add other session providers (#5963)

vendor/github.com/syndtr/goleveldb/leveldb/key.go

@@ -0,0 +1,143 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// ErrInternalKeyCorrupted records internal key corruption.
+type ErrInternalKeyCorrupted struct {
+	Ikey   []byte
+	Reason string
+}
+
+func (e *ErrInternalKeyCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: internal key %q corrupted: %s", e.Ikey, e.Reason)
+}
+
+func newErrInternalKeyCorrupted(ikey []byte, reason string) error {
+	return errors.NewErrCorrupted(storage.FileDesc{}, &ErrInternalKeyCorrupted{append([]byte{}, ikey...), reason})
+}
+
+type keyType uint
+
+func (kt keyType) String() string {
+	switch kt {
+	case keyTypeDel:
+		return "d"
+	case keyTypeVal:
+		return "v"
+	}
+	return fmt.Sprintf("<invalid:%#x>", uint(kt))
+}
+
+// Value types encoded as the last component of internal keys.
+// Don't modify; this value are saved to disk.
+const (
+	keyTypeDel = keyType(0)
+	keyTypeVal = keyType(1)
+)
+
+// keyTypeSeek defines the keyType that should be passed when constructing an
+// internal key for seeking to a particular sequence number (since we
+// sort sequence numbers in decreasing order and the value type is
+// embedded as the low 8 bits in the sequence number in internal keys,
+// we need to use the highest-numbered ValueType, not the lowest).
+const keyTypeSeek = keyTypeVal
+
+const (
+	// Maximum value possible for sequence number; the 8-bits are
+	// used by value type, so its can packed together in single
+	// 64-bit integer.
+	keyMaxSeq = (uint64(1) << 56) - 1
+	// Maximum value possible for packed sequence number and type.
+	keyMaxNum = (keyMaxSeq << 8) | uint64(keyTypeSeek)
+)
+
+// Maximum number encoded in bytes.
+var keyMaxNumBytes = make([]byte, 8)
+
+func init() {
+	binary.LittleEndian.PutUint64(keyMaxNumBytes, keyMaxNum)
+}
+
+type internalKey []byte
+
+func makeInternalKey(dst, ukey []byte, seq uint64, kt keyType) internalKey {
+	if seq > keyMaxSeq {
+		panic("leveldb: invalid sequence number")
+	} else if kt > keyTypeVal {
+		panic("leveldb: invalid type")
+	}
+
+	dst = ensureBuffer(dst, len(ukey)+8)
+	copy(dst, ukey)
+	binary.LittleEndian.PutUint64(dst[len(ukey):], (seq<<8)|uint64(kt))
+	return internalKey(dst)
+}
+
+func parseInternalKey(ik []byte) (ukey []byte, seq uint64, kt keyType, err error) {
+	if len(ik) < 8 {
+		return nil, 0, 0, newErrInternalKeyCorrupted(ik, "invalid length")
+	}
+	num := binary.LittleEndian.Uint64(ik[len(ik)-8:])
+	seq, kt = uint64(num>>8), keyType(num&0xff)
+	if kt > keyTypeVal {
+		return nil, 0, 0, newErrInternalKeyCorrupted(ik, "invalid type")
+	}
+	ukey = ik[:len(ik)-8]
+	return
+}
+
+func validInternalKey(ik []byte) bool {
+	_, _, _, err := parseInternalKey(ik)
+	return err == nil
+}
+
+func (ik internalKey) assert() {
+	if ik == nil {
+		panic("leveldb: nil internalKey")
+	}
+	if len(ik) < 8 {
+		panic(fmt.Sprintf("leveldb: internal key %q, len=%d: invalid length", []byte(ik), len(ik)))
+	}
+}
+
+func (ik internalKey) ukey() []byte {
+	ik.assert()
+	return ik[:len(ik)-8]
+}
+
+func (ik internalKey) num() uint64 {
+	ik.assert()
+	return binary.LittleEndian.Uint64(ik[len(ik)-8:])
+}
+
+func (ik internalKey) parseNum() (seq uint64, kt keyType) {
+	num := ik.num()
+	seq, kt = uint64(num>>8), keyType(num&0xff)
+	if kt > keyTypeVal {
+		panic(fmt.Sprintf("leveldb: internal key %q, len=%d: invalid type %#x", []byte(ik), len(ik), kt))
+	}
+	return
+}
+
+func (ik internalKey) String() string {
+	if ik == nil {
+		return "<nil>"
+	}
+
+	if ukey, seq, kt, err := parseInternalKey(ik); err == nil {
+		return fmt.Sprintf("%s,%s%d", shorten(string(ukey)), kt, seq)
+	}
+	return fmt.Sprintf("<invalid:%#x>", []byte(ik))
+}