//! # simd-adler32

//!

//! A SIMD-accelerated Adler-32 hash algorithm implementation.

//!

//! ## Features

//!

//! - No dependencies

//! - Support `no_std` (with `default-features = false`)

//! - Runtime CPU feature detection (when `std` enabled)

//! - Blazing fast performance on as many targets as possible (currently only x86 and x86_64)

//! - Default to scalar implementation when simd not available

//!

//! ## Quick start

//!

//! > Cargo.toml

//!

//! ```toml

//! [dependencies]

//! simd-adler32 = "*"

//! ```

//!

//! > example.rs

//!

//! ```rust

//! use simd_adler32::Adler32;

//!

//! let mut adler = Adler32::new();

//! adler.write(b"rust is pretty cool, man");

//! let hash = adler.finish();

//!

//! println!("{}", hash);

//! // 1921255656

//! ```

//!

//! ## Feature flags

//!

//! * `std` - Enabled by default

//!

//! Enables std support, see [CPU Feature Detection](#cpu-feature-detection) for runtime

//! detection support.

//! * `nightly`

//!

//! Enables nightly features required for avx512 support.

//!

//! * `const-generics` - Enabled by default

//!

//! Enables const-generics support allowing for user-defined array hashing by value.  See

//! [`Adler32Hash`] for details.

//!

//! ## Support

//!

//! **CPU Features**

//!

//! | impl | arch             | feature |

//! | ---- | ---------------- | ------- |

//! | ✅   | `x86`, `x86_64`  | avx512  |

//! | ✅   | `x86`, `x86_64`  | avx2    |

//! | ✅   | `x86`, `x86_64`  | ssse3   |

//! | ✅   | `x86`, `x86_64`  | sse2    |

//! | 🚧   | `arm`, `aarch64` | neon    |

//! |      | `wasm32`         | simd128 |

//!

//! **MSRV** `1.36.0`\*\*

//!

//! Minimum supported rust version is tested before a new version is published. [**] Feature

//! `const-generics` needs to disabled to build on rustc versions `<1.51` which can be done

//! by updating your dependency definition to the following.

//!

//! ## CPU Feature Detection

//! simd-adler32 supports both runtime and compile time CPU feature detection using the

//! `std::is_x86_feature_detected` macro when the `Adler32` struct is instantiated with

//! the `new` fn.  

//!

//! Without `std` feature enabled simd-adler32 falls back to compile time feature detection

//! using `target-feature` or `target-cpu` flags supplied to rustc. See [https://rust-lang.github.io/packed_simd/perf-guide/target-feature/rustflags.html](https://rust-lang.github.io/packed_simd/perf-guide/target-feature/rustflags.html)

//! for more information.

//!

//! Feature detection tries to use the fastest supported feature first.

#![cfg_attr(not(feature = "std"), no_std)]

#![cfg_attr(feature = "nightly", feature(stdsimd, avx512_target_feature))]

#[doc(hidden)]

pub mod hash;

#[doc(hidden)]

pub mod imp;

pub use hash::*;

use imp::{get_imp, Adler32Imp};

/// An adler32 hash generator type.

#[derive(Clone)]

pub struct Adler32 {

  a: u16,

  b: u16,

  update: Adler32Imp,

}

impl Adler32 {

  /// Constructs a new `Adler32`.

  ///

  /// Potential overhead here due to runtime feature detection although in testing on 100k

  /// and 10k random byte arrays it was not really noticeable.

  ///

  /// # Examples

  /// ```rust

  /// use simd_adler32::Adler32;

  ///

  /// let mut adler = Adler32::new();

  /// ```

  pub fn new() -> Self {

    Default::default()

  }

  /// Constructs a new `Adler32` using existing checksum.

  ///

  /// Potential overhead here due to runtime feature detection although in testing on 100k

  /// and 10k random byte arrays it was not really noticeable.

  ///

  /// # Examples

  /// ```rust

  /// use simd_adler32::Adler32;

  ///

  /// let mut adler = Adler32::from_checksum(0xdeadbeaf);

  /// ```

  pub fn from_checksum(checksum: u32) -> Self {

    Self {

      a: checksum as u16,

      b: (checksum >> 16) as u16,

      update: get_imp(),

    }

  }

  /// Computes hash for supplied data and stores results in internal state.

  pub fn write(&mut self, data: &[u8]) {

    let (a, b) = (self.update)(self.a, self.b, data);

    self.a = a;

    self.b = b;

  }

  /// Returns the hash value for the values written so far.

  ///

  /// Despite its name, the method does not reset the hasher’s internal state. Additional

  /// writes will continue from the current value. If you need to start a fresh hash

  /// value, you will have to use `reset`.

  pub fn finish(&self) -> u32 {

    (u32::from(self.b) << 16) | u32::from(self.a)

  }

  /// Resets the internal state.

  pub fn reset(&mut self) {

    self.a = 1;

    self.b = 0;

  }

}

/// Compute Adler-32 hash on `Adler32Hash` type.

///

/// # Arguments

/// * `hash` - A Adler-32 hash-able type.

///

/// # Examples

/// ```rust

/// use simd_adler32::adler32;

///

/// let hash = adler32(b"Adler-32");

/// println!("{}", hash); // 800813569

/// ```

pub fn adler32<H: Adler32Hash>(hash: &H) -> u32 {

  hash.hash()

}

/// A Adler-32 hash-able type.

pub trait Adler32Hash {

  /// Feeds this value into `Adler32`.

  fn hash(&self) -> u32;

}

impl Default for Adler32 {

  fn default() -> Self {

    Self {

      a: 1,

      b: 0,

      update: get_imp(),

    }

  }

}

#[cfg(feature = "std")]

pub mod read {

  //! Reader-based hashing.

  //!

  //! # Example

  //! ```rust

  //! use std::io::Cursor;

  //! use simd_adler32::read::adler32;

  //!

  //! let mut reader = Cursor::new(b"Hello there");

  //! let hash = adler32(&mut reader).unwrap();

  //!

  //! println!("{}", hash) // 800813569

  //! ```

  use crate::Adler32;

  use std::io::{Read, Result};

  /// Compute Adler-32 hash on reader until EOF.

  ///

  /// # Example

  /// ```rust

  /// use std::io::Cursor;

  /// use simd_adler32::read::adler32;

  ///

  /// let mut reader = Cursor::new(b"Hello there");

  /// let hash = adler32(&mut reader).unwrap();

  ///

  /// println!("{}", hash) // 800813569

  /// ```

  pub fn adler32<R: Read>(reader: &mut R) -> Result<u32> {

    let mut hash = Adler32::new();

    let mut buf = [0; 4096];

    loop {

      match reader.read(&mut buf) {

        Ok(0) => return Ok(hash.finish()),

        Ok(n) => {

          hash.write(&buf[..n]);

        }

        Err(err) => return Err(err),

      }

    }

  }

}

#[cfg(feature = "std")]

pub mod bufread {

  //! BufRead-based hashing.

  //!

  //! Separate `BufRead` trait implemented to allow for custom buffer size optimization.

  //!

  //! # Example

  //! ```rust

  //! use std::io::{Cursor, BufReader};

  //! use simd_adler32::bufread::adler32;

  //!

  //! let mut reader = Cursor::new(b"Hello there");

  //! let mut reader = BufReader::new(reader);

  //! let hash = adler32(&mut reader).unwrap();

  //!

  //! println!("{}", hash) // 800813569

  //! ```

  use crate::Adler32;

  use std::io::{BufRead, ErrorKind, Result};

  /// Compute Adler-32 hash on buf reader until EOF.

  ///

  /// # Example

  /// ```rust

  /// use std::io::{Cursor, BufReader};

  /// use simd_adler32::bufread::adler32;

  ///

  /// let mut reader = Cursor::new(b"Hello there");

  /// let mut reader = BufReader::new(reader);

  /// let hash = adler32(&mut reader).unwrap();

  ///

  /// println!("{}", hash) // 800813569

  /// ```

  pub fn adler32<R: BufRead>(reader: &mut R) -> Result<u32> {

    let mut hash = Adler32::new();

    loop {

      let consumed = match reader.fill_buf() {

        Ok(buf) => {

          if buf.is_empty() {

            return Ok(hash.finish());

          }

          hash.write(buf);

          buf.len()

        }

        Err(err) => match err.kind() {

          ErrorKind::Interrupted => continue,

          ErrorKind::UnexpectedEof => return Ok(hash.finish()),

          _ => return Err(err),

        },

      };

      reader.consume(consumed);

    }

  }

}

#[cfg(test)]

mod tests {

  #[test]

  fn test_from_checksum() {

    let buf = b"rust is pretty cool man";

    let sum = 0xdeadbeaf;

    let mut simd = super::Adler32::from_checksum(sum);

    let mut adler = adler::Adler32::from_checksum(sum);

    simd.write(buf);

    adler.write_slice(buf);

    let simd = simd.finish();

    let scalar = adler.checksum();

    assert_eq!(simd, scalar);

  }

}