blob: 35f793c8c89c4a04eed8bc1713c4278265616b6f [file] [log] [blame]
// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <lib/zircon-internal/thread_annotations.h>
#include <lib/zx/eventpair.h>
#include <stdint.h>
#include <stdlib.h>
#include <zircon/types.h>
#include <fbl/mutex.h>
class Fifo {
// The eventpair given to this will be used to signal when the Fifo is
// readable (via the DEVICE_SIGNAL_READABLE signal). WRITABLE signals are not
// issued, since the consumer of this class uses it to implement the RX queue
// on the console and not the TX queue.
explicit Fifo(zx::eventpair event) : event_{std::move(event)} {}
// Fill the given buffer with data from this FIFO. Since short reads may
// occur, a new string piece is returned which refers to the same buffer as
// |in|, but may be shorter.
zx_status_t Read(uint8_t* buffer, size_t len, size_t* actual);
zx_status_t Write(const uint8_t* buffer, size_t len, size_t* actual);
// The public facing size is one byte smaller than the actual size, due to the
// use of a sentinel byte for detecting the full case.
static inline constexpr uint32_t kFifoSize = 255;
zx_status_t ReadByteLocked(uint8_t* out) TA_REQ(lock_);
zx_status_t WriteByteLocked(uint8_t x) TA_REQ(lock_);
bool IsEmptyLocked() TA_REQ(lock_) { return head_ == tail_; }
bool IsFullLocked() TA_REQ(lock_) { return ((head_ + 1) & kFifoMask) == tail_; }
static inline constexpr uint32_t kFifoMask = kFifoSize;
fbl::Mutex lock_;
uint8_t data_[kFifoSize + 1] TA_GUARDED(lock_) = {};
uint32_t head_ TA_GUARDED(lock_) = 0;
uint32_t tail_ TA_GUARDED(lock_) = 0;
zx::eventpair event_;