Function ExampleIndex_Load

s2/index_test.go:16–103

()

)

func ExampleIndex_Load() {
	fatalErr := func(err error) {
		if err != nil {
			panic(err)
		}
	}

	// Create a test corpus
	tmp := make([]byte, 5<<20)
	rng := rand.New(rand.NewSource(0xbeefcafe))
	rng.Read(tmp)
	// Make it compressible...
	for i, v := range tmp {
		tmp[i] = '0' + v&3
	}
	// Compress it...
	var buf bytes.Buffer
	// We use smaller blocks just for the example...
	enc := s2.NewWriter(&buf, s2.WriterBlockSize(100<<10))
	err := enc.EncodeBuffer(tmp)
	fatalErr(err)

	// Close and get index...
	idxBytes, err := enc.CloseIndex()
	fatalErr(err)

	// This is our compressed stream...
	compressed := buf.Bytes()

	var once sync.Once
	for wantOffset := int64(0); wantOffset < int64(len(tmp)); wantOffset += 555555 {
		// Let's assume we want to read from uncompressed offset 'i'
		// and we cannot seek in input, but we have the index.
		want := tmp[wantOffset:]

		// Load the index.
		var index s2.Index
		_, err = index.Load(idxBytes)
		fatalErr(err)

		// Find offset in file:
		compressedOffset, uncompressedOffset, err := index.Find(wantOffset)
		fatalErr(err)

		// Offset the input to the compressed offset.
		// Notice how we do not provide any bytes before the offset.
		input := io.Reader(bytes.NewBuffer(compressed[compressedOffset:]))
		if _, ok := input.(io.Seeker); !ok {
			// Notice how the input cannot be seeked...
			once.Do(func() {
				fmt.Println("Input does not support seeking...")
			})
		} else {
			panic("did you implement seeking on bytes.Buffer?")
		}

		// When creating the decoder we must specify that it should not
		// expect a stream identifier at the beginning og the frame.