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#import "XADRC4Handle.h"
@implementation XADRC4Handle
-(id)initWithHandle:(CSHandle *)handle key:(NSData *)keydata
{
if((self=[super initWithName:[handle name] length:[handle fileSize]]))
{
parent=[handle retain];
startoffs=[parent offsetInFile];
key=[keydata retain];
rc4=nil;
}
return self;
}
-(void)dealloc
{
[parent release];
[key release];
[rc4 release];
[super dealloc];
}
-(void)resetStream
{
[rc4 release];
rc4=[(XADRC4Engine *)[XADRC4Engine alloc] initWithKey:key];
}
-(int)streamAtMost:(int)num toBuffer:(void *)buffer
{
int actual=[parent readAtMost:num toBuffer:buffer];
[rc4 encryptBytes:buffer length:actual];
return actual;
}
@end
@implementation XADRC4Engine
+(XADRC4Engine *)engineWithKey:(NSData *)key
{
return [[(XADRC4Engine *)[[self class] alloc] initWithKey:key] autorelease];
}
-(id)initWithKey:(NSData *)key
{
if((self=[super init]))
{
const uint8_t *keybytes=[key bytes];
int keylength=[key length];
for(i=0;i<256;i++) s[i]=i;
j=0;
for(i=0;i<256;i++)
{
j=(j+s[i]+keybytes[i%keylength])&255;
int tmp=s[i]; s[i]=s[j]; s[j]=tmp;
}
i=j=0;
}
return self;
}
-(NSData *)encryptedData:(NSData *)data
{
NSMutableData *res=[NSMutableData dataWithData:data];
[self encryptBytes:[res mutableBytes] length:[res length]];
return [NSData dataWithData:res];
}
-(void)encryptBytes:(unsigned char *)bytes length:(int)length
{
for(int n=0;n<length;n++)
{
i=(i+1)&255;
j=(j+s[i])&255;
int tmp=s[i]; s[i]=s[j]; s[j]=tmp;
bytes[n]^=s[(s[i]+s[j])&255];
}
}
-(void)skipBytes:(int)length
{
for(int n=0;n<length;n++)
{
i=(i+1)&255;
j=(j+s[i])&255;
int tmp=s[i]; s[i]=s[j]; s[j]=tmp;
}
}
@end
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