1 files changed, 255 insertions, 0 deletions
diff --git a/src/hash/maphash/maphash_test.go b/src/hash/maphash/maphash_test.go
new file mode 100644
index 0000000..7526989
--- /dev/null
+++ b/src/hash/maphash/maphash_test.go
@@ -0,0 +1,255 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package maphash
+
+import (
+	"bytes"
+	"fmt"
+	"hash"
+	"testing"
+)
+
+func TestUnseededHash(t *testing.T) {
+	m := map[uint64]struct{}{}
+	for i := 0; i < 1000; i++ {
+		h := new(Hash)
+		m[h.Sum64()] = struct{}{}
+	}
+	if len(m) < 900 {
+		t.Errorf("empty hash not sufficiently random: got %d, want 1000", len(m))
+	}
+}
+
+func TestSeededHash(t *testing.T) {
+	s := MakeSeed()
+	m := map[uint64]struct{}{}
+	for i := 0; i < 1000; i++ {
+		h := new(Hash)
+		h.SetSeed(s)
+		m[h.Sum64()] = struct{}{}
+	}
+	if len(m) != 1 {
+		t.Errorf("seeded hash is random: got %d, want 1", len(m))
+	}
+}
+
+func TestHashGrouping(t *testing.T) {
+	b := bytes.Repeat([]byte("foo"), 100)
+	hh := make([]*Hash, 7)
+	for i := range hh {
+		hh[i] = new(Hash)
+	}
+	for _, h := range hh[1:] {
+		h.SetSeed(hh[0].Seed())
+	}
+	hh[0].Write(b)
+	hh[1].WriteString(string(b))
+
+	writeByte := func(h *Hash, b byte) {
+		err := h.WriteByte(b)
+		if err != nil {
+			t.Fatalf("WriteByte: %v", err)
+		}
+	}
+	writeSingleByte := func(h *Hash, b byte) {
+		_, err := h.Write([]byte{b})
+		if err != nil {
+			t.Fatalf("Write single byte: %v", err)
+		}
+	}
+	writeStringSingleByte := func(h *Hash, b byte) {
+		_, err := h.WriteString(string([]byte{b}))
+		if err != nil {
+			t.Fatalf("WriteString single byte: %v", err)
+		}
+	}
+
+	for i, x := range b {
+		writeByte(hh[2], x)
+		writeSingleByte(hh[3], x)
+		if i == 0 {
+			writeByte(hh[4], x)
+		} else {
+			writeSingleByte(hh[4], x)
+		}
+		writeStringSingleByte(hh[5], x)
+		if i == 0 {
+			writeByte(hh[6], x)
+		} else {
+			writeStringSingleByte(hh[6], x)
+		}
+	}
+
+	sum := hh[0].Sum64()
+	for i, h := range hh {
+		if sum != h.Sum64() {
+			t.Errorf("hash %d not identical to a single Write", i)
+		}
+	}
+
+	if sum1 := Bytes(hh[0].Seed(), b); sum1 != hh[0].Sum64() {
+		t.Errorf("hash using Bytes not identical to a single Write")
+	}
+
+	if sum1 := String(hh[0].Seed(), string(b)); sum1 != hh[0].Sum64() {
+		t.Errorf("hash using String not identical to a single Write")
+	}
+}
+
+func TestHashBytesVsString(t *testing.T) {
+	s := "foo"
+	b := []byte(s)
+	h1 := new(Hash)
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	n1, err1 := h1.WriteString(s)
+	if n1 != len(s) || err1 != nil {
+		t.Fatalf("WriteString(s) = %d, %v, want %d, nil", n1, err1, len(s))
+	}
+	n2, err2 := h2.Write(b)
+	if n2 != len(b) || err2 != nil {
+		t.Fatalf("Write(b) = %d, %v, want %d, nil", n2, err2, len(b))
+	}
+	if h1.Sum64() != h2.Sum64() {
+		t.Errorf("hash of string and bytes not identical")
+	}
+}
+
+func TestHashHighBytes(t *testing.T) {
+	// See issue 34925.
+	const N = 10
+	m := map[uint64]struct{}{}
+	for i := 0; i < N; i++ {
+		h := new(Hash)
+		h.WriteString("foo")
+		m[h.Sum64()>>32] = struct{}{}
+	}
+	if len(m) < N/2 {
+		t.Errorf("from %d seeds, wanted at least %d different hashes; got %d", N, N/2, len(m))
+	}
+}
+
+func TestRepeat(t *testing.T) {
+	h1 := new(Hash)
+	h1.WriteString("testing")
+	sum1 := h1.Sum64()
+
+	h1.Reset()
+	h1.WriteString("testing")
+	sum2 := h1.Sum64()
+
+	if sum1 != sum2 {
+		t.Errorf("different sum after reseting: %#x != %#x", sum1, sum2)
+	}
+
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	h2.WriteString("testing")
+	sum3 := h2.Sum64()
+
+	if sum1 != sum3 {
+		t.Errorf("different sum on the same seed: %#x != %#x", sum1, sum3)
+	}
+}
+
+func TestSeedFromSum64(t *testing.T) {
+	h1 := new(Hash)
+	h1.WriteString("foo")
+	x := h1.Sum64() // seed generated here
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	h2.WriteString("foo")
+	y := h2.Sum64()
+	if x != y {
+		t.Errorf("hashes don't match: want %x, got %x", x, y)
+	}
+}
+
+func TestSeedFromSeed(t *testing.T) {
+	h1 := new(Hash)
+	h1.WriteString("foo")
+	_ = h1.Seed() // seed generated here
+	x := h1.Sum64()
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	h2.WriteString("foo")
+	y := h2.Sum64()
+	if x != y {
+		t.Errorf("hashes don't match: want %x, got %x", x, y)
+	}
+}
+
+func TestSeedFromFlush(t *testing.T) {
+	b := make([]byte, 65)
+	h1 := new(Hash)
+	h1.Write(b) // seed generated here
+	x := h1.Sum64()
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	h2.Write(b)
+	y := h2.Sum64()
+	if x != y {
+		t.Errorf("hashes don't match: want %x, got %x", x, y)
+	}
+}
+
+func TestSeedFromReset(t *testing.T) {
+	h1 := new(Hash)
+	h1.WriteString("foo")
+	h1.Reset() // seed generated here
+	h1.WriteString("foo")
+	x := h1.Sum64()
+	h2 := new(Hash)
+	h2.SetSeed(h1.Seed())
+	h2.WriteString("foo")
+	y := h2.Sum64()
+	if x != y {
+		t.Errorf("hashes don't match: want %x, got %x", x, y)
+	}
+}
+
+// Make sure a Hash implements the hash.Hash and hash.Hash64 interfaces.
+var _ hash.Hash = &Hash{}
+var _ hash.Hash64 = &Hash{}
+
+func benchmarkSize(b *testing.B, size int) {
+	h := &Hash{}
+	buf := make([]byte, size)
+	s := string(buf)
+
+	b.Run("Write", func(b *testing.B) {
+		b.SetBytes(int64(size))
+		for i := 0; i < b.N; i++ {
+			h.Reset()
+			h.Write(buf)
+			h.Sum64()
+		}
+	})
+
+	b.Run("Bytes", func(b *testing.B) {
+		b.SetBytes(int64(size))
+		seed := h.Seed()
+		for i := 0; i < b.N; i++ {
+			Bytes(seed, buf)
+		}
+	})
+
+	b.Run("String", func(b *testing.B) {
+		b.SetBytes(int64(size))
+		seed := h.Seed()
+		for i := 0; i < b.N; i++ {
+			String(seed, s)
+		}
+	})
+}
+
+func BenchmarkHash(b *testing.B) {
+	sizes := []int{4, 8, 16, 32, 64, 256, 320, 1024, 4096, 16384}
+	for _, size := range sizes {
+		b.Run(fmt.Sprint("n=", size), func(b *testing.B) {
+			benchmarkSize(b, size)
+		})
+	}
+}