Solving the challenge 0105

0105/kv_entry.go

@@ -1,20 +1,66 @@
 package db0105
 
 import (
+	"encoding/binary"
 	"errors"
+    "hash/crc32"
 	"io"
 )
 
 type Entry struct {
+    crc32   []byte
 	key     []byte
 	val     []byte
 	deleted bool
 }
 
-func (ent *Entry) Encode() []byte
+func (ent *Entry) Encode() []byte {
+	data := make([]byte, 4+4+4+1+len(ent.key)+len(ent.val))
+	binary.LittleEndian.PutUint32(data[4:8], uint32(len(ent.key)))
+	copy(data[13:], ent.key)
+	if ent.deleted {
+		data[12] = 1
+	} else {
+		binary.LittleEndian.PutUint32(data[8:12], uint32(len(ent.val)))
+		copy(data[13+len(ent.key):], ent.val)
+	}
+    checksum := crc32.ChecksumIEEE(data[4:])
+    binary.LittleEndian.PutUint32(data[0:4], checksum)
+	return data
+}
 
 var ErrBadSum = errors.New("bad checksum")
 
-func (ent *Entry) Decode(r io.Reader) error
+func (ent *Entry) Decode(r io.Reader) error {
+	var header [13]byte
+	if _, err := io.ReadFull(r, header[:]); err != nil {
+		return err
+	}
+	klen := int(binary.LittleEndian.Uint32(header[4:8]))
+	vlen := int(binary.LittleEndian.Uint32(header[8:12]))
+	deleted := header[12]
+
+	data := make([]byte, klen+vlen)
+	if _, err := io.ReadFull(r, data); err != nil {
+		return err
+	}
+
+    checksum := crc32.NewIEEE()
+    checksum.Write(header[4:])
+    checksum.Write(data)
+
+    if checksum.Sum32() != binary.LittleEndian.Uint32(header[0:4]) {
+        return ErrBadSum
+    }
+
+	ent.key = data[:klen]
+	if deleted != 0 {
+		ent.deleted = true
+	} else {
+		ent.deleted = false
+		ent.val = data[klen:]
+	}
+	return nil
+}
 
 // QzBQWVJJOUhU https://trialofcode.org/

0105/log.go

@@ -1,6 +1,7 @@
 package db0105
 
 import (
+    "io"
 	"os"
 )
 
@@ -25,6 +26,16 @@ func (log *Log) Write(ent *Entry) error {
 	return log.fp.Sync() // fsync
 }
 
-func (log *Log) Read(ent *Entry) (eof bool, err error)
+func (log *Log) Read(ent *Entry) (eof bool, err error) {
+	err = ent.Decode(log.fp)
+	if err == io.EOF || err == io.ErrUnexpectedEOF || err == ErrBadSum {
+		return true, nil
+	} else if err != nil {
+		return false, err
+        
+	} else {
+		return false, nil
+	}
+}
 
 // QzBQWVJJOUhU https://trialofcode.org/