61 lines
1.4 KiB
Go
61 lines
1.4 KiB
Go
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package filename
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import (
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"encoding/base64"
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"encoding/binary"
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"github.com/klauspost/compress/huff0"
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)
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// Encode will encode the string and return a base64 (url) compatible version of it.
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// Calling Decode with the returned string should always succeed.
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// It is not a requirement that the input string is valid utf-8.
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func Encode(s string) string {
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initCoders()
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bestSize := len(s)
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bestTable := tableUncompressed
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org := []byte(s)
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bestOut := []byte(s)
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// Try all tables and choose the best
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for i, enc := range encTables[:] {
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if len(org) <= 1 || len(org) > maxLength {
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// Use the uncompressed
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break
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}
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if enc == nil {
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continue
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}
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// Try to encode using table.
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err := func() error {
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encTableLocks[i].Lock()
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defer encTableLocks[i].Unlock()
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out, _, err := huff0.Compress1X(org, enc)
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if err != nil {
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return err
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}
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if len(out) < bestSize {
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bestOut = bestOut[:len(out)]
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bestTable = i
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bestSize = len(out)
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copy(bestOut, out)
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}
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return nil
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}()
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// If input is a single byte repeated store as RLE or save uncompressed.
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if err == huff0.ErrUseRLE {
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if len(org) > 2 {
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// Encode as one byte repeated since it will be smaller than uncompressed.
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n := binary.PutUvarint(bestOut, uint64(len(org)))
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bestOut = bestOut[:n+1]
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bestOut[n] = org[0]
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bestSize = n + 1
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bestTable = tableRLE
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}
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break
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}
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}
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return string(encodeURL[bestTable]) + base64.URLEncoding.EncodeToString(bestOut)
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}
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