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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/message_util.h"
#include "base/metrics/histogram_macros.h"
#include "base/notreached.h"
namespace midi {
size_t GetMessageLength(uint8_t status_byte) {
if (status_byte < 0x80)
return 0;
if (0x80 <= status_byte && status_byte <= 0xbf)
return 3;
if (0xc0 <= status_byte && status_byte <= 0xdf)
return 2;
if (0xe0 <= status_byte && status_byte <= 0xef)
return 3;
switch (status_byte) {
case 0xf0:
return 0;
case 0xf1:
return 2;
case 0xf2:
return 3;
case 0xf3:
return 2;
case 0xf4: // Reserved
case 0xf5: // Reserved
return 0;
case 0xf6:
return 1;
case 0xf7:
return 0;
case 0xf8:
case 0xf9:
case 0xfa:
case 0xfb:
case 0xfc:
case 0xfd:
case 0xfe:
case 0xff:
return 1;
default:
NOTREACHED();
return 0;
}
}
bool IsDataByte(uint8_t data) {
return (data & 0x80) == 0;
}
bool IsSystemRealTimeMessage(uint8_t data) {
return 0xf8 <= data;
}
bool IsSystemMessage(uint8_t data) {
return 0xf0 <= data;
}
bool IsValidWebMIDIData(const std::vector<uint8_t>& data) {
bool in_sysex = false;
size_t sysex_start_offset = 0;
size_t waiting_data_length = 0;
for (size_t i = 0; i < data.size(); ++i) {
const uint8_t current = data[i];
if (IsSystemRealTimeMessage(current))
continue; // Real time message can be placed at any point.
if (waiting_data_length > 0) {
if (!IsDataByte(current))
return false; // Error: |current| should have been data byte.
--waiting_data_length;
continue; // Found data byte as expected.
}
if (in_sysex) {
if (data[i] == kEndOfSysExByte) {
in_sysex = false;
UMA_HISTOGRAM_COUNTS_1M("Media.Midi.SysExMessageSizeUpTo1MB",
static_cast<base::HistogramBase::Sample>(
i - sysex_start_offset + 1));
} else if (!IsDataByte(current)) {
return false; // Error: |current| should have been data byte.
}
continue; // Found data byte as expected.
}
if (current == kSysExByte) {
in_sysex = true;
sysex_start_offset = i;
continue; // Found SysEX
}
waiting_data_length = GetMessageLength(current);
if (waiting_data_length == 0)
return false; // Error: |current| should have been a valid status byte.
--waiting_data_length; // Found status byte
}
return waiting_data_length == 0 && !in_sysex;
}
} // namespace midi
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