// Copyright (c) 2013, Facebook, Inc. All rights reserved. // This source code is licensed under the BSD-style license found in the // LICENSE file in the root directory of this source tree. An additional grant // of patent rights can be found in the PATENTS file in the same directory. // // Copyright (c) 2011 The LevelDB Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. See the AUTHORS file for names of contributors. // // This file contains the specification, but not the implementations, // of the types/operations/etc. that should be defined by a platform // specific port_<platform>.h file. Use this file as a reference for // how to port this package to a new platform. #ifndef STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_ #define STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_ namespace rocksdb { namespace port { // TODO(jorlow): Many of these belong more in the environment class rather than // here. We should try moving them and see if it affects perf. // The following boolean constant must be true on a little-endian machine // and false otherwise. static const bool kLittleEndian = true /* or some other expression */; // ------------------ Threading ------------------- // A Mutex represents an exclusive lock. class Mutex { public: Mutex(); ~Mutex(); // Lock the mutex. Waits until other lockers have exited. // Will deadlock if the mutex is already locked by this thread. void Lock(); // Unlock the mutex. // REQUIRES: This mutex was locked by this thread. void Unlock(); // Optionally crash if this thread does not hold this mutex. // The implementation must be fast, especially if NDEBUG is // defined. The implementation is allowed to skip all checks. void AssertHeld(); }; class CondVar { public: explicit CondVar(Mutex* mu); ~CondVar(); // Atomically release *mu and block on this condition variable until // either a call to SignalAll(), or a call to Signal() that picks // this thread to wakeup. // REQUIRES: this thread holds *mu void Wait(); // If there are some threads waiting, wake up at least one of them. void Signal(); // Wake up all waiting threads. void SignallAll(); }; // Thread-safe initialization. // Used as follows: // static port::OnceType init_control = LEVELDB_ONCE_INIT; // static void Initializer() { ... do something ...; } // ... // port::InitOnce(&init_control, &Initializer); typedef intptr_t OnceType; #define LEVELDB_ONCE_INIT 0 extern void InitOnce(port::OnceType*, void (*initializer)()); // A type that holds a pointer that can be read or written atomically // (i.e., without word-tearing.) class AtomicPointer { private: intptr_t rep_; public: // Initialize to arbitrary value AtomicPointer(); // Initialize to hold v explicit AtomicPointer(void* v) : rep_(v) { } // Read and return the stored pointer with the guarantee that no // later memory access (read or write) by this thread can be // reordered ahead of this read. void* Acquire_Load() const; // Set v as the stored pointer with the guarantee that no earlier // memory access (read or write) by this thread can be reordered // after this store. void Release_Store(void* v); // Read the stored pointer with no ordering guarantees. void* NoBarrier_Load() const; // Set va as the stored pointer with no ordering guarantees. void NoBarrier_Store(void* v); }; // ------------------ Compression ------------------- // Store the snappy compression of "input[0,input_length-1]" in *output. // Returns false if snappy is not supported by this port. extern bool Snappy_Compress(const char* input, size_t input_length, std::string* output); // If input[0,input_length-1] looks like a valid snappy compressed // buffer, store the size of the uncompressed data in *result and // return true. Else return false. extern bool Snappy_GetUncompressedLength(const char* input, size_t length, size_t* result); // Attempt to snappy uncompress input[0,input_length-1] into *output. // Returns true if successful, false if the input is invalid lightweight // compressed data. // // REQUIRES: at least the first "n" bytes of output[] must be writable // where "n" is the result of a successful call to // Snappy_GetUncompressedLength. extern bool Snappy_Uncompress(const char* input_data, size_t input_length, char* output); // ------------------ Miscellaneous ------------------- // If heap profiling is not supported, returns false. // Else repeatedly calls (*func)(arg, data, n) and then returns true. // The concatenation of all "data[0,n-1]" fragments is the heap profile. extern bool GetHeapProfile(void (*func)(void*, const char*, int), void* arg); } // namespace port } // namespace rocksdb #endif // STORAGE_LEVELDB_PORT_PORT_EXAMPLE_H_