126 lines
4.0 KiB
Go
126 lines
4.0 KiB
Go
package state
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import (
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"bytes"
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"errors"
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"fmt"
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)
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// indexerSingle implements both memdb.Indexer and memdb.SingleIndexer. It may
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// be used in a memdb.IndexSchema to specify functions that generate the index
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// value for memdb.Txn operations.
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type indexerSingle struct {
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// readIndex is used by memdb for Txn.Get, Txn.First, and other operations
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// that read data.
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readIndex
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// writeIndex is used by memdb for Txn.Insert, Txn.Delete, for operations
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// that write data to the index.
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writeIndex
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}
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// indexerMulti implements both memdb.Indexer and memdb.MultiIndexer. It may
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// be used in a memdb.IndexSchema to specify functions that generate the index
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// value for memdb.Txn operations.
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type indexerMulti struct {
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// readIndex is used by memdb for Txn.Get, Txn.First, and other operations
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// that read data.
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readIndex
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// writeIndexMulti is used by memdb for Txn.Insert, Txn.Delete, for operations
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// that write data to the index.
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writeIndexMulti
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}
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// indexerSingleWithPrefix is a indexerSingle which also supports prefix queries.
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type indexerSingleWithPrefix struct {
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readIndex
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writeIndex
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prefixIndex
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}
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// readIndex implements memdb.Indexer. It exists so that a function can be used
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// to provide the interface.
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//
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// Unlike memdb.Indexer, a readIndex function accepts only a single argument. To
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// generate an index from multiple values, use a struct type with multiple fields.
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type readIndex func(arg interface{}) ([]byte, error)
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func (f readIndex) FromArgs(args ...interface{}) ([]byte, error) {
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if len(args) != 1 {
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return nil, fmt.Errorf("index supports only a single arg")
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}
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return f(args[0])
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}
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var errMissingValueForIndex = fmt.Errorf("object is missing a value for this index")
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// writeIndex implements memdb.SingleIndexer. It exists so that a function
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// can be used to provide this interface.
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//
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// Instead of a bool return value, writeIndex expects errMissingValueForIndex to
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// indicate that an index could not be build for the object. It will translate
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// this error into a false value to satisfy the memdb.SingleIndexer interface.
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type writeIndex func(raw interface{}) ([]byte, error)
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func (f writeIndex) FromObject(raw interface{}) (bool, []byte, error) {
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v, err := f(raw)
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if errors.Is(err, errMissingValueForIndex) {
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return false, nil, nil
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}
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return err == nil, v, err
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}
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// writeIndexMulti implements memdb.MultiIndexer. It exists so that a function
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// can be used to provide this interface.
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//
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// Instead of a bool return value, writeIndexMulti expects errMissingValueForIndex to
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// indicate that an index could not be build for the object. It will translate
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// this error into a false value to satisfy the memdb.MultiIndexer interface.
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type writeIndexMulti func(raw interface{}) ([][]byte, error)
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func (f writeIndexMulti) FromObject(raw interface{}) (bool, [][]byte, error) {
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v, err := f(raw)
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if errors.Is(err, errMissingValueForIndex) {
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return false, nil, nil
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}
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return err == nil, v, err
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}
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// prefixIndex implements memdb.PrefixIndexer. It exists so that a function
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// can be used to provide this interface.
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type prefixIndex func(args interface{}) ([]byte, error)
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func (f prefixIndex) PrefixFromArgs(args ...interface{}) ([]byte, error) {
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if len(args) != 1 {
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return nil, fmt.Errorf("index supports only a single arg")
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}
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return f(args[0])
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}
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const null = "\x00"
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// indexBuilder is a buffer used to construct memdb index values.
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type indexBuilder bytes.Buffer
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func newIndexBuilder(cap int) *indexBuilder {
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buff := make([]byte, 0, cap)
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b := bytes.NewBuffer(buff)
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return (*indexBuilder)(b)
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}
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// String appends the string and a null terminator to the buffer.
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func (b *indexBuilder) String(v string) {
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(*bytes.Buffer)(b).WriteString(v)
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(*bytes.Buffer)(b).WriteString(null)
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}
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// Raw appends the bytes without a null terminator to the buffer. Raw should
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// only be used when v has a fixed length, or when building the last segment of
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// a prefix index.
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func (b *indexBuilder) Raw(v []byte) {
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(*bytes.Buffer)(b).Write(v)
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}
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func (b *indexBuilder) Bytes() []byte {
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return (*bytes.Buffer)(b).Bytes()
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}
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