- Sungnyemun.org

I've added a "Erlang code bits" category, where I'll dump [hopefully] useful snippets of code that could be of use to other people. The first two are rinder.erl, an implementation of the Morris-Pratt algorithm, from Christian Rinderknecht's teaching materials; and png.erl, a project to enable manipulation of PNG files in Erlang. This file has only a couple of functions for the moment, which read the IHDR header and return basic data on the file {width, height, bitDepth, colourType, compression, filter, interlace}. More to come soon.

I had mentioned several times, in a casual manner, on the RB-NUG list that I was working on an ID3v2 class. That thing had started as a request by a customer who needed to see/show artwork in MP3 files.

As usual, every time I set foot in terra incognita I start poking, thinking it'll be a quick hack, and whaddayaknow, I'm in for a long trip... This time it took an inordinately long time, due to day-time jobs [yeah, plural] issues and a lack of interest among the RB fellows.

However one fellow kept bugging me to add a save function, and I finally came around to it, and thanks to this RB fellow, I was able to produce the first Release Candidate for this RB class.

I am currently cleaning it up and ironing out the last few bugs, watch this space for more...

Following a discussion on the RB-NUG on encryption in sqlite/RB Databases, I decided to hack together a quick AES encryption/decryption. I got the rijndael C implementation, compiled it as a dynamic/shared library on Mac OS X and Linux, and wrote a quick RB module to go with it.

You basically have two functions [each with a _VERBOSE alternate that enables you to follow what's happening in the Terminal – CLI apps only]:

• Function ComputeKeyMaterial(mb As MemoryBlock) As MemoryBlock
    This function takes a Memory block containing [keyLength/8] bytes and return a properly formatted keyMaterial to be used in the two functions below.
• Function AES_DECRYPT(keyMaterial As MemoryBlock, inBuffer As MemoryBlock) As MemoryBlock
    keyMaterial should be 128, 192 or 256 bits long.
• Function AES_DECRYPT(keyMaterial As MemoryBlock, inBuffer As MemoryBlock) As MemoryBlock

That's pretty much it. The few tests I made so far seem to work, as you can see for yourself with the sample project: it's a command-line app, you can launch it without any arguments or add some clear text to encrypt [between quotes just to be safe...]. Let me know of any issues you may encounter...

Downloads

• The Mac OS X Version
• The Linux Version
• Build your own dylib/.so from the sources... build script included!

No restriction and no warranties. Use at your own risk and for your own pleasure!

[S]FTP transfers in RB made easy

One thing that is sorely missing in RB is SFTP transfers. The closest way I ever came was to use curl in a shell class. But it's a kludge. After a discussion on a blog, I started poking around libcurl's C API, and managed to produce quite easily an upload method in RB with a gazillion Declares [13 if I remember correctly]. All you needed was a copy of libcurl.dylib on your system. You had the option to do FTP or SFTP, thanks to the CURLOPT_FTP_SSL option. So we get both transfer protocols for the price of one. Sweet...

Then came the download part. For some obscure technical reason [curl needs a callback method, and the parameters are almost impossible to implement in RB], I had to write the download method in C, and compile that into a dynamic library. Which is a pain, since there goes cross-platformness. On the other hand, I linked statically to curllib, so now all you need is the dylib and the curllib module. The [compiled] demo application has a "Frameworks" folder inside the bundle, containing the dylib. A demo account is provided, which allows you 5 transfers before it locks up. To purchase an account, click on the button below.

Sample upload code

Dim ssl As Integer
curllib.Init("user@test","CURL4RB 7DAF-ED42-AFAD")
// Identify yourself. This is the demo login.
if f<>nil Then
  if cbSFTP.Value Then
    ssl=curllib.SSL_TRANSFER
  else
    ssl=curllib.NO_SSL
  end if
  curllib.Upload(f, efLogin.Text, efPwd.Text, efURL.Text, ssl)
end if

As you can see it is very straightforward. The transfer is synchronous: the app will wait for the transfer to succeed [or fail]. I will implement the asynchronous interface later.

Requirements

You need the curlFTP.dylib and the curllib Module; curlFTP.dylib goes into a "Frameworks" folder inside the app's bundle [Mach-0]. It is Mac OS X only for the moment. I will try to provide a Linux version soon. As for Windows, I'll have to work on it more.

Necessary evil

Download

Get the demo here. The demo mode can be unlocked without having to download another version.

MD5 (libcurl4RB.tgz) = a73ddb936d1d573d96bbd2687eb4c9df

Updates

I have uploaded a new version [2005.12.22]; the previous one seemed to require curl, despite my saying it didn't. Compile-time snafu, I guess – or lack of XCode foo. So I switched to linking dynamically to libcurl, which you'll need to install. Other dependencies are met with standard OS X install. Sorry about that. Will try to fix that later.

Features:
There are three methods available:

• getFTP(URL As String, targetFolderItem As FolderItem, isSSL As Integer)
• putFTP(file2upload As FolderItem, Login As String, Pwd As String, URL As String, isSSL As Integer)
• curllib.getHTTP(URL As String) As String

isSSL can be set with: curllib.SSL_TRANSFER and curllib.NO_SSL

This little dylib was meant to be used mainly for [S]FTP transfers, but since it's all there, I added the HTTP[S] get, and could possibly add more. Useful for quick jobbies, I guess...

Dependencies

dda> otool -L curlFTP.dylib 
curlFTP.dylib:
        curlFTP.dylib (compatibility version 0.0.0, current version 0.0.0)
        /usr/lib/libcurl.2.dylib (compatibility version 3.0.0, current version 3.2.0)
        /usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.0.0)
        /usr/lib/libcrypto.0.9.7.dylib (compatibility version 0.9.7, current version 0.9.7)
        /usr/lib/libssl.0.9.7.dylib (compatibility version 0.9.7, current version 0.9.7)
        /System/Library/Frameworks/Carbon.framework/Versions/A/Carbon (compatibility version 2.0.0, current version 128.0.0)
        /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 71.1.4)