Diff: BigInt.cpp

Revision:

4:773aed3156c5

Parent:

3:3fa3ceb0c69d

Child:

5:beeb31f340a7

--- a/BigInt.cpp	Fri Sep 20 15:55:19 2013 +0000
+++ b/BigInt.cpp	Fri Oct 04 10:46:51 2013 +0000
@@ -75,7 +75,7 @@
         delete[] bits;
     bits = new uint32_t[l];
     memset(bits, 0, sizeof(uint32_t)*l);
-    for(int i = 0; i < length; ++i)
+    for(int i = length-1; i >=0; --i)
         bits[i/4] |= data[i] << ((i%4)*8);
 }
 
@@ -232,7 +232,33 @@
     if(b == 1)
         return (result = a);
         
-        
+    
+    result.size = a.size + b.size;
+    result.bits = new uint32_t[num(result.size)];
+    memset(result.bits, 0, sizeof(uint32_t)*num(result.size));
+    uint32_t carry = 0;
+    for(int i = 0; i < num(result.size); ++i)
+    {
+        uint32_t tmpA = 0, tmpB = 0;
+        if(i < num(a.size))
+            tmpA = a.bits[i];
+
+        if(i < num(b.size))
+            tmpB = b.bits[i];
+ 
+        uint64_t tmp = (uint64_t)tmpA * (uint64_t)tmpB + (uint64_t)carry;        
+        result.bits[i] = tmp;
+        carry = tmp >> 32;
+    }
+    
+    // trim result
+    uint8_t *tmp = (uint8_t*)result.bits;
+    uint32_t newSize = result.size;
+    while(tmp[newSize-1] == 0 && newSize > 0)
+        newSize--;
+    if(num(newSize) < num(result.size))
+        result.bits = (uint32_t*)realloc(result.bits, sizeof(uint32_t)*num(newSize)); 
+    result.size = newSize;
     
     return result;
 }