av/media/libstagefright/codecs/amrnb/common/src/norm_s.cpp

/* ------------------------------------------------------------------
 * 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.
****************************************************************************************/
/*

 Pathname: ./gsm-amr/c/src/norm_s.c

------------------------------------------------------------------------------
 REVISION HISTORY

 Description: Created separate file for the norm_s function. Sync'ed up
          with the current template and fixed tabs.

 Description: Updated input/output definition and module description to
          be the same as the equivalent assembly file (norm_s.asm).

 Description: Updated definition of var1 to be the same as that in the
          assembly file (norm_s.asm).

 Description: Removed conditional code that updates WMOPS counter

 Who:                       Date:
 Description:

------------------------------------------------------------------------------
 INPUT AND OUTPUT DEFINITIONS

 Inputs:
    var1 = 16 bit signed integer of type Word16, whose value falls
           in the range: 0x8000 <= var1 <= 0x7fff

 Local Stores/Buffers/Pointers Needed:
    None

 Global Stores/Buffers/Pointers Needed:
    None

 Outputs:
    var_out = number of left shifts need to normalize var1 (Word16)

 Pointers and Buffers Modified:
    None

 Local Stores Modified:
    None

 Global Stores Modified:
    None

------------------------------------------------------------------------------
 FUNCTION DESCRIPTION

 This function produces the number of left shifts needed to normalize the 16
 bit variable var1 for positive values on the interval with minimum of 0x4000
 and maximum of 0x7fff, and for negative values on the interval with minimum
 of 0x8000 and maximum of 0xc000. Note that when var1 is zero, the resulting
 output var_out is set to zero.

------------------------------------------------------------------------------
 REQUIREMENTS

 None

------------------------------------------------------------------------------
 REFERENCES

 [1] basicop2.c, ETS Version 2.0.0, February 8, 1999

------------------------------------------------------------------------------
 PSEUDO-CODE

Word16 norm_s (Word16 var1)
{
    Word16 var_out;

    if (var1 == 0)
    {
        var_out = 0;
    }
    else
    {
        if (var1 == (Word16) 0xffff)
        {
            var_out = 15;
        }
        else
        {
            if (var1 < 0)
            {
                var1 = ~var1;
            }
            for (var_out = 0; var1 < 0x4000; var_out++)
            {
                var1 <<= 1;
            }
        }
    }

#if (WMOPS)
    multiCounter[currCounter].norm_s++;
#endif
    return (var_out);
}

------------------------------------------------------------------------------
 RESOURCES USED
   When the code is written for a specific target processor the
     the resources used should be documented below.

 STACK USAGE: [stack count for this module] + [variable to represent
          stack usage for each subroutine called]

     where: [stack usage variable] = stack usage for [subroutine
         name] (see [filename].ext)

 DATA MEMORY USED: x words

 PROGRAM MEMORY USED: x words

 CLOCK CYCLES: [cycle count equation for this module] + [variable
           used to represent cycle count for each subroutine
           called]

     where: [cycle count variable] = cycle count for [subroutine
        name] (see [filename].ext)

------------------------------------------------------------------------------
*/


/*----------------------------------------------------------------------------
; 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
; Function Prototype declaration
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; EXTERNAL FUNCTION REFERENCES
; Declare functions defined elsewhere and referenced in this module
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/

/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/
#if !( defined(PV_ARM_V5) || defined(PV_ARM_GCC_V5) )

Word16 norm_s(Word16 var1)
{
    /*----------------------------------------------------------------------------
    ; Define all local variables
    ----------------------------------------------------------------------------*/

    Word16 var_out = 0;

    /*----------------------------------------------------------------------------
    ; Function body here
    ----------------------------------------------------------------------------*/

    if (var1)
    {
        Word16 y = var1 - (var1 < 0);
        var1 = y ^(y >> 15);

        while (!(0x4000 & var1))
        {
            var_out++;
            if ((0x2000 & var1))
            {
                break;
            }
            var_out++;
            if ((0x1000 & var1))
            {
                break;
            }
            var_out++;
            if ((0x0800 & var1))
            {
                break;
            }
            var_out++;
            var1 <<= 4;
        }
    }

    /*----------------------------------------------------------------------------
    ; Return nothing or data or data pointer
    ----------------------------------------------------------------------------*/
    return (var_out);
}

#endif