1// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file. See the AUTHORS file for names of contributors.
4//
5// This file contains the specification, but not the implementations,
6// of the types/operations/etc. that should be defined by a platform
7// specific port_<platform>.h file.  Use this file as a reference for
8// how to port this package to a new platform.
9
10#ifndef STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
11#define STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
12
13#include "port/thread_annotations.h"
14
15namespace leveldb {
16namespace port {
17
18// TODO(jorlow): Many of these belong more in the environment class rather than
19//               here. We should try moving them and see if it affects perf.
20
21// ------------------ Threading -------------------
22
23// A Mutex represents an exclusive lock.
24class LOCKABLE Mutex {
25 public:
26  Mutex();
27  ~Mutex();
28
29  // Lock the mutex.  Waits until other lockers have exited.
30  // Will deadlock if the mutex is already locked by this thread.
31  void Lock() EXCLUSIVE_LOCK_FUNCTION();
32
33  // Unlock the mutex.
34  // REQUIRES: This mutex was locked by this thread.
35  void Unlock() UNLOCK_FUNCTION();
36
37  // Optionally crash if this thread does not hold this mutex.
38  // The implementation must be fast, especially if NDEBUG is
39  // defined.  The implementation is allowed to skip all checks.
40  void AssertHeld() ASSERT_EXCLUSIVE_LOCK();
41};
42
43class CondVar {
44 public:
45  explicit CondVar(Mutex* mu);
46  ~CondVar();
47
48  // Atomically release *mu and block on this condition variable until
49  // either a call to SignalAll(), or a call to Signal() that picks
50  // this thread to wakeup.
51  // REQUIRES: this thread holds *mu
52  void Wait();
53
54  // If there are some threads waiting, wake up at least one of them.
55  void Signal();
56
57  // Wake up all waiting threads.
58  void SignallAll();
59};
60
61// ------------------ Compression -------------------
62
63// Store the snappy compression of "input[0,input_length-1]" in *output.
64// Returns false if snappy is not supported by this port.
65bool Snappy_Compress(const char* input, size_t input_length,
66                     std::string* output);
67
68// If input[0,input_length-1] looks like a valid snappy compressed
69// buffer, store the size of the uncompressed data in *result and
70// return true.  Else return false.
71bool Snappy_GetUncompressedLength(const char* input, size_t length,
72                                  size_t* result);
73
74// Attempt to snappy uncompress input[0,input_length-1] into *output.
75// Returns true if successful, false if the input is invalid lightweight
76// compressed data.
77//
78// REQUIRES: at least the first "n" bytes of output[] must be writable
79// where "n" is the result of a successful call to
80// Snappy_GetUncompressedLength.
81bool Snappy_Uncompress(const char* input_data, size_t input_length,
82                       char* output);
83
84// ------------------ Miscellaneous -------------------
85
86// If heap profiling is not supported, returns false.
87// Else repeatedly calls (*func)(arg, data, n) and then returns true.
88// The concatenation of all "data[0,n-1]" fragments is the heap profile.
89bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg);
90
91// Extend the CRC to include the first n bytes of buf.
92//
93// Returns zero if the CRC cannot be extended using acceleration, else returns
94// the newly extended CRC value (which may also be zero).
95uint32_t AcceleratedCRC32C(uint32_t crc, const char* buf, size_t size);
96
97}  // namespace port
98}  // namespace leveldb
99
100#endif  // STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_
101