在看本文前，请先看“BLE广播中的数据包”，至少要知道什么是定时包、扫描回复包。
广播数据由定时包和扫描回复包组成。绝大多数情部下，等回调到didDiscoverPeripheral，会已收到这个包。但偶尔会出现只收到定时包，至少ios14、ios15、ios16都出现过。
一、ios
1.1 开始扫描
-(void)scanPeripherals:(const char*)uuid
{
// [bleManager scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey:@YES}];
NSMutableArray* uuidArray = [[NSMutableArray alloc] init];
if (uuid && uuid[0] != '\0') {
[uuidArray addObject: [CBUUID UUIDWithString: [[NSString alloc] initWithUTF8String:uuid]]];
}
[bleManager scanForPeripheralsWithServices:uuidArray options:@{CBCentralManagerScanOptionAllowDuplicatesKey:@YES,
CBCentralManagerOptionShowPowerAlertKey:@YES}];
}- CBCentralManagerScanOptionAllowDuplicatesKey。控制扫描到重复设备时，是否还要调用didDiscoverPeripheral。设置为yes表示扫描到重复设备，依旧调用didDiscoverPeripheral。由于有可能出现扫描时只收到定时包，又恰好出现在第一次扫描到这设备时，如果不重复，app此轮扫描会认为这peripheral就只有定时包中那些字段。为得到完整广播包，必须把CBCentralManagerScanOptionAllowDuplicatesKey设为true。
- CBCentralManagerOptionShowPowerAlertKey。网上有说它设为YES， 是在蓝牙未打开的时候显示弹框。但我测试下来，没用。但个人认希望有这功能，就设置为YES。
1.2 扫描到一个peripheral后的回调
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:
(CBPeripheral *)peripheral2 advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI
{
const char* name = [peripheral2.name UTF8String];
if (name == NULL || name[0] == '\0') {
// don't support "empty" name.
// "empty" name maybe result very much "fake" ble device.
return;
}检查广播数据中是否有name字段，若没有name字段，忽略这个广播。这意味着，这要求peripheral必须广播name字段。
bool field_increase = false;
// field: service_uuid
NSArray* service_uuids = [advertisementData objectForKey:@"kCBAdvDataServiceUUIDs"];
int uuid_count = service_uuids != NULL? (int)(long)[service_uuids count]: 0;
// field: manufacturer_data
NSData* manufacturer_data = [advertisementData objectForKey:@"kCBAdvDataManufacturerData"];
// NSLog(@"[SDL_uikitble.m]discover peripheral: %@", peripheral2.name);
SDL_BlePeripheral* peripheral = discover_peripheral_uh_cookie((__bridge void *)(peripheral2), name);
if (peripheral->cookie != NULL) {
if (name != NULL) {
if (peripheral->name == NULL) {
NSLog(@"[SDL_uikitble.m]%@ it is duplicatesKey, but has name", peripheral2.name);
field_increase = true;
} else {
if (SDL_strcmp(peripheral->name, name) != 0) {
field_increase = true;
}
}
}
if (uuid_count != 0 && peripheral->uuid == NULL) {
NSLog(@"[SDL_uikitble.m]%@ it is duplicatesKey, but has kCBAdvDataServiceUUIDs", peripheral2.name);
field_increase = true;对这peripheral，之前扫描到时没有ServiceUUID，此次扫描到时有ServiceUUID。原因应该是这peripherl把ServiceUUID放在了扫描回复包，之前扫描到的没有收到扫描回复包。
}
if (manufacturer_data != NULL) {
if (peripheral->manufacturer_data == NULL) {
NSLog(@"[SDL_uikitble.m]%@ it is duplicatesKey, but has kCBAdvDataManufacturerData", peripheral2.name);
field_increase = true;
} else {
int oc_len = (int)[manufacturer_data length];
if (oc_len != peripheral->manufacturer_data_len ||
SDL_memcmp(peripheral->manufacturer_data, [manufacturer_data bytes], oc_len) != 0) {
field_increase = true;
}
}
}
}“peripheral->cookie != NULL”，意味着这是个重复设备。这时要检查关注的字段，如果有增加或修改了，还是要告诉app发现了新设备。如果多了字段，原因应该是上次没收到扫描回复包，这次收到了。如查修改了，应该是在两次扫描间隔，peripheral改了相关该字段值，像修改Name、ManufacturerData。通常来说，一旦定了uuid后，就不会去修改它的值，这里针对uuid就只判断是否增加，不判断修改。
关注字段只有三个：Name，ServiceUUID、ManufacturerData。
if (peripheral->cookie == NULL || field_increase) {
if (peripheral->cookie != NULL) {
UIKit_ReleaseCookie(peripheral);
}
peripheral->cookie = (void *)CFBridgingRetain(peripheral2);
// this peripheral must result to call discover_peripheral_bh
peripheral->discovered = SDL_FALSE;discovered置为SDL_FALSE，让这peripheral是新设备。discovered作用见底下的discover_peripheral_bh。
// parse KCBAdvDataServiceUUIDs, result maybe like 1809,ccc0
size_t require_size = 0;
for (int at = 0; at < uuid_count; at ++) {
const char* uuid = [[[service_uuids objectAtIndex: at] UUIDString] UTF8String];
require_size += SDL_strlen(uuid) + 1; // , or \0'
}
if (require_size) {
peripheral->uuid = (char*)SDL_malloc(require_size);
}
int start = 0;
for (int at = 0; at < uuid_count; at ++) {
if (at) {
peripheral->uuid[start] = ',';
start ++;
}
const char* uuid = [[[service_uuids objectAtIndex: at] UUIDString] UTF8String];
size_t s = SDL_strlen(uuid);
memcpy(peripheral->uuid + start, uuid, s);
start += s;
if (at == uuid_count - 1) {
peripheral->uuid[start] = '\0';
}
}
// kCBAdvDataManufacturerData, only copy.
if (manufacturer_data) {
peripheral->manufacturer_data_len = (int)[manufacturer_data length];
peripheral->manufacturer_data = (unsigned char*)SDL_malloc(peripheral->manufacturer_data_len);
memcpy(peripheral->manufacturer_data, [manufacturer_data bytes], peripheral->manufacturer_data_len);
}
if (!peripheral->discovered) {
peripheral->discovered = SDL_TRUE;
// try to reduce times of call call discover_peripheral_bh.
discover_peripheral_bh(peripheral, [RSSI intValue]);扫描到设备的频率是不低的，尽可能减少app收到“发现periperhal”。这里用了discovered字段，在开始扫描时，会把所有peripheral->discovered置为SDL_FALSE。只有此轮扫描发现的“新”设备才会发向app。
} }