89 lines
2.2 KiB
Go
89 lines
2.2 KiB
Go
package chunk
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import (
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"errors"
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"fmt"
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"io"
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"strconv"
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"strings"
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)
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var (
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ErrRabinMin = errors.New("rabin min must be greater than 16")
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ErrSize = errors.New("chunker size muster greater than 0")
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)
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// FromString returns a Splitter depending on the given string:
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// it supports "default" (""), "size-{size}", "rabin", "rabin-{blocksize}" and
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// "rabin-{min}-{avg}-{max}".
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func FromString(r io.Reader, chunker string) (Splitter, error) {
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switch {
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case chunker == "" || chunker == "default":
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return DefaultSplitter(r), nil
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case strings.HasPrefix(chunker, "size-"):
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sizeStr := strings.Split(chunker, "-")[1]
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size, err := strconv.Atoi(sizeStr)
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if err != nil {
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return nil, err
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} else if size <= 0 {
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return nil, ErrSize
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}
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return NewSizeSplitter(r, int64(size)), nil
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case strings.HasPrefix(chunker, "rabin"):
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return parseRabinString(r, chunker)
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default:
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return nil, fmt.Errorf("unrecognized chunker option: %s", chunker)
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}
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}
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func parseRabinString(r io.Reader, chunker string) (Splitter, error) {
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parts := strings.Split(chunker, "-")
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switch len(parts) {
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case 1:
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return NewRabin(r, uint64(DefaultBlockSize)), nil
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case 2:
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size, err := strconv.Atoi(parts[1])
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if err != nil {
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return nil, err
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}
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return NewRabin(r, uint64(size)), nil
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case 4:
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sub := strings.Split(parts[1], ":")
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if len(sub) > 1 && sub[0] != "min" {
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return nil, errors.New("first label must be min")
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}
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min, err := strconv.Atoi(sub[len(sub)-1])
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if err != nil {
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return nil, err
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}
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if min < 16 {
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return nil, ErrRabinMin
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}
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sub = strings.Split(parts[2], ":")
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if len(sub) > 1 && sub[0] != "avg" {
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log.Error("sub == ", sub)
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return nil, errors.New("second label must be avg")
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}
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avg, err := strconv.Atoi(sub[len(sub)-1])
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if err != nil {
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return nil, err
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}
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sub = strings.Split(parts[3], ":")
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if len(sub) > 1 && sub[0] != "max" {
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return nil, errors.New("final label must be max")
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}
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max, err := strconv.Atoi(sub[len(sub)-1])
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if err != nil {
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return nil, err
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}
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return NewRabinMinMax(r, uint64(min), uint64(avg), uint64(max)), nil
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default:
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return nil, errors.New("incorrect format (expected 'rabin' 'rabin-[avg]' or 'rabin-[min]-[avg]-[max]'")
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}
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}
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