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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root 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.
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 {
// 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 {
explicit CondVar(Mutex* mu);
// 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;
extern void InitOnce(port::OnceType*, void (*initializer)());
// ------------------ 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);
} // namespace port
} // namespace rocksdb