Friday, February 15, 2013
How to find me
It came to my attention this week that people are finding me via Google, which (unsurprisingly) links to here. I've been blogging for a couple of years at Secure Mac Programming, and I'm on twitter as @iwasleeg. I'm +Graham Lee on Google Plus, too. My email is graham at iamleeg dot com.
Wednesday, May 12, 2010
LLVM projects you may not be aware of
All Mac and iPhone OS developers must by now be familiar with LLVM, the Low-Level Virtual Machine compiler that Apple has backed in preference to GCC (presumably at least partially because because GCC 4.5 is now a GPLv3 project, in addition to technical problems with improving the older compiler). You'll also be familiar with Clang, the modular C/ObjC/C++ lexer/parser that can be used as an LLVM front-end, or as a library for providing static analysis, refactoring and other code comprehension facilities. And of course MacRuby uses LLVM's optimisation libraries.
The LLVM umbrella also covers a number of other projects that Mac/iPhone developers may not yet have heard about, but which nonetheless are pretty cool. This post is just a little tour of some of those. There are other projects that have made use of LLVM code, but which aren't part of the compiler project - they are not the subject of this post.
LibC++ is a C++ library, targeting 100% compatibility with the C++0x (draft) standard.
KLEE looks very cool. It's a "symbolic execution tool", capable of automatically generating unit tests for software with high degrees of coverage (well over 90%). Additionally, given information about an application's constraints and requirements it can automatically discover bugs, generating failing tests to demonstrate the bug and become part of the test suite. There's a paper describing KLEE including a walkthrough of discovering a bug in tr, and tutorials in its use.
vmkit is a substrate layer for running bytecode. It takes high-level bytecode (currently JVM bytecode or IL, the bytecode of the .Net runtime) and translates it to IR, the LLVM intermediate representation. In doing so it can make use of LLVM's optimisations and make better decisions regarding garbage collection.
The LLVM umbrella also covers a number of other projects that Mac/iPhone developers may not yet have heard about, but which nonetheless are pretty cool. This post is just a little tour of some of those. There are other projects that have made use of LLVM code, but which aren't part of the compiler project - they are not the subject of this post.
LibC++ is a C++ library, targeting 100% compatibility with the C++0x (draft) standard.
KLEE looks very cool. It's a "symbolic execution tool", capable of automatically generating unit tests for software with high degrees of coverage (well over 90%). Additionally, given information about an application's constraints and requirements it can automatically discover bugs, generating failing tests to demonstrate the bug and become part of the test suite. There's a paper describing KLEE including a walkthrough of discovering a bug in tr, and tutorials in its use.
vmkit is a substrate layer for running bytecode. It takes high-level bytecode (currently JVM bytecode or IL, the bytecode of the .Net runtime) and translates it to IR, the LLVM intermediate representation. In doing so it can make use of LLVM's optimisations and make better decisions regarding garbage collection.
Wednesday, April 28, 2010
WWDC dates announced
The entire of Twitter has imploded after noticing that Apple has announced the dates for WWDC, this year June 7-11. That's too short notice for me to go, and having only recently started working again after a few months concentrating solely on Professional Cocoa Application Security, I can't scrape together the few thousand pounds needed to reserve flights, hotel and ticket at a month's notice.
I hope that those of you who are going have a great time. The conference looks decidedly thin on Mac content this year, and while I still class myself as more of a Mac developer than an iP* developer that shouldn't be too much of a problem. The main value in WWDC is in the social/networking side first, the labs second, and the lecture content third - so as long as you can find an engineer in the labs who remembers how a Mac works, you'll probably still have a great week and learn a lot.
I hope that those of you who are going have a great time. The conference looks decidedly thin on Mac content this year, and while I still class myself as more of a Mac developer than an iP* developer that shouldn't be too much of a problem. The main value in WWDC is in the social/networking side first, the labs second, and the lecture content third - so as long as you can find an engineer in the labs who remembers how a Mac works, you'll probably still have a great week and learn a lot.
Thursday, April 15, 2010
The difference between NSTableView and UITableView
A number of times, I've chased myself down rat holes in iPhone projects because I've created a design or implementation that assumes UITableView and NSTableView are similar objects. They aren't.
The main problem I come across is related to how the cells are treated in Cocoa and in Cocoa touch. An AppKit table comprises columns, each of which uses a cell to display its content. A cell contains the drawing and event-handling stuff of a view, but nothing to do with its place in the view hierarchy or responder chain. It's essentially a light-weight view. For each row in the table, NSTableColumn takes its cell, configures it for the content in that row and then draws the cell at its location in the column. No matter how many rows there are, a single cell is used.
UIKit works differently. Of course a UITableView only has one column, but it also displays views rather than cells. This is good, but leads to the key distinction that always trips me up: you can't use the same view more than once in a table view. Of course, sections in a UITableView will often have more than one row, but each row that is visible on-screen will needs its own instance of UITableViewCell (which is a subclass of UIView, and therefore a view in the traditional sense rather than a cell). If you try to re-use the same instance multiple times, the table view will configure each row but only the last one it prepared will be drawn.
So what's this -reuseIdentifier? stuff? That's related to caching views for scrolling. Imagine a table view with 10 rows, of which 4 can be seen on screen at once. Each uses the same type of cell in this example. When the table view first becomes visible there will be 4 UITableViewCell instances in use, displaying rows 0-3. Now you start to scroll the view. UITableView finds it needs an extra cell to display row 4, which is now partially on-screen and row 0 is starting to slide off. When row 0 disappears completely, the table view could just delete its cell - but rather than do that, it adds it to a queue of reusable cells. When row 5 starts to appear, the table view can re-use the object it's already created for row 0, because it's the same type of cell as the one for row 5 and is currently unused.
So, that's that really. Note to self: don't treat UIKit like it's just AppKit, you'll end up wasting a day of code.
The main problem I come across is related to how the cells are treated in Cocoa and in Cocoa touch. An AppKit table comprises columns, each of which uses a cell to display its content. A cell contains the drawing and event-handling stuff of a view, but nothing to do with its place in the view hierarchy or responder chain. It's essentially a light-weight view. For each row in the table, NSTableColumn takes its cell, configures it for the content in that row and then draws the cell at its location in the column. No matter how many rows there are, a single cell is used.
UIKit works differently. Of course a UITableView only has one column, but it also displays views rather than cells. This is good, but leads to the key distinction that always trips me up: you can't use the same view more than once in a table view. Of course, sections in a UITableView will often have more than one row, but each row that is visible on-screen will needs its own instance of UITableViewCell (which is a subclass of UIView, and therefore a view in the traditional sense rather than a cell). If you try to re-use the same instance multiple times, the table view will configure each row but only the last one it prepared will be drawn.
So what's this -reuseIdentifier? stuff? That's related to caching views for scrolling. Imagine a table view with 10 rows, of which 4 can be seen on screen at once. Each uses the same type of cell in this example. When the table view first becomes visible there will be 4 UITableViewCell instances in use, displaying rows 0-3. Now you start to scroll the view. UITableView finds it needs an extra cell to display row 4, which is now partially on-screen and row 0 is starting to slide off. When row 0 disappears completely, the table view could just delete its cell - but rather than do that, it adds it to a queue of reusable cells. When row 5 starts to appear, the table view can re-use the object it's already created for row 0, because it's the same type of cell as the one for row 5 and is currently unused.
So, that's that really. Note to self: don't treat UIKit like it's just AppKit, you'll end up wasting a day of code.
Friday, April 02, 2010
On writing a book
Well, I've performed my final author's review, and Professional Cocoa Application Security is all with the printers. This post is about my experiences writing the book, not the book material itself.
My original motivation for writing PCAS was that it was a topic someone needed to talk about, and nobody had hitherto done the talking. I was actually initially approached by Wiley to see if I'd write anything at all - their commissioning editor had seen my Objective-C FAQ and this blog, and liked my style. I said that I didn't want to write a book, I wanted to write this book. It was the best way I could pay back the community that has helped me so much in the years I've been a Mac developer.
It took about 6 months to write the draft - my original estimate was much shorter but once we realised I couldn't meet that we revised it, after which I stayed on track with the updated schedule. That's six months of nearly full time work. Some other books probably don't take so long, but in this case I had set myself a very ambitious scope and needed to research quite a lot of the topics before I could write on them. If you've already got a series of blog posts, training material or something that you just want to turn into a book, I can imagine the drafting process being much quicker.
I've found that book authorship is not the best vehicle for self-study. You get a biased view of the material, looking for things that would be interesting to readers rather than things you will need to use yourself. Because the goal of the book is to provide utility to the readers, you end up with a gotcha-oriented approach to research, looking for the subtle benefits or issues that are not obvious on a casual inspection. That said, it was still a good motivation to learn about the technologies I wrote about, so I'm glad I did it. Parts of the writing process were a lot of fun: I got to find out about some cool frameworks and APIs, absorb loads of information and re-emit it in a form that is, I hope, engaging and interesting. I've looked at my bookshelves and have about 6ft of books that I used as source material - and that doesn't include websites, ebooks and journal papers. On the other hand, I'm not going to deny that I had occasional days that just felt like a long slog to get the day's section written. I didn't mind solving hard problems, but there are some subjects that just seem impossible to say anything interesting about. It's when writing those sections that you find yourself staring at a half-written sentence for an hour, wondering just what it was you were thinking when you wrote the ToC.
You're not going to get rich off the advance :). I was in a good position where I could live off practically no income while writing, meaning that devoting a few months to producing the drafts was not a problem. What I have become rich in is exposure and recognition, even before the book was published. Because both the proposal and the book content must be peer-reviewed by a technical reviewer, "I am writing a book" says "there are people out there who trust that I know my subject". Of course, "I have written a book and you can read it" carries more weight, so I expect this exposure to increase after publication.
I've worked on reviewing proposals too, and the things you really need to make sure if you are trying to punt a proposal to publishers are:
This theme carries on into the review process for the actual content. The technical reviewer (a role I've also taken before) is not just there to check that the code compiles. Responsibilities include verifying the accuracy of the content and appropriateness for the target reader, and indeed review comments I've made on book drafts have been split roughly evenly between "this isn't quite right" and "your reader won't understand this" (though I'm more verbose in the actual review).
So, in short, you will not make money writing a book. You will gain kudos and satisfaction. If you've got something that you think the world desperately needs to know, and you know that you can explain it in a way the world will want to pay attention to, then by all means write! If you want to make a few thousand dollars, or want an easy project between apps, then I'd suggest finding something else. Writing's fun, and it's worthwhile, but it's certainly not an easy life.
My original motivation for writing PCAS was that it was a topic someone needed to talk about, and nobody had hitherto done the talking. I was actually initially approached by Wiley to see if I'd write anything at all - their commissioning editor had seen my Objective-C FAQ and this blog, and liked my style. I said that I didn't want to write a book, I wanted to write this book. It was the best way I could pay back the community that has helped me so much in the years I've been a Mac developer.
It took about 6 months to write the draft - my original estimate was much shorter but once we realised I couldn't meet that we revised it, after which I stayed on track with the updated schedule. That's six months of nearly full time work. Some other books probably don't take so long, but in this case I had set myself a very ambitious scope and needed to research quite a lot of the topics before I could write on them. If you've already got a series of blog posts, training material or something that you just want to turn into a book, I can imagine the drafting process being much quicker.
I've found that book authorship is not the best vehicle for self-study. You get a biased view of the material, looking for things that would be interesting to readers rather than things you will need to use yourself. Because the goal of the book is to provide utility to the readers, you end up with a gotcha-oriented approach to research, looking for the subtle benefits or issues that are not obvious on a casual inspection. That said, it was still a good motivation to learn about the technologies I wrote about, so I'm glad I did it. Parts of the writing process were a lot of fun: I got to find out about some cool frameworks and APIs, absorb loads of information and re-emit it in a form that is, I hope, engaging and interesting. I've looked at my bookshelves and have about 6ft of books that I used as source material - and that doesn't include websites, ebooks and journal papers. On the other hand, I'm not going to deny that I had occasional days that just felt like a long slog to get the day's section written. I didn't mind solving hard problems, but there are some subjects that just seem impossible to say anything interesting about. It's when writing those sections that you find yourself staring at a half-written sentence for an hour, wondering just what it was you were thinking when you wrote the ToC.
You're not going to get rich off the advance :). I was in a good position where I could live off practically no income while writing, meaning that devoting a few months to producing the drafts was not a problem. What I have become rich in is exposure and recognition, even before the book was published. Because both the proposal and the book content must be peer-reviewed by a technical reviewer, "I am writing a book" says "there are people out there who trust that I know my subject". Of course, "I have written a book and you can read it" carries more weight, so I expect this exposure to increase after publication.
I've worked on reviewing proposals too, and the things you really need to make sure if you are trying to punt a proposal to publishers are:
- You need to tell the publishers that the market for your book exists, who is in that market and how big it is. They're not going to go and look for the buyers on your behalf (but they will get a reviewer to make sure you're not talking bullshit).
- Having identified your reader, the goals and content of the book must be appropriate to the reader. Don't put an introduction to Xcode in your Advanced iPad Apps book, just to make up an example.
This theme carries on into the review process for the actual content. The technical reviewer (a role I've also taken before) is not just there to check that the code compiles. Responsibilities include verifying the accuracy of the content and appropriateness for the target reader, and indeed review comments I've made on book drafts have been split roughly evenly between "this isn't quite right" and "your reader won't understand this" (though I'm more verbose in the actual review).
So, in short, you will not make money writing a book. You will gain kudos and satisfaction. If you've got something that you think the world desperately needs to know, and you know that you can explain it in a way the world will want to pay attention to, then by all means write! If you want to make a few thousand dollars, or want an easy project between apps, then I'd suggest finding something else. Writing's fun, and it's worthwhile, but it's certainly not an easy life.
Tuesday, March 30, 2010
Rehearsals in beta!
I have a new application, Rehearsals, an online practice diary for musicians. If that sounds like the kind of thing you're interested in, and you have Mac OS X 10.6 or newer, then please download the beta release and test it out. There's absolutely no charge, and if you submit feedback to support <at> rehearsalsapp <dot> com you'll be eligible for a free licence for version 1.0 once that's released. There are no limitations on the beta version, so please do download and start using it!
You can follow @rehearsals_app for updates to the beta programme (new releases are automatically downloaded using Sparkle, if you enable it in the app).
You can follow @rehearsals_app for updates to the beta programme (new releases are automatically downloaded using Sparkle, if you enable it in the app).
Tuesday, March 02, 2010
How to hire Graham Lee
There are few people who can say that when it comes to Cocoa application security, they wrote the book. In fact, I can think of only one: me. I've just put the final draft together for Professional Cocoa Application Security
and it will hit the shops in June: click the link to purchase through my Amazon affiliate programme.
Now that the book's more-or-less complete, I can turn my attention to other interesting projects: by which I mean yours! If your application could benefit from a developer with plenty of security experience and knowledge to share in a pragmatic fashion, or a software engineer who led development of a complex Cocoa application from its legacy PowerPlant origins through Snow Leopard readiness, or a programmer who has worked on performance enhancement in networking systems and low-level daemon code on Darwin and other UNIX platforms, then your project will benefit from an infusion of the Graham Lee magic. Even if you have some NeXTSTEP or OPENSTEP code that needs maintaining, I can help you out: I've been using Cocoa for about as long as Apple has.
Send an email to iamleeg <at> securemacprogramming <dot> com and let's talk about your project. The good news is that for the moment I am available, you probably can afford me[*], and I really want to help make your product better. Want to find out more about my expertise? Check out my section on the MDN show, and the MDN security column.
[*] It came up at NSConference that a number of devs thought I carry a premium due to the conference appearances, podcasts and other material I produce. Because I believe that honesty is the best policy, I want to come out and say that I don't charge any such premium. My rates are consistent with other contractors with my level of experience, and I even provide a discounted rate for NGOs and academic institutions.
and it will hit the shops in June: click the link to purchase through my Amazon affiliate programme.Now that the book's more-or-less complete, I can turn my attention to other interesting projects: by which I mean yours! If your application could benefit from a developer with plenty of security experience and knowledge to share in a pragmatic fashion, or a software engineer who led development of a complex Cocoa application from its legacy PowerPlant origins through Snow Leopard readiness, or a programmer who has worked on performance enhancement in networking systems and low-level daemon code on Darwin and other UNIX platforms, then your project will benefit from an infusion of the Graham Lee magic. Even if you have some NeXTSTEP or OPENSTEP code that needs maintaining, I can help you out: I've been using Cocoa for about as long as Apple has.
Send an email to iamleeg <at> securemacprogramming <dot> com and let's talk about your project. The good news is that for the moment I am available, you probably can afford me[*], and I really want to help make your product better. Want to find out more about my expertise? Check out my section on the MDN show, and the MDN security column.
[*] It came up at NSConference that a number of devs thought I carry a premium due to the conference appearances, podcasts and other material I produce. Because I believe that honesty is the best policy, I want to come out and say that I don't charge any such premium. My rates are consistent with other contractors with my level of experience, and I even provide a discounted rate for NGOs and academic institutions.
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