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view libtwamr/inv_sqrt.h @ 602:72cdae602d6e

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libgsmhr1/dec_func.c: rm unused static functions In the original code, sp_dec.c held two kinds of functions: those needed only as part of the decoder, and those used by both decoder and encoder engines. In this library, we have moved the latter class of functions to dec_func.c module. Almost all static functions from the original sp_dec.c, with the exception of aToRc(), are needed only on sp_dec.c side of the new divide - remove them from dec_func.c, where they became dead code.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 04 Dec 2025 18:58:22 +0000
parents 54f6bc41ed10
children
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/*
********************************************************************************
*
*      GSM AMR-NB speech codec   R98   Version 7.6.0   December 12, 2001
*                                R99   Version 3.3.0                
*                                REL-4 Version 4.1.0                
*
********************************************************************************
*
*      File             : inv_sqrt.h
*      Purpose          : Computes 1/sqrt(L_x),  where  L_x is positive.
*                       : If L_x is negative or zero, the result is
*                       : 1 (3fff ffff).
*      Description      : The function 1/sqrt(L_x) is approximated by a table 
*                       : and linear interpolation. The inverse square root is 
*                       : computed using the following steps:
*               1- Normalization of L_x.
*               2- If (30-exponent) is even then shift right once.
*               3- exponent = (30-exponent)/2  +1
*               4- i = bit25-b31 of L_x;  16<=i<=63  because of normalization.
*               5- a = bit10-b24
*               6- i -=16
*               7- L_y = table[i]<<16 - (table[i] - table[i+1]) * a * 2
*               8- L_y >>= exponent
*
********************************************************************************
*/
#ifndef inv_sqrt_h
#define inv_sqrt_h "$Id $"
 
/*
********************************************************************************
*                         INCLUDE FILES
********************************************************************************
*/
#include "typedef.h"

/*
********************************************************************************
*                         DEFINITION OF DATA TYPES
********************************************************************************
*/
 
/*
********************************************************************************
*                         DECLARATION OF PROTOTYPES
********************************************************************************
*/
 
Word32 Inv_sqrt (      /* (o) : output value   (range: 0<=val<1)            */
    Word32 L_x           /* (i) : input value    (range: 0<=val<=7fffffff)    */
);
 
#endif