must export Operation struct fields for serialization. Fixes for TestWALRecovery tests and skiplist on TTL expiry should mark keys with tombstone value instead of actually deleting key.

Author: Alex Gaetano Padula

README.md

@@ -9,22 +9,30 @@ pkg: github.com/guycipher/k4
 cpu: 11th Gen Intel(R) Core(TM) i7-11700K @ 3.60GHz
 BenchmarkK4_Put
 BenchmarkK4_Put-16    	  131302	      8762 ns/op
+
+RocksDB vs K4
++=+=+=+=+=+=+=+=
+**RocksDB** 1 million writes sequential key-value pairs default settings = 2.9s-3.1s
+**K4**      1 million writes sequential key-value pairs default settings = 1.7s-1.9s
 ```
 
 ### Features
+- High speed writes and reads
+- Durability
 - Variable length binary keys and values
 - Write-Ahead Logging (WAL)
 - Atomic transactions
-- Paired Compaction
+- Paired compaction
 - Memtable implemented as a skip list
 - Disk-based storage
 - Configurable memtable flush threshold
 - Configurable compaction interval (in seconds)
 - Configurable logging
 - Bloom filter for faster lookups
 - Recovery from WAL
+- Granular page locking
 - Thread-safe
-- Memtable TTL support
+- TTL support
 - No dependencies
 
 
@@ -66,11 +74,12 @@ txn.AddOperation(k4.DELETE, key, nil)
 
 err = txn.Commit()
 
-// Once committed you can rollback before the transaction is cleared
+// Once committed you can rollback before the transaction is removed
+// On commit error the transaction is automatically rolled back
 txn.Rollback()
 
-// Clear the transaction
-txn.Clear() // txn now no longer usable nor existent
+// Remove the transaction after commit or rollback
+txn.Remove() // txn now no longer usable nor existent
 
 ```
 
@@ -114,4 +123,67 @@ if err != nil {
 
 ```
 
+### API
+```go
+
+// Open a new K4 instance
+// you can pass extra arguments to configure memtable such as
+// args[0] = max level, must be an int
+// args[1] = probability, must be a float64
+func Open(directory string, memtableFlushThreshold int, compactionInterval int, logging bool, args ...interface{}) (*K4, error)
+
+// Close the K4 instance gracefully
+func (k4 *K4) Close() error
+
+// Put a key-value pair into the db
+func (k4 *K4) Put(key, value []byte, ttl *time.Duration) error
+
+// Get a value from the db
+func (k4 *K4) Get(key []byte) ([]byte, error)
+
+// Get all key-value pairs not equal to the key
+func (k4 *K4) NGet(key []byte) (map[string][]byte, error)
+
+// Get all key-value pairs greater than the key
+func (k4 *K4) GreaterThan(key []byte) (map[string][]byte, error)
+
+// Get all key-value pairs greater than or equal to the key
+func (k4 *K4) GreaterThanEq(key []byte) (map[string][]byte, error)
+
+// Get all key-value pairs less than the key
+func (k4 *K4) LessThan(key []byte) (map[string][]byte, error)
+
+// Get all key-value pairs less than or equal to the key
+func (k4 *K4) LessThanEq(key []byte) (map[string][]byte, error)
+
+// Get all key-value pairs in the range of startKey and endKey
+func (k4 *K4) Range(startKey, endKey []byte) (map[string][]byte, error)
+
+// Get all key-value pairs not in the range of startKey and endKey
+func (k4 *K4) NRange(startKey, endKey []byte) (map[string][]byte, error)
+
+// Delete a key-value pair from the db
+func (k4 *K4) Delete(key []byte) error
+
+// Begin a transaction
+func (k4 *K4) BeginTransaction() *Transaction
+
+// Add a key-value pair to the transaction OPR_CODE can be PUT or DELETE
+func (txn *Transaction) AddOperation(op OPR_CODE, key, value []byte)
+
+// Remove a transaction after it has been committed
+func (txn *Transaction) Remove(k4 *K4)
+
+// Rollback a transaction (only after commit or error)
+func (txn *Transaction) Rollback(k4 *K4) error
+
+// Commit a transaction
+func (txn *Transaction) Commit(k4 *K4) error
+
+// Recover from WAL file
+// WAL file must be placed in the data directory
+func (k4 *K4) RecoverFromWAL() error
+```
+
+