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49 lines
1.2 KiB
Go
49 lines
1.2 KiB
Go
// Copyright 2014 The lldb Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Anatomy of a WAL file
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WAL file
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A sequence of packets
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WAL packet, parts in slice notation
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[0:4], 4 bytes: N uint32 // network byte order
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[4:4+N], N bytes: payload []byte // gb encoded scalars
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Packets, including the 4 byte 'size' prefix, MUST BE padded to size == 0 (mod
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16). The values of the padding bytes MUST BE zero.
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Encoded scalars first item is a packet type number (packet tag). The meaning of
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any other item(s) of the payload depends on the packet tag.
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Packet definitions
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{wpt00Header int, typ int, s string}
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typ: Must be zero (ACIDFiler0 file).
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s: Any comment string, empty string is okay.
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This packet must be present only once - as the first packet of
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a WAL file.
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{wpt00WriteData int, b []byte, off int64}
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Write data (WriteAt(b, off)).
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{wpt00Checkpoint int, sz int64}
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Checkpoint (Truncate(sz)).
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This packet must be present only once - as the last packet of
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a WAL file.
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{wpt00Empty int}
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The WAL size is of non-zero size due to configured headroom,
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but empty otherwise.
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*/
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package lldb
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//TODO optimize bitfiler/wal/2pc data above final size
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