adler32: Add tests from the standard library

2 files changed, 388 insertions, 0 deletions

diff --git a/internal/adler32/adler32_test.go b/internal/adler32/adler32_test.go
new file mode 100644
index 00000000..e38e0ed8
--- /dev/null
+++ b/internal/adler32/adler32_test.go
@@ -0,0 +1,157 @@
+// Copyright 2009 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 adler32
+
+import (
+	"encoding"
+	"hash"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestHashInterface(t *testing.T) {
+	TestHash(t, func() hash.Hash { return New() })
+}
+
+var golden = []struct {
+	out       uint32
+	in        string
+	halfState string // marshaled hash state after first half of in written, used by TestGoldenMarshal
+}{
+	{0x00000001, "", "adl\x01\x00\x00\x00\x01"},
+	{0x00620062, "a", "adl\x01\x00\x00\x00\x01"},
+	{0x012600c4, "ab", "adl\x01\x00b\x00b"},
+	{0x024d0127, "abc", "adl\x01\x00b\x00b"},
+	{0x03d8018b, "abcd", "adl\x01\x01&\x00\xc4"},
+	{0x05c801f0, "abcde", "adl\x01\x01&\x00\xc4"},
+	{0x081e0256, "abcdef", "adl\x01\x02M\x01'"},
+	{0x0adb02bd, "abcdefg", "adl\x01\x02M\x01'"},
+	{0x0e000325, "abcdefgh", "adl\x01\x03\xd8\x01\x8b"},
+	{0x118e038e, "abcdefghi", "adl\x01\x03\xd8\x01\x8b"},
+	{0x158603f8, "abcdefghij", "adl\x01\x05\xc8\x01\xf0"},
+	{0x3f090f02, "Discard medicine more than two years old.", "adl\x01NU\a\x87"},
+	{0x46d81477, "He who has a shady past knows that nice guys finish last.", "adl\x01\x89\x8e\t\xe9"},
+	{0x40ee0ee1, "I wouldn't marry him with a ten foot pole.", "adl\x01R\t\ag"},
+	{0x16661315, "Free! Free!/A trip/to Mars/for 900/empty jars/Burma Shave", "adl\x01\u007f\xbb\t\x10"},
+	{0x5b2e1480, "The days of the digital watch are numbered.  -Tom Stoppard", "adl\x01\x99:\n~"},
+	{0x8c3c09ea, "Nepal premier won't resign.", "adl\x01\"\x05\x05\x05"},
+	{0x45ac18fd, "For every action there is an equal and opposite government program.", "adl\x01\xcc\xfa\f\x00"},
+	{0x53c61462, "His money is twice tainted: 'taint yours and 'taint mine.", "adl\x01\x93\xa9\n\b"},
+	{0x7e511e63, "There is no reason for any individual to have a computer in their home. -Ken Olsen, 1977", "adl\x01e\xf5\x10\x14"},
+	{0xe4801a6a, "It's a tiny change to the code and not completely disgusting. - Bob Manchek", "adl\x01\xee\x00\f\xb2"},
+	{0x61b507df, "size:  a.out:  bad magic", "adl\x01\x1a\xfc\x04\x1d"},
+	{0xb8631171, "The major problem is with sendmail.  -Mark Horton", "adl\x01mi\b\xdc"},
+	{0x8b5e1904, "Give me a rock, paper and scissors and I will move the world.  CCFestoon", "adl\x01\xe3\n\f\x9f"},
+	{0x7cc6102b, "If the enemy is within range, then so are you.", "adl\x01_\xe0\b\x1e"},
+	{0x700318e7, "It's well we cannot hear the screams/That we create in others' dreams.", "adl\x01ۘ\f\x87"},
+	{0x1e601747, "You remind me of a TV show, but that's all right: I watch it anyway.", "adl\x01\xcc}\v\x83"},
+	{0xb55b0b09, "C is as portable as Stonehedge!!", "adl\x01,^\x05\xad"},
+	{0x39111dd0, "Even if I could be Shakespeare, I think I should still choose to be Faraday. - A. Huxley", "adl\x01M\xd1\x0e\xc8"},
+	{0x91dd304f, "The fugacity of a constituent in a mixture of gases at a given temperature is proportional to its mole fraction.  Lewis-Randall Rule", "adl\x01#\xd8\x17\xd7"},
+	{0x2e5d1316, "How can you write a big system without C++?  -Paul Glick", "adl\x01\x8fU\n\x0f"},
+	{0xd0201df6, "'Invariant assertions' is the most elegant programming technique!  -Tom Szymanski", "adl\x01/\x98\x0e\xc4"},
+	{0x211297c8, strings.Repeat("\xff", 5548) + "8", "adl\x01\x9a\xa6\xcb\xc1"},
+	{0xbaa198c8, strings.Repeat("\xff", 5549) + "9", "adl\x01gu\xcc\xc0"},
+	{0x553499be, strings.Repeat("\xff", 5550) + "0", "adl\x01gu\xcc\xc0"},
+	{0xf0c19abe, strings.Repeat("\xff", 5551) + "1", "adl\x015CͿ"},
+	{0x8d5c9bbe, strings.Repeat("\xff", 5552) + "2", "adl\x015CͿ"},
+	{0x2af69cbe, strings.Repeat("\xff", 5553) + "3", "adl\x01\x04\x10ξ"},
+	{0xc9809dbe, strings.Repeat("\xff", 5554) + "4", "adl\x01\x04\x10ξ"},
+	{0x69189ebe, strings.Repeat("\xff", 5555) + "5", "adl\x01\xd3\xcdϽ"},
+	{0x86af0001, strings.Repeat("\x00", 1e5), "adl\x01\xc3P\x00\x01"},
+	{0x79660b4d, strings.Repeat("a", 1e5), "adl\x01\x81k\x05\xa7"},
+	{0x110588ee, strings.Repeat("ABCDEFGHIJKLMNOPQRSTUVWXYZ", 1e4), "adl\x01e\xd2\xc4p"},
+}
+
+// checksum is a slow but simple implementation of the Adler-32 checksum.
+// It is a straight port of the sample code in RFC 1950 section 9.
+func checksum(p []byte) uint32 {
+	s1, s2 := uint32(1), uint32(0)
+	for _, x := range p {
+		s1 = (s1 + uint32(x)) % mod
+		s2 = (s2 + s1) % mod
+	}
+	return s2<<16 | s1
+}
+
+func TestGolden(t *testing.T) {
+	for _, g := range golden {
+		in := g.in
+		if len(in) > 220 {
+			in = in[:100] + "..." + in[len(in)-100:]
+		}
+		p := []byte(g.in)
+		if got := checksum(p); got != g.out {
+			t.Errorf("simple implementation: checksum(%q) = 0x%x want 0x%x", in, got, g.out)
+			continue
+		}
+		if got := Checksum(p); got != g.out {
+			t.Errorf("optimized implementation: Checksum(%q) = 0x%x want 0x%x", in, got, g.out)
+			continue
+		}
+	}
+}
+
+func TestGoldenMarshal(t *testing.T) {
+	for _, g := range golden {
+		h := New()
+		h2 := New()
+
+		io.WriteString(h, g.in[:len(g.in)/2])
+
+		state, err := h.(encoding.BinaryMarshaler).MarshalBinary()
+		if err != nil {
+			t.Errorf("could not marshal: %v", err)
+			continue
+		}
+
+		stateAppend, err := h.(encoding.BinaryAppender).AppendBinary(make([]byte, 4, 32))
+		if err != nil {
+			t.Errorf("could not marshal: %v", err)
+			continue
+		}
+		stateAppend = stateAppend[4:]
+
+		if string(state) != g.halfState {
+			t.Errorf("checksum(%q) state = %q, want %q", g.in, state, g.halfState)
+			continue
+		}
+
+		if string(stateAppend) != g.halfState {
+			t.Errorf("checksum(%q) state = %q, want %q", g.in, stateAppend, g.halfState)
+			continue
+		}
+
+		if err := h2.(encoding.BinaryUnmarshaler).UnmarshalBinary(state); err != nil {
+			t.Errorf("could not unmarshal: %v", err)
+			continue
+		}
+
+		io.WriteString(h, g.in[len(g.in)/2:])
+		io.WriteString(h2, g.in[len(g.in)/2:])
+
+		if h.Sum32() != h2.Sum32() {
+			t.Errorf("checksum(%q) = 0x%x != marshaled (0x%x)", g.in, h.Sum32(), h2.Sum32())
+		}
+	}
+}
+
+func BenchmarkAdler32KB(b *testing.B) {
+	b.SetBytes(1024)
+	data := make([]byte, 1024)
+	for i := range data {
+		data[i] = byte(i)
+	}
+	h := New()
+	in := make([]byte, 0, h.Size())
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		h.Reset()
+		h.Write(data)
+		h.Sum(in)
+	}
+}
diff --git a/internal/adler32/testhash.go b/internal/adler32/testhash.go
new file mode 100644
index 00000000..cadf8748
--- /dev/null
+++ b/internal/adler32/testhash.go
@@ -0,0 +1,231 @@
+// Copyright 2024 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 adler32
+
+import (
+	"bytes"
+	"hash"
+	"io"
+	"math/rand"
+	"testing"
+	"time"
+)
+
+type MakeHash func() hash.Hash
+
+// TestHash performs a set of tests on hash.Hash implementations, checking the
+// documented requirements of Write, Sum, Reset, Size, and BlockSize.
+func TestHash(t *testing.T, mh MakeHash) {
+	TestHashWithoutClone(t, mh)
+
+	// Test whether the results after cloning are consistent.
+	t.Run("Clone", func(t *testing.T) {
+		h, ok := mh().(hash.Cloner)
+		if !ok {
+			t.Fatalf("%T does not implement hash.Cloner", mh)
+		}
+		h3, err := h.Clone()
+		if err != nil {
+			t.Fatalf("Clone failed: %v", err)
+		}
+		prefix := []byte("tmp")
+		writeToHash(t, h, prefix)
+		h2, err := h.Clone()
+		if err != nil {
+			t.Fatalf("Clone failed: %v", err)
+		}
+		prefixSum := h.Sum(nil)
+		if !bytes.Equal(prefixSum, h2.Sum(nil)) {
+			t.Fatalf("%T Clone results are inconsistent", h)
+		}
+		suffix := []byte("tmp2")
+		writeToHash(t, h, suffix)
+		writeToHash(t, h3, append(prefix, suffix...))
+		compositeSum := h3.Sum(nil)
+		if !bytes.Equal(h.Sum(nil), compositeSum) {
+			t.Fatalf("%T Clone results are inconsistent", h)
+		}
+		if !bytes.Equal(h2.Sum(nil), prefixSum) {
+			t.Fatalf("%T Clone results are inconsistent", h)
+		}
+		writeToHash(t, h2, suffix)
+		if !bytes.Equal(h.Sum(nil), compositeSum) {
+			t.Fatalf("%T Clone results are inconsistent", h)
+		}
+		if !bytes.Equal(h2.Sum(nil), compositeSum) {
+			t.Fatalf("%T Clone results are inconsistent", h)
+		}
+	})
+}
+
+func TestHashWithoutClone(t *testing.T, mh MakeHash) {
+	// Test that Sum returns an appended digest matching output of Size
+	t.Run("SumAppend", func(t *testing.T) {
+		h := mh()
+		rng := newRandReader(t)
+
+		emptyBuff := []byte("")
+		shortBuff := []byte("a")
+		longBuff := make([]byte, h.BlockSize()+1)
+		rng.Read(longBuff)
+
+		// Set of example strings to append digest to
+		prefixes := [][]byte{nil, emptyBuff, shortBuff, longBuff}
+
+		// Go to each string and check digest gets appended to and is correct size.
+		for _, prefix := range prefixes {
+			h.Reset()
+
+			sum := getSum(t, h, prefix) // Append new digest to prefix
+
+			// Check that Sum didn't alter the prefix
+			if !bytes.Equal(sum[:len(prefix)], prefix) {
+				t.Errorf("Sum alters passed buffer instead of appending; got %x, want %x", sum[:len(prefix)], prefix)
+			}
+
+			// Check that the appended sum wasn't affected by the prefix
+			if expectedSum := getSum(t, h, nil); !bytes.Equal(sum[len(prefix):], expectedSum) {
+				t.Errorf("Sum behavior affected by data in the input buffer; got %x, want %x", sum[len(prefix):], expectedSum)
+			}
+
+			// Check size of append
+			if got, want := len(sum)-len(prefix), h.Size(); got != want {
+				t.Errorf("Sum appends number of bytes != Size; got %v , want %v", got, want)
+			}
+		}
+	})
+
+	// Test that Hash.Write never returns error.
+	t.Run("WriteWithoutError", func(t *testing.T) {
+		h := mh()
+		rng := newRandReader(t)
+
+		emptySlice := []byte("")
+		shortSlice := []byte("a")
+		longSlice := make([]byte, h.BlockSize()+1)
+		rng.Read(longSlice)
+
+		// Set of example strings to append digest to
+		slices := [][]byte{emptySlice, shortSlice, longSlice}
+
+		for _, slice := range slices {
+			writeToHash(t, h, slice) // Writes and checks Write doesn't error
+		}
+	})
+
+	t.Run("ResetState", func(t *testing.T) {
+		h := mh()
+		rng := newRandReader(t)
+
+		emptySum := getSum(t, h, nil)
+
+		// Write to hash and then Reset it and see if Sum is same as emptySum
+		writeEx := make([]byte, h.BlockSize())
+		rng.Read(writeEx)
+		writeToHash(t, h, writeEx)
+		h.Reset()
+		resetSum := getSum(t, h, nil)
+
+		if !bytes.Equal(emptySum, resetSum) {
+			t.Errorf("Reset hash yields different Sum than new hash; got %x, want %x", emptySum, resetSum)
+		}
+	})
+
+	// Check that Write isn't reading from beyond input slice's bounds
+	t.Run("OutOfBoundsRead", func(t *testing.T) {
+		h := mh()
+		blockSize := h.BlockSize()
+		rng := newRandReader(t)
+
+		msg := make([]byte, blockSize)
+		rng.Read(msg)
+		writeToHash(t, h, msg)
+		expectedDigest := getSum(t, h, nil) // Record control digest
+
+		h.Reset()
+
+		// Make a buffer with msg in the middle and data on either end
+		buff := make([]byte, blockSize*3)
+		endOfPrefix, startOfSuffix := blockSize, blockSize*2
+
+		copy(buff[endOfPrefix:startOfSuffix], msg)
+		rng.Read(buff[:endOfPrefix])
+		rng.Read(buff[startOfSuffix:])
+
+		writeToHash(t, h, buff[endOfPrefix:startOfSuffix])
+		testDigest := getSum(t, h, nil)
+
+		if !bytes.Equal(testDigest, expectedDigest) {
+			t.Errorf("Write affected by data outside of input slice bounds; got %x, want %x", testDigest, expectedDigest)
+		}
+	})
+
+	// Test that multiple calls to Write is stateful
+	t.Run("StatefulWrite", func(t *testing.T) {
+		h := mh()
+		rng := newRandReader(t)
+
+		prefix, suffix := make([]byte, h.BlockSize()), make([]byte, h.BlockSize())
+		rng.Read(prefix)
+		rng.Read(suffix)
+
+		// Write prefix then suffix sequentially and record resulting hash
+		writeToHash(t, h, prefix)
+		writeToHash(t, h, suffix)
+		serialSum := getSum(t, h, nil)
+
+		h.Reset()
+
+		// Write prefix and suffix at the same time and record resulting hash
+		writeToHash(t, h, append(prefix, suffix...))
+		compositeSum := getSum(t, h, nil)
+
+		// Check that sequential writing results in the same as writing all at once
+		if !bytes.Equal(compositeSum, serialSum) {
+			t.Errorf("two successive Write calls resulted in a different Sum than a single one; got %x, want %x", compositeSum, serialSum)
+		}
+	})
+}
+
+// Helper function for writing. Verifies that Write does not error.
+func writeToHash(t *testing.T, h hash.Hash, p []byte) {
+	t.Helper()
+
+	before := make([]byte, len(p))
+	copy(before, p)
+
+	n, err := h.Write(p)
+	if err != nil || n != len(p) {
+		t.Errorf("Write returned error; got (%v, %v), want (nil, %v)", err, n, len(p))
+	}
+
+	if !bytes.Equal(p, before) {
+		t.Errorf("Write modified input slice; got %x, want %x", p, before)
+	}
+}
+
+// Helper function for getting Sum. Checks that Sum doesn't change hash state.
+func getSum(t *testing.T, h hash.Hash, buff []byte) []byte {
+	t.Helper()
+
+	testBuff := make([]byte, len(buff))
+	copy(testBuff, buff)
+
+	sum := h.Sum(buff)
+	testSum := h.Sum(testBuff)
+
+	// Check that Sum doesn't change underlying hash state
+	if !bytes.Equal(sum, testSum) {
+		t.Errorf("successive calls to Sum yield different results; got %x, want %x", sum, testSum)
+	}
+
+	return sum
+}
+
+func newRandReader(t *testing.T) io.Reader {
+	seed := time.Now().UnixNano()
+	t.Logf("Deterministic RNG seed: 0x%x", seed)
+	return rand.New(rand.NewSource(seed))
+}