fp_mul.c

00001 /* TomsFastMath, a fast ISO C bignum library.
00002  * 
00003  * This project is meant to fill in where LibTomMath
00004  * falls short.  That is speed ;-)
00005  *
00006  * This project is public domain and free for all purposes.
00007  * 
00008  * Tom St Denis, tomstdenis@gmail.com
00009  */
00010 #include <tfm.h>
00011 
00012 /* c = a * b */
00013 void fp_mul(fp_int *A, fp_int *B, fp_int *C)
00014 {
00015     int   y, yy;
00016 
00017     /* call generic if we're out of range */
00018     if (A->used + B->used > FP_SIZE) {
00019        fp_mul_comba(A, B, C);
00020        return ;
00021     }
00022 
00023      y  = MAX(A->used, B->used);
00024      yy = MIN(A->used, B->used);
00025     /* pick a comba (unrolled 4/8/16/32 x or rolled) based on the size
00026        of the largest input.  We also want to avoid doing excess mults if the 
00027        inputs are not close to the next power of two.  That is, for example,
00028        if say y=17 then we would do (32-17)^2 = 225 unneeded multiplications 
00029     */
00030 
00031 #ifdef TFM_MUL3
00032         if (y <= 3) {
00033            fp_mul_comba3(A,B,C);
00034            return;
00035         }
00036 #endif
00037 #ifdef TFM_MUL4
00038         if (y == 4) {
00039            fp_mul_comba4(A,B,C);
00040            return;
00041         }
00042 #endif
00043 #ifdef TFM_MUL6
00044         if (y <= 6) {
00045            fp_mul_comba6(A,B,C);
00046            return;
00047         }
00048 #endif
00049 #ifdef TFM_MUL7
00050         if (y == 7) {
00051            fp_mul_comba7(A,B,C);
00052            return;
00053         }
00054 #endif
00055 #ifdef TFM_MUL8
00056         if (y == 8) {
00057            fp_mul_comba8(A,B,C);
00058            return;
00059         }
00060 #endif
00061 #ifdef TFM_MUL9
00062         if (y == 9) {
00063            fp_mul_comba9(A,B,C);
00064            return;
00065         }
00066 #endif
00067 #ifdef TFM_MUL12
00068         if (y <= 12) {
00069            fp_mul_comba12(A,B,C);
00070            return;
00071         }
00072 #endif
00073 #ifdef TFM_MUL17
00074         if (y <= 17) {
00075            fp_mul_comba17(A,B,C);
00076            return;
00077         }
00078 #endif
00079 
00080 #ifdef TFM_SMALL_SET
00081         if (y <= 16) {
00082            fp_mul_comba_small(A,B,C);
00083            return;
00084         }
00085 #endif        
00086 #if defined(TFM_MUL20)
00087         if (y <= 20) {
00088            fp_mul_comba20(A,B,C);
00089            return;
00090         }
00091 #endif
00092 #if defined(TFM_MUL24)
00093         if (yy >= 16 && y <= 24) {
00094            fp_mul_comba24(A,B,C);
00095            return;
00096         }
00097 #endif
00098 #if defined(TFM_MUL28)
00099         if (yy >= 20 && y <= 28) {
00100            fp_mul_comba28(A,B,C);
00101            return;
00102         }
00103 #endif
00104 #if defined(TFM_MUL32)
00105         if (yy >= 24 && y <= 32) {
00106            fp_mul_comba32(A,B,C);
00107            return;
00108         }
00109 #endif
00110 #if defined(TFM_MUL48)
00111         if (yy >= 40 && y <= 48) {
00112            fp_mul_comba48(A,B,C);
00113            return;
00114         }
00115 #endif        
00116 #if defined(TFM_MUL64)
00117         if (yy >= 56 && y <= 64) {
00118            fp_mul_comba64(A,B,C);
00119            return;
00120         }
00121 #endif
00122         fp_mul_comba(A,B,C);
00123 }
00124 
00125 
00126 /* $Source: /cvs/libtom/tomsfastmath/src/mul/fp_mul.c,v $ */
00127 /* $Revision: 1.1 $ */
00128 /* $Date: 2006/12/31 21:25:53 $ */