github.com/BlockABC/godash@v0.0.0-20191112120524-f4aa3a32c566/database/driver.go (about)

     1  // Copyright (c) 2015-2016 The btcsuite developers
     2  // Copyright (c) 2016 The Dash developers
     3  // Use of this source code is governed by an ISC
     4  // license that can be found in the LICENSE file.
     5  
     6  package database
     7  
     8  import (
     9  	"fmt"
    10  
    11  	"github.com/btcsuite/btclog"
    12  )
    13  
    14  // Driver defines a structure for backend drivers to use when they registered
    15  // themselves as a backend which implements the DB interface.
    16  type Driver struct {
    17  	// DbType is the identifier used to uniquely identify a specific
    18  	// database driver.  There can be only one driver with the same name.
    19  	DbType string
    20  
    21  	// Create is the function that will be invoked with all user-specified
    22  	// arguments to create the database.  This function must return
    23  	// ErrDbExists if the database already exists.
    24  	Create func(args ...interface{}) (DB, error)
    25  
    26  	// Open is the function that will be invoked with all user-specified
    27  	// arguments to open the database.  This function must return
    28  	// ErrDbDoesNotExist if the database has not already been created.
    29  	Open func(args ...interface{}) (DB, error)
    30  
    31  	// UseLogger uses a specified Logger to output package logging info.
    32  	UseLogger func(logger btclog.Logger)
    33  }
    34  
    35  // driverList holds all of the registered database backends.
    36  var drivers = make(map[string]*Driver)
    37  
    38  // RegisterDriver adds a backend database driver to available interfaces.
    39  // ErrDbTypeRegistered will be retruned if the database type for the driver has
    40  // already been registered.
    41  func RegisterDriver(driver Driver) error {
    42  	if _, exists := drivers[driver.DbType]; exists {
    43  		str := fmt.Sprintf("driver %q is already registered",
    44  			driver.DbType)
    45  		return makeError(ErrDbTypeRegistered, str, nil)
    46  	}
    47  
    48  	drivers[driver.DbType] = &driver
    49  	return nil
    50  }
    51  
    52  // SupportedDrivers returns a slice of strings that represent the database
    53  // drivers that have been registered and are therefore supported.
    54  func SupportedDrivers() []string {
    55  	supportedDBs := make([]string, 0, len(drivers))
    56  	for _, drv := range drivers {
    57  		supportedDBs = append(supportedDBs, drv.DbType)
    58  	}
    59  	return supportedDBs
    60  }
    61  
    62  // Create initializes and opens a database for the specified type.  The
    63  // arguments are specific to the database type driver.  See the documentation
    64  // for the database driver for further details.
    65  //
    66  // ErrDbUnknownType will be returned if the the database type is not registered.
    67  func Create(dbType string, args ...interface{}) (DB, error) {
    68  	drv, exists := drivers[dbType]
    69  	if !exists {
    70  		str := fmt.Sprintf("driver %q is not registered", dbType)
    71  		return nil, makeError(ErrDbUnknownType, str, nil)
    72  	}
    73  
    74  	return drv.Create(args...)
    75  }
    76  
    77  // Open opens an existing database for the specified type.  The arguments are
    78  // specific to the database type driver.  See the documentation for the database
    79  // driver for further details.
    80  //
    81  // ErrDbUnknownType will be returned if the the database type is not registered.
    82  func Open(dbType string, args ...interface{}) (DB, error) {
    83  	drv, exists := drivers[dbType]
    84  	if !exists {
    85  		str := fmt.Sprintf("driver %q is not registered", dbType)
    86  		return nil, makeError(ErrDbUnknownType, str, nil)
    87  	}
    88  
    89  	return drv.Open(args...)
    90  }