259 lines
8.0 KiB
C++
259 lines
8.0 KiB
C++
/* ------------------------------------------------------------------
|
|
* 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);
|
|
}
|
|
|