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Diffstat (limited to 'nylsf/GSM610/add.c')
| -rw-r--r-- | nylsf/GSM610/add.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/nylsf/GSM610/add.c b/nylsf/GSM610/add.c new file mode 100644 index 0000000..613ed57 --- /dev/null +++ b/nylsf/GSM610/add.c @@ -0,0 +1,249 @@ +/* + * 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. + */ + +/* + * See private.h for the more commonly used macro versions. + */ + +#include <stdio.h> +#include <assert.h> + +#include "config.h" // RBD +#include "gsm610_priv.h" +#include "gsm.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; + + return SASR_L( (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_asr (word a, int n) +{ + if (n >= 16) return -(a < 0); + if (n <= -16) return 0; + if (n < 0) return a << -n; + + return SASR_W (a, (word) 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; + + return SASR_L (a, (word) n); +} + +/* +** 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_W +** 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; +} +/* +** Do not edit or modify anything in this comment block. +** The arch-tag line is a file identity tag for the GNU Arch +** revision control system. +** +** arch-tag: a7398579-e2e1-4733-aa2d-4c6efc0c58ff +*/ + |