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block.go
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block.go
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package nitro
import (
"encoding/binary"
"errors"
)
var (
errBlockFull = errors.New("Block full")
)
type blockPtr uint64
type dataBlock struct {
buf []byte
offset int
}
func newDataBlock(bs []byte) *dataBlock {
return &dataBlock{
buf: bs[:cap(bs)],
}
}
func (db *dataBlock) Get() []byte {
if db == nil {
return nil
}
if db.offset+2 < blockSize {
l := int(binary.BigEndian.Uint16(db.buf[db.offset : db.offset+2]))
if l == 0 {
db.offset = blockSize
return nil
}
db.offset += 2
offset := db.offset
db.offset += l
return db.buf[offset : offset+l]
}
return nil
}
func (db *dataBlock) GetItems() [][]byte {
var itms [][]byte
for offset := 0; offset+2 < blockSize; {
l := int(binary.BigEndian.Uint16(db.buf[offset : offset+2]))
if l == 0 {
break
}
offset += 2
itms = append(itms, db.buf[offset:offset+l])
offset += l
}
return itms
}
func (db *dataBlock) Write(itm []byte) error {
newLen := db.offset + 2 + len(itm)
if newLen > len(db.buf) {
return errBlockFull
}
binary.BigEndian.PutUint16(db.buf[db.offset:db.offset+2], uint16(len(itm)))
db.offset += 2
copy(db.buf[db.offset:db.offset+len(itm)], itm)
db.offset += len(itm)
return nil
}
func (db *dataBlock) IsEmpty() bool {
return db.offset == 0
}
func (db *dataBlock) Reset() {
db.offset = 0
}
func (db *dataBlock) Bytes() []byte {
offset := db.offset
// Set 2 byte len = 0
if offset+1 < len(db.buf) {
db.buf[offset] = 0
db.buf[offset+1] = 0
offset += 2
}
return db.buf[:offset]
}