diff options
author | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
---|---|---|
committer | rsc <devnull@localhost> | 2004-03-21 14:06:38 +0000 |
commit | b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb (patch) | |
tree | deaa85427ae73a045ddef39395bd286f9d3dc2ff /src/libmp/port/mpright.c | |
parent | 498bb22174aa2c76493e8c67b92949271131ebfb (diff) | |
download | plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.gz plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.tar.bz2 plan9port-b3f61791f1e9095ce8ae9c6d6415b4ee94e2f7eb.zip |
Add libmp.
Diffstat (limited to 'src/libmp/port/mpright.c')
-rw-r--r-- | src/libmp/port/mpright.c | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/src/libmp/port/mpright.c b/src/libmp/port/mpright.c new file mode 100644 index 00000000..03039177 --- /dev/null +++ b/src/libmp/port/mpright.c @@ -0,0 +1,54 @@ +#include "os.h" +#include <mp.h> +#include "dat.h" + +// res = b >> shift +void +mpright(mpint *b, int shift, mpint *res) +{ + int d, l, r, i; + mpdigit this, last; + + res->sign = b->sign; + if(b->top==0){ + res->top = 0; + return; + } + + // a negative right shift is a left shift + if(shift < 0){ + mpleft(b, -shift, res); + return; + } + + if(res != b) + mpbits(res, b->top*Dbits - shift); + d = shift/Dbits; + r = shift - d*Dbits; + l = Dbits - r; + + // shift all the bits out == zero + if(d>=b->top){ + res->top = 0; + return; + } + + // special case digit shifts + if(r == 0){ + for(i = 0; i < b->top-d; i++) + res->p[i] = b->p[i+d]; + } else { + last = b->p[d]; + for(i = 0; i < b->top-d-1; i++){ + this = b->p[i+d+1]; + res->p[i] = (this<<l) | (last>>r); + last = this; + } + res->p[i++] = last>>r; + } + while(i > 0 && res->p[i-1] == 0) + i--; + res->top = i; + if(i==0) + res->sign = 1; +} |