100 lines
1.8 KiB
Go
100 lines
1.8 KiB
Go
package change
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import (
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"io"
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"git.crumpington.com/public/jldb/lib/errs"
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)
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// ----------------------------------------------------------------------------
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// Change
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// ----------------------------------------------------------------------------
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// The Change type encodes a change (store / delete) to be applied to a
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// pagefile.
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type Change struct {
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CollectionID uint64
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ItemID uint64
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Store bool
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Data []byte
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WritePageIDs []uint64
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ClearPageIDs []uint64
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}
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func (ch Change) writeTo(w io.Writer) error {
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dataSize := int64(len(ch.Data))
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if !ch.Store {
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dataSize = -1
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}
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err := writeBin(w,
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ch.CollectionID,
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ch.ItemID,
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dataSize,
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uint64(len(ch.WritePageIDs)),
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uint64(len(ch.ClearPageIDs)),
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ch.WritePageIDs,
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ch.ClearPageIDs)
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if err != nil {
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return err
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}
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if ch.Store {
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if _, err := w.Write(ch.Data); err != nil {
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return errs.IO.WithErr(err)
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}
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}
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return nil
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}
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func (ch *Change) readFrom(r io.Reader) error {
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var pageCount, clearCount uint64
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var dataSize int64
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err := readBin(r,
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&ch.CollectionID,
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&ch.ItemID,
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&dataSize,
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&pageCount,
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&clearCount)
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if err != nil {
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return err
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}
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if uint64(cap(ch.WritePageIDs)) < pageCount {
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ch.WritePageIDs = make([]uint64, pageCount)
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}
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ch.WritePageIDs = ch.WritePageIDs[:pageCount]
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if uint64(cap(ch.ClearPageIDs)) < clearCount {
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ch.ClearPageIDs = make([]uint64, clearCount)
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}
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ch.ClearPageIDs = ch.ClearPageIDs[:clearCount]
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if err = readBin(r, ch.WritePageIDs); err != nil {
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return err
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}
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if err = readBin(r, ch.ClearPageIDs); err != nil {
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return err
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}
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ch.Store = dataSize != -1
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if ch.Store {
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if int64(cap(ch.Data)) < dataSize {
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ch.Data = make([]byte, dataSize)
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}
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ch.Data = ch.Data[:dataSize]
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if _, err := r.Read(ch.Data); err != nil {
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return errs.IO.WithErr(err)
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}
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} else {
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ch.Data = ch.Data[:0]
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}
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return nil
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}
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