pkg/db: move from db

1 files changed, 248 insertions, 0 deletions

diff --git a/pkg/db/db.go b/pkg/db/db.go
new file mode 100644
index 000000000..0277cb3d1
--- /dev/null
+++ b/pkg/db/db.go
@@ -0,0 +1,248 @@
+// Copyright 2017 syzkaller project authors. All rights reserved.
+// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
+
+// Package db implements a simple key-value database.
+// The database is cached in memory and mirrored on disk.
+// It is used to store corpus in syz-manager and syz-hub.
+// The database strives to minimize number of disk accesses
+// as they can be slow in virtualized environments (GCE).
+package db
+
+import (
+	"bufio"
+	"bytes"
+	"compress/flate"
+	"encoding/binary"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+
+	. "github.com/google/syzkaller/pkg/log"
+)
+
+type DB struct {
+	Records map[string]Record // in-memory cache, must not be modified directly
+
+	filename    string
+	uncompacted int           // number of records in the file
+	pending     *bytes.Buffer // pending writes to the file
+}
+
+type Record struct {
+	Val []byte
+	Seq uint64
+}
+
+func Open(filename string) (*DB, error) {
+	db := &DB{
+		filename: filename,
+	}
+	f, err := os.OpenFile(db.filename, os.O_RDONLY|os.O_CREATE, 0640)
+	if err != nil {
+		return nil, err
+	}
+	db.Records, db.uncompacted = deserializeDB(bufio.NewReader(f))
+	f.Close()
+	if len(db.Records) == 0 || db.uncompacted/10*9 > len(db.Records) {
+		db.compact()
+	}
+	return db, nil
+}
+
+func (db *DB) Save(key string, val []byte, seq uint64) {
+	if seq == seqDeleted {
+		panic("reserved seq")
+	}
+	if rec, ok := db.Records[key]; ok && seq == rec.Seq && bytes.Equal(val, rec.Val) {
+		return
+	}
+	db.Records[key] = Record{val, seq}
+	db.serialize(key, val, seq)
+	db.uncompacted++
+}
+
+func (db *DB) Delete(key string) {
+	if _, ok := db.Records[key]; !ok {
+		return
+	}
+	delete(db.Records, key)
+	db.serialize(key, nil, seqDeleted)
+	db.uncompacted++
+}
+
+func (db *DB) Flush() error {
+	if db.uncompacted/10*9 > len(db.Records) {
+		db.compact()
+		return nil
+	}
+	if db.pending == nil {
+		return nil
+	}
+	f, err := os.OpenFile(db.filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0640)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if _, err := f.Write(db.pending.Bytes()); err != nil {
+		return err
+	}
+	db.pending = nil
+	return nil
+}
+
+func (db *DB) compact() error {
+	buf := new(bytes.Buffer)
+	serializeHeader(buf)
+	for key, rec := range db.Records {
+		serializeRecord(buf, key, rec.Val, rec.Seq)
+	}
+	f, err := os.Create(db.filename + ".tmp")
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if _, err := f.Write(buf.Bytes()); err != nil {
+		return err
+	}
+	f.Close()
+	if err := os.Rename(f.Name(), db.filename); err != nil {
+		return err
+	}
+	db.uncompacted = len(db.Records)
+	db.pending = nil
+	return nil
+}
+
+func (db *DB) serialize(key string, val []byte, seq uint64) {
+	if db.pending == nil {
+		db.pending = new(bytes.Buffer)
+	}
+	serializeRecord(db.pending, key, val, seq)
+}
+
+const (
+	dbMagic    = uint32(0xbaddb)
+	recMagic   = uint32(0xfee1bad)
+	curVersion = uint32(1)
+	seqDeleted = ^uint64(0)
+)
+
+func serializeHeader(w *bytes.Buffer) {
+	binary.Write(w, binary.LittleEndian, dbMagic)
+	binary.Write(w, binary.LittleEndian, curVersion)
+}
+
+func serializeRecord(w *bytes.Buffer, key string, val []byte, seq uint64) {
+	binary.Write(w, binary.LittleEndian, recMagic)
+	binary.Write(w, binary.LittleEndian, uint32(len(key)))
+	w.WriteString(key)
+	binary.Write(w, binary.LittleEndian, seq)
+	if seq == seqDeleted {
+		if len(val) != 0 {
+			panic("deleting record with value")
+		}
+		return
+	}
+	if len(val) == 0 {
+		binary.Write(w, binary.LittleEndian, uint32(len(val)))
+	} else {
+		lenPos := len(w.Bytes())
+		binary.Write(w, binary.LittleEndian, uint32(0))
+		startPos := len(w.Bytes())
+		fw, err := flate.NewWriter(w, flate.BestCompression)
+		if err != nil {
+			panic(err)
+		}
+		if _, err := fw.Write(val); err != nil {
+			panic(err)
+		}
+		fw.Flush()
+		fw.Close()
+		binary.Write(bytes.NewBuffer(w.Bytes()[lenPos:lenPos:lenPos+8]), binary.LittleEndian, uint32(len(w.Bytes())-startPos))
+	}
+}
+
+func deserializeDB(r *bufio.Reader) (records map[string]Record, uncompacted int) {
+	records = make(map[string]Record)
+	ver, err := deserializeHeader(r)
+	if err != nil {
+		Logf(0, "failed to deserialize database header: %v", err)
+		return
+	}
+	_ = ver
+	for {
+		key, val, seq, err := deserializeRecord(r)
+		if err == io.EOF {
+			return
+		}
+		if err != nil {
+			Logf(0, "failed to deserialize database record: %v", err)
+			return
+		}
+		uncompacted++
+		if seq == seqDeleted {
+			delete(records, key)
+		} else {
+			records[key] = Record{val, seq}
+		}
+	}
+}
+
+func deserializeHeader(r *bufio.Reader) (uint32, error) {
+	var magic, ver uint32
+	if err := binary.Read(r, binary.LittleEndian, &magic); err != nil {
+		if err == io.EOF {
+			return curVersion, nil
+		}
+		return 0, err
+	}
+	if magic != dbMagic {
+		return 0, fmt.Errorf("bad db header: 0x%x", magic)
+	}
+	if err := binary.Read(r, binary.LittleEndian, &ver); err != nil {
+		return 0, err
+	}
+	if ver == 0 || ver > curVersion {
+		return 0, fmt.Errorf("bad db version: %v", ver)
+	}
+	return ver, nil
+}
+
+func deserializeRecord(r *bufio.Reader) (key string, val []byte, seq uint64, err error) {
+	var magic uint32
+	if err = binary.Read(r, binary.LittleEndian, &magic); err != nil {
+		return
+	}
+	if magic != recMagic {
+		err = fmt.Errorf("bad record header: 0x%x", magic)
+		return
+	}
+	var keyLen uint32
+	if err = binary.Read(r, binary.LittleEndian, &keyLen); err != nil {
+		return
+	}
+	keyBuf := make([]byte, keyLen)
+	if _, err = io.ReadFull(r, keyBuf); err != nil {
+		return
+	}
+	key = string(keyBuf)
+	if err = binary.Read(r, binary.LittleEndian, &seq); err != nil {
+		return
+	}
+	if seq == seqDeleted {
+		return
+	}
+	var valLen uint32
+	if err = binary.Read(r, binary.LittleEndian, &valLen); err != nil {
+		return
+	}
+	if valLen != 0 {
+		fr := flate.NewReader(&io.LimitedReader{r, int64(valLen)})
+		if val, err = ioutil.ReadAll(fr); err != nil {
+			return
+		}
+		fr.Close()
+	}
+	return
+}