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ops.go
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ops.go
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package barrel
import (
"bytes"
"fmt"
"hash/crc32"
"time"
"github.com/mr-karan/barreldb/internal/datafile"
)
func (b *Barrel) get(k string) (Record, error) {
// Check for entry in KeyDir.
meta, ok := b.keydir[k]
if !ok {
return Record{}, ErrNoKey
}
var (
// Header object for decoding the binary data into it.
header Header
reader *datafile.DataFile
)
// Set the current file ID as the default.
reader = b.df
// Check if the ID is different from the current ID.
if meta.FileID != b.df.ID() {
reader, ok = b.stale[meta.FileID]
if !ok {
return Record{}, fmt.Errorf("error looking up for the db file for the given id: %d", meta.FileID)
}
}
// Read the file with the given offset.
data, err := reader.Read(meta.RecordPos, meta.RecordSize)
if err != nil {
return Record{}, fmt.Errorf("error reading data from file: %v", err)
}
// Decode the header.
if err := header.decode(data); err != nil {
return Record{}, fmt.Errorf("error decoding header: %v", err)
}
var (
// Get the offset position in record to start reading the value from.
valPos = meta.RecordSize - int(header.ValSize)
// Read the value from the record.
val = data[valPos:]
)
record := Record{
Header: header,
Key: k,
Value: val,
}
return record, nil
}
func (b *Barrel) put(df *datafile.DataFile, k string, val []byte, expiry *time.Time) error {
// Prepare header.
header := Header{
Checksum: crc32.ChecksumIEEE(val),
Timestamp: uint32(time.Now().Unix()),
KeySize: uint32(len(k)),
ValSize: uint32(len(val)),
}
// Check for expiry.
if expiry != nil {
header.Expiry = uint32(expiry.Unix())
} else {
header.Expiry = 0
}
// Prepare the record.
record := Record{
Key: k,
Value: val,
}
// Get the buffer from the pool for writing data.
buf := b.bufPool.Get().(*bytes.Buffer)
defer b.bufPool.Put(buf)
// Resetting the buffer is important since the length of bytes written should be reset on each `set` operation.
defer buf.Reset()
// Encode header.
header.encode(buf)
// Write key/value.
buf.WriteString(k)
buf.Write(val)
// Append to underlying file.
offset, err := df.Write(buf.Bytes())
if err != nil {
return fmt.Errorf("error writing data to file: %v", err)
}
// Add entry to KeyDir.
// We just save the value of key and some metadata for faster lookups.
// The value is only stored in disk.
b.keydir[k] = Meta{
Timestamp: int(record.Header.Timestamp),
RecordSize: len(buf.Bytes()),
RecordPos: offset + len(buf.Bytes()),
FileID: df.ID(),
}
// Ensure filesystem's in memory buffer is flushed to disk.
if b.opts.alwaysFSync {
if err := df.Sync(); err != nil {
return fmt.Errorf("error syncing file to disk: %v", err)
}
}
return nil
}
func (b *Barrel) delete(k string) error {
// Store an empty tombstone value for the given key.
if err := b.put(b.df, k, []byte{}, nil); err != nil {
return err
}
// Delete it from the map as well.
delete(b.keydir, k)
return nil
}