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/*
* Copyright 2017 Google
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#import "FNextPushId.h"
#import "FUtilities.h"
static NSString *const PUSH_CHARS = @"-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz";
@implementation FNextPushId
+ (NSString *) get:(NSTimeInterval)currentTime {
static long long lastPushTime = 0;
static int lastRandChars[12];
long long now = (long long)(currentTime * 1000);
BOOL duplicateTime = now == lastPushTime;
lastPushTime = now;
unichar timeStampChars[8];
for(int i = 7; i >= 0; i--) {
timeStampChars[i] = [PUSH_CHARS characterAtIndex:(now % 64)];
now = (long long)floor(now / 64);
}
NSMutableString* id = [[NSMutableString alloc] init];
[id appendString:[NSString stringWithCharacters:timeStampChars length:8]];
if(!duplicateTime) {
for(int i = 0; i < 12; i++) {
lastRandChars[i] = (int)floor(arc4random() % 64);
}
}
else {
int i = 0;
for(i = 11; i >= 0 && lastRandChars[i] == 63; i--) {
lastRandChars[i] = 0;
}
lastRandChars[i]++;
}
for(int i = 0; i < 12; i++) {
[id appendFormat:@"%C", [PUSH_CHARS characterAtIndex:lastRandChars[i]]];
}
return [NSString stringWithString:id];
}
@end
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