ref: 7218a569ea0124a0a25dffd3e93b91bde67bdca7
dir: /amr-wb/oper_32b.c/
/*****************************************************************************
* $Id: oper_32b.c,v 1.1 2007/02/15 23:22:35 robs Exp $
*
* This file contains operations in double precision. *
* These operations are not standard double precision operations. *
* They are used where single precision is not enough but the full 32 bits *
* precision is not necessary. For example, the function Div_32() has a *
* 24 bits precision which is enough for our purposes. *
* *
* The double precision numbers use a special representation: *
* *
* L_32 = hi<<16 + lo<<1 *
* *
* L_32 is a 32 bit integer. *
* hi and lo are 16 bit signed integers. *
* As the low part also contains the sign, this allows fast multiplication. *
* *
* 0x8000 0000 <= L_32 <= 0x7fff fffe. *
* *
* We will use DPF (Double Precision Format )in this file to specify *
* this special format. *
*****************************************************************************
*/
#include "typedef.h"
#include "basic_op.h"
#include "oper_32b.h"
#include "count.h"
/*****************************************************************************
* *
* Function L_Extract() *
* *
* Extract from a 32 bit integer two 16 bit DPF. *
* *
* Arguments: *
* *
* L_32 : 32 bit integer. *
* 0x8000 0000 <= L_32 <= 0x7fff ffff. *
* hi : b16 to b31 of L_32 *
* lo : (L_32 - hi<<16)>>1 *
*****************************************************************************
*/
void L_Extract (Word32 L_32, Word16 *hi, Word16 *lo)
{
*hi = extract_h (L_32);
*lo = extract_l (L_msu (L_shr (L_32, 1), *hi, 16384));
return;
}
/*****************************************************************************
* *
* Function L_Comp() *
* *
* Compose from two 16 bit DPF a 32 bit integer. *
* *
* L_32 = hi<<16 + lo<<1 *
* *
* Arguments: *
* *
* hi msb *
* lo lsf (with sign) *
* *
* Return Value : *
* *
* 32 bit long signed integer (Word32) whose value falls in the *
* range : 0x8000 0000 <= L_32 <= 0x7fff fff0. *
* *
*****************************************************************************
*/
Word32 L_Comp (Word16 hi, Word16 lo)
{
Word32 L_32;
L_32 = L_deposit_h (hi);
return (L_mac (L_32, lo, 1)); /* = hi<<16 + lo<<1 */
}
/*****************************************************************************
* Function Mpy_32() *
* *
* Multiply two 32 bit integers (DPF). The result is divided by 2**31 *
* *
* L_32 = (hi1*hi2)<<1 + ( (hi1*lo2)>>15 + (lo1*hi2)>>15 )<<1 *
* *
* This operation can also be viewed as the multiplication of two Q31 *
* number and the result is also in Q31. *
* *
* Arguments: *
* *
* hi1 hi part of first number *
* lo1 lo part of first number *
* hi2 hi part of second number *
* lo2 lo part of second number *
* *
*****************************************************************************
*/
Word32 Mpy_32 (Word16 hi1, Word16 lo1, Word16 hi2, Word16 lo2)
{
Word32 L_32;
L_32 = L_mult (hi1, hi2);
L_32 = L_mac (L_32, mult (hi1, lo2), 1);
L_32 = L_mac (L_32, mult (lo1, hi2), 1);
return (L_32);
}
/*****************************************************************************
* Function Mpy_32_16() *
* *
* Multiply a 16 bit integer by a 32 bit (DPF). The result is divided *
* by 2**15 *
* *
* *
* L_32 = (hi1*lo2)<<1 + ((lo1*lo2)>>15)<<1 *
* *
* Arguments: *
* *
* hi hi part of 32 bit number. *
* lo lo part of 32 bit number. *
* n 16 bit number. *
* *
*****************************************************************************
*/
Word32 Mpy_32_16 (Word16 hi, Word16 lo, Word16 n)
{
Word32 L_32;
L_32 = L_mult (hi, n);
L_32 = L_mac (L_32, mult (lo, n), 1);
return (L_32);
}
/*****************************************************************************
* *
* Function Name : Div_32 *
* *
* Purpose : *
* Fractional integer division of two 32 bit numbers. *
* L_num / L_denom. *
* L_num and L_denom must be positive and L_num < L_denom. *
* L_denom = denom_hi<<16 + denom_lo<<1 *
* denom_hi is a normalize number. *
* *
* Inputs : *
* *
* L_num *
* 32 bit long signed integer (Word32) whose value falls in the *
* range : 0x0000 0000 < L_num < L_denom *
* *
* L_denom = denom_hi<<16 + denom_lo<<1 (DPF) *
* *
* denom_hi *
* 16 bit positive normalized integer whose value falls in the *
* range : 0x4000 < hi < 0x7fff *
* denom_lo *
* 16 bit positive integer whose value falls in the *
* range : 0 < lo < 0x7fff *
* *
* Return Value : *
* *
* L_div *
* 32 bit long signed integer (Word32) whose value falls in the *
* range : 0x0000 0000 <= L_div <= 0x7fff ffff. *
* *
* Algorithm: *
* *
* - find = 1/L_denom. *
* First approximation: approx = 1 / denom_hi *
* 1/L_denom = approx * (2.0 - L_denom * approx ) *
* *
* - result = L_num * (1/L_denom) *
*****************************************************************************
*/
Word32 Div_32 (Word32 L_num, Word16 denom_hi, Word16 denom_lo)
{
Word16 approx, hi, lo, n_hi, n_lo;
Word32 L_32;
/* First approximation: 1 / L_denom = 1/denom_hi */
approx = div_s ((Word16) 0x3fff, denom_hi);
/* 1/L_denom = approx * (2.0 - L_denom * approx) */
L_32 = Mpy_32_16 (denom_hi, denom_lo, approx);
L_32 = L_sub ((Word32) 0x7fffffffL, L_32);
L_Extract (L_32, &hi, &lo);
L_32 = Mpy_32_16 (hi, lo, approx);
/* L_num * (1/L_denom) */
L_Extract (L_32, &hi, &lo);
L_Extract (L_num, &n_hi, &n_lo);
L_32 = Mpy_32 (n_hi, n_lo, hi, lo);
L_32 = L_shl (L_32, 2);
return (L_32);
}