mult.h

实现3GPP的GSM中AMR语音的CODECS。

/* ------------------------------------------------------------------
 * Copyright (C) 2008 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/include/mult.h

     Date: 08/11/2000

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

 Description: Created separate header file for mult function.

 Description: Changed prototype of the mult() function. Instead of using global
			  a pointer to overflow flag is now passed into the function.

 Description: Updated copyright information.
			  Updated variable name from "overflow" to "pOverflow" to match
			  with original function declaration.

 Description: Moved _cplusplus #ifdef after Include section.

 Description: Providing support for ARM and Linux-ARM assembly instructions.

 Description:

------------------------------------------------------------------------------
 INCLUDE DESCRIPTION

 This file contains all the constant definitions and prototype definitions
 needed by the mult function.

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

#ifndef	MULT_H
#define	MULT_H

/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/

#include	"basicop_malloc.h"

/*--------------------------------------------------------------------------*/
#ifdef __cplusplus
extern "C"
{
#endif

    /*----------------------------------------------------------------------------
    ; MACROS
    ; Define module specific macros here
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; DEFINES
    ; Include all pre-processor statements here.
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; EXTERNAL VARIABLES REFERENCES
    ; Declare variables used in this module but defined elsewhere
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; SIMPLE TYPEDEF'S
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; ENUMERATED TYPEDEF'S
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; STRUCTURES TYPEDEF'S
    ----------------------------------------------------------------------------*/

    /*----------------------------------------------------------------------------
    ; GLOBAL FUNCTION DEFINITIONS
    ; Function Prototype declaration
    ----------------------------------------------------------------------------*/
#if defined(PV_ARM)

    __inline Word16 mult(Word16 var1, Word16 var2, Flag *pOverflow)
    {
        Word32 product;

        OSCL_UNUSED_ARG(pOverflow);

        __asm
        {
            SMULBB product, var1, var2
            MOV    product, product, ASR #15
            CMP    product, 0x7FFF
            MOVGE  product, 0x7FFF
        }

        return ((Word16) product);
    }

#elif defined(PV_ARM_GCC)

    __inline Word16 mult(Word16 var1, Word16 var2, Flag *pOverflow)
    {
        register Word32 ra = var1;
        register Word32 rb = var2;
        Word32 product;
        Word32 temp = 0x7FFF;

        OSCL_UNUSED_ARG(pOverflow);

        asm volatile("smulbb %0, %1, %2"
             : "=r"(product)
                             : "r"(ra), "r"(rb)
                            );
        asm volatile("mov %0, %1, ASR #15"
             : "=r"(product)
                             : "r"(product)
                            );
        asm volatile("cmp %0, %1"
             : "=r"(product)
                             : "r"(temp)
                            );
        asm volatile("movge %0, %1"
             : "=r"(product)
                             : "r"(temp)
                            );

        return ((Word16) product);
    }

#else /* C EQUIVALENT */

    static inline Word16 mult(Word16 var1, Word16 var2, Flag *pOverflow)
    {
        register Word32 product;

        product = ((Word32) var1 * var2) >> 15;

        /* Saturate result (if necessary). */
        /* var1 * var2 >0x00007fff is the only case */
        /* that saturation occurs. */

        if (product > 0x00007fffL)
        {
            *pOverflow = 1;
            product = (Word32) MAX_16;
        }


        /* Return the product as a 16 bit value by type casting Word32 to Word16 */

        return ((Word16) product);
    }

#endif
    /*----------------------------------------------------------------------------
    ; END
    ----------------------------------------------------------------------------*/
#ifdef __cplusplus
}
#endif

#endif	/* _MULT_H_ */