input L_var1 right var2 107 positions with rounding. If var2 is negative, the function 108 arithmetically shifts L_var1 left by -var2 and zero fills the -var2 LSB of 109 the result. The result is saturated in case of underflows or overflows, i.e., 110 111 - If var2 is greater than zero : 112 if (L_sub(L_shl(L_shr(L_var1,var2),1),L_shr(L_var1,sub(var2,1)))) 113 is equal to zero 114 then 115 L_shr_r(L_var1,var2) = L_shr(L_var1,var2) 116 else 117 L_shr_r(L_var1,var2) = L_add(L_shr(L_var1,var2),1) 118 - If var2 is less than or equal to zero : 119 L_shr_r(L_var1,var2) = L_shr(L_var1,var2). 120 121 ------------------------------------------------------------------------------ 122 REQUIREMENTS 123 124 None 125 126 ------------------------------------------------------------------------------ 127 REFERENCES 128 129 [1] L_shr_r() function in basic_op2.c, UMTS GSM AMR speech codec, R99 - 130 Version 3.2.0, March 2, 2001 131 132 ------------------------------------------------------------------------------ 133 PSEUDO-CODE 134 135 Word32 L_shr_r (Word32 L_var1, Word16 var2) 136 { 137 Word32 L_var_out; 138 139 * The reference ETSI code uses a global flag for Overflow. In the actual 140 * implementation a pointer to Overflow flag is passed in as a parameter to the 141 * function L_shr() 142 143 if (var2 > 31) 144 { 145 L_var_out = 0; 146 } 147 else 148 { 149 L_var_out = L_shr (L_var1, var2); 150 #if (WMOPS) 151 multiCounter[currCounter].L_shr--; 152 #endif 153 if (var2 > 0) 154 { 155 if ((L_var1 & ((Word32) 1 << (var2 - 1))) != 0) 156 { 157 L_var_out++; 158 } 159 } 160 } 161 #if (WMOPS) 162 multiCounter[currCounter].L_shr_r++; 163 #endif 164 return (L_var_out); 165 } 166 167 ------------------------------------------------------------------------------ 168 RESOURCES USED [optional] 169 170 When the code is written for a specific target processor the 171 the resources used should be documented below. 172 173 HEAP MEMORY USED: x bytes 174 175 STACK MEMORY USED: x bytes 176 177 CLOCK CYCLES: (cycle count equation for this function) + (variable 178 used to represent cycle count for each subroutine 179 called) 180 where: (cycle count variable) = cycle count for [subroutine 181 name] 182 183 ------------------------------------------------------------------------------ 184 CAUTION [optional] 185 [State any special notes, constraints or cautions for users of this function] 186 187 ------------------------------------------------------------------------------ 188 */ 189 190 /*---------------------------------------------------------------------------- 191 ; FUNCTION CODE 192 ----------------------------------------------------------------------------*/ 193 Word32 L_shr_r(register Word32 L_var1, register Word16 var2, Flag *pOverflow) 194 { 195 Word32 result; 196 197 if (var2 > 31) 198 { 199 result = 0; 200 } 201 else 202 { 203 result = L_shr(L_var1, var2, pOverflow); 204 205 if (var2 > 0) 206 { 207 if ((L_var1 & ((Word32) 1 << (var2 - 1))) != 0) 208 { 209 result++; 210 } 211 } 212 } 213 return (result); 214 } 215
