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package bolt
var (
InvalidTransactionError = &Error{"txn is invalid", nil}
BucketAlreadyExistsError = &Error{"bucket already exists", nil}
)
const (
ps_modify = 1
ps_rootonly = 2
ps_first = 4
ps_last = 8
)
type txnid uint64
type Transaction struct {
id int
db *DB
meta *meta
sys *sys
pages map[pgid]*page
}
// init initializes the transaction and associates it with a database.
func (t *Transaction) init(db *DB) {
t.db = db
t.meta = db.meta()
t.pages = nil
t.sys = &sys{}
t.sys.read(t.page(t.meta.sys))
}
func (t *Transaction) Close() error {
// TODO: Close buckets.
return nil
}
func (t *Transaction) DB() *DB {
return t.db
}
// Bucket retrieves a bucket by name.
func (t *Transaction) Bucket(name string) *Bucket {
// Lookup bucket from the system page.
b := t.sys.get(name)
if b == nil {
return nil
}
return &Bucket{
bucket: b,
name: name,
transaction: t,
}
}
// Cursor creates a cursor associated with a given bucket.
func (t *Transaction) Cursor(name string) *Cursor {
b := t.Bucket(name)
if b == nil {
return nil
}
return b.Cursor()
}
// Get retrieves the value for a key in a named bucket.
func (t *Transaction) Get(name string, key []byte) []byte {
c := t.Cursor(name)
if c == nil {
return nil
}
return c.Get(key)
}
// Stat returns information about a bucket's internal structure.
func (t *Transaction) Stat(name string) *Stat {
// TODO
return nil
}
// page returns a reference to the page with a given id.
// If page has been written to then a temporary bufferred page is returned.
func (t *Transaction) page(id pgid) *page {
// Check the dirty pages first.
if t.pages != nil {
if p, ok := t.pages[id]; ok {
return p
}
}
// Otherwise return directly from the mmap.
return t.db.page(id)
}
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