switch back to the C brotli default of 5 bytes of backwards info for the hashing function for prior copies

Author: danielrh

src/bin/integration_tests.rs

@@ -385,7 +385,7 @@ fn test_random_then_unicode_9() {
     roundtrip_helper(RANDOM_THEN_UNICODE, 9, 22, false);
 }
 #[cfg(feature="std")]
-const random_then_unicode_compressed_size_9_5 : usize = 136542;
+const random_then_unicode_compressed_size_9_5 : usize = 136126;
 #[cfg(feature="std")]
 const random_then_unicode_compressed_size_9_5x : usize = 136045;
 
@@ -412,7 +412,7 @@ const alice_compressed_size_11 : usize = 46510;
 
 
 #[cfg(not(feature="std"))] // approx log
-const random_then_unicode_compressed_size_9_5 : usize = 136719;
+const random_then_unicode_compressed_size_9_5 : usize = 136409;
 #[cfg(not(feature="std"))] // approx log
 const random_then_unicode_compressed_size_9_5x : usize = 136095;
 

src/enc/backward_references/mod.rs

@@ -679,17 +679,17 @@ impl<Alloc: alloc::Allocator<u16> + alloc::Allocator<u32>> AnyHasher for H9<Allo
     }
   #[inline(always)]
     fn HashBytes(&self, data: &[u8]) -> usize {
-        let h: u32 = BROTLI_UNALIGNED_LOAD32(data).wrapping_mul(kHashMul32);
-        let thirty_two : usize = 32;
+        let h: u64 = (BROTLI_UNALIGNED_LOAD32(data) as u64| ((data[4] as u64) << 32)).wrapping_mul(kHashMul64Long);
+        let thirty_two : usize = 64;
         (h >> (thirty_two.wrapping_sub(H9_BUCKET_BITS))) as usize
     }
   #[inline(always)]
     fn HashTypeLength(&self) -> usize {
-        4
+        5
     }
   #[inline(always)]
     fn StoreLookahead(&self) -> usize {
-        4
+        5
     }
     fn PrepareDistanceCache(&self, distance_cache: &mut [i32]) {
         let num_distances = H9_NUM_LAST_DISTANCES_TO_CHECK as i32;