70 lines
2.5 KiB
Go
70 lines
2.5 KiB
Go
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// Package headers provides headers for the db binary files
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package headers
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import (
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"encoding/binary"
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"errors"
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)
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type Headers struct {
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HeaderString []byte // Header string
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PageSize uint64 // Page size for chunks
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DBVersion uint16 // Version of the db
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// Reserved for future use.
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WAL bool // Enable write-ahead-logging
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Commit []byte // SHA256 sum of the current DB - Could be switched to ULID/UUID in future.
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}
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// constant HeaderString
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const HeaderString = "zutto/db/"
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//Commit data length - mapped to be 32 bytes for now, to match SHA256SUM
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const CommitDataLength = 32
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// Static lengths of the headers HeaderString length(uint16, 2 bytes)- Pagesize (uint64, 8 bytes) + DBVersion (int16, 2 bytes) + WAL (int8//bool, 1 byte) + Commit (SHA256 32 bytes)
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const StaticHeadersLength = 13 + CommitDataLength
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// Generate generates []byte output from the headers
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func (h *Headers) Generate() *[]byte {
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var HeaderStringLength int = len(h.HeaderString)
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//Output array
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var data []byte = make([]byte, HeaderStringLength+StaticHeadersLength)
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//Headerstring
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binary.LittleEndian.PutUint16(data[0:2], uint16(HeaderStringLength))
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copy(data[2:2+HeaderStringLength], h.HeaderString[:])
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//add the simpler metadata
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binary.LittleEndian.PutUint64(data[2+HeaderStringLength:10+HeaderStringLength], h.PageSize)
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binary.LittleEndian.PutUint16(data[10+HeaderStringLength:12+HeaderStringLength], h.DBVersion)
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//Convert bool-value to byte with a helper function true = byte(1), false = byte(0)
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data[12+HeaderStringLength] = ToSingleByte(h.WAL)
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//commit data, extr
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copy(data[13+HeaderStringLength:13+CommitDataLength+HeaderStringLength], h.Commit[0:CommitDataLength])
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return &data
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}
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// Parse parses the headers
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// Accepts 2 parameters, Input *[]byte's and Padding
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// Returns error in case of errors.
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func (h *Headers) Parse(Input *[]byte, Padding int) error {
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if Padding+len((*Input)) < StaticHeadersLength {
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return errors.New("Input was not correct length")
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}
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var HeaderStringLength int = int(binary.LittleEndian.Uint16((*Input)[Padding : Padding+2]))
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h.HeaderString = (*Input)[2+Padding : Padding+2+HeaderStringLength]
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h.PageSize = binary.LittleEndian.Uint64((*Input)[2+HeaderStringLength+Padding : Padding+10+HeaderStringLength])
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h.DBVersion = binary.LittleEndian.Uint16((*Input)[10+HeaderStringLength+Padding : Padding+12+HeaderStringLength])
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h.WAL = ByteToBool((*Input)[12+HeaderStringLength])
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h.Commit = ((*Input)[13+HeaderStringLength+Padding : Padding+13+CommitDataLength+HeaderStringLength])
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return nil
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}
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