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Comment:Implemented commands/pdc using predictor. Made predictor's Compressor(...) return an io.Writer.
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SHA1: c9f3a59cb6f8359e28b9333fb4f6a661a94c44df
User & Date: spaskalev on 2014-12-19 21:54:39.534
Other Links: manifest | tags
Context
2014-12-20
11:52
[predictor] Removed the buffer from the context struct, allocate the input slice buffer on creation with make. check-in: 723ffeb1fd user: spaskalev tags: trunk
2014-12-19
21:54
Implemented commands/pdc using predictor. Made predictor's Compressor(...) return an io.Writer. check-in: c9f3a59cb6 user: spaskalev tags: trunk
2014-12-16
23:29
Removed err variable from compressor check-in: 0f4bc650d1 user: spaskalev tags: trunk
Changes
Side-by-Side Diff Ignore Whitespace Patch
Added src/0dev.org/commands/pdc/main.go version [3c0c8016e1].
Modified src/0dev.org/commands/plaindiff/main.go from [f98671241a] to [b2d6e402f0]. 
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package main

import (
	diff "0dev.org/diff"
	"bufio"
	"fmt"
	"hash"
	"hash/fnv"
	"io"
	"os"
)

const usage = "Usage: plaindiff <file1> <file2>"
const usage = "Usage: plaindiff <file1> <file2>\n"

func main() {
	var args []string = os.Args
	if len(args) != 3 {
		os.Stderr.WriteString(usage)
		os.Exit(1)
	}
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Modified src/0dev.org/predictor/predictor.go from [2cc1907fb9] to [c65cc5c256].
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type context struct {
	table  [1 << 16]byte
	buffer [1 << 3]byte
	input  []byte
	hash   uint16
}

type compressor func([]byte) error
// Returns a closure over the provided writer that compresses data when called.

func (w compressor) Write(data []byte) (int, error) {
	return len(data), w(data)
}

// Returns an io.Writer implementation that wraps the provided io.Writer
// and compresses data according to the predictor algorithm
//
// It can buffer data as the predictor mandates 8-byte blocks with a header.
// A call with no data will force a flush.
func Compressor(writer io.Writer) func([]byte) error {
func Compressor(writer io.Writer) io.Writer {
	var ctx context
	ctx.input = ctx.buffer[:0]

	// Forward declaration as it is required for recursion
	var write func(data []byte) error
	var write compressor

	write = func(data []byte) error {
		var (
			blockSize    int = 8
			bufferLength int = len(ctx.input)
		)
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		return nil
	}

	return write
}

// A function type alias so that it can have methods attached to it
type reader func([]byte) (int, error)
type decompressor func([]byte) (int, error)

// Required to implement io.Reader
func (r reader) Read(output []byte) (int, error) {
func (r decompressor) Read(output []byte) (int, error) {
	return r(output)
}

// TODO - document
// Returns an io.Reader implementation that wraps the provided io.Reader
// and decompresses data according to the predictor algorithm
func Decompressor(wrapped io.Reader) io.Reader {
	var ctx context
	ctx.input = ctx.buffer[:0]

	return reader(func(output []byte) (int, error) {
	return decompressor(func(output []byte) (int, error) {
		var (
			err       error
			flags     byte
			readCount int
		)

		// Sanity check for space to read into
︙
Modified src/0dev.org/predictor/predictor_test.go from [73a8f932ed] to [dd11cf49de].
︙
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func TestCompressorSample(t *testing.T) {
	var (
		buf bytes.Buffer
		err error
	)

	out := Compressor(&buf)
	err = out(input)
	_, err = out.Write(input)
	if err != nil {
		t.Error(err)
	}

	err = out(nil)
	_, err = out.Write(nil)
	if err != nil {
		t.Error(err)
	}

	result := buf.Bytes()
	delta := diff.Diff(diff.D{len(result), len(output), func(i, j int) bool { return result[i] == output[j] }})
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	var trace []byte = make([]byte, 0)

	for len(data) > 0 {
		if step <= len(data) {

			trace = append(trace, data[:step]...)

			err = compressor(data[:step])
			_, err = compressor.Write(data[:step])
			if err != nil {
				return err
			}
			data = data[step:]
		} else {
			step = len(data)
		}
	}

	// Flush the compressor
	err = compressor(nil)
	_, err = compressor.Write(nil)
	if err != nil {
		return err
	}

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