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