//! The SHA family of hashes.
//!
//! SHA, or Secure Hash Algorithms, are a family of cryptographic hashing algorithms published by
//! the National Institute of Standards and Technology (NIST).  Hash algorithms such as those in
//! the SHA family are used to map data of an arbitrary size to a fixed-size string of bytes.
//! As cryptographic hashing algorithms, these mappings have the property of being irreversable.
//! This property makes hash algorithms like these excellent for uses such as verifying the
//! contents of a file- if you know the hash you expect beforehand, then you can verify that the
//! data you have is correct if it hashes to the same value.
//!
//! # Examples
//!
//! When dealing with data that becomes available in chunks, such as while buffering data from IO,
//! you can create a hasher that you can repeatedly update to add bytes to.
//!
//! ```rust
//! extern crate openssl;
//! extern crate hex;
//!
//! use openssl::sha;
//!
//! fn main() {
//!     let mut hasher = sha::Sha256::new();
//!
//!     hasher.update(b"Hello, ");
//!     hasher.update(b"world");
//!
//!     let hash = hasher.finish();
//!     println!("Hashed \"Hello, world\" to {}", hex::encode(hash));
//! }
//! ```
//!
//! On the other hand, if you already have access to all of the data you woud like to hash, you
//! may prefer to use the slightly simpler method of simply calling the hash function corresponding
//! to the algorithm you want to use.
//!
//! ```rust
//! extern crate openssl;
//! extern crate hex;
//!
//! use openssl::sha::sha256;
//!
//! fn main() {
//!     let hash = sha256(b"your data or message");
//!     println!("Hash = {}", hex::encode(hash));
//! }
//! ```
use ffi;
use libc::c_void;
use std::mem;

/// Computes the SHA1 hash of some data.
///
/// # Warning
///
/// SHA1 is known to be insecure - it should not be used unless required for
/// compatibility with existing systems.
#[inline]
pub fn sha1(data: &[u8]) -> [u8; 20] {
    unsafe {
        let mut hash: [u8; 20] = mem::uninitialized();
        ffi::SHA1(data.as_ptr(), data.len(), hash.as_mut_ptr());
        hash
    }
}

/// Computes the SHA224 hash of some data.
#[inline]
pub fn sha224(data: &[u8]) -> [u8; 28] {
    unsafe {
        let mut hash: [u8; 28] = mem::uninitialized();
        ffi::SHA224(data.as_ptr(), data.len(), hash.as_mut_ptr());
        hash
    }
}

/// Computes the SHA256 hash of some data.
#[inline]
pub fn sha256(data: &[u8]) -> [u8; 32] {
    unsafe {
        let mut hash: [u8; 32] = mem::uninitialized();
        ffi::SHA256(data.as_ptr(), data.len(), hash.as_mut_ptr());
        hash
    }
}

/// Computes the SHA384 hash of some data.
#[inline]
pub fn sha384(data: &[u8]) -> [u8; 48] {
    unsafe {
        let mut hash: [u8; 48] = mem::uninitialized();
        ffi::SHA384(data.as_ptr(), data.len(), hash.as_mut_ptr());
        hash
    }
}

/// Computes the SHA512 hash of some data.
#[inline]
pub fn sha512(data: &[u8]) -> [u8; 64] {
    unsafe {
        let mut hash: [u8; 64] = mem::uninitialized();
        ffi::SHA512(data.as_ptr(), data.len(), hash.as_mut_ptr());
        hash
    }
}

/// An object which calculates a SHA1 hash of some data.
///
/// # Warning
///
/// SHA1 is known to be insecure - it should not be used unless required for
/// compatibility with existing systems.
#[derive(Clone)]
pub struct Sha1(ffi::SHA_CTX);

impl Sha1 {
    /// Creates a new hasher.
    #[inline]
    pub fn new() -> Sha1 {
        unsafe {
            let mut ctx = mem::uninitialized();
            ffi::SHA1_Init(&mut ctx);
            Sha1(ctx)
        }
    }

    /// Feeds some data into the hasher.
    ///
    /// This can be called multiple times.
    #[inline]
    pub fn update(&mut self, buf: &[u8]) {
        unsafe {
            ffi::SHA1_Update(&mut self.0, buf.as_ptr() as *const c_void, buf.len());
        }
    }

    /// Returns the hash of the data.
    #[inline]
    pub fn finish(mut self) -> [u8; 20] {
        unsafe {
            let mut hash: [u8; 20] = mem::uninitialized();
            ffi::SHA1_Final(hash.as_mut_ptr(), &mut self.0);
            hash
        }
    }
}

/// An object which calculates a SHA224 hash of some data.
#[derive(Clone)]
pub struct Sha224(ffi::SHA256_CTX);

impl Sha224 {
    /// Creates a new hasher.
    #[inline]
    pub fn new() -> Sha224 {
        unsafe {
            let mut ctx = mem::uninitialized();
            ffi::SHA224_Init(&mut ctx);
            Sha224(ctx)
        }
    }

    /// Feeds some data into the hasher.
    ///
    /// This can be called multiple times.
    #[inline]
    pub fn update(&mut self, buf: &[u8]) {
        unsafe {
            ffi::SHA224_Update(&mut self.0, buf.as_ptr() as *const c_void, buf.len());
        }
    }

    /// Returns the hash of the data.
    #[inline]
    pub fn finish(mut self) -> [u8; 28] {
        unsafe {
            let mut hash: [u8; 28] = mem::uninitialized();
            ffi::SHA224_Final(hash.as_mut_ptr(), &mut self.0);
            hash
        }
    }
}

/// An object which calculates a SHA256 hash of some data.
#[derive(Clone)]
pub struct Sha256(ffi::SHA256_CTX);

impl Sha256 {
    /// Creates a new hasher.
    #[inline]
    pub fn new() -> Sha256 {
        unsafe {
            let mut ctx = mem::uninitialized();
            ffi::SHA256_Init(&mut ctx);
            Sha256(ctx)
        }
    }

    /// Feeds some data into the hasher.
    ///
    /// This can be called multiple times.
    #[inline]
    pub fn update(&mut self, buf: &[u8]) {
        unsafe {
            ffi::SHA256_Update(&mut self.0, buf.as_ptr() as *const c_void, buf.len());
        }
    }

    /// Returns the hash of the data.
    #[inline]
    pub fn finish(mut self) -> [u8; 32] {
        unsafe {
            let mut hash: [u8; 32] = mem::uninitialized();
            ffi::SHA256_Final(hash.as_mut_ptr(), &mut self.0);
            hash
        }
    }
}

/// An object which calculates a SHA384 hash of some data.
#[derive(Clone)]
pub struct Sha384(ffi::SHA512_CTX);

impl Sha384 {
    /// Creates a new hasher.
    #[inline]
    pub fn new() -> Sha384 {
        unsafe {
            let mut ctx = mem::uninitialized();
            ffi::SHA384_Init(&mut ctx);
            Sha384(ctx)
        }
    }

    /// Feeds some data into the hasher.
    ///
    /// This can be called multiple times.
    #[inline]
    pub fn update(&mut self, buf: &[u8]) {
        unsafe {
            ffi::SHA384_Update(&mut self.0, buf.as_ptr() as *const c_void, buf.len());
        }
    }

    /// Returns the hash of the data.
    #[inline]
    pub fn finish(mut self) -> [u8; 48] {
        unsafe {
            let mut hash: [u8; 48] = mem::uninitialized();
            ffi::SHA384_Final(hash.as_mut_ptr(), &mut self.0);
            hash
        }
    }
}

/// An object which calculates a SHA512 hash of some data.
#[derive(Clone)]
pub struct Sha512(ffi::SHA512_CTX);

impl Sha512 {
    /// Creates a new hasher.
    #[inline]
    pub fn new() -> Sha512 {
        unsafe {
            let mut ctx = mem::uninitialized();
            ffi::SHA512_Init(&mut ctx);
            Sha512(ctx)
        }
    }

    /// Feeds some data into the hasher.
    ///
    /// This can be called multiple times.
    #[inline]
    pub fn update(&mut self, buf: &[u8]) {
        unsafe {
            ffi::SHA512_Update(&mut self.0, buf.as_ptr() as *const c_void, buf.len());
        }
    }

    /// Returns the hash of the data.
    #[inline]
    pub fn finish(mut self) -> [u8; 64] {
        unsafe {
            let mut hash: [u8; 64] = mem::uninitialized();
            ffi::SHA512_Final(hash.as_mut_ptr(), &mut self.0);
            hash
        }
    }
}

#[cfg(test)]
mod test {
    use hex;

    use super::*;

    #[test]
    fn standalone_1() {
        let data = b"abc";
        let expected = "a9993e364706816aba3e25717850c26c9cd0d89d";

        assert_eq!(hex::encode(sha1(data)), expected);
    }

    #[test]
    fn struct_1() {
        let expected = "a9993e364706816aba3e25717850c26c9cd0d89d";

        let mut hasher = Sha1::new();
        hasher.update(b"a");
        hasher.update(b"bc");
        assert_eq!(hex::encode(hasher.finish()), expected);
    }

    #[test]
    fn cloning_allows_incremental_hashing() {
        let expected = "a9993e364706816aba3e25717850c26c9cd0d89d";

        let mut hasher = Sha1::new();
        hasher.update(b"a");

        let mut incr_hasher = hasher.clone();
        incr_hasher.update(b"bc");

        assert_eq!(hex::encode(incr_hasher.finish()), expected);
        assert_ne!(hex::encode(hasher.finish()), expected);
    }

    #[test]
    fn standalone_224() {
        let data = b"abc";
        let expected = "23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7";

        assert_eq!(hex::encode(sha224(data)), expected);
    }

    #[test]
    fn struct_224() {
        let expected = "23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7";

        let mut hasher = Sha224::new();
        hasher.update(b"a");
        hasher.update(b"bc");
        assert_eq!(hex::encode(hasher.finish()), expected);
    }

    #[test]
    fn standalone_256() {
        let data = b"abc";
        let expected = "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad";

        assert_eq!(hex::encode(sha256(data)), expected);
    }

    #[test]
    fn struct_256() {
        let expected = "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad";

        let mut hasher = Sha256::new();
        hasher.update(b"a");
        hasher.update(b"bc");
        assert_eq!(hex::encode(hasher.finish()), expected);
    }

    #[test]
    fn standalone_384() {
        let data = b"abc";
        let expected =
            "cb00753f45a35e8bb5a03d699ac65007272c32ab0eded1631a8b605a43ff5bed8086072ba1e\
             7cc2358baeca134c825a7";

        assert_eq!(hex::encode(&sha384(data)[..]), expected);
    }

    #[test]
    fn struct_384() {
        let expected =
            "cb00753f45a35e8bb5a03d699ac65007272c32ab0eded1631a8b605a43ff5bed8086072ba1e\
             7cc2358baeca134c825a7";

        let mut hasher = Sha384::new();
        hasher.update(b"a");
        hasher.update(b"bc");
        assert_eq!(hex::encode(&hasher.finish()[..]), expected);
    }

    #[test]
    fn standalone_512() {
        let data = b"abc";
        let expected =
            "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274\
             fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f";

        assert_eq!(hex::encode(&sha512(data)[..]), expected);
    }

    #[test]
    fn struct_512() {
        let expected =
            "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274\
             fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f";

        let mut hasher = Sha512::new();
        hasher.update(b"a");
        hasher.update(b"bc");
        assert_eq!(hex::encode(&hasher.finish()[..]), expected);
    }
}