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driver.go
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driver.go
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package database
import (
"fmt"
"io"
nurl "net/url"
"sync"
)
var (
ErrLocked = fmt.Errorf("unable to acquire lock")
)
const NilVersion int = -1
var driversMu sync.RWMutex
var drivers = make(map[string]Driver)
type Driver interface {
Open(url string) (Driver, error)
Close() error
Lock() error
Unlock() error
// when version = NilVersion, "deinitialize"
// migration can be nil, in that case, just store version
Run(version int, migration io.Reader) error
// version > 0: regular version
// version -1: nil version (const NilVersion)
// version < -1: will panic
Version() (int, error)
Drop() error
}
func Open(url string) (Driver, error) {
u, err := nurl.Parse(url)
if err != nil {
return nil, err
}
if u.Scheme == "" {
return nil, fmt.Errorf("database driver: invalid URL scheme")
}
driversMu.RLock()
d, ok := drivers[u.Scheme]
driversMu.RUnlock()
if !ok {
return nil, fmt.Errorf("database driver: unknown driver %v (forgotton import?)", u.Scheme)
}
return d.Open(url)
}
func Register(name string, driver Driver) {
driversMu.Lock()
defer driversMu.Unlock()
if driver == nil {
panic("Register driver is nil")
}
if _, dup := drivers[name]; dup {
panic("Register called twice for driver " + name)
}
drivers[name] = driver
}