mirror of https://github.com/hak5/bolt.git
70 lines
1.5 KiB
Go
70 lines
1.5 KiB
Go
package bolt
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import (
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"errors"
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"hash/fnv"
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"unsafe"
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)
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const magic uint32 = 0xED0CDAED
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var (
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// ErrInvalid is returned when a data file is not a Bolt-formatted database.
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ErrInvalid = errors.New("invalid database")
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// ErrVersionMismatch is returned when the data file was created with a
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// different version of Bolt.
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ErrVersionMismatch = errors.New("version mismatch")
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// ErrChecksum is returned when either meta page checksum does not match.
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ErrChecksum = errors.New("checksum error")
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)
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type meta struct {
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magic uint32
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version uint32
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pageSize uint32
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flags uint32
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root bucket
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freelist pgid
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pgid pgid
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txid txid
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checksum uint64
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}
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// validate checks the marker bytes and version of the meta page to ensure it matches this binary.
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func (m *meta) validate() error {
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if m.checksum != 0 && m.checksum != m.sum64() {
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return ErrChecksum
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} else if m.magic != magic {
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return ErrInvalid
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} else if m.version != version {
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return ErrVersionMismatch
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}
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return nil
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}
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// copy copies one meta object to another.
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func (m *meta) copy(dest *meta) {
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*dest = *m
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}
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// write writes the meta onto a page.
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func (m *meta) write(p *page) {
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// Page id is either going to be 0 or 1 which we can determine by the transaction ID.
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p.id = pgid(m.txid % 2)
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p.flags |= metaPageFlag
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// Calculate the checksum.
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m.checksum = m.sum64()
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m.copy(p.meta())
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}
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// generates the checksum for the meta.
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func (m *meta) sum64() uint64 {
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var h = fnv.New64a()
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_, _ = h.Write((*[unsafe.Offsetof(meta{}.checksum)]byte)(unsafe.Pointer(m))[:])
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return h.Sum64()
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}
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