1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #import "MIDIMessage.h" 18 19 const uint8_t kMIDINoChannel = -1; 20 21 MIDIMessageType MIDIMessageTypeFromStatus(MIDIByte status) { 22 if (status < MIDIMessageSysEx) { 23 return (status & 0xF0) >> 4; 24 } else { 25 return status; 26 } 27 } 28 29 MIDIChannel MIDIChannelFromStatus(MIDIByte status) { 30 if (status < MIDIMessageSysEx) { 31 return (status & 0x0F) + 1; 32 } else { 33 return -1; 34 } 35 } 36 37 NSData *MIDIMessageBody(NSData *message) { 38 if (message.length == 0) { 39 return nil; 40 } 41 42 const MIDIByte *bytes = (const MIDIByte *)message.bytes; 43 44 // Slice off any header/trailer bytes. 45 if (MIDIMessageTypeFromStatus(bytes[0]) == MIDIMessageSysEx) { 46 NSCAssert(bytes[message.length - 1] == MIDIMessageSysExEnd, @"SysEx message without trailer."); 47 return [message subdataWithRange:NSMakeRange(1, message.length - 2)]; 48 } else { 49 return [message subdataWithRange:NSMakeRange(1, message.length - 1)]; 50 } 51 } 52 53 MIDIByte MIDIStatusByte(MIDIMessageType type, MIDIChannel channel) { 54 if (type >= MIDIMessageSysEx) { 55 return type; 56 } else { 57 return (type << 4) | (channel - 1); 58 } 59 } 60 61 NSData *MIDIChannelMessageCreate(MIDIMessageType type, MIDIChannel channel, NSData *body) { 62 NSMutableData *message = 63 [[NSMutableData alloc] initWithCapacity:body.length + 2]; // +2 for status and SysEx trailer 64 65 const MIDIByte status = MIDIStatusByte(type, channel); 66 [message appendBytes:&status length:1]; 67 [message appendData:body]; 68 69 if (type == MIDIMessageSysEx) { 70 const MIDIByte trailer = MIDIMessageSysEx; 71 [message appendBytes:&trailer length:1]; 72 } 73 74 return message; 75 } 76 77 NSData *MIDIMessageCreateSimple1(MIDIMessageType type, MIDIChannel channel, MIDIByte first) { 78 NSCAssert(type != MIDIMessageSysEx, @"MIDIMessageCreateSimple1 cannot create SysEx messages."); 79 80 NSMutableData *message = [[NSMutableData alloc] initWithCapacity:2]; // Status + Data 81 82 const MIDIByte status = MIDIStatusByte(type, channel); 83 [message appendBytes:&status length:1]; 84 [message appendBytes:&first length:1]; 85 86 return message; 87 } 88 89 NSData *MIDIMessageCreateSimple2(MIDIMessageType type, 90 MIDIChannel channel, 91 MIDIByte first, 92 MIDIByte second) { 93 NSCAssert(type != MIDIMessageSysEx, @"MIDIMessageCreateSimple2 cannot create SysEx messages."); 94 95 NSMutableData *message = [[NSMutableData alloc] initWithCapacity:3]; // Status + Data + Data 96 97 const MIDIByte status = MIDIStatusByte(type, channel); 98 [message appendBytes:&status length:1]; 99 [message appendBytes:&first length:1]; 100 [message appendBytes:&second length:1]; 101 102 return message; 103 } 104
