55 lines
1.2 KiB
Go
55 lines
1.2 KiB
Go
package chunk
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import (
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"hash/fnv"
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"io"
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"github.com/whyrusleeping/chunker"
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)
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// IpfsRabinPoly is the irreducible polynomial of degree 53 used by for Rabin.
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var IpfsRabinPoly = chunker.Pol(17437180132763653)
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// Rabin implements the Splitter interface and splits content with Rabin
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// fingerprints.
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type Rabin struct {
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r *chunker.Chunker
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reader io.Reader
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}
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// NewRabin creates a new Rabin splitter with the given
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// average block size.
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func NewRabin(r io.Reader, avgBlkSize uint64) *Rabin {
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min := avgBlkSize / 3
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max := avgBlkSize + (avgBlkSize / 2)
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return NewRabinMinMax(r, min, avgBlkSize, max)
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}
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// NewRabinMinMax returns a new Rabin splitter which uses
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// the given min, average and max block sizes.
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func NewRabinMinMax(r io.Reader, min, avg, max uint64) *Rabin {
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h := fnv.New32a()
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ch := chunker.New(r, IpfsRabinPoly, h, avg, min, max)
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return &Rabin{
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r: ch,
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reader: r,
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}
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}
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// NextBytes reads the next bytes from the reader and returns a slice.
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func (r *Rabin) NextBytes() ([]byte, error) {
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ch, err := r.r.Next()
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if err != nil {
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return nil, err
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}
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return ch.Data, nil
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}
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// Reader returns the io.Reader associated to this Splitter.
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func (r *Rabin) Reader() io.Reader {
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return r.reader
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}
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