79 lines
2.2 KiB
Go
79 lines
2.2 KiB
Go
// Copyright (C) 2018 Storj Labs, Inc.
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// See LICENSE for copying information.
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package eestream
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import (
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"bytes"
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"encoding/binary"
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"io"
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"storj.io/storj/pkg/ranger"
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)
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const (
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uint32Size = 4
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)
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func makePadding(dataLen int64, blockSize int) []byte {
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amount := dataLen + uint32Size
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r := amount % int64(blockSize)
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padding := uint32Size
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if r > 0 {
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padding += blockSize - int(r)
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}
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paddingBytes := bytes.Repeat([]byte{0}, padding)
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binary.BigEndian.PutUint32(paddingBytes[padding-uint32Size:], uint32(padding))
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return paddingBytes
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}
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// Pad takes a Ranger and returns another Ranger that is a multiple of
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// blockSize in length. The return value padding is a convenience to report how
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// much padding was added.
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func Pad(data ranger.Ranger, blockSize int) (
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rr ranger.Ranger, padding int) {
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paddingBytes := makePadding(data.Size(), blockSize)
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return ranger.Concat(data, ranger.ByteRanger(paddingBytes)), len(paddingBytes)
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}
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// Unpad takes a previously padded Ranger data source and returns an unpadded
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// ranger, given the amount of padding. This is preferable to UnpadSlow if you
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// can swing it.
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func Unpad(data ranger.Ranger, padding int) (ranger.Ranger, error) {
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return ranger.Subrange(data, 0, data.Size()-int64(padding))
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}
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// UnpadSlow is like Unpad, but does not require the amount of padding.
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// UnpadSlow will have to do extra work to make up for this missing information.
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func UnpadSlow(data ranger.Ranger) (ranger.Ranger, error) {
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var p [uint32Size]byte
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_, err := io.ReadFull(data.Range(data.Size()-uint32Size, uint32Size), p[:])
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if err != nil {
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return nil, Error.Wrap(err)
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}
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return Unpad(data, int(binary.BigEndian.Uint32(p[:])))
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}
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// PadReader is like Pad but works on a basic Reader instead of a Ranger.
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func PadReader(data io.Reader, blockSize int) io.Reader {
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cr := newCountingReader(data)
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return io.MultiReader(cr, ranger.LazyReader(func() io.Reader {
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return bytes.NewReader(makePadding(cr.N, blockSize))
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}))
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}
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type countingReader struct {
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R io.Reader
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N int64
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}
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func newCountingReader(r io.Reader) *countingReader {
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return &countingReader{R: r}
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}
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func (cr *countingReader) Read(p []byte) (n int, err error) {
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n, err = cr.R.Read(p)
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cr.N += int64(n)
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return n, err
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}
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