README
¶
CDB golang implementation
cdb is a fast, reliable, simple package for creating and reading constant databases see docs for more details
Advantages
- Iterator support
- Thread safe for reading
- Lazily key, value reading using io.SectionReader
- Buffered disc write
Example
f, _ := os.Create("test.cdb")
defer f.Close()
handle := cdb.New()
data := []struct {
key, value string
}{
{"key1", "value1"},
{"key2", "value2"},
{"key3", "value3"},
{"key4", "value4"},
{"key5", "value5"},
{"key6", "value6"},
{"key7", "value7"},
}
writer, err := handle.GetWriter(f)
if err != nil {
t.Error(err)
}
for _, c := range data {
writer.Put([]byte(c.key), []byte(c.value))
}
writer.Close()
reader, _ := handle.GetReader(f)
for _, c := range data {
value, err := reader.Get([]byte(c.key))
}
Performance tricks
- File
mmapshows better performance. Example.
Documentation
¶
Overview ¶
Package cdb provides interfaces for a data structure of the Constant Database proposed by Daniel J. Bernstein http://cr.yp.to/cdb.html
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ErrEmptyCDB = errors.New("cdb is empty")
var ErrEntryNotFound = errors.New("cdb entry not found")
EntryDoesNotExists could be returned for Get method is cdb has no such key
var ErrOutOfMemory = errors.New("OutOfMemory. CDB can handle any database up to 4 gigabytes")
ErrOutOfMemory tells that it was an attempt to create a cdb database up to 4 gigabytes
Functions ¶
Types ¶
type CDB ¶
type CDB struct {
Hasher
}
CDB is an associative array: it maps strings (“keys”) to strings (“data”).
func (*CDB) GetWriter ¶
func (cdb *CDB) GetWriter(writer io.WriteSeeker) (Writer, error)
GetWriter returns a new Writer object.
func (*CDB) SetHash ¶
SetHash tells the cdb to use the given hash function for calculations. Given hash will be used only for new instances of Reader, Writer.
h := cdb.New() h.GetWriter(f) ... do some work ( here we use default Hasher ) h.SetHash(fnv.Hash32) h.GetReader(f) - only new instances will be use fnv.Hash32
type Iterator ¶
type Iterator interface {
// Next moves the iterator to the next record. Returns true on success otherwise returns false.
Next() (bool, error)
// Record returns the current record. This method is lazy. It means, a data is read on require.
Record() Record
// HasNext tells if the iterator can be moved to the next record.
HasNext() bool
// Key returns key's []byte slice. It is usually easier to use and
// faster then iterator.Record().Key().
// Because it doesn't requiers allocation for record copy.
Key() ([]byte, error)
// ValueBytes returns values's []byte slice. It is usually easier to use and
// faster then iterator.Record().Key().
// Because it doesn't requiers allocation for record copy.
Value() ([]byte, error)
}
Iterator provides API for iterating through database's records. Do not share object between multiple goroutines.
type Reader ¶
type Reader interface {
// Get returns the first value associated with the given key
Get(key []byte) ([]byte, error)
// Has returns true if the given key exists, otherwise returns false.
Has(key []byte) (bool, error)
// Iterator returns a new Iterator object that points on the first record.
Iterator() (Iterator, error)
// IteratorAt returns a new Iterator object that points on the first record associated with the given key.
IteratorAt(key []byte) (Iterator, error)
// Size returns the size of the dataset
Size() int
}
Reader provides API for retrieving values, iterating through dataset. All methods are thread safe.
Source Files
Directories