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package bolt
const (
ps_modify = 1
ps_rootonly = 2
ps_first = 4
ps_last = 8
)
type txnid uint64
type Transaction struct {
db *DB
meta *meta
buckets *buckets
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.buckets = &buckets{}
t.buckets.read(t.page(t.meta.buckets))
}
// id returns the transaction id.
func (t *Transaction) id() txnid {
return t.meta.txnid
}
func (t *Transaction) Close() {
t.db.removeTransaction(t)
}
func (t *Transaction) DB() *DB {
return t.db
}
// Bucket retrieves a bucket by name.
func (t *Transaction) Bucket(name string) *Bucket {
b := t.buckets.get(name)
if b == nil {
return nil
}
return &Bucket{
bucket: b,
name: name,
transaction: t,
}
}
// Buckets retrieves a list of all buckets.
func (t *Transaction) Buckets() []*Bucket {
warn("[pending] Transaction.Buckets()") // TODO
return nil
}
// 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)
}
// 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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