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//! Pure Rust implementation of the [SHA-1][1] cryptographic hash algorithm
//! with optional hardware-specific optimizations.
//!
//! # 🚨 Warning: Cryptographically Broken! 🚨
//!
//! The SHA-1 hash function should be considered cryptographically broken and
//! unsuitable for further use in any security critical capacity, as it is
//! [practically vulnerable to chosen-prefix collisions][2].
//!
//! We provide this crate for legacy interoperability purposes only.
//!
//! # Usage
//!
//! ```rust
//! use hex_literal::hex;
//! use sha1::{Sha1, Digest};
//!
//! // create a Sha1 object
//! let mut hasher = Sha1::new();
//!
//! // process input message
//! hasher.update(b"hello world");
//!
//! // acquire hash digest in the form of GenericArray,
//! // which in this case is equivalent to [u8; 20]
//! let result = hasher.finalize();
//! assert_eq!(result[..], hex!("2aae6c35c94fcfb415dbe95f408b9ce91ee846ed"));
//! ```
//!
//! Also see [RustCrypto/hashes][3] readme.
//!
//! [1]: https://en.wikipedia.org/wiki/SHA-1
//! [2]: https://sha-mbles.github.io/
//! [3]: https://github.com/RustCrypto/hashes

#![no_std]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![doc(
    html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg",
    html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/6ee8e381/logo.svg",
    html_root_url = "https://docs.rs/sha-1/0.10.0"
)]
#![warn(missing_docs, rust_2018_idioms)]

pub use digest::{self, Digest};

use core::{fmt, slice::from_ref};
use digest::{
    block_buffer::Eager,
    core_api::{
        AlgorithmName, Block, BlockSizeUser, Buffer, BufferKindUser, CoreWrapper, FixedOutputCore,
        OutputSizeUser, Reset, UpdateCore,
    },
    generic_array::typenum::{Unsigned, U20, U64},
    HashMarker, Output,
};

mod compress;

#[cfg(feature = "compress")]
pub use compress::compress;
#[cfg(not(feature = "compress"))]
use compress::compress;

const STATE_LEN: usize = 5;

/// Core SHA-1 hasher state.
#[derive(Clone)]
pub struct Sha1Core {
    h: [u32; STATE_LEN],
    block_len: u64,
}

impl HashMarker for Sha1Core {}

impl BlockSizeUser for Sha1Core {
    type BlockSize = U64;
}

impl BufferKindUser for Sha1Core {
    type BufferKind = Eager;
}

impl OutputSizeUser for Sha1Core {
    type OutputSize = U20;
}

impl UpdateCore for Sha1Core {
    #[inline]
    fn update_blocks(&mut self, blocks: &[Block<Self>]) {
        self.block_len += blocks.len() as u64;
        compress(&mut self.h, blocks);
    }
}

impl FixedOutputCore for Sha1Core {
    #[inline]
    fn finalize_fixed_core(&mut self, buffer: &mut Buffer<Self>, out: &mut Output<Self>) {
        let bs = Self::BlockSize::U64;
        let bit_len = 8 * (buffer.get_pos() as u64 + bs * self.block_len);

        let mut h = self.h;
        buffer.len64_padding_be(bit_len, |b| compress(&mut h, from_ref(b)));
        for (chunk, v) in out.chunks_exact_mut(4).zip(h.iter()) {
            chunk.copy_from_slice(&v.to_be_bytes());
        }
    }
}

impl Default for Sha1Core {
    #[inline]
    fn default() -> Self {
        Self {
            h: [0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0],
            block_len: 0,
        }
    }
}

impl Reset for Sha1Core {
    #[inline]
    fn reset(&mut self) {
        *self = Default::default();
    }
}

impl AlgorithmName for Sha1Core {
    fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("Sha1")
    }
}

impl fmt::Debug for Sha1Core {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("Sha1Core { ... }")
    }
}

/// SHA-1 hasher state.
pub type Sha1 = CoreWrapper<Sha1Core>;