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// Copyright 2013 The Chromium 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 "media/midi/midi_message_queue.h"
#include <algorithm>
#include "base/logging.h"
#include "media/midi/midi_message_util.h"
namespace media {
namespace midi {
namespace {
const uint8 kSysEx = 0xf0;
const uint8 kEndOfSysEx = 0xf7;
bool IsDataByte(uint8 data) {
return (data & 0x80) == 0;
}
bool IsFirstStatusByte(uint8 data) {
return !IsDataByte(data) && data != kEndOfSysEx;
}
bool IsSystemRealTimeMessage(uint8 data) {
return 0xf8 <= data;
}
bool IsSystemMessage(uint8 data) {
return 0xf0 <= data;
}
} // namespace
MidiMessageQueue::MidiMessageQueue(bool allow_running_status)
: allow_running_status_(allow_running_status) {}
MidiMessageQueue::~MidiMessageQueue() {}
void MidiMessageQueue::Add(const std::vector<uint8>& data) {
queue_.insert(queue_.end(), data.begin(), data.end());
}
void MidiMessageQueue::Add(const uint8* data, size_t length) {
queue_.insert(queue_.end(), data, data + length);
}
void MidiMessageQueue::Get(std::vector<uint8>* message) {
message->clear();
while (true) {
if (queue_.empty())
return;
const uint8 next = queue_.front();
queue_.pop_front();
// "System Real Time Messages" is a special kind of MIDI messages, which can
// appear at arbitrary byte position of MIDI stream. Here we reorder
// "System Real Time Messages" prior to |next_message_| so that each message
// can be clearly separated as a complete MIDI message.
if (IsSystemRealTimeMessage(next)) {
message->push_back(next);
return;
}
// Here |next_message_[0]| may contain the previous status byte when
// |allow_running_status_| is true. Following condition fixes up
// |next_message_| if running status condition is not fulfilled.
if (!next_message_.empty() &&
((next_message_[0] == kSysEx && IsFirstStatusByte(next)) ||
(next_message_[0] != kSysEx && !IsDataByte(next)))) {
// An invalid data sequence is found or running status condition is not
// fulfilled.
next_message_.clear();
}
if (next_message_.empty()) {
if (IsFirstStatusByte(next)) {
next_message_.push_back(next);
} else {
// MIDI protocol doesn't provide any error correction mechanism in
// physical layers, and incoming messages can be corrupted, and should
// be corrected here.
}
continue;
}
// Here we can assume |next_message_| starts with a valid status byte.
const uint8 status_byte = next_message_[0];
next_message_.push_back(next);
if (status_byte == kSysEx) {
if (next == kEndOfSysEx) {
std::swap(*message, next_message_);
next_message_.clear();
return;
}
continue;
}
DCHECK(IsDataByte(next));
DCHECK_NE(kSysEx, status_byte);
const size_t target_len = GetMidiMessageLength(status_byte);
if (next_message_.size() < target_len)
continue;
if (next_message_.size() == target_len) {
std::swap(*message, next_message_);
next_message_.clear();
if (allow_running_status_ && !IsSystemMessage(status_byte)) {
// Speculatively keep the status byte in case of running status. If this
// assumption is not true, |next_message_| will be cleared anyway.
// Note that system common messages should reset the running status.
next_message_.push_back(status_byte);
}
return;
}
NOTREACHED();
}
}
} // namespace midi
} // namespace media
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