| /* ------------------------------------------------------------------ |
| * Copyright (C) 1998-2009 PacketVideo |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
| * express or implied. |
| * See the License for the specific language governing permissions |
| * and limitations under the License. |
| * ------------------------------------------------------------------- |
| */ |
| /**************************************************************************************** |
| Portions of this file are derived from the following 3GPP standard: |
| |
| 3GPP TS 26.073 |
| ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec |
| Available from http://www.3gpp.org |
| |
| (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) |
| Permission to distribute, modify and use this file under the standard license |
| terms listed above has been obtained from the copyright holder. |
| ****************************************************************************************/ |
| /* |
| |
| Filename: /audio/gsm_amr/c/src/shr.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Created separate file for the shr function. Sync'ed up with |
| the current template and fixed tabs. |
| |
| Description: 1. Modified code by seperating var2=0 condition. |
| 2. Changed Input range definitions. |
| |
| Description: Made changes based on review meeting. |
| 1. Changed Overflow definition. |
| 2. Removed pseudo-code. |
| 3. Deleted (var2>15&&var1!=0) condition. |
| 4. Moved var2>0 condition in front of var2<0 condition. |
| |
| Description: Changed the function prototype to pass in a pointer to the |
| overflow flag instead of using global data. |
| |
| Description: Made changes per formal review. Updated template. |
| Removed code that updates MOPS counter. |
| Changed parameter name from "overflow" and "pOverflow". |
| Optimized code by eliminating unnecessary typecasting. |
| Filled in the PSEUDO CODE section |
| |
| Description: Further optimized typecasting for overflow case |
| |
| Who: Date: |
| Description: |
| ------------------------------------------------------------------------------ |
| ------------------------------------------------------------------------------ |
| MODULE DESCRIPTION |
| Shift right function with overflow control |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "basic_op.h" |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; [Define module specific macros here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; [Include all pre-processor statements here. Include conditional |
| ; compile variables also.] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; [List function prototypes here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL VARIABLE DEFINITIONS |
| ; [Variable declaration - defined here and used outside this module] |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /* |
| ------------------------------------------------------------------------------ |
| FUNCTION NAME: shr |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| var1 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var2 <= 0x0000 7fff. |
| |
| pOverflow = pointer to overflow (Flag) |
| |
| Outputs: |
| pOverflow -> 1 if the shift operation resulted in overflow |
| |
| Returns: |
| product = Shifted result limited to 16 bits (Word16) |
| |
| Global Variables Used: |
| None |
| |
| Local Variables Needed: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function arithmetically shifts the 16 bit input var1 right var2 positions |
| with sign extension. If var2 is negative, arithmetically shift var1 left by |
| -var2 with sign extension. Saturate the result in case of underflows or |
| overflows. |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| None |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] shr() function in basic_op2.c, UMTS GSM AMR speech codec, R99 - |
| Version 3.2.0, March 2, 2001 |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| Word16 shr_std (Word16 var1, Word16 var2) |
| { |
| Word16 var_out; |
| |
| if (var2 < 0) |
| { |
| if (var2 < -16) |
| var2 = -16; |
| var_out = shl_std (var1, -var2); |
| #if (WMOPS) |
| mult_stdiCounter[currCounter].shl_std--; |
| #endif |
| } |
| else |
| { |
| if (var2 >= 15) |
| { |
| var_out = (var1 < 0) ? -1 : 0; |
| } |
| else |
| { |
| if (var1 < 0) |
| { |
| var_out = ~((~var1) >> var2); |
| } |
| else |
| { |
| var_out = var1 >> var2; |
| } |
| } |
| } |
| |
| #if (WMOPS) |
| mult_stdiCounter[currCounter].shr_std++; |
| #endif |
| return (var_out); |
| } |
| ------------------------------------------------------------------------------ |
| RESOURCES USED [optional] |
| |
| When the code is written for a specific target processor the |
| the resources used should be documented below. |
| |
| HEAP MEMORY USED: x bytes |
| |
| STACK MEMORY USED: x bytes |
| |
| CLOCK CYCLES: (cycle count equation for this function) + (variable |
| used to represent cycle count for each subroutine |
| called) |
| where: (cycle count variable) = cycle count for [subroutine |
| name] |
| |
| ------------------------------------------------------------------------------ |
| CAUTION [optional] |
| [State any special notes, constraints or cautions for users of this function] |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| Word16 shr(Word16 var1, Word16 var2, Flag *pOverflow) |
| { |
| Word16 result; |
| Word32 temp_res; |
| |
| if (var2 != 0) |
| { |
| if (var2 > 0) |
| { |
| if (var2 >= 15) |
| { |
| result = ((var1 < 0) ? -1 : 0); |
| } |
| else |
| { |
| if (var1 < 0) |
| { |
| result = (~((~var1) >> var2)); |
| } |
| else |
| { |
| result = (var1 >> var2); |
| } |
| } |
| } |
| else |
| { |
| if (var2 < -16) |
| { |
| var2 = -16; |
| } |
| |
| var2 = -var2; /* Shift right negative is equivalent */ |
| /* to shifting left positive. */ |
| |
| temp_res = ((Word32) var1) << var2; |
| result = (Word16)(temp_res); |
| |
| if (temp_res != (Word32) result) |
| { |
| *pOverflow = 1; |
| result = ((var1 > 0) ? MAX_16 : MIN_16); |
| } |
| } |
| |
| } |
| else |
| { |
| result = var1; |
| } |
| |
| return (result); |
| } |
| |
