Merge "Implement SipHasher" into main am: d53df1b115

Original change: https://android-review.googlesource.com/c/platform/build/+/3243780

Change-Id: I5917a9b03103b335c2b6d6468f18365d12c7d6ac
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

tools/aconfig/aconfig_storage_file/src/flag_table.rs

@@ -150,7 +150,7 @@ impl FlagTableNode {
     /// Calculate node bucket index
     pub fn find_bucket_index(package_id: u32, flag_name: &str, num_buckets: u32) -> u32 {
         let full_flag_name = package_id.to_string() + "/" + flag_name;
-        get_bucket_index(&full_flag_name, num_buckets)
+        get_bucket_index(full_flag_name.as_bytes(), num_buckets)
     }
 }
 

tools/aconfig/aconfig_storage_file/src/lib.rs

@@ -37,19 +37,20 @@ pub mod flag_table;
 pub mod flag_value;
 pub mod package_table;
 pub mod protos;
+pub mod sip_hasher13;
 pub mod test_utils;
 
 use anyhow::anyhow;
 use std::cmp::Ordering;
-use std::collections::hash_map::DefaultHasher;
 use std::fs::File;
-use std::hash::{Hash, Hasher};
+use std::hash::Hasher;
 use std::io::Read;
 
 pub use crate::flag_info::{FlagInfoBit, FlagInfoHeader, FlagInfoList, FlagInfoNode};
 pub use crate::flag_table::{FlagTable, FlagTableHeader, FlagTableNode};
 pub use crate::flag_value::{FlagValueHeader, FlagValueList};
 pub use crate::package_table::{PackageTable, PackageTableHeader, PackageTableNode};
+pub use crate::sip_hasher13::SipHasher13;
 
 use crate::AconfigStorageError::{
     BytesParseFail, HashTableSizeLimit, InvalidFlagValueType, InvalidStoredFlagType,
@@ -211,10 +212,12 @@ pub fn get_table_size(entries: u32) -> Result<u32, AconfigStorageError> {
 }
 
 /// Get the corresponding bucket index given the key and number of buckets
-pub(crate) fn get_bucket_index<T: Hash>(val: &T, num_buckets: u32) -> u32 {
+pub(crate) fn get_bucket_index(val: &[u8], num_buckets: u32) -> u32 {
-    let mut s = DefaultHasher::new();
+    let mut s = SipHasher13::new();
-    val.hash(&mut s);
+    s.write(val);
-    (s.finish() % num_buckets as u64) as u32
+    s.write_u8(0xff);
+    let ret = (s.finish() % num_buckets as u64) as u32;
+    ret
 }
 
 /// Read and parse bytes as u8

tools/aconfig/aconfig_storage_file/src/package_table.rs

@@ -146,7 +146,7 @@ impl PackageTableNode {
     /// construction side (aconfig binary) and consumption side (flag read lib)
     /// use the same method of hashing
     pub fn find_bucket_index(package: &str, num_buckets: u32) -> u32 {
-        get_bucket_index(&package, num_buckets)
+        get_bucket_index(package.as_bytes(), num_buckets)
     }
 }
 

tools/aconfig/aconfig_storage_file/src/sip_hasher13.rs

@@ -0,0 +1,327 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! An implementation of SipHash13
+
+use std::cmp;
+use std::mem;
+use std::ptr;
+use std::slice;
+
+use std::hash::Hasher;
+
+/// An implementation of SipHash 2-4.
+///
+#[derive(Debug, Clone, Default)]
+pub struct SipHasher13 {
+    k0: u64,
+    k1: u64,
+    length: usize, // how many bytes we've processed
+    state: State,  // hash State
+    tail: u64,     // unprocessed bytes le
+    ntail: usize,  // how many bytes in tail are valid
+}
+
+#[derive(Debug, Clone, Copy, Default)]
+#[repr(C)]
+struct State {
+    // v0, v2 and v1, v3 show up in pairs in the algorithm,
+    // and simd implementations of SipHash will use vectors
+    // of v02 and v13. By placing them in this order in the struct,
+    // the compiler can pick up on just a few simd optimizations by itself.
+    v0: u64,
+    v2: u64,
+    v1: u64,
+    v3: u64,
+}
+
+macro_rules! compress {
+    ($state:expr) => {{
+        compress!($state.v0, $state.v1, $state.v2, $state.v3)
+    }};
+    ($v0:expr, $v1:expr, $v2:expr, $v3:expr) => {{
+        $v0 = $v0.wrapping_add($v1);
+        $v1 = $v1.rotate_left(13);
+        $v1 ^= $v0;
+        $v0 = $v0.rotate_left(32);
+        $v2 = $v2.wrapping_add($v3);
+        $v3 = $v3.rotate_left(16);
+        $v3 ^= $v2;
+        $v0 = $v0.wrapping_add($v3);
+        $v3 = $v3.rotate_left(21);
+        $v3 ^= $v0;
+        $v2 = $v2.wrapping_add($v1);
+        $v1 = $v1.rotate_left(17);
+        $v1 ^= $v2;
+        $v2 = $v2.rotate_left(32);
+    }};
+}
+
+/// Load an integer of the desired type from a byte stream, in LE order. Uses
+/// `copy_nonoverlapping` to let the compiler generate the most efficient way
+/// to load it from a possibly unaligned address.
+///
+/// Unsafe because: unchecked indexing at i..i+size_of(int_ty)
+macro_rules! load_int_le {
+    ($buf:expr, $i:expr, $int_ty:ident) => {{
+        debug_assert!($i + mem::size_of::<$int_ty>() <= $buf.len());
+        let mut data = 0 as $int_ty;
+        ptr::copy_nonoverlapping(
+            $buf.get_unchecked($i),
+            &mut data as *mut _ as *mut u8,
+            mem::size_of::<$int_ty>(),
+        );
+        data.to_le()
+    }};
+}
+
+/// Load an u64 using up to 7 bytes of a byte slice.
+///
+/// Unsafe because: unchecked indexing at start..start+len
+#[inline]
+unsafe fn u8to64_le(buf: &[u8], start: usize, len: usize) -> u64 {
+    debug_assert!(len < 8);
+    let mut i = 0; // current byte index (from LSB) in the output u64
+    let mut out = 0;
+    if i + 3 < len {
+        out = load_int_le!(buf, start + i, u32) as u64;
+        i += 4;
+    }
+    if i + 1 < len {
+        out |= (load_int_le!(buf, start + i, u16) as u64) << (i * 8);
+        i += 2
+    }
+    if i < len {
+        out |= (*buf.get_unchecked(start + i) as u64) << (i * 8);
+        i += 1;
+    }
+    debug_assert_eq!(i, len);
+    out
+}
+
+impl SipHasher13 {
+    /// Creates a new `SipHasher13` with the two initial keys set to 0.
+    #[inline]
+    pub fn new() -> SipHasher13 {
+        SipHasher13::new_with_keys(0, 0)
+    }
+
+    /// Creates a `SipHasher13` that is keyed off the provided keys.
+    #[inline]
+    pub fn new_with_keys(key0: u64, key1: u64) -> SipHasher13 {
+        let mut sip_hasher = SipHasher13 {
+            k0: key0,
+            k1: key1,
+            length: 0,
+            state: State { v0: 0, v1: 0, v2: 0, v3: 0 },
+            tail: 0,
+            ntail: 0,
+        };
+        sip_hasher.reset();
+        sip_hasher
+    }
+
+    #[inline]
+    fn c_rounds(state: &mut State) {
+        compress!(state);
+    }
+
+    #[inline]
+    fn d_rounds(state: &mut State) {
+        compress!(state);
+        compress!(state);
+        compress!(state);
+    }
+
+    #[inline]
+    fn reset(&mut self) {
+        self.length = 0;
+        self.state.v0 = self.k0 ^ 0x736f6d6570736575;
+        self.state.v1 = self.k1 ^ 0x646f72616e646f6d;
+        self.state.v2 = self.k0 ^ 0x6c7967656e657261;
+        self.state.v3 = self.k1 ^ 0x7465646279746573;
+        self.ntail = 0;
+    }
+
+    // Specialized write function that is only valid for buffers with len <= 8.
+    // It's used to force inlining of write_u8 and write_usize, those would normally be inlined
+    // except for composite types (that includes slices and str hashing because of delimiter).
+    // Without this extra push the compiler is very reluctant to inline delimiter writes,
+    // degrading performance substantially for the most common use cases.
+    #[inline]
+    fn short_write(&mut self, msg: &[u8]) {
+        debug_assert!(msg.len() <= 8);
+        let length = msg.len();
+        self.length += length;
+
+        let needed = 8 - self.ntail;
+        let fill = cmp::min(length, needed);
+        if fill == 8 {
+            // safe to call since msg hasn't been loaded
+            self.tail = unsafe { load_int_le!(msg, 0, u64) };
+        } else {
+            // safe to call since msg hasn't been loaded, and fill <= msg.len()
+            self.tail |= unsafe { u8to64_le(msg, 0, fill) } << (8 * self.ntail);
+            if length < needed {
+                self.ntail += length;
+                return;
+            }
+        }
+        self.state.v3 ^= self.tail;
+        Self::c_rounds(&mut self.state);
+        self.state.v0 ^= self.tail;
+
+        // Buffered tail is now flushed, process new input.
+        self.ntail = length - needed;
+        // safe to call since number of `needed` bytes has been loaded
+        // and self.ntail + needed == msg.len()
+        self.tail = unsafe { u8to64_le(msg, needed, self.ntail) };
+    }
+}
+
+impl Hasher for SipHasher13 {
+    // see short_write comment for explanation
+    #[inline]
+    fn write_usize(&mut self, i: usize) {
+        // safe to call, since convert the pointer to u8
+        let bytes = unsafe {
+            slice::from_raw_parts(&i as *const usize as *const u8, mem::size_of::<usize>())
+        };
+        self.short_write(bytes);
+    }
+
+    // see short_write comment for explanation
+    #[inline]
+    fn write_u8(&mut self, i: u8) {
+        self.short_write(&[i]);
+    }
+
+    #[inline]
+    fn write(&mut self, msg: &[u8]) {
+        let length = msg.len();
+        self.length += length;
+
+        let mut needed = 0;
+
+        // loading unprocessed byte from last write
+        if self.ntail != 0 {
+            needed = 8 - self.ntail;
+            // safe to call, since msg hasn't been processed
+            // and cmp::min(length, needed) < 8
+            self.tail |= unsafe { u8to64_le(msg, 0, cmp::min(length, needed)) } << 8 * self.ntail;
+            if length < needed {
+                self.ntail += length;
+                return;
+            } else {
+                self.state.v3 ^= self.tail;
+                Self::c_rounds(&mut self.state);
+                self.state.v0 ^= self.tail;
+                self.ntail = 0;
+            }
+        }
+
+        // Buffered tail is now flushed, process new input.
+        let len = length - needed;
+        let left = len & 0x7;
+
+        let mut i = needed;
+        while i < len - left {
+            // safe to call since if i < len - left, it means msg has at least 1 byte to load
+            let mi = unsafe { load_int_le!(msg, i, u64) };
+
+            self.state.v3 ^= mi;
+            Self::c_rounds(&mut self.state);
+            self.state.v0 ^= mi;
+
+            i += 8;
+        }
+
+        // safe to call since if left == 0, since this call will load nothing
+        // if left > 0, it means there are number of `left` bytes in msg
+        self.tail = unsafe { u8to64_le(msg, i, left) };
+        self.ntail = left;
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        let mut state = self.state;
+
+        let b: u64 = ((self.length as u64 & 0xff) << 56) | self.tail;
+
+        state.v3 ^= b;
+        Self::c_rounds(&mut state);
+        state.v0 ^= b;
+
+        state.v2 ^= 0xff;
+        Self::d_rounds(&mut state);
+
+        state.v0 ^ state.v1 ^ state.v2 ^ state.v3
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use std::hash::{Hash, Hasher};
+    use std::string::String;
+
+    #[test]
+    // this test point locks down the value list serialization
+    fn test_sip_hash13_string_hash() {
+        let mut sip_hash13 = SipHasher13::new();
+        let test_str1 = String::from("com.google.android.test");
+        test_str1.hash(&mut sip_hash13);
+        assert_eq!(17898838669067067585, sip_hash13.finish());
+
+        let test_str2 = String::from("adfadfadf adfafadadf 1231241241");
+        test_str2.hash(&mut sip_hash13);
+        assert_eq!(13543518987672889310, sip_hash13.finish());
+    }
+
+    #[test]
+    fn test_sip_hash13_write() {
+        let mut sip_hash13 = SipHasher13::new();
+        let test_str1 = String::from("com.google.android.test");
+        sip_hash13.write(test_str1.as_bytes());
+        sip_hash13.write_u8(0xff);
+        assert_eq!(17898838669067067585, sip_hash13.finish());
+
+        let mut sip_hash132 = SipHasher13::new();
+        let test_str1 = String::from("com.google.android.test");
+        sip_hash132.write(test_str1.as_bytes());
+        assert_eq!(9685440969685209025, sip_hash132.finish());
+        sip_hash132.write(test_str1.as_bytes());
+        assert_eq!(6719694176662736568, sip_hash132.finish());
+
+        let mut sip_hash133 = SipHasher13::new();
+        let test_str2 = String::from("abcdefg");
+        test_str2.hash(&mut sip_hash133);
+        assert_eq!(2492161047327640297, sip_hash133.finish());
+
+        let mut sip_hash134 = SipHasher13::new();
+        let test_str3 = String::from("abcdefgh");
+        test_str3.hash(&mut sip_hash134);
+        assert_eq!(6689927370435554326, sip_hash134.finish());
+    }
+
+    #[test]
+    fn test_sip_hash13_write_short() {
+        let mut sip_hash13 = SipHasher13::new();
+        sip_hash13.write_u8(0x61);
+        assert_eq!(4644417185603328019, sip_hash13.finish());
+    }
+}

tools/aconfig/aconfig_storage_file/srcs/android/aconfig/storage/SipHasher13.java

@@ -0,0 +1,119 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.aconfig.storage;
+
+public class SipHasher13 {
+    static class State {
+        private long v0;
+        private long v2;
+        private long v1;
+        private long v3;
+
+        public State(long k0, long k1) {
+            v0 = k0 ^ 0x736f6d6570736575L;
+            v1 = k1 ^ 0x646f72616e646f6dL;
+            v2 = k0 ^ 0x6c7967656e657261L;
+            v3 = k1 ^ 0x7465646279746573L;
+        }
+
+        public void compress(long m) {
+            v3 ^= m;
+            cRounds();
+            v0 ^= m;
+        }
+
+        public long finish() {
+            v2 ^= 0xff;
+            dRounds();
+            return v0 ^ v1 ^ v2 ^ v3;
+        }
+
+        private void cRounds() {
+            v0 += v1;
+            v1 = rotateLeft(v1, 13);
+            v1 ^= v0;
+            v0 = rotateLeft(v0, 32);
+            v2 += v3;
+            v3 = rotateLeft(v3, 16);
+            v3 ^= v2;
+            v0 += v3;
+            v3 = rotateLeft(v3, 21);
+            v3 ^= v0;
+            v2 += v1;
+            v1 = rotateLeft(v1, 17);
+            v1 ^= v2;
+            v2 = rotateLeft(v2, 32);
+        }
+
+        private void dRounds() {
+            for (int i = 0; i < 3; i++) {
+                v0 += v1;
+                v1 = rotateLeft(v1, 13);
+                v1 ^= v0;
+                v0 = rotateLeft(v0, 32);
+                v2 += v3;
+                v3 = rotateLeft(v3, 16);
+                v3 ^= v2;
+                v0 += v3;
+                v3 = rotateLeft(v3, 21);
+                v3 ^= v0;
+                v2 += v1;
+                v1 = rotateLeft(v1, 17);
+                v1 ^= v2;
+                v2 = rotateLeft(v2, 32);
+            }
+        }
+
+        private static long rotateLeft(long value, int shift) {
+            return (value << shift) | value >>> (64 - shift);
+        }
+    }
+
+    public static long hash(byte[] data) {
+        State state = new State(0, 0);
+        int len = data.length;
+        int left = len & 0x7;
+        int index = 0;
+
+        while (index < len - left) {
+            long mi = loadLe(data, index, 8);
+            index += 8;
+            state.compress(mi);
+        }
+
+        // padding the end with 0xff to be consistent with rust
+        long m = (0xffL << (left * 8)) | loadLe(data, index, left);
+        if (left == 0x7) {
+            // compress the m w-2
+            state.compress(m);
+            m = 0L;
+        }
+        // len adds 1 since padded 0xff
+        m |= (((len + 1) & 0xffL) << 56);
+        state.compress(m);
+
+        return state.finish();
+    }
+
+    private static long loadLe(byte[] data, int offset, int size) {
+        long m = 0;
+        for (int i = 0; i < size; i++) {
+            m |= (data[i + offset] & 0xffL) << (i * 8);
+        }
+        return m;
+    }
+}

tools/aconfig/aconfig_storage_file/tests/srcs/SipHasher13Test.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.aconfig.storage.test;
+
+import static org.junit.Assert.assertEquals;
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import android.aconfig.storage.SipHasher13;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class SipHasher13Test {
+    @Test
+    public void testSipHash_hashString() throws Exception {
+        String testStr = "com.google.android.test";
+        long result = SipHasher13.hash(testStr.getBytes(UTF_8));
+        assertEquals(0xF86572EFF9C4A0C1L, result);
+
+        testStr = "abcdefg";
+        result = SipHasher13.hash(testStr.getBytes(UTF_8));
+        assertEquals(0x2295EF44BD078AE9L, result);
+
+        testStr = "abcdefgh";
+        result = SipHasher13.hash(testStr.getBytes(UTF_8));
+        assertEquals(0x5CD7657FA7F96C16L, result);
+    }
+}