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Diffstat (limited to 'vendor/github.com/syndtr/goleveldb/leveldb/table/table.go')
| -rw-r--r-- | vendor/github.com/syndtr/goleveldb/leveldb/table/table.go | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/table/table.go b/vendor/github.com/syndtr/goleveldb/leveldb/table/table.go new file mode 100644 index 0000000..beacdc1 --- /dev/null +++ b/vendor/github.com/syndtr/goleveldb/leveldb/table/table.go @@ -0,0 +1,177 @@ +// 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 table allows read and write sorted key/value. +package table + +import ( + "encoding/binary" +) + +/* +Table: + +Table is consist of one or more data blocks, an optional filter block +a metaindex block, an index block and a table footer. Metaindex block +is a special block used to keep parameters of the table, such as filter +block name and its block handle. Index block is a special block used to +keep record of data blocks offset and length, index block use one as +restart interval. The key used by index block are the last key of preceding +block, shorter separator of adjacent blocks or shorter successor of the +last key of the last block. Filter block is an optional block contains +sequence of filter data generated by a filter generator. + +Table data structure: + + optional + / + +--------------+--------------+--------------+------+-------+-----------------+-------------+--------+ + | data block 1 | ... | data block n | filter block | metaindex block | index block | footer | + +--------------+--------------+--------------+--------------+-----------------+-------------+--------+ + + Each block followed by a 5-bytes trailer contains compression type and checksum. + +Table block trailer: + + +---------------------------+-------------------+ + | compression type (1-byte) | checksum (4-byte) | + +---------------------------+-------------------+ + + The checksum is a CRC-32 computed using Castagnoli's polynomial. Compression + type also included in the checksum. + +Table footer: + + +------------------- 40-bytes -------------------+ + / \ + +------------------------+--------------------+------+-----------------+ + | metaindex block handle / index block handle / ---- | magic (8-bytes) | + +------------------------+--------------------+------+-----------------+ + + The magic are first 64-bit of SHA-1 sum of "http://code.google.com/p/leveldb/". + +NOTE: All fixed-length integer are little-endian. +*/ + +/* +Block: + +Block is consist of one or more key/value entries and a block trailer. +Block entry shares key prefix with its preceding key until a restart +point reached. A block should contains at least one restart point. +First restart point are always zero. + +Block data structure: + + + restart point + restart point (depends on restart interval) + / / + +---------------+---------------+---------------+---------------+---------+ + | block entry 1 | block entry 2 | ... | block entry n | trailer | + +---------------+---------------+---------------+---------------+---------+ + +Key/value entry: + + +---- key len ----+ + / \ + +-------+---------+-----------+---------+--------------------+--------------+----------------+ + | shared (varint) | not shared (varint) | value len (varint) | key (varlen) | value (varlen) | + +-----------------+---------------------+--------------------+--------------+----------------+ + + Block entry shares key prefix with its preceding key: + Conditions: + restart_interval=2 + entry one : key=deck,value=v1 + entry two : key=dock,value=v2 + entry three: key=duck,value=v3 + The entries will be encoded as follow: + + + restart point (offset=0) + restart point (offset=16) + / / + +-----+-----+-----+----------+--------+-----+-----+-----+---------+--------+-----+-----+-----+----------+--------+ + | 0 | 4 | 2 | "deck" | "v1" | 1 | 3 | 2 | "ock" | "v2" | 0 | 4 | 2 | "duck" | "v3" | + +-----+-----+-----+----------+--------+-----+-----+-----+---------+--------+-----+-----+-----+----------+--------+ + \ / \ / \ / + +----------- entry one -----------+ +----------- entry two ----------+ +---------- entry three ----------+ + + The block trailer will contains two restart points: + + +------------+-----------+--------+ + | 0 | 16 | 2 | + +------------+-----------+---+----+ + \ / \ + +-- restart points --+ + restart points length + +Block trailer: + + +-- 4-bytes --+ + / \ + +-----------------+-----------------+-----------------+------------------------------+ + | restart point 1 | .... | restart point n | restart points len (4-bytes) | + +-----------------+-----------------+-----------------+------------------------------+ + + +NOTE: All fixed-length integer are little-endian. +*/ + +/* +Filter block: + +Filter block consist of one or more filter data and a filter block trailer. +The trailer contains filter data offsets, a trailer offset and a 1-byte base Lg. + +Filter block data structure: + + + offset 1 + offset 2 + offset n + trailer offset + / / / / + +---------------+---------------+---------------+---------+ + | filter data 1 | ... | filter data n | trailer | + +---------------+---------------+---------------+---------+ + +Filter block trailer: + + +- 4-bytes -+ + / \ + +---------------+---------------+---------------+-------------------------------+------------------+ + | data 1 offset | .... | data n offset | data-offsets offset (4-bytes) | base Lg (1-byte) | + +-------------- +---------------+---------------+-------------------------------+------------------+ + + +NOTE: All fixed-length integer are little-endian. +*/ + +const ( + blockTrailerLen = 5 + footerLen = 48 + + magic = "\x57\xfb\x80\x8b\x24\x75\x47\xdb" + + // The block type gives the per-block compression format. + // These constants are part of the file format and should not be changed. + blockTypeNoCompression = 0 + blockTypeSnappyCompression = 1 + + // Generate new filter every 2KB of data + filterBaseLg = 11 + filterBase = 1 << filterBaseLg +) + +type blockHandle struct { + offset, length uint64 +} + +func decodeBlockHandle(src []byte) (blockHandle, int) { + offset, n := binary.Uvarint(src) + length, m := binary.Uvarint(src[n:]) + if n == 0 || m == 0 { + return blockHandle{}, 0 + } + return blockHandle{offset, length}, n + m +} + +func encodeBlockHandle(dst []byte, b blockHandle) int { + n := binary.PutUvarint(dst, b.offset) + m := binary.PutUvarint(dst[n:], b.length) + return n + m +} |