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| 1 // Copyright 2013 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #include "media/midi/message_util.h" |
| 6 |
| 7 #include "base/logging.h" |
| 8 #include "base/metrics/histogram_macros.h" |
| 9 |
| 10 namespace midi { |
| 11 |
| 12 size_t GetMessageLength(uint8_t status_byte) { |
| 13 if (status_byte < 0x80) |
| 14 return 0; |
| 15 if (0x80 <= status_byte && status_byte <= 0xbf) |
| 16 return 3; |
| 17 if (0xc0 <= status_byte && status_byte <= 0xdf) |
| 18 return 2; |
| 19 if (0xe0 <= status_byte && status_byte <= 0xef) |
| 20 return 3; |
| 21 |
| 22 switch (status_byte) { |
| 23 case 0xf0: |
| 24 return 0; |
| 25 case 0xf1: |
| 26 return 2; |
| 27 case 0xf2: |
| 28 return 3; |
| 29 case 0xf3: |
| 30 return 2; |
| 31 case 0xf4: // Reserved |
| 32 case 0xf5: // Reserved |
| 33 return 0; |
| 34 case 0xf6: |
| 35 return 1; |
| 36 case 0xf7: |
| 37 return 0; |
| 38 case 0xf8: |
| 39 case 0xf9: |
| 40 case 0xfa: |
| 41 case 0xfb: |
| 42 case 0xfc: |
| 43 case 0xfd: |
| 44 case 0xfe: |
| 45 case 0xff: |
| 46 return 1; |
| 47 default: |
| 48 NOTREACHED(); |
| 49 return 0; |
| 50 } |
| 51 } |
| 52 |
| 53 bool IsDataByte(uint8_t data) { |
| 54 return (data & 0x80) == 0; |
| 55 } |
| 56 |
| 57 bool IsSystemRealTimeMessage(uint8_t data) { |
| 58 return 0xf8 <= data; |
| 59 } |
| 60 |
| 61 bool IsSystemMessage(uint8_t data) { |
| 62 return 0xf0 <= data; |
| 63 } |
| 64 |
| 65 bool IsValidWebMIDIData(const std::vector<uint8_t>& data) { |
| 66 bool in_sysex = false; |
| 67 size_t sysex_start_offset = 0; |
| 68 size_t waiting_data_length = 0; |
| 69 for (size_t i = 0; i < data.size(); ++i) { |
| 70 const uint8_t current = data[i]; |
| 71 if (IsSystemRealTimeMessage(current)) |
| 72 continue; // Real time message can be placed at any point. |
| 73 if (waiting_data_length > 0) { |
| 74 if (!IsDataByte(current)) |
| 75 return false; // Error: |current| should have been data byte. |
| 76 --waiting_data_length; |
| 77 continue; // Found data byte as expected. |
| 78 } |
| 79 if (in_sysex) { |
| 80 if (data[i] == kEndOfSysExByte) { |
| 81 in_sysex = false; |
| 82 UMA_HISTOGRAM_COUNTS("Media.Midi.SysExMessageSizeUpTo1MB", |
| 83 static_cast<base::HistogramBase::Sample>( |
| 84 i - sysex_start_offset + 1)); |
| 85 } else if (!IsDataByte(current)) { |
| 86 return false; // Error: |current| should have been data byte. |
| 87 } |
| 88 continue; // Found data byte as expected. |
| 89 } |
| 90 if (current == kSysExByte) { |
| 91 in_sysex = true; |
| 92 sysex_start_offset = i; |
| 93 continue; // Found SysEX |
| 94 } |
| 95 waiting_data_length = GetMessageLength(current); |
| 96 if (waiting_data_length == 0) |
| 97 return false; // Error: |current| should have been a valid status byte. |
| 98 --waiting_data_length; // Found status byte |
| 99 } |
| 100 return waiting_data_length == 0 && !in_sysex; |
| 101 } |
| 102 |
| 103 } // namespace midi |
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