1  // Copyright (c) 2015-2016 The btcsuite developers
 2  // Use of this source code is governed by an ISC
 3  // license that can be found in the LICENSE file.
 4  
 5  package database
 6  
 7  import (
 8  	"fmt"
 9  
10  	"github.com/btcsuite/btclog"
11  )
12  
13  // Driver defines a structure for backend drivers to use when they registered
14  // themselves as a backend which implements the DB interface.
15  type Driver struct {
16  	// DbType is the identifier used to uniquely identify a specific
17  	// database driver.  There can be only one driver with the same name.
18  	DbType string
19  
20  	// Create is the function that will be invoked with all user-specified
21  	// arguments to create the database.  This function must return
22  	// ErrDbExists if the database already exists.
23  	Create func(args ...interface{}) (DB, error)
24  
25  	// Open is the function that will be invoked with all user-specified
26  	// arguments to open the database.  This function must return
27  	// ErrDbDoesNotExist if the database has not already been created.
28  	Open func(args ...interface{}) (DB, error)
29  
30  	// UseLogger uses a specified Logger to output package logging info.
31  	UseLogger func(logger btclog.Logger)
32  }
33  
34  // driverList holds all of the registered database backends.
35  var drivers = make(map[string]*Driver)
36  
37  // RegisterDriver adds a backend database driver to available interfaces.
38  // ErrDbTypeRegistered will be returned if the database type for the driver has
39  // already been registered.
40  func RegisterDriver(driver Driver) error {
41  	if _, exists := drivers[driver.DbType]; exists {
42  		str := fmt.Sprintf("driver %q is already registered",
43  			driver.DbType)
44  		return makeError(ErrDbTypeRegistered, str, nil)
45  	}
46  
47  	drivers[driver.DbType] = &driver
48  	return nil
49  }
50  
51  // SupportedDrivers returns a slice of strings that represent the database
52  // drivers that have been registered and are therefore supported.
53  func SupportedDrivers() []string {
54  	supportedDBs := make([]string, 0, len(drivers))
55  	for _, drv := range drivers {
56  		supportedDBs = append(supportedDBs, drv.DbType)
57  	}
58  	return supportedDBs
59  }
60  
61  // Create initializes and opens a database for the specified type.  The
62  // arguments are specific to the database type driver.  See the documentation
63  // for the database driver for further details.
64  //
65  // ErrDbUnknownType will be returned if the the database type is not registered.
66  func Create(dbType string, args ...interface{}) (DB, error) {
67  	drv, exists := drivers[dbType]
68  	if !exists {
69  		str := fmt.Sprintf("driver %q is not registered", dbType)
70  		return nil, makeError(ErrDbUnknownType, str, nil)
71  	}
72  
73  	return drv.Create(args...)
74  }
75  
76  // Open opens an existing database for the specified type.  The arguments are
77  // specific to the database type driver.  See the documentation for the database
78  // driver for further details.
79  //
80  // ErrDbUnknownType will be returned if the the database type is not registered.
81  func Open(dbType string, args ...interface{}) (DB, error) {
82  	drv, exists := drivers[dbType]
83  	if !exists {
84  		str := fmt.Sprintf("driver %q is not registered", dbType)
85  		return nil, makeError(ErrDbUnknownType, str, nil)
86  	}
87  
88  	return drv.Open(args...)
89  }