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Comment:Removed goto from predictor's compressor, added more tests that invoke both compress/decompress
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SHA1: 10013ae7898828f7bcb015ad656fd2ee55b28c1c
User & Date: spaskalev on 2014-12-16 16:04:52
Other Links: manifest | tags
Context
2014-12-16
22:56
Reworked the compressor's buffering code, switched to table testing, add step testing for the compressor. Code coverage at 88.3% check-in: 1847f77062 user: spaskalev tags: trunk
16:04
Removed goto from predictor's compressor, added more tests that invoke both compress/decompress check-in: 10013ae789 user: spaskalev tags: trunk
04:03
Fixed issues with both compressor and decompressor, added more tests check-in: b838653282 user: spaskalev tags: trunk
Changes
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Modified src/0dev.org/predictor/predictor.go from [f0ba5a860c] to [0cc123a3c6].

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		)

		// Force a flush if we are called with no data to write
		if len(data) == 0 {
			if len(ctx.input) == 0 {
				return nil
			}
			data = ctx.input

			// We can't have more than 7 bytes in the buffer so this is safe
			blockSize = len(ctx.input)
			data, blockSize, bufferLength = ctx.input, len(ctx.input), 0
			goto write
		}

		// Check if there are pending bytes in the buffer
		if len(data) < blockSize || bufferLength > 0 {
			// Check whether we have enough bytes for a complete block
			if len(data) > 8-bufferLength {
				// Fill the buffer ...
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			} else {
				// Add the insufficient data to the buffer and return
				ctx.input = append(ctx.input, data...)
				return nil
			}
		}

	write:
		var buf []byte = make([]byte, 1, blockSize+1)

		var blocks int = len(data) / blockSize
		if blocks == 0 {
			blocks++
		}

		for block := 0; block < blocks; block++ {
		for block := 0; block < len(data)/blockSize; block++ {
			for i := 0; i < blockSize; i++ {
				var current byte = data[(block*blockSize)+i]
				if ctx.table[ctx.hash] == current {
					// Guess was right - don't output
					buf[0] |= 1 << uint(i)
				} else {
					// Guess was wrong, output char
					ctx.table[ctx.hash] = current
					buf = append(buf, current)
				}
				ctx.hash = (ctx.hash << 4) ^ uint16(current)
			}

			_, err = writer.Write(buf)
			if err != nil {
				return err
			}

			// Reset the flags and buffer for the next iteration
			buf[0] ^= buf[0]
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Modified src/0dev.org/predictor/predictor_test.go from [0cbbd433d4] to [717a9810a3]. 

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package predictor

import (
	diff "0dev.org/diff"
	"bytes"
	"fmt"
	"io/ioutil"
	"testing"
)

// Sample input from RFC1978 - PPP Predictor Compression Protocol
var input = []byte{0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x0a,
	0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x0a,
	0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x0a,
	0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x0a,
	0x41, 0x42, 0x41, 0x42, 0x41, 0x42, 0x41, 0x0a,
	0x42, 0x41, 0x42, 0x41, 0x42, 0x41, 0x42, 0x0a,
	0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x0a}

// Sample output from RFC1978 - PPP Predictor Compression Protocol
var output = []byte{0x60, 0x41, 0x41, 0x41, 0x41, 0x41, 0x0a, 0x60,
	0x41, 0x41, 0x41, 0x41, 0x41, 0x0a, 0x6f, 0x41,
	0x0a, 0x6f, 0x41, 0x0a, 0x41, 0x42, 0x41, 0x42,
	0x41, 0x42, 0x0a, 0x60, 0x42, 0x41, 0x42, 0x41,
	0x42, 0x0a, 0x60, 0x78, 0x78, 0x78, 0x78, 0x78, 0x0a}

func TestCompressor(t *testing.T) {
func TestCompressorSample(t *testing.T) {
	var (
		buf bytes.Buffer
		err error
	)

	out := Compressor(&buf)
	err = out(input)
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	delta := diff.Diff(diff.D{len(result), len(output), func(i, j int) bool { return result[i] == output[j] }})

	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		t.Error("Unexpected compressed output", delta)
	}
}

func TestDecompressor(t *testing.T) {
func TestDecompressorSample(t *testing.T) {
	in := Decompressor(bytes.NewReader(output))
	result, err := ioutil.ReadAll(in)
	if err != nil {
		t.Error("Unexpected error while decompressing", err)
	}

	delta := diff.Diff(diff.D{len(result), len(input),
		func(i, j int) bool { return result[i] == input[j] }})

	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		t.Error("Unexpected decompressed output", delta)
	}
}

func TestPartial(t *testing.T) {
	var (
		input []byte = []byte{0, 1, 2, 3, 4, 5, 6}
		buf   bytes.Buffer
		err   error
func TestEmptyCycle(t *testing.T) {
	var input []byte = []byte{}

	if err := cycle(input); err != nil {
		t.Error(err)
	}
}

func TestPartialCycle(t *testing.T) {
	var input []byte = []byte{0, 1, 2, 3}

	if err := cycle(input); err != nil {
		t.Error(err)
	}
}

func TestBlockCycle(t *testing.T) {
	var input []byte = []byte{0, 1, 2, 3, 4, 5, 6, 7}

	if err := cycle(input); err != nil {
		t.Error(err)
	}
}

func TestBlockPartialCycle(t *testing.T) {
	var input []byte = []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}

	if err := cycle(input); err != nil {
		t.Error(err)
	}
}

func TestDualBlockCycle(t *testing.T) {
	var input []byte = []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15}

	if err := cycle(input); err != nil {
		t.Error(err)
	}
}

func cycle(input []byte) error {
	var (
		buf bytes.Buffer
		err error
	)

	// Create a compressor and write the given data
	out := Compressor(&buf)
	err = out(input)
	compressor := Compressor(&buf)
	err = compressor(input)
	if err != nil {
		t.Error(err)
		return err
	}

	// Flush the compressor
	err = out(nil)
	err = compressor(nil)
	if err != nil {
		t.Error(err)
		return err
	}

	// Attempt to decompress the data
	compressed := buf.Bytes()
	decompressed, err := ioutil.ReadAll(Decompressor(bytes.NewReader(compressed)))
	if err != nil {
		return err

	}

	// Diff the result against the initial input
	delta := diff.Diff(diff.D{len(input), len(decompressed),
		func(i, j int) bool { return input[i] == decompressed[j] }})

	// Return a well-formated error if any differences are found
	if len(delta.Added) > 0 || len(delta.Removed) > 0 {
		t.Error("Unexpected decompressed output", delta)
		return fmt.Errorf("Unexpected decompressed output %v\ninput:  %#x\noutput: %#x\n",
		t.Errorf("%#x", input)
		t.Errorf("%#x", decompressed)
			delta, input, decompressed)
	}
}

	// All is good :)
	return nil
}

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