Random posts about codingThe slider carousel by html5rocks now comes with an example in dart. I may have loaded to many images into the single page, might take a few seconds to load. The source code can be found on github. Dart provides a simpler way to deal with client side programming, cleaner syntax and simple access to the DOM. Go Dart!
Simply add your command implementations to the Terminal.dart by adding commands to the CMDS list and providing functions to the matching switch statement.
With in the next day or so the dart-web-terminal should include an example with filesystem API in dart.
While Dart is still Alpha these builtin may not be written in stone, so try not to depend on them too much. They can and do provide you with some neat access to native functionality you would commonly need when written shell/system applications.
By including #import(‘dart:builtin’); you can view the builtin dart files from DartEditor. Currently the DartEditor might show warnings when including this module but runtime should not be affected. The truth of the matter is, if you explicitly include ‘dart:builtin’ or not, it is still available to you from implicit inclusion in the DartVM.
The following should give an idea of what built in objects are accessible and how they may be used. The examples should not be considered best practices, just an idea of how you could use them and that they exist. The code is taken from a sample that can be found on Github
Directory
[sourcecode lang=”java”]
Directory d;
if (l.length >= 2) {
d = new Directory(l[1]);
} else {
d = new Directory(".");
}
d.dirHandler = (var dir) {
print("${dir}");
};
d.fileHandler = (var file) {
print("${file}");
};
d.list(true);
[/sourcecode]
File
[sourcecode lang=”java”]
File f = new File(l[0]);
if (!f.existsSync()) {
print("Error: file does not exist");
return;
}
RandomAccessFile r = f.openSync(FileMode.READ);
int length = r.lengthSync();
List buffer = new List(length);
int readLength = r.readListSync(buffer, 0, length);
r.close();
String s = new String.fromCharCodes(buffer);
print(s);
[/sourcecode]
ChunkedInputStream
[sourcecode lang=”java”]
ChunkedInputStream chunkedInputStream = new ChunkedInputStream(f.openInputStream(), 16);
List c = chunkedInputStream.read();
while(c!=null) {
StringBuffer sb = new StringBuffer();
c.forEach((int b) {
sb.add("0x");
if (b.toRadixString(16).length == 1) {
sb.add("0");
}
sb.add(b.toRadixString(16));
sb.add(" ");
});
print(sb.toString());
c = chunkedInputStream.read();
}
[/sourcecode]
InputStream
OutputStream
[sourcecode lang=”java”]
File src = new File(arg[1]);
File dest = new File(arg[2]);
var srcStream = src.openInputStream();
var destStream = dest.openOutputStream();
destStream.write(srcStream.read());
srcStream.close();
destStream.close();
[/sourcecode]
StringInputStream
DynamicListInputStream
ListInputStream
ListOutputStream
Platform
[sourcecode lang=”java”]
Platform p = new Platform();
print(‘{"operatingSystem":${p.operatingSystem()},"numberOfProcessors":${p.numberOfProcessors()},"pathSeparator":${p.pathSeparator()}}’);
[/sourcecode]
Process
[sourcecode lang=”java”]
Process ps = new Process.start(‘ps’, []);
StringBuffer messages = new StringBuffer();
ps.exitHandler = (int status) {
ps.close();
print(messages.toString());
};
ps.stdout.dataHandler = () => _readAll(ps.stdout, messages);
ps.stderr.dataHandler = () => _readAll(ps.stderr, messages);
[/sourcecode]
ServerSocket
[sourcecode lang=”java”]
// initialize the server
serverSocket = new ServerSocket(host, 0, 5);
if (serverSocket == null) {
throw "can’t get server socket";
}
serverSocket.connectionHandler = onConnect;
print("accepting connections on ${host}:${serverSocket.port}");
[/sourcecode]
Socket
[sourcecode lang=”java”]
sendSocket = new Socket(host, serverSocket.port);
if (sendSocket == null) {
throw "can’t get send socket";
}
// send first 4 bytes immediately
for (int i = 0; i < 4; i++) {
sendByte();
}
// send next 4 bytes slowly
new Timer.repeating((Timer t) {
sendByte();
if (bytesSent == bytesTotal) {
sendSocket.close();
t.cancel();
print("finished sending");
}
}, 500);
[/sourcecode]
SocketInputStream
SocketOutputStream
Timer
[sourcecode lang=”java”]
<pre> if (l.length >= 2) {
try {
milliSeconds = (Math.parseInt(l[1]).abs()*milliSeconds);
} catch (BadNumberFormatException ex) {}
}
timer = new Timer((var t) {
print("\nTime elapsed on Timer");
}, milliSeconds);
[/sourcecode]
For those interested in trying Dartium on MacOSX, here is a build of Dartium from Dart’s bleeding_edge. I have just tested it enough to run hello world at the moment. I’d like to get feed back on how it runs for others if possible.
[sourcecode lang=”bash”]wget http://dl.dropbox.com/u/33138127/dartium_macosx/Chromium.app.tar.gz wget http://dl.dropbox.com/u/33138127/dartium_macosx/Chromium.app.tar.gz.md5 wget http://dl.dropbox.com/u/33138127/dartium_macosx/README.txt md5sum -c Chromium.app.tar.gz.md5 [/sourcecode]
It might be best to refer to this previous post for any additional information.
A library consists of (a possibly empty) set of imports, and a set of top level declarations. A top level declaration is either a class (7), an interface (8), a type declaration, a function (6) or a variable declaration (5).Lets dive in and create one main application and one cipher application that will be a library.
Now if we #import CipherLib from filesystem path into our MainApplication both main functions should conflict.
Why this happens is clearly defined in the specification.
Imports assume a global namespace of libraries (at least per isolate). They also assume the library is in control, rather than the other way around. It is a compile-time error if a name N is introduced into the library scope of a library A, and either: N is declared by A, OR Another import introduces N into the scope of A. This implies that it is a load-time error for a library to import itself, as the names of its members will be duplicated.The MainAppication can be adjusted by adding the prefix parameter to the #import declaration. Now from the prefixed name we can call the main method.
From this point lets add another library, will call it XORCipher which will call its library “CipherLib”. The XORCipher and CaesarCipher will have libraries named “CipherLib”, both have functions that have the same name but take different parameters. Now we shall run into a problem that could be presented when using others libraries or code, we have conflicting names in the global namespace of our main application.
The way we resolve this is by adding prefix to one or both libraries and call them from the fully qualified names.[sourcecode lang=”java”]
#import(‘../CaesarCipher/CaesarCipher.dart’, prefix:"Caesar");
#import(‘../XORCipher/XORCipher.dart’, prefix:"XOR");
void main() {
String s = "HELLOWORLD";
print("${s}");
s = XOR.EncryptDecrypt(s);
print("After encrypt XOR ${s}");
s = XOR.EncryptDecrypt(s);
print("After decrypt XOR ${s}");
s = Caesar.EncryptDecrypt(s, true);
print("After encrypt Caesar ${s}");
s = Caesar.EncryptDecrypt(s, false);
print("After decrypt Caesar ${s}");
}
[/sourcecode]
Another way to encapsulate source code using libraries is to use the #source declaration in a #library and then to #import the library into your application. From the language specifications: An include directive specifics a URI where a Dart compilation unit that should be incorporated into the current library may be found. A compilation unit is a sequence of top level declarations. Compiling an include directive of the form #source(s); causes the Dart system to attempt to compile the contents of the URI that is the value of s. The top level declarations at that URI are then compiled by the Dart compiler in the scope of the current library. It is a compile-time error if the contents of the URI are not a valid compilation unit. It is a compile-time error if s is not a compile-time constant.An example of this type of library can be seen in HashLib/hashlib.dart:[sourcecode lang=”java”] #library(‘hashlib’); #source(‘hasher.dart’); #source(‘hasherimpl.dart’); #source(‘aphash.dart’); #source(‘bkdrhash.dart’); #source(‘dekhash.dart’); #source(‘djbhash.dart’); #source(‘elfhash.dart’); #source(‘jshash.dart’); #source(‘pjwhash.dart’); #source(‘rshash.dart’); #source(‘sdbmhash.dart’); #source(‘nullhash.dart’); #source(‘bphash.dart’); #source(‘fnvhash.dart’); [/sourcecode] Another great example of this can be seen in John Evans LUCA UI Framework unit test code. He needed access to some internal dom objects but wanted to preserve the ability to use the elegantly designed html library. [sourcecode lang=”java”] #import(‘dart:html’); #import(‘dart:dom’, prefix:’dom’); #import(‘../unit_test_framework/UnitTestFramework.dart’); #import(‘../core/LUCA_UI_Framework.dart’); [/sourcecode] Its not uncommon to run into instances where two libraries or source files may define classes, interfaces, functions, type definitions that have similar names in other libraries or source files. The best way to work in these types of situations is to add a prefix where your #import are. A very common one that people run into is with “html”, Node and Element class. So individuals wanting to create some type of search or sorting might also want to use the Node name, best answer would be to prefix “html” or your own library code. After your able to reference the library by its fully qualified name, instead of assuming it was globally included. This does feel similar to the using alias in C#, but with a feeling of inversion of control to the library. References: Sample code dart-using-prefix-example Language specification
At the moment Dartium builds are not available on Googles continuous integration server. So I decided to distribute a release build for Linux 32bit . Based on the wiki directions its simple enough for anyone to generate, I felt the need to distribute a build for those who don’t have the time to invest in downloading/configuring/building. An important tip testing dart code in Dartium is to include the additional script call that executes the entry into main(). This is done by adding an additional <script>{}</script> following the line where the dart code is loaded.
The build of Dartium provide is from Rev: 116980
wget http://gsdview.appspot.com/dart-editor-archive-continuous/latest/DartBuild-linux.gtk.x86.zip wget http://dl.dropbox.com/u/33138127/dartium/dartium-linux-32bit-Release.tar.gz wget http://dl.dropbox.com/u/33138127/dartium/dartium-linux-32bit-Release.tar.gz.md5 wget http://dl.dropbox.com/u/33138127/dartium/README.txt md5sum -c dartium-linux-32bit-Release.tar.gz.md5
wget http://dl.dropbox.com/u/33138127/dartium/dartium-browser.desktop vim dartium-browser.desktop wget http://dl.dropbox.com/u/33138127/dartium/dartium-browser.desktop.ubuntu.install.sh sudo ./dartium-browser.desktop.ubuntu.install.sh
Adjust the html to properly execute dart.
Watch dart in its metal state.
Links:http://dl.dropbox.com/u/33138127/dartium/dartium-browser.desktop http://dl.dropbox.com/u/33138127/dartium/dartium-browser.desktop.ubuntu.install.sh http://dl.dropbox.com/u/33138127/dartium/dartium-linux-32bit-Release.tar.gz http://dl.dropbox.com/u/33138127/dartium/dartium-linux-32bit-Release.tar.gz.md5 http://dl.dropbox.com/u/33138127/dartium/README.txt