FreeCalypso > hg > gsm-codec-lib
view libgsmefr/oper_32b.c @ 162:b98aebd94d1f
gsmefr-dlcap-parse utility written
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Thu, 15 Dec 2022 23:47:12 +0000 |
parents | 92479d9a8e38 |
children | 3da7ab45910d |
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/***************************************************************************** * * * 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 "gsm_efr.h" #include "typedef.h" #include "namespace.h" #include "basic_op.h" #include "oper_32b.h" #include "no_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); }