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 15 namespace leveldb {
16 namespace 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.
24 class 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 43 class 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.
65 bool 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.
71 bool 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.
81 bool 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.
89 bool 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).
95 uint32_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