90 lines
2.1 KiB
Go
90 lines
2.1 KiB
Go
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package filename
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import (
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"encoding/base64"
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"sync"
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"github.com/klauspost/compress/huff0"
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)
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// encodeURL is base64 url encoding values.
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const encodeURL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
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// decodeMap will return x = decodeMap[encodeURL[byte(x)]] - 1 if x >= 0 and x < 64, otherwise -1 is returned.
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var decodeMap [256]byte
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// maxLength is the maximum length that will be attempted to be compressed.
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const maxLength = 256
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var (
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initOnce sync.Once // Used to control init of tables.
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encTables [64]*huff0.Scratch // Encoders.
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encTableLocks [64]sync.Mutex // Temporary locks for encoders since they are stateful.
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decTables [64]*huff0.Decoder // Stateless decoders.
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)
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const (
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tableUncompressed = 0
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tableRLE = 61
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tableCustom = 62
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tableReserved = 63
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)
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// predefined tables as base64 URL encoded string.
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var tablesData = [64]string{
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// Uncompressed
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tableUncompressed: "",
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// ncw home directory
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1: "MRDIEtAAMAzDMAzDSjX_ybu0w97bb-L3b2mR-rUl5LXW3lZII43kIDMzM1NXu3okgQs=",
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// ncw images
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2: "IhDIAEAA______-Pou_4Sf5z-uS-39MVWjullFLKM7EBECs=",
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// ncw Google Drive:
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3: "JxDQAIIBMDMzMwOzbv7nJJCyd_m_9D2llCarnQX33nvvlFKEhUxAAQ==",
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// Hex
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4: "ExDoSTD___-tfXfhJ0hKSkryTxU=",
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// Base64
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5: "JRDIcQf_______8PgIiIiIgINkggARHlkQwSSCCBxHFYINHdfXI=",
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// Special tables:
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// Compressed data has its own table.
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tableCustom: "",
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// Reserved for extension.
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tableReserved: "",
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}
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func initCoders() {
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initOnce.Do(func() {
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// Init base 64 decoder.
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for i, v := range encodeURL {
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decodeMap[v] = byte(i) + 1
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}
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// Initialize encoders and decoders.
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for i, dataString := range tablesData {
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if len(dataString) == 0 {
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continue
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}
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data, err := base64.URLEncoding.DecodeString(dataString)
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if err != nil {
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panic(err)
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}
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s, _, err := huff0.ReadTable(data, nil)
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if err != nil {
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panic(err)
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}
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// We want to save at least len(in) >> 5
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s.WantLogLess = 5
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s.Reuse = huff0.ReusePolicyMust
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encTables[i] = s
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decTables[i] = s.Decoder()
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}
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// Add custom table type.
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var s huff0.Scratch
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s.Reuse = huff0.ReusePolicyNone
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encTables[tableCustom] = &s
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decTables[tableCustom] = nil
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})
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}
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