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cursor.go
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cursor.go
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package mdb
/*
#cgo LDFLAGS: -L/usr/local/lib -llmdb
#cgo CFLAGS: -I/usr/local/include
#include <stdlib.h>
#include <stdio.h>
#include <lmdb.h>
*/
import "C"
import (
// "fmt"
"errors"
"unsafe"
"bytes"
"encoding/gob"
)
// MDB_cursor_op
const (
FIRST = iota
FIRST_DUP
GET_BOTH
GET_RANGE
GET_CURRENT
GET_MULTIPLE
LAST
LAST_DUP
NEXT
NEXT_DUP
NEXT_MULTIPLE
NEXT_NODUP
PREV
PREV_DUP
PREV_NODUP
SET
SET_KEY
SET_RANGE
)
func (cursor *Cursor) Close() error {
if cursor._cursor == nil {
return errors.New("Cursor already closed")
}
C.mdb_cursor_close(cursor._cursor)
cursor._cursor = nil
return nil
}
func (cursor *Cursor) Txn() *Txn {
var _txn *C.MDB_txn
_txn = C.mdb_cursor_txn(cursor._cursor)
if _txn != nil {
return &Txn{_txn}
}
return nil
}
func (cursor *Cursor) DBI() DBI {
var _dbi C.MDB_dbi
_dbi = C.mdb_cursor_dbi(cursor._cursor)
return DBI(_dbi)
}
// Retrieves the low-level MDB cursor.
func (cursor *Cursor) MdbCursor() *C.MDB_cursor {
return cursor._cursor
}
func (cursor *Cursor) Get(set_key []byte, op uint) (key, val []byte, err error) {
var ckey C.MDB_val
var cval C.MDB_val
if set_key != nil && (op == SET || op == SET_KEY || op == SET_RANGE) {
ckey.mv_size = C.size_t(len(set_key))
ckey.mv_data = unsafe.Pointer(&set_key[0])
}
ret := C.mdb_cursor_get(cursor._cursor, &ckey, &cval, C.MDB_cursor_op(op))
if ret != SUCCESS {
err = Errno(ret)
key = nil
val = nil
return
}
err = nil
key = C.GoBytes(ckey.mv_data, C.int(ckey.mv_size))
val = C.GoBytes(cval.mv_data, C.int(cval.mv_size))
return
}
func (cursor *Cursor) GetGo(set_key interface {}, op uint, key, val interface{}) error {
var err error
var bset_key []byte
if set_key != nil {
var key_buffer bytes.Buffer
encoder := gob.NewEncoder(&key_buffer)
err = encoder.Encode(set_key)
if err != nil {
return err
}
bset_key = key_buffer.Bytes()
}
bkey, bval, err := cursor.Get(bset_key, op)
if err != nil {
return err
}
buf := bytes.NewReader(bkey)
decoder := gob.NewDecoder(buf)
err = decoder.Decode(key)
if err != nil {
return err
}
buf = bytes.NewReader(bval)
decoder = gob.NewDecoder(buf)
err = decoder.Decode(val)
if err != nil {
return err
}
return nil
}
func (cursor *Cursor) Put(key, val []byte, flags uint) error {
ckey := &C.MDB_val{mv_size: C.size_t(len(key)),
mv_data: unsafe.Pointer(&key[0])}
cval := &C.MDB_val{mv_size: C.size_t(len(val)),
mv_data: unsafe.Pointer(&val[0])}
ret := C.mdb_cursor_put(cursor._cursor, ckey, cval, C.uint(flags))
if ret != SUCCESS {
return Errno(ret)
}
return nil
}
func (cursor *Cursor) PutGo(key, val interface {}, flags uint) error {
var bkey bytes.Buffer
encoder := gob.NewEncoder(&bkey)
err := encoder.Encode(key)
if err != nil {
return err
}
var bval bytes.Buffer
encoder = gob.NewEncoder(&bval)
err = encoder.Encode(val)
if err != nil {
return err
}
return cursor.Put(bkey.Bytes(), bval.Bytes(), flags)
}
func (cursor *Cursor) Del(flags uint) error {
ret := C.mdb_cursor_del(cursor._cursor, C.uint(flags))
if ret != SUCCESS {
return Errno(ret)
}
return nil
}
func (cursor *Cursor) Count() (uint64, error) {
var _size C.size_t
ret := C.mdb_cursor_count(cursor._cursor, &_size)
if ret != SUCCESS {
return 0, Errno(ret)
}
return uint64(_size), nil
}