From d7c37b9060aa92331faeef49b4e65ce69bcf8853 Mon Sep 17 00:00:00 2001
From: Eduard Urbach <admin@akyoto.dev>
Date: Sun, 23 Jul 2023 11:40:22 +0200
Subject: [PATCH] Added more tests

---
 Benchmarks_test.go |  4 +++
 hash.go            |  4 +--
 hash_test.go       | 61 +++++++++++++++++++++++++++-------------------
 3 files changed, 42 insertions(+), 27 deletions(-)

diff --git a/Benchmarks_test.go b/Benchmarks_test.go
index 2e85bef..97b5d6a 100644
--- a/Benchmarks_test.go
+++ b/Benchmarks_test.go
@@ -8,10 +8,14 @@ import (
 )
 
 func BenchmarkSize(b *testing.B) {
+	b.Run("7", bench(7))
 	b.Run("8", bench(8))
 	b.Run("16", bench(16))
+	b.Run("17", bench(17))
 	b.Run("32", bench(32))
+	b.Run("33", bench(33))
 	b.Run("64", bench(64))
+	b.Run("65", bench(65))
 	b.Run("128", bench(128))
 	b.Run("256", bench(256))
 	b.Run("512", bench(512))
diff --git a/hash.go b/hash.go
index f650194..3b6a1e7 100644
--- a/hash.go
+++ b/hash.go
@@ -13,7 +13,7 @@ func add(x uint64, in []byte) uint64 {
 	var i int
 
 	// Cache lines on modern processors are 64 bytes long.
-	// A single uint64 consumes 64 bits (8 bytes).
+	// A single uint64 consumes 8 bytes.
 	// That means we should read 8 uint64 at a time.
 	for ; i < len(in)-63; i += 64 {
 		words := (*[8]uint64)(unsafe.Pointer(&in[i]))
@@ -46,5 +46,5 @@ func add(x uint64, in []byte) uint64 {
 }
 
 func mix(x uint64, b uint64) uint64 {
-	return (x + b) * 0x50003
+	return (x + b) * 0xD0003
 }
diff --git a/hash_test.go b/hash_test.go
index 0f3c813..db98e6d 100644
--- a/hash_test.go
+++ b/hash_test.go
@@ -7,42 +7,53 @@ import (
 	"git.akyoto.dev/go/hash"
 )
 
+// Hashes generated in tests will be saved to check for collisions.
 var hashes = map[uint64][]byte{}
 
-func TestTinyCollisions(t *testing.T) {
-	for size := 1; size < 8; size++ {
-		tmp := make([]byte, size)
-		index := 0
+// addHash adds a new hash and checks for collisions.
+func addHash(t *testing.T, sum uint64, data []byte) {
+	saved, found := hashes[sum]
 
-		for i := 0; i < 256; i++ {
-			tmp[index] += 1
-			h := hash.Bytes(tmp)
-			previous, found := hashes[h]
+	if found && !bytes.Equal(saved, data) {
+		t.Fatalf("collision between %v and %v:\nhash %064b", saved, data, sum)
+	}
 
-			if found && !bytes.Equal(tmp, previous) {
-				t.Fatalf("collision between %v and %v:\nhash %064b", previous, tmp, h)
-			}
+	save := make([]byte, len(data))
+	copy(save, data)
+	hashes[sum] = save
+}
 
-			save := make([]byte, size)
-			copy(save, tmp)
-			hashes[h] = save
-			index = (index + 1) % size
+// TestTiny hashes every single permutation that is 1-32 bytes long.
+func TestTiny(t *testing.T) {
+	for size := 1; size <= 32; size++ {
+		data := make([]byte, size)
+
+		for i := 0; i <= 255*size; i++ {
+			sum := hash.Bytes(data)
+			addHash(t, sum, data)
+			data[i%size] += 1
 		}
 	}
 }
 
-func TestZeroedCollisions(t *testing.T) {
+// TestZeroed hashes completely zeroed buffers that are 1-8192 bytes long.
+func TestZeroed(t *testing.T) {
 	zero := make([]byte, 8192)
 
 	for size := 1; size <= len(zero); size++ {
-		tmp := zero[:size]
-		h := hash.Bytes(tmp)
-		previous, found := hashes[h]
-
-		if found && !bytes.Equal(tmp, previous) {
-			t.Fatalf("collision between %v and %v:\nhash %064b", previous, tmp, h)
-		}
-
-		hashes[h] = tmp
+		data := zero[:size]
+		sum := hash.Bytes(data)
+		addHash(t, sum, data)
+	}
+}
+
+// TestSameByte hashes every byte repetition that is 1-512 bytes long.
+func TestSameByte(t *testing.T) {
+	for b := 1; b < 256; b++ {
+		for size := 1; size <= 512; size++ {
+			data := bytes.Repeat([]byte{byte(b)}, size)
+			sum := hash.Bytes(data)
+			addHash(t, sum, data)
+		}
 	}
 }