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data.go
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data.go
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package data
import (
"encoding/binary"
"fmt"
"os"
"github.com/infinivision/gaeadb/errmsg"
)
func New(dir string) (*data, error) {
var size uint64
d := &data{dir: dir}
for i := 0; ; i++ {
fp, err := openFile(d.fileName(i))
switch {
case err == nil:
size = fp.size
d.size += fp.size
d.fs = append(d.fs, fp)
case os.IsNotExist(err):
if len(d.fs) == 0 {
fp, err := newFile(d.fileName(len(d.fs)))
if err != nil {
return nil, err
}
if err := fp.write(0, []byte(Magic)); err != nil {
fp.close()
return nil, err
}
d.fs = append(d.fs, fp)
fp.size += uint64(len(Magic))
} else {
d.size -= size
}
return d, nil
default:
d.Close()
return nil, err
}
}
}
func (d *data) Close() error {
for _, fp := range d.fs {
fp.close()
}
return nil
}
func (d *data) Flush() error {
for _, fp := range d.fs {
fp.flush()
}
return nil
}
func (d *data) Del(o uint64) error {
return nil
}
func (d *data) Read(o uint64) ([]byte, error) {
for i, j := 0, len(d.fs); i < j; i++ {
if o < d.fs[i].size {
return d.fs[i].read(int64(o))
}
o -= d.fs[i].size
}
return nil, errmsg.NotExist
}
func (d *data) Load(o uint64, size int) ([]byte, error) {
for i, j := 0, len(d.fs); i < j; i++ {
if o < d.fs[i].size {
return d.fs[i].load(int64(o), size)
}
o -= d.fs[i].size
}
return nil, errmsg.NotExist
}
func (d *data) Write(o uint64, data []byte) error {
data = append(header(data), data...)
for i, j := 0, len(d.fs); i < j; i++ {
if o < d.fs[i].size {
return d.fs[i].write(o, data)
}
o -= d.fs[i].size
}
return errmsg.OutOfSpace
}
func (d *data) Alloc(data []byte) (uint64, error) {
m := uint64(len(data) + HeaderSize)
d.Lock()
defer d.Unlock()
for {
size := d.size
n := len(d.fs) - 1
if o, err := d.fs[n].alloc(m); err != nil {
fp, err := newFile(d.fileName(n + 1))
if err != nil {
return 0, err
}
d.size += d.fs[n].size
d.fs = append(d.fs, fp)
} else {
return size + o, nil
}
}
}
func (d *data) fileName(idx int) string {
return fmt.Sprintf("%s%c%v.DAT", d.dir, os.PathSeparator, idx)
}
func header(data []byte) []byte {
buf := make([]byte, HeaderSize)
binary.LittleEndian.PutUint16(buf, uint16(len(data)))
return buf
}
func newFile(path string) (*file, error) {
fp, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0664)
if err != nil {
return nil, err
}
return &file{fp: fp, size: 0}, nil
}
func openFile(path string) (*file, error) {
fp, err := os.OpenFile(path, os.O_RDWR, 0)
if err != nil {
return nil, err
}
st, err := fp.Stat()
if err != nil {
fp.Close()
return nil, err
}
return &file{fp: fp, size: uint64(st.Size())}, nil
}