...

pkg/data/ourdb/factory.go

@@ -0,0 +1,80 @@
+package ourdb
+
+import (
+	"os"
+)
+
+const mbyte = 1000000
+
+// OurDBConfig contains configuration options for creating a new database
+type OurDBConfig struct {
+	RecordNrMax    uint32
+	RecordSizeMax  uint32
+	FileSize       uint32
+	Path           string
+	IncrementalMode bool
+	Reset          bool
+}
+
+// DefaultConfig returns a default configuration
+func DefaultConfig() OurDBConfig {
+	return OurDBConfig{
+		RecordNrMax:    16777216 - 1,    // max size of records
+		RecordSizeMax:  1024 * 4,        // max size in bytes of a record, is 4 KB default
+		FileSize:       500 * (1 << 20), // 500MB
+		IncrementalMode: true,
+	}
+}
+
+// New creates a new database with the given configuration
+func New(config OurDBConfig) (*OurDB, error) {
+	// Determine appropriate keysize based on configuration
+	var keysize uint8 = 4
+
+	if config.RecordNrMax < 65536 {
+		keysize = 2
+	} else if config.RecordNrMax < 16777216 {
+		keysize = 3
+	} else {
+		keysize = 4
+	}
+
+	if float64(config.RecordSizeMax*config.RecordNrMax)/2 > mbyte*10 {
+		keysize = 6 // will use multiple files
+	}
+
+	// Create lookup table
+	l, err := NewLookup(LookupConfig{
+		Size:            config.RecordNrMax,
+		KeySize:         keysize,
+		IncrementalMode: config.IncrementalMode,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Reset database if requested
+	if config.Reset {
+		os.RemoveAll(config.Path)
+	}
+
+	// Create database directory
+	if err := os.MkdirAll(config.Path, 0755); err != nil {
+		return nil, err
+	}
+
+	// Create database instance
+	db := &OurDB{
+		path:            config.Path,
+		lookup:          l,
+		fileSize:        config.FileSize,
+		incrementalMode: config.IncrementalMode,
+	}
+
+	// Load existing data if available
+	if err := db.Load(); err != nil {
+		return nil, err
+	}
+
+	return db, nil
+}