Catfish-Man

As of iOS 11/macOS High Sierra, and only including ones in Foundation and CoreFoundation

Strings:

_NSCFString - a CFStringRef or CFMutableStringRef. This is the most common type of string object currently.
    - May have 8 bit (ASCII) or 16 bit (UTF-16) backing store
_NSCFConstantString - a compile time constant CFStringRef, like you'd get with @"foo"
    - May also be generated by dynamic string creation if matches a string in a pre-baked table of common strings called the StringROM
NSBigMutableString - an NSString backed by a CFStorage (https://github.com/opensource-apple/CF/blob/master/CFStorage.h) for faster handling of very large strings
NSCheapMutableString - a very limited NSMutableString that allows for zero-copy initialization. Used in NSFileManager for temporarily wrapping stack buffers.

Catfish-Man

#import <Foundation/Foundation.h>
#import <time.h>
#import <os/lock.h>

#define ITERS 2000
#define NSEC_PER_ITER(time) (((double)time * (double)NSEC_PER_SEC) / (double)ITERS)

#define TEST(body, name) do {\
    start = [NSDate date];\
    for (int i = 0; i < ITERS; i++) {\

Catfish-Man

//  Created by David Smith on 5/29/17.
//  Copyright © 2017 Unseen University. All rights reserved.
//
//  Localization- and encoding-safe solution to Coraline Ada's challenge here: https://twitter.com/CoralineAda/status/869204799027372032
//  Very lightly tested. Probably contains bugs.

import Foundation

func tweetStorm(input uncanonicalizedInput:String, handle:String?) -> [String] {
    let input = uncanonicalizedInput.precomposedStringWithCanonicalMapping //twitter requires NFC

Catfish-Man

Let's Reinvent Modern CPU Caches!

In The Beginning, programs were hard-coded, entered directly with switches. Values would be input, and then results would output,
but couldn't really be stored. We'll draw this like so:

Input -> Fixed Calculations -> Output

An early improvement in generality was the addition of storage (ENIAC eventually gained 100 words of magnetic core memory),
leaving us with something along these lines:

Catfish-Man

static id cachedObject;
static NSLock *lock;

id getCachedObject() {
    [lock lock];
    id result = [cachedObject retain];
    [lock unlock];
    return result;
}

Catfish-Man

We're a group of tech employees (@Catfish_Man, @jnadeau, @numist, @jauricchio, and @daagaak) interested in making sure
as many people as possible survive the current state of US politics. For each dollar we donate, our employer
will donate two. We're pooling our resources to do the same for you, so for each dollar you donate to the 
orgs below, we'll also donate one dollar to those orgs, and our employer will donate two: quadruple your donation!
We have $45k set aside for this, so we'll keep matching donations until we've matched that much or 72 hours have passed.

You can send me a tweet/DM (@Catfish_Man) with a screenshot of evidence that you donated (receipt page, whatever works, we're not picky).

Southern Poverty Law Center
Council on American-Islamic Relations

Catfish-Man

#import <Foundation/Foundation.h>
int main(int argc, const char * argv[]) {
    @autoreleasepool {
        const long count = 10000000;
        const char *str1 = "hellohello"; //fits in a tagged pointer
        const char *str2 = "hellohelQo"; //at this character count, can only fit in a tagged pointer by using <8 bits per character, which requires dropping less frequently used chars like 'Q'
        const char *str3 = "Northern Sami"; //this string is encountered frequently enough that it's baked into a perfect hash table in CoreFoundation
        const char *str4 = "hellohellü"; //this string can't be tagged *and* can't be stored using an ASCII backing store

        NSDate *start = [NSDate date];

Catfish-Man

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

NS_ROOT_CLASS
@interface KVOTest

@end

@implementation KVOTest

Catfish-Man

As seen here: https://twitter.com/Catfish_Man/status/721914376664408064

Loosely based on http://inhousecook.blogspot.com/2013/09/paprika-chicken-and-ravioli-with-brown.html

Preheat oven to 375F

Chop off a hunk of onion - we had half of one left, so I took about 3/4" off the center, plus a bit more when that looked skimpy

In an oven-safe pan (I used a big cast iron one) saute the onion over medium-low heat in a few tablespoons of unsalted butter until it's brown and translucent

Catfish-Man

#import <Foundation/Foundation.h>

static const char *alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

NSString *badKey(int idx) {
    char *buffer = malloc(4096);
    memset(buffer, 'A', 4096 * sizeof(char));
    //NSString hashes the beginning, middle, and end of long strings, so we want our keys to differ only in other places.
    //-isEqual: also compares from front to back, so to exaggerate the problem, I placed the differences in the keys about 3/4 of the way through the string
    buffer[3072] = alphabet[arc4random_uniform(52)];