Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

2 files changed, 433 insertions, 0 deletions

diff --git a/vendor/adler/src/algo.rs b/vendor/adler/src/algo.rs
new file mode 100644
index 0000000..650cffa
--- /dev/null
+++ b/vendor/adler/src/algo.rs
@@ -0,0 +1,146 @@
+use crate::Adler32;
+use std::ops::{AddAssign, MulAssign, RemAssign};
+
+impl Adler32 {
+    pub(crate) fn compute(&mut self, bytes: &[u8]) {
+        // The basic algorithm is, for every byte:
+        //   a = (a + byte) % MOD
+        //   b = (b + a) % MOD
+        // where MOD = 65521.
+        //
+        // For efficiency, we can defer the `% MOD` operations as long as neither a nor b overflows:
+        // - Between calls to `write`, we ensure that a and b are always in range 0..MOD.
+        // - We use 32-bit arithmetic in this function.
+        // - Therefore, a and b must not increase by more than 2^32-MOD without performing a `% MOD`
+        //   operation.
+        //
+        // According to Wikipedia, b is calculated as follows for non-incremental checksumming:
+        //   b = n×D1 + (n−1)×D2 + (n−2)×D3 + ... + Dn + n*1 (mod 65521)
+        // Where n is the number of bytes and Di is the i-th Byte. We need to change this to account
+        // for the previous values of a and b, as well as treat every input Byte as being 255:
+        //   b_inc = n×255 + (n-1)×255 + ... + 255 + n*65520
+        // Or in other words:
+        //   b_inc = n*65520 + n(n+1)/2*255
+        // The max chunk size is thus the largest value of n so that b_inc <= 2^32-65521.
+        //   2^32-65521 = n*65520 + n(n+1)/2*255
+        // Plugging this into an equation solver since I can't math gives n = 5552.18..., so 5552.
+        //
+        // On top of the optimization outlined above, the algorithm can also be parallelized with a
+        // bit more work:
+        //
+        // Note that b is a linear combination of a vector of input bytes (D1, ..., Dn).
+        //
+        // If we fix some value k<N and rewrite indices 1, ..., N as
+        //
+        //   1_1, 1_2, ..., 1_k, 2_1, ..., 2_k, ..., (N/k)_k,
+        //
+        // then we can express a and b in terms of sums of smaller sequences kb and ka:
+        //
+        //   ka(j) := D1_j + D2_j + ... + D(N/k)_j where j <= k
+        //   kb(j) := (N/k)*D1_j + (N/k-1)*D2_j + ... + D(N/k)_j where j <= k
+        //
+        //  a = ka(1) + ka(2) + ... + ka(k) + 1
+        //  b = k*(kb(1) + kb(2) + ... + kb(k)) - 1*ka(2) - ...  - (k-1)*ka(k) + N
+        //
+        // We use this insight to unroll the main loop and process k=4 bytes at a time.
+        // The resulting code is highly amenable to SIMD acceleration, although the immediate speedups
+        // stem from increased pipeline parallelism rather than auto-vectorization.
+        //
+        // This technique is described in-depth (here:)[https://software.intel.com/content/www/us/\
+        // en/develop/articles/fast-computation-of-fletcher-checksums.html]
+
+        const MOD: u32 = 65521;
+        const CHUNK_SIZE: usize = 5552 * 4;
+
+        let mut a = u32::from(self.a);
+        let mut b = u32::from(self.b);
+        let mut a_vec = U32X4([0; 4]);
+        let mut b_vec = a_vec;
+
+        let (bytes, remainder) = bytes.split_at(bytes.len() - bytes.len() % 4);
+
+        // iterate over 4 bytes at a time
+        let chunk_iter = bytes.chunks_exact(CHUNK_SIZE);
+        let remainder_chunk = chunk_iter.remainder();
+        for chunk in chunk_iter {
+            for byte_vec in chunk.chunks_exact(4) {
+                let val = U32X4::from(byte_vec);
+                a_vec += val;
+                b_vec += a_vec;
+            }
+            b += CHUNK_SIZE as u32 * a;
+            a_vec %= MOD;
+            b_vec %= MOD;
+            b %= MOD;
+        }
+        // special-case the final chunk because it may be shorter than the rest
+        for byte_vec in remainder_chunk.chunks_exact(4) {
+            let val = U32X4::from(byte_vec);
+            a_vec += val;
+            b_vec += a_vec;
+        }
+        b += remainder_chunk.len() as u32 * a;
+        a_vec %= MOD;
+        b_vec %= MOD;
+        b %= MOD;
+
+        // combine the sub-sum results into the main sum
+        b_vec *= 4;
+        b_vec.0[1] += MOD - a_vec.0[1];
+        b_vec.0[2] += (MOD - a_vec.0[2]) * 2;
+        b_vec.0[3] += (MOD - a_vec.0[3]) * 3;
+        for &av in a_vec.0.iter() {
+            a += av;
+        }
+        for &bv in b_vec.0.iter() {
+            b += bv;
+        }
+
+        // iterate over the remaining few bytes in serial
+        for &byte in remainder.iter() {
+            a += u32::from(byte);
+            b += a;
+        }
+
+        self.a = (a % MOD) as u16;
+        self.b = (b % MOD) as u16;
+    }
+}
+
+#[derive(Copy, Clone)]
+struct U32X4([u32; 4]);
+
+impl U32X4 {
+    fn from(bytes: &[u8]) -> Self {
+        U32X4([
+            u32::from(bytes[0]),
+            u32::from(bytes[1]),
+            u32::from(bytes[2]),
+            u32::from(bytes[3]),
+        ])
+    }
+}
+
+impl AddAssign<Self> for U32X4 {
+    fn add_assign(&mut self, other: Self) {
+        for (s, o) in self.0.iter_mut().zip(other.0.iter()) {
+            *s += o;
+        }
+    }
+}
+
+impl RemAssign<u32> for U32X4 {
+    fn rem_assign(&mut self, quotient: u32) {
+        for s in self.0.iter_mut() {
+            *s %= quotient;
+        }
+    }
+}
+
+impl MulAssign<u32> for U32X4 {
+    fn mul_assign(&mut self, rhs: u32) {
+        for s in self.0.iter_mut() {
+            *s *= rhs;
+        }
+    }
+}
diff --git a/vendor/adler/src/lib.rs b/vendor/adler/src/lib.rs
new file mode 100644
index 0000000..c7aa380
--- /dev/null
+++ b/vendor/adler/src/lib.rs
@@ -0,0 +1,287 @@
+//! Adler-32 checksum implementation.
+//!
+//! This implementation features:
+//!
+//! - Permissively licensed (0BSD) clean-room implementation.
+//! - Zero dependencies.
+//! - Zero `unsafe`.
+//! - Decent performance (3-4 GB/s).
+//! - `#![no_std]` support (with `default-features = false`).
+
+#![doc(html_root_url = "https://docs.rs/adler/1.0.2")]
+// Deny a few warnings in doctests, since rustdoc `allow`s many warnings by default
+#![doc(test(attr(deny(unused_imports, unused_must_use))))]
+#![cfg_attr(docsrs, feature(doc_cfg))]
+#![warn(missing_debug_implementations)]
+#![forbid(unsafe_code)]
+#![cfg_attr(not(feature = "std"), no_std)]
+
+#[cfg(not(feature = "std"))]
+extern crate core as std;
+
+mod algo;
+
+use std::hash::Hasher;
+
+#[cfg(feature = "std")]
+use std::io::{self, BufRead};
+
+/// Adler-32 checksum calculator.
+///
+/// An instance of this type is equivalent to an Adler-32 checksum: It can be created in the default
+/// state via [`new`] (or the provided `Default` impl), or from a precalculated checksum via
+/// [`from_checksum`], and the currently stored checksum can be fetched via [`checksum`].
+///
+/// This type also implements `Hasher`, which makes it easy to calculate Adler-32 checksums of any
+/// type that implements or derives `Hash`. This also allows using Adler-32 in a `HashMap`, although
+/// that is not recommended (while every checksum is a hash function, they are not necessarily a
+/// good one).
+///
+/// # Examples
+///
+/// Basic, piecewise checksum calculation:
+///
+/// ```
+/// use adler::Adler32;
+///
+/// let mut adler = Adler32::new();
+///
+/// adler.write_slice(&[0, 1, 2]);
+/// adler.write_slice(&[3, 4, 5]);
+///
+/// assert_eq!(adler.checksum(), 0x00290010);
+/// ```
+///
+/// Using `Hash` to process structures:
+///
+/// ```
+/// use std::hash::Hash;
+/// use adler::Adler32;
+///
+/// #[derive(Hash)]
+/// struct Data {
+///     byte: u8,
+///     word: u16,
+///     big: u64,
+/// }
+///
+/// let mut adler = Adler32::new();
+///
+/// let data = Data { byte: 0x1F, word: 0xABCD, big: !0 };
+/// data.hash(&mut adler);
+///
+/// // hash value depends on architecture endianness
+/// if cfg!(target_endian = "little") {
+///     assert_eq!(adler.checksum(), 0x33410990);
+/// }
+/// if cfg!(target_endian = "big") {
+///     assert_eq!(adler.checksum(), 0x331F0990);
+/// }
+///
+/// ```
+///
+/// [`new`]: #method.new
+/// [`from_checksum`]: #method.from_checksum
+/// [`checksum`]: #method.checksum
+#[derive(Debug, Copy, Clone)]
+pub struct Adler32 {
+    a: u16,
+    b: u16,
+}
+
+impl Adler32 {
+    /// Creates a new Adler-32 instance with default state.
+    #[inline]
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Creates an `Adler32` instance from a precomputed Adler-32 checksum.
+    ///
+    /// This allows resuming checksum calculation without having to keep the `Adler32` instance
+    /// around.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// # use adler::Adler32;
+    /// let parts = [
+    ///     "rust",
+    ///     "acean",
+    /// ];
+    /// let whole = adler::adler32_slice(b"rustacean");
+    ///
+    /// let mut sum = Adler32::new();
+    /// sum.write_slice(parts[0].as_bytes());
+    /// let partial = sum.checksum();
+    ///
+    /// // ...later
+    ///
+    /// let mut sum = Adler32::from_checksum(partial);
+    /// sum.write_slice(parts[1].as_bytes());
+    /// assert_eq!(sum.checksum(), whole);
+    /// ```
+    #[inline]
+    pub fn from_checksum(sum: u32) -> Self {
+        Adler32 {
+            a: sum as u16,
+            b: (sum >> 16) as u16,
+        }
+    }
+
+    /// Returns the calculated checksum at this point in time.
+    #[inline]
+    pub fn checksum(&self) -> u32 {
+        (u32::from(self.b) << 16) | u32::from(self.a)
+    }
+
+    /// Adds `bytes` to the checksum calculation.
+    ///
+    /// If efficiency matters, this should be called with Byte slices that contain at least a few
+    /// thousand Bytes.
+    pub fn write_slice(&mut self, bytes: &[u8]) {
+        self.compute(bytes);
+    }
+}
+
+impl Default for Adler32 {
+    #[inline]
+    fn default() -> Self {
+        Adler32 { a: 1, b: 0 }
+    }
+}
+
+impl Hasher for Adler32 {
+    #[inline]
+    fn finish(&self) -> u64 {
+        u64::from(self.checksum())
+    }
+
+    fn write(&mut self, bytes: &[u8]) {
+        self.write_slice(bytes);
+    }
+}
+
+/// Calculates the Adler-32 checksum of a byte slice.
+///
+/// This is a convenience function around the [`Adler32`] type.
+///
+/// [`Adler32`]: struct.Adler32.html
+pub fn adler32_slice(data: &[u8]) -> u32 {
+    let mut h = Adler32::new();
+    h.write_slice(data);
+    h.checksum()
+}
+
+/// Calculates the Adler-32 checksum of a `BufRead`'s contents.
+///
+/// The passed `BufRead` implementor will be read until it reaches EOF (or until it reports an
+/// error).
+///
+/// If you only have a `Read` implementor, you can wrap it in `std::io::BufReader` before calling
+/// this function.
+///
+/// # Errors
+///
+/// Any error returned by the reader are bubbled up by this function.
+///
+/// # Examples
+///
+/// ```no_run
+/// # fn run() -> Result<(), Box<dyn std::error::Error>> {
+/// use adler::adler32;
+///
+/// use std::fs::File;
+/// use std::io::BufReader;
+///
+/// let file = File::open("input.txt")?;
+/// let mut file = BufReader::new(file);
+///
+/// adler32(&mut file)?;
+/// # Ok(()) }
+/// # fn main() { run().unwrap() }
+/// ```
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub fn adler32<R: BufRead>(mut reader: R) -> io::Result<u32> {
+    let mut h = Adler32::new();
+    loop {
+        let len = {
+            let buf = reader.fill_buf()?;
+            if buf.is_empty() {
+                return Ok(h.checksum());
+            }
+
+            h.write_slice(buf);
+            buf.len()
+        };
+        reader.consume(len);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn zeroes() {
+        assert_eq!(adler32_slice(&[]), 1);
+        assert_eq!(adler32_slice(&[0]), 1 | 1 << 16);
+        assert_eq!(adler32_slice(&[0, 0]), 1 | 2 << 16);
+        assert_eq!(adler32_slice(&[0; 100]), 0x00640001);
+        assert_eq!(adler32_slice(&[0; 1024]), 0x04000001);
+        assert_eq!(adler32_slice(&[0; 1024 * 1024]), 0x00f00001);
+    }
+
+    #[test]
+    fn ones() {
+        assert_eq!(adler32_slice(&[0xff; 1024]), 0x79a6fc2e);
+        assert_eq!(adler32_slice(&[0xff; 1024 * 1024]), 0x8e88ef11);
+    }
+
+    #[test]
+    fn mixed() {
+        assert_eq!(adler32_slice(&[1]), 2 | 2 << 16);
+        assert_eq!(adler32_slice(&[40]), 41 | 41 << 16);
+
+        assert_eq!(adler32_slice(&[0xA5; 1024 * 1024]), 0xd5009ab1);
+    }
+
+    /// Example calculation from https://en.wikipedia.org/wiki/Adler-32.
+    #[test]
+    fn wiki() {
+        assert_eq!(adler32_slice(b"Wikipedia"), 0x11E60398);
+    }
+
+    #[test]
+    fn resume() {
+        let mut adler = Adler32::new();
+        adler.write_slice(&[0xff; 1024]);
+        let partial = adler.checksum();
+        assert_eq!(partial, 0x79a6fc2e); // from above
+        adler.write_slice(&[0xff; 1024 * 1024 - 1024]);
+        assert_eq!(adler.checksum(), 0x8e88ef11); // from above
+
+        // Make sure that we can resume computing from the partial checksum via `from_checksum`.
+        let mut adler = Adler32::from_checksum(partial);
+        adler.write_slice(&[0xff; 1024 * 1024 - 1024]);
+        assert_eq!(adler.checksum(), 0x8e88ef11); // from above
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn bufread() {
+        use std::io::BufReader;
+        fn test(data: &[u8], checksum: u32) {
+            // `BufReader` uses an 8 KB buffer, so this will test buffer refilling.
+            let mut buf = BufReader::new(data);
+            let real_sum = adler32(&mut buf).unwrap();
+            assert_eq!(checksum, real_sum);
+        }
+
+        test(&[], 1);
+        test(&[0; 1024], 0x04000001);
+        test(&[0; 1024 * 1024], 0x00f00001);
+        test(&[0xA5; 1024 * 1024], 0xd5009ab1);
+    }
+}