71 lines
2.2 KiB
Go
71 lines
2.2 KiB
Go
package bigcache
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import (
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"encoding/binary"
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"reflect"
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"unsafe"
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)
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const (
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timestampSizeInBytes = 8 // Number of bytes used for timestamp
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hashSizeInBytes = 8 // Number of bytes used for hash
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keySizeInBytes = 2 // Number of bytes used for size of entry key
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headersSizeInBytes = timestampSizeInBytes + hashSizeInBytes + keySizeInBytes // Number of bytes used for all headers
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)
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func wrapEntry(timestamp uint64, hash uint64, key string, entry []byte, buffer *[]byte) []byte {
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keyLength := len(key)
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blobLength := len(entry) + headersSizeInBytes + keyLength
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if blobLength > len(*buffer) {
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*buffer = make([]byte, blobLength)
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}
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blob := *buffer
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binary.LittleEndian.PutUint64(blob, timestamp)
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binary.LittleEndian.PutUint64(blob[timestampSizeInBytes:], hash)
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binary.LittleEndian.PutUint16(blob[timestampSizeInBytes+hashSizeInBytes:], uint16(keyLength))
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copy(blob[headersSizeInBytes:], key)
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copy(blob[headersSizeInBytes+keyLength:], entry)
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return blob[:blobLength]
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}
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func readEntry(data []byte) []byte {
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length := binary.LittleEndian.Uint16(data[timestampSizeInBytes+hashSizeInBytes:])
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// copy on read
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dst := make([]byte, len(data)-int(headersSizeInBytes+length))
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copy(dst, data[headersSizeInBytes+length:])
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return dst
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}
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func readTimestampFromEntry(data []byte) uint64 {
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return binary.LittleEndian.Uint64(data)
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}
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func readKeyFromEntry(data []byte) string {
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length := binary.LittleEndian.Uint16(data[timestampSizeInBytes+hashSizeInBytes:])
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// copy on read
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dst := make([]byte, length)
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copy(dst, data[headersSizeInBytes:headersSizeInBytes+length])
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return bytesToString(dst)
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}
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func bytesToString(b []byte) string {
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bytesHeader := (*reflect.SliceHeader)(unsafe.Pointer(&b))
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strHeader := reflect.StringHeader{Data: bytesHeader.Data, Len: bytesHeader.Len}
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return *(*string)(unsafe.Pointer(&strHeader))
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}
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func readHashFromEntry(data []byte) uint64 {
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return binary.LittleEndian.Uint64(data[timestampSizeInBytes:])
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}
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func resetKeyFromEntry(data []byte) {
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binary.LittleEndian.PutUint64(data[timestampSizeInBytes:], 0)
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}
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