sparsehash_test.go

package sparsehash

import (
	"bytes"
	"encoding/binary"
	"flag"
	"fmt"
	"hash"
	"io/ioutil"
	"os"
	"testing"

	"github.com/spaolacci/murmur3"
	"gopkg.in/tylerb/is.v1"
)

func newMurmur3() hash.Hash {
	return murmur3.New128()
}

var tempDir string

func TestMain(m *testing.M) {
	flag.Parse()

	// Make a temp area for test files
	tempDir, _ = ioutil.TempDir(os.TempDir(), "sparsehash_test_data")
	ret := m.Run()
	os.RemoveAll(tempDir)
	os.Exit(ret)
}

func addSize(buffer []byte, size int) {
	binary.PutUvarint(buffer, uint64(size))
}

func TestCustom(t *testing.T) {
	const sampleFile = "sample"
	var hash []byte
	var err error

	is := is.New(t)

	sampleSize := 3
	sampleThreshold := 45
	sparse := Hasher{
		SubHasher:     newMurmur3,
		SampleSize:    int64(sampleSize),
		SizeThreshold: int64(sampleThreshold),
	}

	// empty file
	ioutil.WriteFile(sampleFile, []byte{}, 0666)
	hash, err = sparse.SumFile(sampleFile)
	is.NotErr(err)
	is.Equal(hash, make([]byte, 16))

	// small file
	ioutil.WriteFile(sampleFile, []byte("hello"), 0666)
	hash, err = sparse.SumFile(sampleFile)
	addSize(hash, len("hello"))

	hashStr := fmt.Sprintf("%x", hash)
	is.Equal(hashStr, "05d8a7b341bd9b025b1e906a48ae1d19")

	/* boundary tests using the custom sample size */
	size := sampleThreshold

	// test that changing the gaps between sample zones does not affect the hash
	data := bytes.Repeat([]byte{'A'}, size)
	ioutil.WriteFile(sampleFile, data, 0666)
	h1, _ := sparse.SumFile(sampleFile)

	data[sampleSize] = 'B'
	data[size-sampleSize-1] = 'B'
	ioutil.WriteFile(sampleFile, data, 0666)
	h2, _ := sparse.SumFile(sampleFile)
	is.Equal(h1, h2)

	// test that changing a byte on the edge (but within) a sample zone
	// does change the hash
	data = bytes.Repeat([]byte{'A'}, size)
	data[sampleSize-1] = 'B'
	ioutil.WriteFile(sampleFile, data, 0666)
	h3, _ := sparse.SumFile(sampleFile)
	is.NotEqual(h1, h3)

	data = bytes.Repeat([]byte{'A'}, size)
	data[size/2] = 'B'
	ioutil.WriteFile(sampleFile, data, 0666)
	h4, _ := sparse.SumFile(sampleFile)
	is.NotEqual(h1, h4)
	is.NotEqual(h3, h4)

	data = bytes.Repeat([]byte{'A'}, size)
	data[size/2+sampleSize-1] = 'B'
	ioutil.WriteFile(sampleFile, data, 0666)
	h5, _ := sparse.SumFile(sampleFile)
	is.NotEqual(h1, h5)
	is.NotEqual(h3, h5)
	is.NotEqual(h4, h5)

	data = bytes.Repeat([]byte{'A'}, size)
	data[size-sampleSize] = 'B'
	ioutil.WriteFile(sampleFile, data, 0666)
	h6, _ := sparse.SumFile(sampleFile)
	is.NotEqual(h1, h6)
	is.NotEqual(h3, h6)
	is.NotEqual(h4, h6)
	is.NotEqual(h5, h6)

	// test sampleSize < 1
	sparse = Hasher{
		SubHasher:     newMurmur3,
		SampleSize:    0,
		SizeThreshold: int64(size),
	}
	data = bytes.Repeat([]byte{'A'}, size)
	ioutil.WriteFile(sampleFile, data, 0666)
	hash, _ = sparse.SumFile(sampleFile)
	addSize(hash, size)
	hashStr = fmt.Sprintf("%x", hash)
	is.Equal(hashStr, "2d9123b54d37e9b8f94ab37a7eca6f40")

	os.Remove(sampleFile)
}