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author | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
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committer | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
commit | b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb (patch) | |
tree | deaa85427ae73a045ddef39395bd286f9d3dc2ff /src/libmp/port/mpleft.c | |
parent | 498bb22174aa2c76493e8c67b92949271131ebfb (diff) | |
download | plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.gz plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.bz2 plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.zip |
Add libmp.
Diffstat (limited to 'src/libmp/port/mpleft.c')
-rw-r--r-- | src/libmp/port/mpleft.c | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/src/libmp/port/mpleft.c b/src/libmp/port/mpleft.c new file mode 100644 index 00000000..cdcdff74 --- /dev/null +++ b/src/libmp/port/mpleft.c @@ -0,0 +1,52 @@ +#include "os.h" +#include <mp.h> +#include "dat.h" + +// res = b << shift +void +mpleft(mpint *b, int shift, mpint *res) +{ + int d, l, r, i, otop; + mpdigit this, last; + + res->sign = b->sign; + if(b->top==0){ + res->top = 0; + return; + } + + // a negative left shift is a right shift + if(shift < 0){ + mpright(b, -shift, res); + return; + } + + // b and res may be the same so remember the old top + otop = b->top; + + // shift + mpbits(res, otop*Dbits + shift); // overkill + res->top = DIGITS(otop*Dbits + shift); + d = shift/Dbits; + l = shift - d*Dbits; + r = Dbits - l; + + if(l == 0){ + for(i = otop-1; i >= 0; i--) + res->p[i+d] = b->p[i]; + } else { + last = 0; + for(i = otop-1; i >= 0; i--) { + this = b->p[i]; + res->p[i+d+1] = (last<<l) | (this>>r); + last = this; + } + res->p[d] = last<<l; + } + for(i = 0; i < d; i++) + res->p[i] = 0; + + // normalize + while(res->top > 0 && res->p[res->top-1] == 0) + res->top--; +} |