From 9d245d5d5015e1aa3e9bf9dd4860696f9c5fdfe1 Mon Sep 17 00:00:00 2001
From: Connor Horman <chorman64@gmail.com>
Date: Sun, 27 Aug 2023 15:36:40 -0400
Subject: [PATCH] feat(lcrust-stdlib): Implement SipHash and
 `core::hash::lcrust::hash_str`

---
 lcrust/libraries/libcore/src/hash.rs         | 56 ++++++++++++++++++++
 lcrust/libraries/libcore/src/hash/siphash.rs | 35 ++++++++++--
 2 files changed, 88 insertions(+), 3 deletions(-)

diff --git a/lcrust/libraries/libcore/src/hash.rs b/lcrust/libraries/libcore/src/hash.rs
index 2fb287be..c63a4da1 100644
--- a/lcrust/libraries/libcore/src/hash.rs
+++ b/lcrust/libraries/libcore/src/hash.rs
@@ -141,3 +141,59 @@ impl SipHasher {
         Self(siphash::SipHasher::new_with_keys(k0, k1))
     }
 }
+
+impl Hasher for SipHasher {
+    #[inline]
+    fn write(&mut self, x: &[u8]) {
+        self.0.write(x)
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+}
+
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub struct SipHasher13(siphash::SipHasher<1, 3>);
+
+impl Default for SipHasher13 {
+    pub fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl SipHasher13 {
+    pub const fn new() -> Self {
+        Self::new_with_keys(0, 0);
+    }
+
+    pub const fn new_with_keys(k0: u64, k1: u64) -> Self {
+        Self(siphash::SipHasher::new_with_keys(k0, k1))
+    }
+}
+
+impl Hasher for SipHasher13 {
+    #[inline]
+    fn write(&mut self, x: &[u8]) {
+        self.0.write(x)
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.0.finish()
+    }
+}
+
+#[unstable(feature = "lcrust_abi_symbols")]
+pub mod lcrust {
+    #[inline]
+    #[lcrust::force_export]
+    #[lang = "lcrust_hash_str_symbol"]
+    pub fn hash_str(x: &str, k0: u64, k1: u64) -> u64 {
+        let mut hasher = super::siphash::SipHash::<2, 4>::new_with_keys(k0, k1);
+        hasher.write(x);
+
+        hasher.finish()
+    }
+}
diff --git a/lcrust/libraries/libcore/src/hash/siphash.rs b/lcrust/libraries/libcore/src/hash/siphash.rs
index ba3689cd..2452fe4a 100644
--- a/lcrust/libraries/libcore/src/hash/siphash.rs
+++ b/lcrust/libraries/libcore/src/hash/siphash.rs
@@ -25,8 +25,21 @@ impl<const C: usize, const D: usize> SipHasher<C, D> {
 }
 
 impl<const C: usize, const D: usize> Hasher for SipHasher<C, D> {
+    #[inline]
     fn write(&mut self, mut s: &[u8]) {
 
+        if ntail > 0{
+            let required = s.len().min(8-ntail);
+            let (l,r) = s.split_at(required);
+
+            crate::mem::transmute(&self.tail)[ntail..][..required].copy_from_slice(l);
+
+            s = r;
+            if required+ntail==8{
+                self.update(self.tail.to_le());
+                self.ntail = 0;
+            }
+        }
 
         let chunks_exact = s.chunks_exact(8);
         let remainder = chunks_exact.remainder();
@@ -38,15 +51,31 @@ impl<const C: usize, const D: usize> Hasher for SipHasher<C, D> {
 
         if !remainder.is_empty() {
             let mut bytes = [0u8; 8];
-            bytes[..remainder.len()].copy_from_slice(remainder);
-            let word = u64::from_ne_bytes(bytes);
-            self.update(word);
+            self.ntail = remainder.len();
+            bytes[..self.ntail].copy_from_slice(remainder);
+            self.tail = u64::from_ne_bytes(bytes);
+            
         }
     }
 
+    #[inline]
     fn finish(&self) -> u64 {
         let mut state = self.0;
 
+        if self.ntail >= 0{
+            let mut val = self.tail.to_le();
+
+            if cfg!(target_endian = "big"){
+                val >>= ((8-ntail)<<3);
+            }
+
+            state.update_before_rounds(word);
+            for _ in 0..C {
+                state.round();
+            }
+            state.update_after_rounds(word);
+        }
+
         state.update_before_final();
 
         for _ in 0..D {