ceph/src/rocksdb/port/port_example.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5 //
   6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
   9 //
  10 // This file contains the specification, but not the implementations,
  11 // of the types/operations/etc. that should be defined by a platform
  12 // specific port_<platform>.h file.  Use this file as a reference for
  13 // how to port this package to a new platform.
  14
  15 #pragma once
  16
  17 namespace ROCKSDB_NAMESPACE {
  18 namespace port {
  19
  20 // TODO(jorlow): Many of these belong more in the environment class rather than
  21 //               here. We should try moving them and see if it affects perf.
  22
  23 // The following boolean constant must be true on a little-endian machine
  24 // and false otherwise.
  25 static const bool kLittleEndian = true /* or some other expression */;
  26
  27 // ------------------ Threading -------------------
  28
  29 // A Mutex represents an exclusive lock.
  30 class Mutex {
  31  public:
  32   Mutex();
  33   ~Mutex();
  34
  35   // Lock the mutex.  Waits until other lockers have exited.
  36   // Will deadlock if the mutex is already locked by this thread.
  37   void Lock();
  38
  39   // Unlock the mutex.
  40   // REQUIRES: This mutex was locked by this thread.
  41   void Unlock();
  42
  43   // Optionally crash if this thread does not hold this mutex.
  44   // The implementation must be fast, especially if NDEBUG is
  45   // defined.  The implementation is allowed to skip all checks.
  46   void AssertHeld();
  47 };
  48
  49 class CondVar {
  50  public:
  51   explicit CondVar(Mutex* mu);
  52   ~CondVar();
  53
  54   // Atomically release *mu and block on this condition variable until
  55   // either a call to SignalAll(), or a call to Signal() that picks
  56   // this thread to wakeup.
  57   // REQUIRES: this thread holds *mu
  58   void Wait();
  59
  60   // If there are some threads waiting, wake up at least one of them.
  61   void Signal();
  62
  63   // Wake up all waiting threads.
  64   void SignallAll();
  65 };
  66
  67 // Thread-safe initialization.
  68 // Used as follows:
  69 //      static port::OnceType init_control = LEVELDB_ONCE_INIT;
  70 //      static void Initializer() { ... do something ...; }
  71 //      ...
  72 //      port::InitOnce(&init_control, &Initializer);
  73 typedef intptr_t OnceType;
  74 #define LEVELDB_ONCE_INIT 0
  75 extern void InitOnce(port::OnceType*, void (*initializer)());
  76
  77 // ------------------ Compression -------------------
  78
  79 // Store the snappy compression of "input[0,input_length-1]" in *output.
  80 // Returns false if snappy is not supported by this port.
  81 extern bool Snappy_Compress(const char* input, size_t input_length,
  82                             std::string* output);
  83
  84 // If input[0,input_length-1] looks like a valid snappy compressed
  85 // buffer, store the size of the uncompressed data in *result and
  86 // return true.  Else return false.
  87 extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
  88                                          size_t* result);
  89
  90 // Attempt to snappy uncompress input[0,input_length-1] into *output.
  91 // Returns true if successful, false if the input is invalid lightweight
  92 // compressed data.
  93 //
  94 // REQUIRES: at least the first "n" bytes of output[] must be writable
  95 // where "n" is the result of a successful call to
  96 // Snappy_GetUncompressedLength.
  97 extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
  98                               char* output);
  99
 100 }  // namespace port
 101 }  // namespace ROCKSDB_NAMESPACE