Swiftgram/Source/Details/ASTraceEvent.m

//
//  ASTraceEvent.m
//  Texture
//
//  Copyright (c) 2014-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the /ASDK-Licenses directory of this source tree. An additional
//  grant of patent rights can be found in the PATENTS file in the same directory.
//
//  Modifications to this file made after 4/13/2017 are: Copyright (c) 2017-present,
//  Pinterest, Inc.  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
//

#import <AsyncDisplayKit/ASTraceEvent.h>
#import <QuartzCore/QuartzCore.h>

static NSString *const ASTraceEventThreadDescriptionKey = @"ASThreadTraceEventDescription";

@interface ASTraceEvent ()
@property (nonatomic, strong, readonly) NSString *objectDescription;
@property (nonatomic, strong, readonly) NSString *threadDescription;
@end

@implementation ASTraceEvent

- (instancetype)initWithBacktrace:(NSArray<NSString *> *)backtrace format:(NSString *)format arguments:(va_list)args
{
  self = [super init];
  if (self != nil) {
    static NSTimeInterval refTime;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
      refTime = CACurrentMediaTime();
    });
    
    // Create the format string passed to us.
    _message = [[NSString alloc] initWithFormat:format arguments:args];
	  
    NSThread *thread = [NSThread currentThread];
    NSString *threadDescription = thread.name;
    if (threadDescription.length == 0) {
      if ([thread isMainThread]) {
        threadDescription = @"Main";
      } else {
        // If the bg thread has no name, we cache a 4-character ptr string to identify it by
        // inside the thread dictionary.
        NSMutableDictionary *threadDict = thread.threadDictionary;
        threadDescription = threadDict[ASTraceEventThreadDescriptionKey];
        if (threadDescription == nil) {
          // Want these to be 4-chars to line up with "Main". It's possible that a collision could happen
          // here but it's so unbelievably likely to impact development, the risk is acceptable.
          NSString *ptrString = [NSString stringWithFormat:@"%p", thread];
          threadDescription = [ptrString substringFromIndex:MAX(0, ptrString.length - 4)];
          threadDict[ASTraceEventThreadDescriptionKey] = threadDescription;
        }
      }
    }
    _threadDescription = threadDescription;

    _backtrace = backtrace;
    _timestamp = CACurrentMediaTime() - refTime;
  }
  return self;
}

- (NSString *)description
{
  return [NSString stringWithFormat:@"<(%@) t=%7.3f: %@>", _threadDescription, _timestamp, _message];
}

@end