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David Hoerl dhoerl

  • New Jersey, USA
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dhoerl / Asymmetric.swift
Last active Dec 23, 2018
Implement asymmetric cryptography for distributed app where keys can both be stored as strings
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// Asymmetric.swift
// Created by David Hoerl on 12/23/18.
// Copyright © 2018 David Hoerl. All rights reserved.
This is the portion you need in the distributed app, which uses the public key that can appear in plain text
dhoerl / DavidTop10
Created May 13, 2015
Swift: David's Top 10 "Do This" List
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David's Top 10: Do That When Writing Swift
1) Purchase Dash (OS X and iOS) and get Swift from (invaluable reference, I use it daily!)
2) Use Enums for UIView tags and SegmentedControl segments;
enum MyViews: Int { case OKButton=1...} then switch MyViews(rawValue: view.tag)
also for states (somewhat replaces C's X-Macros, helps during debugging)
dhoerl / AppDelegate(category).m
Created Jul 26, 2012
Keychain Wrapper for dictionary (NSData) not a single NSString
View AppDelegate(category).m
static NSString *kcIdentifier = @"MyApp";
@implementation LTAppDelegate (KeyChain)
- (void)keychainInit
self.keychainDict = [NSMutableDictionary dictionaryWithCapacity:7];
KeychainItemWrapper *item = [[KeychainItemWrapper alloc] initWithIdentifier:kcIdentifier accessGroup:nil];
[self.keychainDict setObject:@"" forKey:kcEmailAddress];
dhoerl / freeDiskSpace.m
Created Jun 20, 2012
Getting the Free Disk Space on an iOS device
View freeDiskSpace.m
- (uint64_t)freeDiskspace
uint64_t totalFreeSpace = 0;
__autoreleasing NSError *error = nil;
NSString *path = [self applicationDocumentsDirectory];
NSDictionary *dictionary = [[NSFileManager defaultManager] attributesOfFileSystemForPath:path error: &error];
if (dictionary) {
NSNumber *freeFileSystemSizeInBytes = [dictionary objectForKey:NSFileSystemFreeSize];
dhoerl / MyWebFetcher.m
Created Mar 16, 2012
iOS SSL based NSURLConnection to a site using a self-signed certificate
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#if ! __has_feature(objc_arc)
static CFArrayRef certs;
@implementation MyWebFetcher
+ (void)initialize
dhoerl / README.txt
Created Jan 29, 2012
std::string using printf style format strings
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Prefer printf to the C++ iosstream methods? Now you can create a string using printf style format strings, and also append formatted string to existing strings.
Inspired by:
dhoerl / README.txt
Created Jan 28, 2012
UITableViewCells from a NIB - better than Apple's iOS 5 code
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Reloading the NIB is expensive. Better to load it once, then instantiate the objects when you need a cell. Note that you can add UIImageViews etc to the nib, even multiple cells, using this method (Apple's "registerNIB" iOS5 allows only one top level object - one UITableViewCell. Bug 10580062 "iOS5 tableView registerNib: overly restrictive"
So my code is below - you read in the NIB once (in +initialize like I did or in viewDidload - whatever. From then on, you instantiate the nib into objects then pick the one you need. This is much more efficient than loading the nib over and over.
dhoerl / HowTo.txt
Created Jan 27, 2012
Converting a NSDictionary to a Binary PList
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When I posted this on Apple’s Cocoadev listserver, I never did get pointers to code to convert a NSDictionary to a binary formatted plist, but did get pointers to look at NSPropertyListSerialization - something I had already (mis)read a few times.
The description for the dataFromPropertyList class method seems confusing if you don't understand that you can create a property list with no keys: that is, you can create one with a single compliant object, and the key becomes "root".
So, in the unlikely event that some else someday has the same mental block, here is actual tested code that takes a NSDictionary and creates a binary plist file:
NSDictionary *dict;
char *payload = "This is the payload";
dict = [NSDictionary dictionaryWithObjectsAndKeys:
dhoerl / LTActionSheet.h
Created Jan 27, 2012
UIActionSheet Subclass providing ability to set Font and Alignment for the message. Please advice if your app with it gets accepted.
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LTActionSheet - a UIActionSheet subclass to support customized fonts and alignment
Copyright (C) 2011 by David Hoerl
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
dhoerl / README.txt
Created Jan 27, 2012
View README.txt
I had a business need to provide the mean value of a process based on its bell-shaped histogram. Now, normally that would be an easy thing to do—there is a standard formula to get the mean and standard deviation.
However, in my case, the histogram has a skew. One side does not tail off to zero, but to some value midway between the peak value and zero.
After lots of googling, I found a paper written in 1993 by Brown and Hwang titled How To Approximate a Histogram by a Normal Density ( After purchasing a copy, I inquired if the author’s had software that implemented their algorithms. When the answer came back, I had to dig deep and turn their formulas into code, One integral had no series sum solution, so I had to really really dig deep and figure out how to do the conversion myself.
By intent I did all the conversion on my own time, and after I got everything working I sent the C Code to the authors in case anyone else ever asks.
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