algorithm

package
v1.3.11 Latest Latest
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 Go to latest Published: Dec 23, 2024 License: MIT Imports: 2 Imported by: 0

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algorithm

circ2buffer_test.go

TestCreateC2Buffer

MakeC2Buffer(BLOCK_SIZE)
TestWriteBlock

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)
TestWritingUnderCapacityGivesEmptyEvicted

b := MakeC2Buffer(2)
b.Write([]byte{1, 2})

if len(b.Evicted()) != 0 {
	t.Fatal("Evicted should have been empty:", b.Evicted())
}
TestWritingMultipleBytesWhenBufferIsNotFull

b := MakeC2Buffer(3)
b.Write([]byte{1, 2})
b.Write([]byte{3, 4})

ev := b.Evicted()

if len(ev) != 1 || ev[0] != 1 {
	t.Fatal("Evicted should have been [1,]:", ev)
}
TestEvictedRegession1

b := MakeC2Buffer(4)

b.Write([]byte{7, 6})
b.Write([]byte{5, 1, 2})
b.Write([]byte{3, 4})

ev := b.Evicted()
if len(ev) != 2 || ev[0] != 6 || ev[1] != 5 {
	t.Fatalf("Unexpected evicted [6,5]: %v", ev)
}
TestGetBlock

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)

block := b.GetBlock()

if len(block) != BLOCK_SIZE {
	t.Fatal("Wrong block size returned")
}

for i, by := range block {
	if byte(i) != by {
		t.Errorf("byte %v does not match", i)
	}
}
TestWriteTwoBlocksGet

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)
b.Write(incrementBlock2)

if bytes.Compare(b.GetBlock(), incrementBlock2) != 0 {
	t.Errorf("Get block did not return the right value: %s", b.GetBlock())
}
TestWriteSingleByteGetSingleByte

b := MakeC2Buffer(BLOCK_SIZE)
singleByte := []byte{0}
b.Write(singleByte)

if bytes.Compare(b.GetBlock(), singleByte) != 0 {
	t.Errorf("Get block did not return the right value: %s", b.GetBlock())
}
TestWriteTwoBlocksGetEvicted

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)
b.Write(incrementBlock2)

if bytes.Compare(b.Evicted(), incrementBlock) != 0 {
	t.Errorf("Evicted did not return the right value: %s", b.Evicted())
}
TestWriteSingleByteReturnsSingleEvictedByte

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock2)
singleByte := []byte{0}

b.Write(singleByte)
e := b.Evicted()

if len(e) != 1 {
	t.Fatalf("Evicted length is not correct: %s", e)
}

if e[0] != byte(10) {
	t.Errorf("Evicted content is not correct: %s", e)
}
TestTruncatingAfterWriting

b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)

evicted := b.Truncate(2)

if len(evicted) != 2 {
	t.Fatalf("Truncate did not return expected evicted length: %v", evicted)
}

if evicted[0] != 0 || evicted[1] != 1 {
	t.Errorf("Unexpected content in evicted: %v", evicted)
}
TestWritingAfterTruncating

// test that after we truncate some content, the next operations
// on the buffer give us the expected results
b := MakeC2Buffer(BLOCK_SIZE)
b.Write(incrementBlock)
b.Truncate(4)

b.Write([]byte{34, 46})

block := b.GetBlock()

if len(block) != BLOCK_SIZE-2 {
	t.Fatalf(
		"Unexpected block length after truncation: %v (%v)",
		block,
		len(block),
	)
}

if bytes.Compare(block, []byte{4, 5, 6, 7, 8, 9, 34, 46}) != 0 {
	t.Errorf(
		"Unexpected block content after truncation: %v (%v)",
		block,
		len(block))
}

crc16-kermit_test.go

TestKermit

a := Kermit([]byte("abcdefg汉字"))
b := Kermit([]byte("abcdefg汉字"))
if a != b {
	t.Error(a, b)
}

crc16_test.go

TestCrc16

a := Crc16([]byte("abcdefg汉字"))
b := Crc16([]byte("abcdefg汉字"))
if a != b {
	t.Error(Crc16([]byte("abcdefg汉字")))
}
TestCrc16s

a := Crc16s("abcdefg汉字")
b := Crc16([]byte("abcdefg汉字"))

if a != b {
	t.Error(Crc16([]byte("abcdefg汉字")))
}

descartes_test.go

TestDescartes

result := DescartesCombine([][]string{{"A", "B"}, {"1", "2", "3"}, {"a", "b", "c", "d"}})

descartMap := make(map[string]bool)
for _, item := range result {
	if ok, _ := testDescartesStrContains([]string{"A", "B"}, item[0]); !ok {
		t.FailNow()
	}

	if ok, _ := testDescartesStrContains([]string{"1", "2", "3"}, item[1]); !ok {
		t.FailNow()
	}

	if ok, _ := testDescartesStrContains([]string{"a", "b", "c", "d"}, item[2]); !ok {
		t.FailNow()
	}
	descartMap[fmt.Sprint(item)] = true
}

if len(descartMap) != 24 {
	t.FailNow()
}

xor_io_test.go

TestXorIO

data := []byte("1234567890abcdefhijklmn")

w := &bytes.Buffer{}

xw := NewXORWriter(w, testXorKey)
_, err := io.Copy(xw, bytes.NewReader(data))
if err != nil {
	t.Fatal(err)
}

cipherBs := w.Bytes()
xr := NewXORReader(bytes.NewReader(cipherBs), testXorKey)
rdata, err := ioutil.ReadAll(xr)
if err != nil {
	t.Fatal(err)
}

if bytes.Compare(data, rdata) != 0 {
	t.FailNow()
}
cipherXor

writerIndex := uint64(0)

f, err := os.Open(testXorOrigFilePath)
if err != nil {
	t.Fatal(err)
}
defer f.Close()

cf, err := os.OpenFile(testXorCrpytoFilePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
if err != nil {
	t.Fatal(err)
}
defer cf.Close()

w := NewXORWriterWithOffset(cf, testXorKey, &writerIndex)

_, err = io.Copy(w, f)
if err != nil {
	t.Fatal(err)
}
TestDeCipherXor

readerIndex := uint64(0)

cipherXor(t)

func() {
	f, err := os.Open(testXorCrpytoFilePath)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()

	r := NewXORReaderWithOffset(f, testXorKey, &readerIndex)

	rf, err := os.OpenFile(testXorRecoverFilePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		t.Fatal(err)
	}
	defer rf.Close()

	_, err = io.Copy(rf, r)
	if err != nil {
		t.Fatal(err)
	}
}()

bs1, _ := ioutil.ReadFile(testXorOrigFilePath)
bs2, _ := ioutil.ReadFile(testXorRecoverFilePath)

if bytes.Compare(bs1, bs2) != 0 {
	t.FailNow()
}
TestXORReaderAt

cipherXor(t)
func() {

	f, err := os.Open(testXorCrpytoFilePath)
	if err != nil {
		t.Fatal(err)
	}
	defer f.Close()

	rf, err := os.OpenFile(testXorRecoverFilePath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		t.Fatal(err)
	}
	defer rf.Close()

	fileInfo, err := os.Stat(testXorCrpytoFilePath)
	if err != nil {
		return
	}
	size := fileInfo.Size()

	for offset := int64(0); offset < size; {
		rdsize := int64(rand.Intn(int(size) / 2))
		if offset+rdsize > size {
			rdsize = size - offset
		}

		t.Logf("read section offset: %v, size: %v\n", offset, rdsize)
		sr := io.NewSectionReader(NewXORReaderAt(f, testXorKey), offset, rdsize)

		_, err = io.Copy(rf, sr)
		if err != nil {
			t.Fatal(err)
		}

		offset += rdsize
	}
}()

bs1, _ := ioutil.ReadFile(testXorOrigFilePath)
bs2, _ := ioutil.ReadFile(testXorRecoverFilePath)

if bytes.Compare(bs1, bs2) != 0 {
	t.FailNow()
}

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func Crc16 

func Crc16(bs []byte) (crc uint16)

func Crc16s added in v1.1.21 

func Crc16s(str string) (crc uint16)

func DescartesCombine 

func DescartesCombine(dimValue [][]string) [][]string

func Kermit 

func Kermit(byteArray []byte) uint16

* * CRC-CCITT (Kermit) * test data source http://www.lammertbies.nl/comm/info/crc-calculation.html

func NewXORReader added in v1.3.4 

func NewXORReader(src io.Reader, key []byte) io.Reader

func NewXORReaderAt added in v1.3.4 

func NewXORReaderAt(src io.ReaderAt, key []byte) io.ReaderAt

func NewXORReaderWithOffset added in v1.3.4 

func NewXORReaderWithOffset(src io.Reader, key []byte, pIndex *uint64) io.Reader

func NewXORWriter added in v1.3.4 

func NewXORWriter(dst io.Writer, key []byte) io.Writer

func NewXORWriterWithOffset added in v1.3.4 

func NewXORWriterWithOffset(dst io.Writer, key []byte, pIndex *uint64) io.Writer

Types

type C2 added in v1.1.35 

type C2 struct {
	// contains filtered or unexported fields
}

C2 is a circular buffer intended to allow you to write a block of data of up to 'blocksize', and retrieve the data evicted by that operation, without allocating any extra slice storage

This requires that it keep at least blocksize*2 data around. In fact, it doubles that again in order to guarantee that both of these bits of information can always be obtained in a single contiguous block of memory.

Other than the cost of the extra memory (4xblocksize), this means that it requires 2 writes for every byte stored.

func MakeC2Buffer added in v1.1.35 

func MakeC2Buffer(blockSize int) *C2

func (*C2) Empty added in v1.1.35 

func (c *C2) Empty() bool

func (*C2) Evicted added in v1.1.35 

func (c *C2) Evicted() []byte

get the data that was evicted by the last write

func (*C2) GetBlock added in v1.1.35 

func (c *C2) GetBlock() []byte

get the current buffer contents of block

func (*C2) Len added in v1.1.35 

func (c *C2) Len() int

func (*C2) Reset added in v1.1.35 

func (c *C2) Reset()

func (*C2) Truncate added in v1.1.35 

func (c *C2) Truncate(byteCount int) (evicted []byte)

Shortens the content of the circular buffer and returns the content removed

func (*C2) Write added in v1.1.35 

func (c *C2) Write(b []byte)

Write new data

type XORReader added in v1.3.4 

type XORReader struct {
	// contains filtered or unexported fields
}

func (*XORReader) Read added in v1.3.4 

func (r *XORReader) Read(p []byte) (int, error)

type XORReaderAt added in v1.3.4 

type XORReaderAt struct {
	// contains filtered or unexported fields
}

func (*XORReaderAt) ReadAt added in v1.3.4 

func (r *XORReaderAt) ReadAt(p []byte, off int64) (int, error)

type XORWriter added in v1.3.4 

type XORWriter struct {
	// contains filtered or unexported fields
}

func (*XORWriter) Write added in v1.3.4 

func (w *XORWriter) Write(p []byte) (int, error)

Source Files

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