syncthing/vendor/github.com/cznic/lldb/2pc_docs.go

45 lines
1.1 KiB
Go

// Copyright 2014 The lldb Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
/*
Anatomy of a WAL file
WAL file
A sequence of packets
WAL packet, parts in slice notation
[0:4], 4 bytes: N uint32 // network byte order
[4:4+N], N bytes: payload []byte // gb encoded scalars
Packets, including the 4 byte 'size' prefix, MUST BE padded to size == 0 (mod
16). The values of the padding bytes MUST BE zero.
Encoded scalars first item is a packet type number (packet tag). The meaning of
any other item(s) of the payload depends on the packet tag.
Packet definitions
{wpt00Header int, typ int, s string}
typ: Must be zero (ACIDFiler0 file).
s: Any comment string, empty string is okay.
This packet must be present only once - as the first packet of
a WAL file.
{wpt00WriteData int, b []byte, off int64}
Write data (WriteAt(b, off)).
{wpt00Checkpoint int, sz int64}
Checkpoint (Truncate(sz)).
This packet must be present only once - as the last packet of
a WAL file.
*/
package lldb
//TODO optimize bitfiler/wal/2pc data above final size