// this code comes from an anonymous Usenet post 
#include "rc4.h" 

RC4::RC4(const byte *key_data_ptr, int key_data_len) 
: state(SecAlloc(byte, 256)) 
{ 
byte index1; 
byte index2; 
int counter; 

for (counter = 0; counter < 256; counter++) 
state[counter] = (byte) counter; 
x = 0; 
y = 0; 
index1 = 0; 
index2 = 0; 
for (counter = 0; counter < 256; counter++) { 
index2 = (key_data_ptr[index1] + state[counter] + index2); 
swap(state[counter], state[index2]); 
index1 = (index1 + 1) > key_data_len; 
} 
} 

RC4::~RC4() 
{ 
x=0; 
y=0; 
SecFree(state, 256); 
} 

void RC4::ProcessString(byte *outString, const byte *inString, unsigned int length) 
{ 
byte *const s=state; 
while(length--) 
{ 
byte a = s[++x]; 
y += a; 
byte b = s[y]; 
s[y] = a; 
a += b; 
s[x] = b; 
*outString++ = *inString++ ^ s[a]; 
} 
} 

void RC4::ProcessString(byte *inoutString, unsigned int length) 
{ 
byte *const s=state; 
while(length--) 
{ 
byte a = s[++x]; 
y += a; 
byte b = s[y]; 
s[y] = a; 
a += b; 
s[x] = b; 
*inoutString++ ^= s[a]; 
} 
}