FreeCalypso > hg > gsm-codec-lib
view libgsmfr2/add.c @ 440:bc736a8654af
.hgignore: add amrefr-decode-r
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Thu, 09 May 2024 00:13:05 +0000 |
parents | a7b593e68ac3 |
children |
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/* * This C source file has been adapted from TU-Berlin libgsm source, * original notice follows: * * Copyright 1992 by Jutta Degener and Carsten Bormann, Technische * Universitaet Berlin. See the accompanying file "COPYRIGHT" for * details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE. */ #include <stdint.h> #include <assert.h> #include "tw_gsmfr.h" #include "typedef.h" #include "ed_state.h" #include "ed_internal.h" #define saturate(x) \ ((x) < MIN_WORD ? MIN_WORD : (x) > MAX_WORD ? MAX_WORD: (x)) word gsm_add (word a, word b) { longword sum = (longword)a + (longword)b; return saturate(sum); } word gsm_sub (word a, word b) { longword diff = (longword)a - (longword)b; return saturate(diff); } word gsm_mult (word a, word b) { if (a == MIN_WORD && b == MIN_WORD) return MAX_WORD; else return SASR( (longword)a * (longword)b, 15 ); } word gsm_mult_r (word a, word b) { if (b == MIN_WORD && a == MIN_WORD) return MAX_WORD; else { longword prod = (longword)a * (longword)b + 16384; prod >>= 15; return prod & 0xFFFF; } } word gsm_abs (word a) { return a < 0 ? (a == MIN_WORD ? MAX_WORD : -a) : a; } longword gsm_L_mult (word a, word b) { assert( a != MIN_WORD || b != MIN_WORD ); return ((longword)a * (longword)b) << 1; } longword gsm_L_add (longword a, longword b) { if (a < 0) { if (b >= 0) return a + b; else { ulongword A = (ulongword)-(a + 1) + (ulongword)-(b + 1); return A >= MAX_LONGWORD ? MIN_LONGWORD :-(longword)A-2; } } else if (b <= 0) return a + b; else { ulongword A = (ulongword)a + (ulongword)b; return A > MAX_LONGWORD ? MAX_LONGWORD : A; } } longword gsm_L_sub (longword a, longword b) { if (a >= 0) { if (b >= 0) return a - b; else { /* a>=0, b<0 */ ulongword A = (ulongword)a + -(b + 1); return A >= MAX_LONGWORD ? MAX_LONGWORD : (A + 1); } } else if (b <= 0) return a - b; else { /* a<0, b>0 */ ulongword A = (ulongword)-(a + 1) + b; return A >= MAX_LONGWORD ? MIN_LONGWORD : -(longword)A - 1; } } static unsigned char const bitoff[ 256 ] = { 8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; word gsm_norm (longword a) /* * the number of left shifts needed to normalize the 32 bit * variable L_var1 for positive values on the interval * * with minimum of * minimum of 1073741824 (01000000000000000000000000000000) and * maximum of 2147483647 (01111111111111111111111111111111) * * * and for negative values on the interval with * minimum of -2147483648 (-10000000000000000000000000000000) and * maximum of -1073741824 ( -1000000000000000000000000000000). * * in order to normalize the result, the following * operation must be done: L_norm_var1 = L_var1 << norm( L_var1 ); * * (That's 'ffs', only from the left, not the right..) */ { assert(a != 0); if (a < 0) { if (a <= -1073741824) return 0; a = ~a; } return a & 0xffff0000 ? ( a & 0xff000000 ? -1 + bitoff[ 0xFF & (a >> 24) ] : 7 + bitoff[ 0xFF & (a >> 16) ] ) : ( a & 0xff00 ? 15 + bitoff[ 0xFF & (a >> 8) ] : 23 + bitoff[ 0xFF & a ] ); } longword gsm_L_asl (longword a, int n) { if (n >= 32) return 0; if (n <= -32) return -(a < 0); if (n < 0) return gsm_L_asr(a, -n); return a << n; } word gsm_asl (word a, int n) { if (n >= 16) return 0; if (n <= -16) return -(a < 0); if (n < 0) return gsm_asr(a, -n); return a << n; } longword gsm_L_asr (longword a, int n) { if (n >= 32) return -(a < 0); if (n <= -32) return 0; if (n < 0) return a << -n; # ifdef SASR return a >> n; # else if (a >= 0) return a >> n; else return -(longword)( -(ulongword)a >> n ); # endif } word gsm_asr (word a, int n) { if (n >= 16) return -(a < 0); if (n <= -16) return 0; if (n < 0) return a << -n; # ifdef SASR return a >> n; # else if (a >= 0) return a >> n; else return -(word)( -(uword)a >> n ); # endif } /* * (From p. 46, end of section 4.2.5) * * NOTE: The following lines gives [sic] one correct implementation * of the div(num, denum) arithmetic operation. Compute div * which is the integer division of num by denum: with denum * >= num > 0 */ word gsm_div (word num, word denum) { longword L_num = num; longword L_denum = denum; word div = 0; int k = 15; /* The parameter num sometimes becomes zero. * Although this is explicitly guarded against in 4.2.5, * we assume that the result should then be zero as well. */ /* assert(num != 0); */ assert(num >= 0 && denum >= num); if (num == 0) return 0; while (k--) { div <<= 1; L_num <<= 1; if (L_num >= L_denum) { L_num -= L_denum; div++; } } return div; }