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Comment:0dev.org/ioutil/SizedReader is now as fast as bufio.Reader if not faster for a buffer of 4096 bytes. Switched pdc to use it for decompression buffering and removed profiling code from the former
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SHA1: 2cec92909fddd24feaed596e3bc146c74d524658
User & Date: spaskalev on 2014-12-24 23:58:32.639
Other Links: manifest | tags
Context
2014-12-25
00:26
Extracted SizedWriter to a sizedWriter struct with a Write() method. check-in: 46da7a6ae9 user: spaskalev tags: trunk
2014-12-24
23:58
0dev.org/ioutil/SizedReader is now as fast as bufio.Reader if not faster for a buffer of 4096 bytes. Switched pdc to use it for decompression buffering and removed profiling code from the former check-in: 2cec92909f user: spaskalev tags: trunk
23:45
Extracted SizedReader to a sizedReader type with a Read() method. Closures seem to be slower in Go 1.4 and there is no real need for SizedReader to be a closure. check-in: b703c38e0b user: spaskalev tags: trunk
Changes
Side-by-Side Diff Ignore Whitespace Patch
Modified src/0dev.org/commands/pdc/main.go from [675059111f] to [dfe0b7b6cf]. 
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package main

import (
	pprof "0dev.org/debug/pprof"
	iou "0dev.org/ioutil"
	predictor "0dev.org/predictor"
	// "bufio"
	"fmt"
	"io"
	"os"
)

func main() {
	var code int
	switch {
	case len(os.Args) == 1:
		code = compress(os.Stdout, os.Stdin)
	case len(os.Args) == 2 && os.Args[1] == "-d":
		code = decompress(os.Stdout, os.Stdin)
	default:
		fmt.Fprintln(os.Stdout, "Usage: pdc [-d]")
	}

	pprof.Stop()

	os.Exit(code)
}

// Compress the data from the given io.Reader and write it to the given io.Writer
// I/O is buffered for better performance
func compress(output io.Writer, input io.Reader) int {
	var (
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// Decompress the data from the given io.Reader and write it to the given io.Writer
// I/O is buffered for better performance
func decompress(output io.Writer, input io.Reader) int {
	var (
		err          error
		buffer       io.Writer = iou.SizedWriter(output, 4096)
		decompressor io.Reader = predictor.Decompressor(iou.SizedReader(input, 4096))
		//decompressor io.Reader = predictor.Decompressor(bufio.NewReader(input))
	)

	_, err = io.Copy(buffer, decompressor)
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error while decompressing.\n", err)
		return 1
	}
︙
Modified src/0dev.org/ioutil/ioutil.go from [c84493a1fe] to [9862ea3396].
︙
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	var (
		count int
		err   error
	)

start:
	// Reply with the buffered data if there is any
	if sr.to-sr.from > 0 {
	if sr.to > 0 {
		count = copy(output, sr.buffer[sr.from:sr.to])

		// Advance the data in the buffer
		sr.from += count

		// Check whether we have reached the end of the buffer
		if sr.to-sr.from == 0 {
		if sr.from == sr.to {
			// Reset the buffer
			sr.from, sr.to = 0, 0

			return count, err
		}

		// Do not propagate an error until the buffer is exhausted
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	// Perform a read into the buffer
	count, err = sr.reader.Read(sr.buffer)

	// Size the buffer down to the read data size
	// and restart if we have successfully read some bytes
	sr.from, sr.to = 0, count
	if sr.to-sr.from > 0 {
	if sr.to > 0 {
		goto start
	}

	// Returning on err/misbehaving noop reader
	return 0, err
}
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