141 lines
3.2 KiB
Go
141 lines
3.2 KiB
Go
package litestream
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import (
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"database/sql"
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"encoding/binary"
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"encoding/hex"
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"fmt"
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"io"
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"os"
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"strconv"
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"strings"
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_ "github.com/mattn/go-sqlite3"
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)
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const (
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MetaDirSuffix = "-litestream"
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WALDirName = "wal"
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WALExt = ".wal"
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GenerationNameLen = 16
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)
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// Checksum computes a running SQLite checksum over a byte slice.
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func Checksum(bo binary.ByteOrder, s0, s1 uint32, b []byte) (uint32, uint32) {
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assert(len(b)%8 == 0, "misaligned checksum byte slice")
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// Iterate over 8-byte units and compute checksum.
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for i := 0; i < len(b); i += 8 {
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s0 += bo.Uint32(b[i:]) + s1
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s1 += bo.Uint32(b[i+4:]) + s0
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}
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return s0, s1
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}
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const (
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// WALHeaderSize is the size of the WAL header, in bytes.
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WALHeaderSize = 32
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// WALFrameHeaderSize is the size of the WAL frame header, in bytes.
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WALFrameHeaderSize = 24
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)
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// calcWALSize returns the size of the WAL, in bytes, for a given number of pages.
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func calcWALSize(pageSize int, n int) int64 {
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return int64(WALHeaderSize + ((WALFrameHeaderSize + pageSize) * n))
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}
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// rollback rolls back tx. Ignores already-rolled-back errors.
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func rollback(tx *sql.Tx) error {
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if err := tx.Rollback(); err != nil && !strings.Contains(err.Error(), `transaction has already been committed or rolled back`) {
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return err
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}
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return nil
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}
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// readWALHeader returns the header read from a WAL file.
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func readWALHeader(filename string) ([]byte, error) {
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f, err := os.Open(filename)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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buf := make([]byte, WALHeaderSize)
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n, err := io.ReadFull(f, buf)
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return buf[:n], err
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}
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// readFileAt reads a slice from a file.
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func readFileAt(filename string, offset, n int64) ([]byte, error) {
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f, err := os.Open(filename)
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if err != nil {
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return nil, err
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}
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defer f.Close()
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buf := make([]byte, n)
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if n, err := f.ReadAt(buf, offset); err != nil {
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return buf[:n], err
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} else if n < len(buf) {
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return buf[:n], io.ErrUnexpectedEOF
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}
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return buf, nil
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}
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func ParseWALFilename(name string) (index int, err error) {
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v, err := strconv.ParseInt(strings.TrimSuffix(name, WALExt), 16, 64)
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if err != nil {
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return 0, fmt.Errorf("invalid wal filename: %q", name)
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}
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return int(v), nil
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}
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func FormatWALFilename(index int) string {
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assert(index >= 0, "wal index must be non-negative")
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return fmt.Sprintf("%016d%s", index, WALExt)
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}
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// HexDump returns hexdump output but with duplicate lines removed.
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func HexDump(b []byte) string {
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const prefixN = len("00000000")
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var output []string
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var prev string
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var ellipsis bool
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lines := strings.Split(strings.TrimSpace(hex.Dump(b)), "\n")
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for i, line := range lines {
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// Add line to output if it is not repeating or the last line.
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if i == 0 || i == len(lines)-1 || trimPrefixN(line, prefixN) != trimPrefixN(prev, prefixN) {
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output = append(output, line)
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prev, ellipsis = line, false
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continue
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}
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// Add an ellipsis for the first duplicate line.
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if !ellipsis {
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output = append(output, "...")
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ellipsis = true
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continue
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}
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}
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return strings.Join(output, "\n")
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}
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func trimPrefixN(s string, n int) string {
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if len(s) < n {
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return ""
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}
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return s[n:]
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}
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func assert(condition bool, message string) {
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if !condition {
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panic("assertion failed: " + message)
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}
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}
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