Pieter Wuille
10 years ago
40 changed files with 602 additions and 282 deletions
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|
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# Contributing |
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|
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We'd love to accept your code patches! However, before we can take them, we |
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have to jump a couple of legal hurdles. |
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|
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## Contributor License Agreements |
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|
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Please fill out either the individual or corporate Contributor License |
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Agreement as appropriate. |
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|
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* If you are an individual writing original source code and you're sure you |
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own the intellectual property, then sign an [individual CLA](https://developers.google.com/open-source/cla/individual). |
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* If you work for a company that wants to allow you to contribute your work, |
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then sign a [corporate CLA](https://developers.google.com/open-source/cla/corporate). |
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|
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Follow either of the two links above to access the appropriate CLA and |
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instructions for how to sign and return it. |
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|
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## Submitting a Patch |
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|
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1. Sign the contributors license agreement above. |
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2. Decide which code you want to submit. A submission should be a set of changes |
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that addresses one issue in the [issue tracker](https://github.com/google/leveldb/issues). |
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Please don't mix more than one logical change per submission, because it makes |
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the history hard to follow. If you want to make a change |
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(e.g. add a sample or feature) that doesn't have a corresponding issue in the |
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issue tracker, please create one. |
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3. **Submitting**: When you are ready to submit, send us a Pull Request. Be |
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sure to include the issue number you fixed and the name you used to sign |
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the CLA. |
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|
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## Writing Code ## |
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|
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If your contribution contains code, please make sure that it follows |
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[the style guide](http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml). |
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Otherwise we will have to ask you to make changes, and that's no fun for anyone. |
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|
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**LevelDB is a fast key-value storage library written at Google that provides an ordered mapping from string keys to string values.** |
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|
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Authors: Sanjay Ghemawat (sanjay@google.com) and Jeff Dean (jeff@google.com) |
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|
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# Features |
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* Keys and values are arbitrary byte arrays. |
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* Data is stored sorted by key. |
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* Callers can provide a custom comparison function to override the sort order. |
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* The basic operations are `Put(key,value)`, `Get(key)`, `Delete(key)`. |
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* Multiple changes can be made in one atomic batch. |
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* Users can create a transient snapshot to get a consistent view of data. |
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* Forward and backward iteration is supported over the data. |
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* Data is automatically compressed using the [Snappy compression library](http://code.google.com/p/snappy). |
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* External activity (file system operations etc.) is relayed through a virtual interface so users can customize the operating system interactions. |
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* [Detailed documentation](http://htmlpreview.github.io/?https://github.com/google/leveldb/blob/master/doc/index.html) about how to use the library is included with the source code. |
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|
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|
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# Limitations |
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* This is not a SQL database. It does not have a relational data model, it does not support SQL queries, and it has no support for indexes. |
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* Only a single process (possibly multi-threaded) can access a particular database at a time. |
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* There is no client-server support builtin to the library. An application that needs such support will have to wrap their own server around the library. |
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|
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# Performance |
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|
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Here is a performance report (with explanations) from the run of the |
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included db_bench program. The results are somewhat noisy, but should |
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be enough to get a ballpark performance estimate. |
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|
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## Setup |
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|
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We use a database with a million entries. Each entry has a 16 byte |
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key, and a 100 byte value. Values used by the benchmark compress to |
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about half their original size. |
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|
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LevelDB: version 1.1 |
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Date: Sun May 1 12:11:26 2011 |
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CPU: 4 x Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz |
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CPUCache: 4096 KB |
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Keys: 16 bytes each |
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Values: 100 bytes each (50 bytes after compression) |
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Entries: 1000000 |
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Raw Size: 110.6 MB (estimated) |
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File Size: 62.9 MB (estimated) |
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|
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## Write performance |
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|
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The "fill" benchmarks create a brand new database, in either |
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sequential, or random order. The "fillsync" benchmark flushes data |
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from the operating system to the disk after every operation; the other |
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write operations leave the data sitting in the operating system buffer |
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cache for a while. The "overwrite" benchmark does random writes that |
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update existing keys in the database. |
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|
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fillseq : 1.765 micros/op; 62.7 MB/s |
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fillsync : 268.409 micros/op; 0.4 MB/s (10000 ops) |
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fillrandom : 2.460 micros/op; 45.0 MB/s |
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overwrite : 2.380 micros/op; 46.5 MB/s |
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|
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Each "op" above corresponds to a write of a single key/value pair. |
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I.e., a random write benchmark goes at approximately 400,000 writes per second. |
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|
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Each "fillsync" operation costs much less (0.3 millisecond) |
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than a disk seek (typically 10 milliseconds). We suspect that this is |
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because the hard disk itself is buffering the update in its memory and |
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responding before the data has been written to the platter. This may |
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or may not be safe based on whether or not the hard disk has enough |
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power to save its memory in the event of a power failure. |
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|
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## Read performance |
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|
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We list the performance of reading sequentially in both the forward |
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and reverse direction, and also the performance of a random lookup. |
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Note that the database created by the benchmark is quite small. |
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Therefore the report characterizes the performance of leveldb when the |
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working set fits in memory. The cost of reading a piece of data that |
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is not present in the operating system buffer cache will be dominated |
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by the one or two disk seeks needed to fetch the data from disk. |
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Write performance will be mostly unaffected by whether or not the |
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working set fits in memory. |
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|
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readrandom : 16.677 micros/op; (approximately 60,000 reads per second) |
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readseq : 0.476 micros/op; 232.3 MB/s |
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readreverse : 0.724 micros/op; 152.9 MB/s |
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|
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LevelDB compacts its underlying storage data in the background to |
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improve read performance. The results listed above were done |
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immediately after a lot of random writes. The results after |
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compactions (which are usually triggered automatically) are better. |
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|
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readrandom : 11.602 micros/op; (approximately 85,000 reads per second) |
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readseq : 0.423 micros/op; 261.8 MB/s |
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readreverse : 0.663 micros/op; 166.9 MB/s |
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|
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Some of the high cost of reads comes from repeated decompression of blocks |
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read from disk. If we supply enough cache to the leveldb so it can hold the |
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uncompressed blocks in memory, the read performance improves again: |
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|
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readrandom : 9.775 micros/op; (approximately 100,000 reads per second before compaction) |
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readrandom : 5.215 micros/op; (approximately 190,000 reads per second after compaction) |
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|
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## Repository contents |
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|
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See doc/index.html for more explanation. See doc/impl.html for a brief overview of the implementation. |
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|
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The public interface is in include/*.h. Callers should not include or |
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rely on the details of any other header files in this package. Those |
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internal APIs may be changed without warning. |
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|
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Guide to header files: |
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|
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* **include/db.h**: Main interface to the DB: Start here |
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* **include/options.h**: Control over the behavior of an entire database, |
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and also control over the behavior of individual reads and writes. |
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|
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* **include/comparator.h**: Abstraction for user-specified comparison function. |
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If you want just bytewise comparison of keys, you can use the default |
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comparator, but clients can write their own comparator implementations if they |
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want custom ordering (e.g. to handle different character encodings, etc.) |
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* **include/iterator.h**: Interface for iterating over data. You can get |
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an iterator from a DB object. |
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* **include/write_batch.h**: Interface for atomically applying multiple |
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updates to a database. |
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* **include/slice.h**: A simple module for maintaining a pointer and a |
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length into some other byte array. |
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* **include/status.h**: Status is returned from many of the public interfaces |
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and is used to report success and various kinds of errors. |
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* **include/env.h**: |
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Abstraction of the OS environment. A posix implementation of this interface is |
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in util/env_posix.cc |
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|
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* **include/table.h, include/table_builder.h**: Lower-level modules that most |
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clients probably won't use directly |
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// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
|
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include <stdio.h> |
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#include "db/dbformat.h" |
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#include "db/filename.h" |
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#include "db/log_reader.h" |
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#include "db/version_edit.h" |
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#include "db/write_batch_internal.h" |
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#include "leveldb/env.h" |
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#include "leveldb/iterator.h" |
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#include "leveldb/options.h" |
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#include "leveldb/status.h" |
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#include "leveldb/table.h" |
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#include "leveldb/write_batch.h" |
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#include "util/logging.h" |
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|
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namespace leveldb { |
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namespace { |
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bool GuessType(const std::string& fname, FileType* type) { |
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size_t pos = fname.rfind('/'); |
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std::string basename; |
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if (pos == std::string::npos) { |
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basename = fname; |
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} else { |
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basename = std::string(fname.data() + pos + 1, fname.size() - pos - 1); |
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} |
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uint64_t ignored; |
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return ParseFileName(basename, &ignored, type); |
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} |
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// Notified when log reader encounters corruption.
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class CorruptionReporter : public log::Reader::Reporter { |
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public: |
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WritableFile* dst_; |
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virtual void Corruption(size_t bytes, const Status& status) { |
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std::string r = "corruption: "; |
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AppendNumberTo(&r, bytes); |
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r += " bytes; "; |
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r += status.ToString(); |
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r.push_back('\n'); |
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dst_->Append(r); |
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} |
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}; |
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|
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// Print contents of a log file. (*func)() is called on every record.
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Status PrintLogContents(Env* env, const std::string& fname, |
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void (*func)(uint64_t, Slice, WritableFile*), |
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WritableFile* dst) { |
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SequentialFile* file; |
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Status s = env->NewSequentialFile(fname, &file); |
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if (!s.ok()) { |
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return s; |
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} |
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CorruptionReporter reporter; |
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reporter.dst_ = dst; |
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log::Reader reader(file, &reporter, true, 0); |
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Slice record; |
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std::string scratch; |
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while (reader.ReadRecord(&record, &scratch)) { |
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(*func)(reader.LastRecordOffset(), record, dst); |
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} |
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delete file; |
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return Status::OK(); |
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} |
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|
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// Called on every item found in a WriteBatch.
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class WriteBatchItemPrinter : public WriteBatch::Handler { |
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public: |
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WritableFile* dst_; |
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virtual void Put(const Slice& key, const Slice& value) { |
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std::string r = " put '"; |
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AppendEscapedStringTo(&r, key); |
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r += "' '"; |
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AppendEscapedStringTo(&r, value); |
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r += "'\n"; |
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dst_->Append(r); |
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} |
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virtual void Delete(const Slice& key) { |
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std::string r = " del '"; |
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AppendEscapedStringTo(&r, key); |
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r += "'\n"; |
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dst_->Append(r); |
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} |
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}; |
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|
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|
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// Called on every log record (each one of which is a WriteBatch)
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// found in a kLogFile.
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static void WriteBatchPrinter(uint64_t pos, Slice record, WritableFile* dst) { |
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std::string r = "--- offset "; |
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AppendNumberTo(&r, pos); |
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r += "; "; |
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if (record.size() < 12) { |
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r += "log record length "; |
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AppendNumberTo(&r, record.size()); |
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r += " is too small\n"; |
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dst->Append(r); |
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return; |
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} |
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WriteBatch batch; |
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WriteBatchInternal::SetContents(&batch, record); |
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r += "sequence "; |
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AppendNumberTo(&r, WriteBatchInternal::Sequence(&batch)); |
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r.push_back('\n'); |
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dst->Append(r); |
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WriteBatchItemPrinter batch_item_printer; |
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batch_item_printer.dst_ = dst; |
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Status s = batch.Iterate(&batch_item_printer); |
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if (!s.ok()) { |
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dst->Append(" error: " + s.ToString() + "\n"); |
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} |
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} |
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|
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Status DumpLog(Env* env, const std::string& fname, WritableFile* dst) { |
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return PrintLogContents(env, fname, WriteBatchPrinter, dst); |
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} |
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|
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// Called on every log record (each one of which is a WriteBatch)
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// found in a kDescriptorFile.
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static void VersionEditPrinter(uint64_t pos, Slice record, WritableFile* dst) { |
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std::string r = "--- offset "; |
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AppendNumberTo(&r, pos); |
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r += "; "; |
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VersionEdit edit; |
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Status s = edit.DecodeFrom(record); |
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if (!s.ok()) { |
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r += s.ToString(); |
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r.push_back('\n'); |
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} else { |
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r += edit.DebugString(); |
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} |
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dst->Append(r); |
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} |
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Status DumpDescriptor(Env* env, const std::string& fname, WritableFile* dst) { |
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return PrintLogContents(env, fname, VersionEditPrinter, dst); |
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} |
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|
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Status DumpTable(Env* env, const std::string& fname, WritableFile* dst) { |
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uint64_t file_size; |
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RandomAccessFile* file = NULL; |
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Table* table = NULL; |
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Status s = env->GetFileSize(fname, &file_size); |
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if (s.ok()) { |
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s = env->NewRandomAccessFile(fname, &file); |
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} |
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if (s.ok()) { |
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// We use the default comparator, which may or may not match the
|
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// comparator used in this database. However this should not cause
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// problems since we only use Table operations that do not require
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// any comparisons. In particular, we do not call Seek or Prev.
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s = Table::Open(Options(), file, file_size, &table); |
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} |
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if (!s.ok()) { |
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delete table; |
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delete file; |
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return s; |
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} |
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ReadOptions ro; |
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ro.fill_cache = false; |
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Iterator* iter = table->NewIterator(ro); |
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std::string r; |
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for (iter->SeekToFirst(); iter->Valid(); iter->Next()) { |
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r.clear(); |
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ParsedInternalKey key; |
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if (!ParseInternalKey(iter->key(), &key)) { |
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r = "badkey '"; |
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AppendEscapedStringTo(&r, iter->key()); |
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r += "' => '"; |
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AppendEscapedStringTo(&r, iter->value()); |
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r += "'\n"; |
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dst->Append(r); |
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} else { |
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r = "'"; |
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AppendEscapedStringTo(&r, key.user_key); |
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r += "' @ "; |
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AppendNumberTo(&r, key.sequence); |
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r += " : "; |
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if (key.type == kTypeDeletion) { |
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r += "del"; |
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} else if (key.type == kTypeValue) { |
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r += "val"; |
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} else { |
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AppendNumberTo(&r, key.type); |
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} |
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r += " => '"; |
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AppendEscapedStringTo(&r, iter->value()); |
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r += "'\n"; |
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dst->Append(r); |
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} |
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} |
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s = iter->status(); |
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if (!s.ok()) { |
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dst->Append("iterator error: " + s.ToString() + "\n"); |
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} |
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|
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delete iter; |
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delete table; |
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delete file; |
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return Status::OK(); |
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} |
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|
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} // namespace
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|
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Status DumpFile(Env* env, const std::string& fname, WritableFile* dst) { |
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FileType ftype; |
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if (!GuessType(fname, &ftype)) { |
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return Status::InvalidArgument(fname + ": unknown file type"); |
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} |
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switch (ftype) { |
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case kLogFile: return DumpLog(env, fname, dst); |
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case kDescriptorFile: return DumpDescriptor(env, fname, dst); |
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case kTableFile: return DumpTable(env, fname, dst); |
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default: |
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break; |
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} |
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return Status::InvalidArgument(fname + ": not a dump-able file type"); |
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} |
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|
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} // namespace leveldb
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@ -0,0 +1,25 @@
@@ -0,0 +1,25 @@
|
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// Copyright (c) 2014 The LevelDB Authors. All rights reserved.
|
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// Use of this source code is governed by a BSD-style license that can be
|
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
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|
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#ifndef STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_ |
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#define STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_ |
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|
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#include <string> |
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#include "leveldb/env.h" |
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#include "leveldb/status.h" |
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|
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namespace leveldb { |
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|
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// Dump the contents of the file named by fname in text format to
|
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// *dst. Makes a sequence of dst->Append() calls; each call is passed
|
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// the newline-terminated text corresponding to a single item found
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// in the file.
|
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//
|
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// Returns a non-OK result if fname does not name a leveldb storage
|
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// file, or if the file cannot be read.
|
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Status DumpFile(Env* env, const std::string& fname, WritableFile* dst); |
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|
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} // namespace leveldb
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|
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#endif // STORAGE_LEVELDB_INCLUDE_DUMPFILE_H_
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@@ -0,0 +1,54 @@
|
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
||||
// Use of this source code is governed by a BSD-style license that can be
|
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
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|
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#include "util/hash.h" |
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#include "util/testharness.h" |
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|
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namespace leveldb { |
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|
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class HASH { }; |
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|
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TEST(HASH, SignedUnsignedIssue) { |
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const unsigned char data1[1] = {0x62}; |
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const unsigned char data2[2] = {0xc3, 0x97}; |
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const unsigned char data3[3] = {0xe2, 0x99, 0xa5}; |
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const unsigned char data4[4] = {0xe1, 0x80, 0xb9, 0x32}; |
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const unsigned char data5[48] = { |
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0x01, 0xc0, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x14, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x04, 0x00, |
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0x00, 0x00, 0x00, 0x14, |
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0x00, 0x00, 0x00, 0x18, |
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0x28, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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0x02, 0x00, 0x00, 0x00, |
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0x00, 0x00, 0x00, 0x00, |
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}; |
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|
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ASSERT_EQ(Hash(0, 0, 0xbc9f1d34), 0xbc9f1d34); |
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ASSERT_EQ( |
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Hash(reinterpret_cast<const char*>(data1), sizeof(data1), 0xbc9f1d34), |
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0xef1345c4); |
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ASSERT_EQ( |
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Hash(reinterpret_cast<const char*>(data2), sizeof(data2), 0xbc9f1d34), |
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0x5b663814); |
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ASSERT_EQ( |
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Hash(reinterpret_cast<const char*>(data3), sizeof(data3), 0xbc9f1d34), |
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0x323c078f); |
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ASSERT_EQ( |
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Hash(reinterpret_cast<const char*>(data4), sizeof(data4), 0xbc9f1d34), |
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0xed21633a); |
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ASSERT_EQ( |
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Hash(reinterpret_cast<const char*>(data5), sizeof(data5), 0x12345678), |
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0xf333dabb); |
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} |
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|
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} // namespace leveldb
|
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|
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int main(int argc, char** argv) { |
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return leveldb::test::RunAllTests(); |
||||
} |
||||
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Reference in new issue