| // Copyright 2013 The Chromium Authors |
| // 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; |
| } |
| NOTREACHED_NORETURN(); |
| } |
| |
| 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 |