The Old New Thing
Practical development throughout the evolution of Windows.
Latest posts
Performance consequences of polling
Polling kills. A program should not poll as a matter of course. Doing so can have serious consequences on system performance. It's like checking your watch every minute to see if it's 3 o'clock yet instead of just setting an alarm. First of all, polling means that a small amount of CPU time gets eaten up at each poll even though there is nothing to do. Even if you tune your polling loop so its CPU usage is only, say, a measly one tenth of one percent, once this program is placed on a Terminal Server with 800 simultaneous connections, your 0.1% CPU has magnified into 80% CPU. Next, the fact that a small snippet...
There are two types of rebates, and you need to be on the alert
Many commenters to my earlier entry on sales in France had questions about rebates. Slate explained the whole rebate thing back in 2003. The short version: There are two types of rebates, manufacturer rebates and retailer rebates. Manufacturer rebates exist because they want the retail price to go down, but they are afraid that if they just lowered the wholesale price, retailers would not pass the savings on to the consumer. A manufacturer's rebate ensures that all the benefit of the price drop goes to the consumer and not to any middle-men. Retailer rebates, on the other hand, are carefully crafted schemes de...
If your callback fails, it's your responsibility to set the error code
There are many cases where a callback function is allowed to halt an operation. For example, you might decide to return to the message to prevent the window from being created, or you might decide to return to one of the many enumeration callback functions such as the callback. When you do this, the enclosing operation will return failure back to its caller: the function returns ; the function returns . Of course, when this happens, the enclosing operation doesn't know why the callback failed; all it knows is that it failed. Consequently, it can't set a meaningful value to be retrieved by the functio...
The vtable does not always go at the start of the object
There is no requirement that it does, and it often doesn't.
How air conditioning revolutionized competitive bicycling
I'm not really interested in sports. Teams, standings, scores, who got traded to what team, none of that is interesting to me. What I am interested in, however, is "meta-sports": The business of sports, the technology of sports, the evolution of techniques, changes in the rules, that sort of thing. That's one of the reasons I'm a fan of the radio program Only a Game. (The other, more important, reason can be summed up in two words: Charlie Pierce.) All that is a rather lengthy lead-in to Transition Game, Nick Schulz's look at the world behind sports. He covers what it is about sports that I like, with none of...
The cost of trying too hard: String searching
There are many algorithms for fast string searching, but the running of a string search is inherently O(n), where n is the length of the string being searched: If m is the length of the string being searched for (which I will call the "target string"), then any algorithm that accesses fewer than n/m elements of the string being searched will have a gap of m unaccessed elements, which is enough room to hide the target string. More advanced string searching algorithms can take advantage of characteristics of the target string, but in the general case, where the target string is of moderate size and ...
From Doom to Gloom: The story of a video game
NPR's Morning Edition developed a series on the subject of flops, and one of their segments was devoted to the rise and fall of John Romero. You can read more about the phenomenon known as Daikatana in a huge series on Gamespot. Set aside at least an hour if you choose to read it. You can also read the Dallas Observer story that opened the floodgates.
The cost of trying too hard: Splay trees
Often, it doesn't pay off to be too clever. Back in the 1980's, I'm told the file system group was working out what in-memory data structures to use to represent the contents of a directory so that looking up a file by name was fast. One of the experiments they tried was the splay tree. Splay trees were developed in 1985 by Sleator and Tarjan as a form of self-rebalancing tree that provides O(log n) amortized cost for locating an item in the tree, where n is the number of items in the tree. (Amortized costing means roughly that the cost of M operations is O(M log n). The cost of an individual opera...
ReadProcessMemory is not a preferred IPC mechanism
Many limitations, some with security implications.