122 lines
3.1 KiB
Go
122 lines
3.1 KiB
Go
package litestream
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import (
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"encoding/binary"
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"io"
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"os"
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)
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// WALFile represents a write-ahead log file.
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type WALFile struct {
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path string
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hdr WALHeader
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f *os.File
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}
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// NewWALFile returns a new instance of WALFile.
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func NewWALFile(path string) *WALFile {
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return &WALFile{path: path}
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}
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func (s *WALFile) Open() error {
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panic("TODO")
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}
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func (s *WALFile) Close() error {
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panic("TODO")
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}
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func (s *WALFile) WriteHeader(hdr WALHeader) error {
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s.hdr = hdr
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panic("TODO")
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}
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func (s *WALFile) WriteFrame(hdr WALFrameHeader, buf []byte) error {
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panic("TODO")
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}
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// WALHeaderSize is the size of the WAL header, in bytes.
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const WALHeaderSize = 32
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type WALHeader struct {
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Magic uint32
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FileFormatVersion uint32
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PageSize uint32
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CheckpointSeqNo uint32
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Salt uint64
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Checksum uint64
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}
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// MarshalTo encodes the header to b.
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// Returns io.ErrShortWrite if len(b) is less than WALHeaderSize.
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func (hdr *WALHeader) MarshalTo(b []byte) error {
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if len(b) < WALHeaderSize {
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return io.ErrShortWrite
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}
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binary.BigEndian.PutUint32(b[0:], hdr.Magic)
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binary.BigEndian.PutUint32(b[4:], hdr.FileFormatVersion)
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binary.BigEndian.PutUint32(b[8:], hdr.PageSize)
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binary.BigEndian.PutUint32(b[12:], hdr.CheckpointSeqNo)
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binary.BigEndian.PutUint64(b[16:], hdr.Salt)
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binary.BigEndian.PutUint64(b[24:], hdr.Checksum)
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return nil
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}
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// Unmarshal decodes the header from b.
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// Returns io.ErrUnexpectedEOF if len(b) is less than WALHeaderSize.
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func (hdr *WALHeader) Unmarshal(b []byte) error {
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if len(b) < WALHeaderSize {
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return io.ErrUnexpectedEOF
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}
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hdr.Magic = binary.BigEndian.Uint32(b[0:])
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hdr.FileFormatVersion = binary.BigEndian.Uint32(b[4:])
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hdr.PageSize = binary.BigEndian.Uint32(b[8:])
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hdr.CheckpointSeqNo = binary.BigEndian.Uint32(b[12:])
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hdr.Salt = binary.BigEndian.Uint64(b[16:])
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hdr.Checksum = binary.BigEndian.Uint64(b[24:])
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return nil
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}
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// WALFrameHeaderSize is the size of the WAL frame header, in bytes.
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const WALFrameHeaderSize = 24
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// WALFrameHeader represents a SQLite WAL frame header.
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type WALFrameHeader struct {
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Pgno uint32
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PageN uint32 // only set for commit records
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Salt uint64
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Checksum uint64
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}
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// IsCommit returns true if the frame represents a commit header.
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func (hdr *WALFrameHeader) IsCommit() bool {
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return hdr.PageN != 0
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}
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// MarshalTo encodes the frame header to b.
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// Returns io.ErrShortWrite if len(b) is less than WALHeaderSize.
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func (hdr *WALFrameHeader) MarshalTo(b []byte) error {
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if len(b) < WALFrameHeaderSize {
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return io.ErrShortWrite
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}
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binary.BigEndian.PutUint32(b[0:], hdr.Pgno)
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binary.BigEndian.PutUint32(b[4:], hdr.PageN)
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binary.BigEndian.PutUint64(b[8:], hdr.Salt)
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binary.BigEndian.PutUint64(b[16:], hdr.Checksum)
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return nil
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}
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// Unmarshal decodes the frame header from b.
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// Returns io.ErrUnexpectedEOF if len(b) is less than WALHeaderSize.
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func (hdr *WALFrameHeader) Unmarshal(b []byte) error {
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if len(b) < WALFrameHeaderSize {
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return io.ErrUnexpectedEOF
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}
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hdr.Pgno = binary.BigEndian.Uint32(b[0:])
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hdr.PageN = binary.BigEndian.Uint32(b[4:])
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hdr.Salt = binary.BigEndian.Uint64(b[8:])
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hdr.Checksum = binary.BigEndian.Uint64(b[16:])
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return nil
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}
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