Add write_* methods for DefaultHasher, SipHasher, SipHasher13…

…, `sip::Hasher`. `sip::Hasher::short_write` is currently unused. It is called by `sip::Hasher::write_{u8,usize}`, but those methods are also unused, because `DefaultHasher`, `SipHasher` and `SipHasher13` don't implement any of the `write_xyz` methods, so all their write operations end up calling `sip::Hasher::write`. I confirmed this by inserting a `panic!` in `sip::Hasher::short_write` and running the tests -- they all passed. This commit adds all the `write_xyz` methods to `DefaultHasher`, `SipHasher`, `SipHasher13` and `sip::Hasher`, which means that `short_write` will be used for all of them. (I haven't properly implemented 128-bit writes in `sip::Hasher` and `SipHasher128`. That could be a follow-up if something thinks it is important.) Some microbenchmarks I wrote show that this commit speeds up default hashing of integers by about 2.5x, and can speed up hash tables that use `DefaultHasher` and have keys that contain integers by up to 30%, though the exact amount depends heavily on the details of the keys and how the table is used. This makes default `Hash{Map,Set}` much more likely to be competitive with `FxHash{Map,Set}`.
rust-lang · Feb 23, 2020 · 96c4e42 · 96c4e42
1 parent f272983
commit 96c4e42
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diff --git a/src/libcore/hash/sip.rs b/src/libcore/hash/sip.rs
@@ -296,6 +296,66 @@ impl<S: Sip> Hasher<S> {
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl super::Hasher for SipHasher {
+    #[inline]
+    fn write_u8(&mut self, i: u8) {
+        self.0.hasher.write_u8(i);
+    }
+
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.0.hasher.write_u16(i);
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.0.hasher.write_u32(i);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.0.hasher.write_u64(i);
+    }
+
+    #[inline]
+    fn write_u128(&mut self, i: u128) {
+        self.0.hasher.write_u128(i);
+    }
+
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        self.0.hasher.write_usize(i);
+    }
+
+    #[inline]
+    fn write_i8(&mut self, i: i8) {
+        self.0.hasher.write_i8(i);
+    }
+
+    #[inline]
+    fn write_i16(&mut self, i: i16) {
+        self.0.hasher.write_i16(i);
+    }
+
+    #[inline]
+    fn write_i32(&mut self, i: i32) {
+        self.0.hasher.write_i32(i);
+    }
+
+    #[inline]
+    fn write_i64(&mut self, i: i64) {
+        self.0.hasher.write_i64(i);
+    }
+
+    #[inline]
+    fn write_i128(&mut self, i: i128) {
+        self.0.hasher.write_i128(i);
+    }
+
+    #[inline]
+    fn write_isize(&mut self, i: isize) {
+        self.0.hasher.write_isize(i);
+    }
+
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         self.0.hasher.write(msg)
@@ -309,6 +369,66 @@ impl super::Hasher for SipHasher {
 
 #[unstable(feature = "hashmap_internals", issue = "none")]
 impl super::Hasher for SipHasher13 {
+    #[inline]
+    fn write_u8(&mut self, i: u8) {
+        self.hasher.write_u8(i);
+    }
+
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.hasher.write_u16(i);
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.hasher.write_u32(i);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.hasher.write_u64(i);
+    }
+
+    #[inline]
+    fn write_u128(&mut self, i: u128) {
+        self.hasher.write_u128(i);
+    }
+
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        self.hasher.write_usize(i);
+    }
+
+    #[inline]
+    fn write_i8(&mut self, i: i8) {
+        self.hasher.write_i8(i);
+    }
+
+    #[inline]
+    fn write_i16(&mut self, i: i16) {
+        self.hasher.write_i16(i);
+    }
+
+    #[inline]
+    fn write_i32(&mut self, i: i32) {
+        self.hasher.write_i32(i);
+    }
+
+    #[inline]
+    fn write_i64(&mut self, i: i64) {
+        self.hasher.write_i64(i);
+    }
+
+    #[inline]
+    fn write_i128(&mut self, i: i128) {
+        self.hasher.write_i128(i);
+    }
+
+    #[inline]
+    fn write_isize(&mut self, i: isize) {
+        self.hasher.write_isize(i);
+    }
+
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         self.hasher.write(msg)
@@ -326,11 +446,55 @@ impl<S: Sip> super::Hasher for Hasher<S> {
         self.short_write(i, i as u64);
     }
 
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.short_write(i, i.to_le() as u64);
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.short_write(i, i.to_le() as u64);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.short_write(i, i.to_le() as u64);
+    }
+
+    // `write_u128` is currently unimplemented.
+
     #[inline]
     fn write_usize(&mut self, i: usize) {
         self.short_write(i, i.to_le() as u64);
     }
 
+    #[inline]
+    fn write_i8(&mut self, i: i8) {
+        self.short_write(i, i as u8 as u64);
+    }
+
+    #[inline]
+    fn write_i16(&mut self, i: i16) {
+        self.short_write(i, (i as u16).to_le() as u64);
+    }
+
+    #[inline]
+    fn write_i32(&mut self, i: i32) {
+        self.short_write(i, (i as u32).to_le() as u64);
+    }
+
+    #[inline]
+    fn write_i64(&mut self, i: i64) {
+        self.short_write(i, (i as u64).to_le() as u64);
+    }
+
+    // `write_i128` is currently unimplemented.
+
+    #[inline]
+    fn write_isize(&mut self, i: isize) {
+        self.short_write(i, (i as usize).to_le() as u64);
+    }
+
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         let length = msg.len();

diff --git a/src/librustc_data_structures/sip128.rs b/src/librustc_data_structures/sip128.rs
@@ -235,6 +235,8 @@ impl Hasher for SipHasher128 {
         self.short_write(i, i.to_le() as u64);
     }
 
+    // `write_u128` is currently unimplemented.
+
     #[inline]
     fn write_usize(&mut self, i: usize) {
         self.short_write(i, i.to_le() as u64);
@@ -260,6 +262,8 @@ impl Hasher for SipHasher128 {
         self.short_write(i, (i as u64).to_le() as u64);
     }
 
+    // `write_i128` is currently unimplemented.
+
     #[inline]
     fn write_isize(&mut self, i: isize) {
         self.short_write(i, (i as usize).to_le() as u64);

diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
@@ -2515,6 +2515,66 @@ impl Default for DefaultHasher {
 
 #[stable(feature = "hashmap_default_hasher", since = "1.13.0")]
 impl Hasher for DefaultHasher {
+    #[inline]
+    fn write_u8(&mut self, i: u8) {
+        self.0.write_u8(i);
+    }
+
+    #[inline]
+    fn write_u16(&mut self, i: u16) {
+        self.0.write_u16(i);
+    }
+
+    #[inline]
+    fn write_u32(&mut self, i: u32) {
+        self.0.write_u32(i);
+    }
+
+    #[inline]
+    fn write_u64(&mut self, i: u64) {
+        self.0.write_u64(i);
+    }
+
+    #[inline]
+    fn write_u128(&mut self, i: u128) {
+        self.0.write_u128(i);
+    }
+
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        self.0.write_usize(i);
+    }
+
+    #[inline]
+    fn write_i8(&mut self, i: i8) {
+        self.0.write_i8(i);
+    }
+
+    #[inline]
+    fn write_i16(&mut self, i: i16) {
+        self.0.write_i16(i);
+    }
+
+    #[inline]
+    fn write_i32(&mut self, i: i32) {
+        self.0.write_i32(i);
+    }
+
+    #[inline]
+    fn write_i64(&mut self, i: i64) {
+        self.0.write_i64(i);
+    }
+
+    #[inline]
+    fn write_i128(&mut self, i: i128) {
+        self.0.write_i128(i);
+    }
+
+    #[inline]
+    fn write_isize(&mut self, i: isize) {
+        self.0.write_isize(i);
+    }
+
     #[inline]
     fn write(&mut self, msg: &[u8]) {
         self.0.write(msg)