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    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    /*!
     * An implementation of the RC4 (also sometimes called ARC4) stream cipher. THIS IMPLEMENTATION IS
     * NOT A FIXED TIME IMPLEMENTATION.
     */

    use buffer::{BufferResult, RefReadBuffer, RefWriteBuffer};
    use symmetriccipher::{Encryptor, Decryptor, SynchronousStreamCipher, SymmetricCipherError};
    use cryptoutil::symm_enc_or_dec;

    #[derive(Copy)]
    pub struct Rc4 {
        i: u8,
        j: u8,
        state: [u8; 256]
    }

    impl Clone for Rc4 { fn clone(&self) -> Rc4 { *self } }

    impl Rc4 {
        pub fn new(key: &[u8]) -> Rc4 {
            assert!(key.len() >= 1 && key.len() <= 256);
            let mut rc4 = Rc4 { i: 0, j: 0, state: [0; 256] };
            for (i, x) in rc4.state.iter_mut().enumerate() {
                *x = i as u8;
            }
            let mut j: u8 = 0;
            for i in 0..256 {
                j = j.wrapping_add(rc4.state[i]).wrapping_add(key[i % key.len()]);
                rc4.state.swap(i, j as usize);
            }
            rc4
        }
        fn next(&mut self) -> u8 {
            self.i = self.i.wrapping_add(1);
            self.j = self.j.wrapping_add(self.state[self.i as usize]);
            self.state.swap(self.i as usize, self.j as usize);
            let k = self.state[(self.state[self.i as usize].wrapping_add(self.state[self.j as usize])) as usize];
            k
        }
    }

    impl SynchronousStreamCipher for Rc4 {
        fn process(&mut self, input: &[u8], output: &mut [u8]) {
            assert!(input.len() == output.len());
            for (x, y) in input.iter().zip(output.iter_mut()) {
                *y = *x ^ self.next();
            }
        }
    }

    impl Encryptor for Rc4 {
        fn encrypt(&mut self, input: &mut RefReadBuffer, output: &mut RefWriteBuffer, _: bool)
                -> Result<BufferResult, SymmetricCipherError> {
            symm_enc_or_dec(self, input, output)
        }
    }

    impl Decryptor for Rc4 {
        fn decrypt(&mut self, input: &mut RefReadBuffer, output: &mut RefWriteBuffer, _: bool)
                -> Result<BufferResult, SymmetricCipherError> {
            symm_enc_or_dec(self, input, output)
        }
    }

    #[cfg(test)]
    mod test {
        use std::iter::repeat;

        use symmetriccipher::SynchronousStreamCipher;
        use rc4::Rc4;

        struct Test {
            key: &'static str,
            input: &'static str,
            output: Vec<u8>
        }

        fn tests() -> Vec<Test> {
            vec![
                Test {
                    key: "Key",
                    input: "Plaintext",
                    output: vec![0xBB, 0xF3, 0x16, 0xE8, 0xD9, 0x40, 0xAF, 0x0A, 0xD3]
                },
                Test {
                    key: "Wiki",
                    input: "pedia",
                    output: vec![0x10, 0x21, 0xBF, 0x04, 0x20]
                },
                Test {
                    key: "Secret",
                    input: "Attack at dawn",
                    output: vec![0x45, 0xA0, 0x1F, 0x64, 0x5F, 0xC3, 0x5B,
                              0x38, 0x35, 0x52, 0x54, 0x4B, 0x9B, 0xF5]
                }
            ]
        }

        #[test]
        fn wikipedia_tests() {
            let tests = tests();
            for t in tests.iter() {
                let mut rc4 = Rc4::new(t.key.as_bytes());
                let mut result: Vec<u8> = repeat(0).take(t.output.len()).collect();
                rc4.process(t.input.as_bytes(), &mut result);
                assert!(result == t.output);
            }
        }
    }

    #[cfg(all(test, feature = "with-bench"))]
    mod bench {
        use test::Bencher;
        use symmetriccipher::SynchronousStreamCipher;
        use rc4::Rc4;

        #[bench]
        pub fn rc4_10(bh: & mut Bencher) {
            let mut rc4 = Rc4::new("key".as_bytes());
            let input = [1u8; 10];
            let mut output = [0u8; 10];
            bh.iter( || {
                rc4.process(&input, &mut output);
            });
            bh.bytes = input.len() as u64;
        }

        #[bench]
        pub fn rc4_1k(bh: & mut Bencher) {
            let mut rc4 = Rc4::new("key".as_bytes());
            let input = [1u8; 1024];
            let mut output = [0u8; 1024];
            bh.iter( || {
                rc4.process(&input, &mut output);
            });
            bh.bytes = input.len() as u64;
        }

        #[bench]
        pub fn rc4_64k(bh: & mut Bencher) {
            let mut rc4 = Rc4::new("key".as_bytes());
            let input = [1u8; 65536];
            let mut output = [0u8; 65536];
            bh.iter( || {
                rc4.process(&input, &mut output);
            });
            bh.bytes = input.len() as u64;
        }
    }

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