lib/model, lib/scanner: Efficient inserts/deletes in the middle of the file

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3527

lib/weakhash/weakhash_test.go

@@ -0,0 +1,188 @@
+// Copyright (C) 2016 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// The existence of this file means we get 0% test coverage rather than no
+// test coverage at all. Remove when implementing an actual test.
+
+package weakhash
+
+import (
+	"bytes"
+	"io/ioutil"
+	"os"
+	"reflect"
+	"testing"
+)
+
+var payload = []byte("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz")
+var hashes = []uint32{
+	64225674,
+	64881038,
+	65536402,
+	66191766,
+	66847130,
+	67502494,
+	68157858,
+	68813222,
+	69468586,
+	70123950,
+	70779314,
+	71434678,
+	72090042,
+	72745406,
+	73400770,
+	74056134,
+	74711498,
+	75366862,
+	76022226,
+	76677590,
+	77332954,
+	77988318,
+	78643682,
+	77595084,
+	74842550,
+	70386080,
+	64225674,
+	64881038,
+	65536402,
+	66191766,
+	66847130,
+	67502494,
+	68157858,
+	68813222,
+	69468586,
+	70123950,
+	70779314,
+	71434678,
+	72090042,
+	72745406,
+	73400770,
+	74056134,
+	74711498,
+	75366862,
+	76022226,
+	76677590,
+	77332954,
+	77988318,
+	78643682,
+	77595084,
+	74842550,
+	70386080,
+	64225674,
+	64881038,
+	65536402,
+	66191766,
+	66847130,
+	67502494,
+	68157858,
+	68813222,
+	69468586,
+	70123950,
+	70779314,
+	71434678,
+	72090042,
+	72745406,
+	73400770,
+	74056134,
+	74711498,
+	75366862,
+	76022226,
+	76677590,
+	77332954,
+	77988318,
+	78643682,
+	77595084,
+	74842550,
+	70386080,
+	64225674,
+	64881038,
+	65536402,
+	66191766,
+	66847130,
+	67502494,
+	68157858,
+	68813222,
+	69468586,
+	70123950,
+	70779314,
+	71434678,
+	72090042,
+	72745406,
+	73400770,
+	74056134,
+	74711498,
+	75366862,
+	76022226,
+	76677590,
+	77332954,
+	77988318,
+	78643682,
+	71893365,
+	71893365,
+}
+
+// Tested using an alternative C implementation at https://gist.github.com/csabahenk/1096262
+func TestHashCorrect(t *testing.T) {
+	h := NewHash(Size)
+	pos := 0
+	for pos < Size {
+		h.Write([]byte{payload[pos]})
+		pos++
+	}
+
+	for i := 0; pos < len(payload); i++ {
+		if h.Sum32() != hashes[i] {
+			t.Errorf("mismatch at %d", i)
+		}
+		h.Write([]byte{payload[pos]})
+		pos++
+	}
+}
+
+func TestFinder(t *testing.T) {
+	f, err := ioutil.TempFile("", "")
+	if err != nil {
+		t.Error(err)
+	}
+	defer os.Remove(f.Name())
+	defer f.Close()
+
+	if _, err := f.Write(payload); err != nil {
+		t.Error(err)
+	}
+
+	hashes := []uint32{64881038, 65536402}
+	finder, err := NewFinder(f.Name(), 4, hashes)
+	if err != nil {
+		t.Error(err)
+	}
+	defer finder.Close()
+
+	expected := map[uint32][]int64{
+		64881038: []int64{1, 27, 53, 79},
+		65536402: []int64{2, 28, 54, 80},
+	}
+	actual := make(map[uint32][]int64)
+
+	b := make([]byte, Size)
+
+	for _, hash := range hashes {
+		_, err := finder.Iterate(hash, b[:4], func(offset int64) bool {
+			if !bytes.Equal(b, payload[offset:offset+4]) {
+				t.Errorf("Not equal at %d: %s != %s", offset, string(b), string(payload[offset:offset+4]))
+			}
+			actual[hash] = append(actual[hash], offset)
+			return true
+		})
+		if err != nil {
+			t.Error(err)
+		}
+	}
+
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Not equal: %#v != %#v", actual, expected)
+	}
+}