Testing some LZ77 compression limits

This post is about data compression algorithms that involve LZ77, or a similar kind of compression. It's mainly about old-school compression algorithms and software. There is some information about LZ77 in my post about LZ77 prehistory. I won't explain it in detail here, but here are some things to know about it. Both the compressor …

Win32 I/O character encoding supplement 2 – setlocale enhancement

This is part of a series of post on using Unicode in Windows command-line applications. Here's the first post. Sometime in 2018, some functions in the Windows 10 C runtime system, and related development SDKs, were enhanced to support UTF-8. This feature is enabled by calling the setlocale function. For reference, Microsoft's current documentation of …

The blocksize field in LHA compression format

This post is about the data compression format I'll call "lh5". It is actually a family of formats that includes the compression methods often named lh{4, 5, 6, 7, 8}. It was most notably used by version 2.x of the old LHA/LZH/LHArc compressed archive format. It was used, often in modified form, in a number …

Win32 I/O character encoding supplement 1 – A Cygwin issue

A while back, I wrote a series of posts about using Unicode in Windows console mode programs: Part 1Part 2Part 3 In Part 2, I said that programmers should probably not be changing the console code page to UTF-8 (65001). And that if they must, they should change it back when they're done. But now …

Win32 I/O character encoding part 3

This is the third, and possibly final, post in my series on Microsoft Windows console mode character encodings. It describes how to use Unicode reasonably cleanly, without the "chcp 65001" hack discussed in Part 2. See Part 1 for a list of the posts in this series. Again, the idea is that you are writing …

Win32 I/O character encoding part 2: chcp 65001

In a previous post, I summarized the character encodings used by Windows console mode programs. This is a short post about a not-very-good mitigation technique for some of the resulting problems. In a future post, I'll go over some better solutions. [Edit 2020-05: Unfortunately, I've had to walk back the advice in this post a …

Large prime numbers

As of this writing, the largest known prime number is 277232917-1. "Not large enough!", I say. Let's write a computer program that will print out a larger prime number. No, not a program that will take billions of years to run. It should take only a few minutes. There is a small catch. Hardly worth …

Summary of some Win32 I/O character encoding behavior

This is the first of a series of post. Here are the others: Part 2Part 3Supplement 1Supplement 2 This post is about programming a Windows Win32 application, mainly one that uses the console (command line). It summarizes the results of some tests I performed. Maybe you ported a Unix utility to Windows, but you find …