I'm trying to generate a Session code based on the following code from PHP in Dart/Flutter:
private $length = 32;
substr(bin2hex(random_bytes($this->length), 0, $this->length);
the problem is that I don't know how to create these random_bytes in dart and then convert them to bin2hex, using DART language.
These functions described above are from PHP (opencart system) which I must to create a hash to specify session from each user connected.
the result expected from this conversion is something like that:
"004959d3386996b8f8b0e6180101059d"
If your goal are just to generate such a hex-string using random numbers, you can do something like this:
import 'dart:math';
void main() {
print(randomHexString(32)); // 1401280aa29717e4940f0845f0d43abd
}
Random _random = Random();
String randomHexString(int length) {
StringBuffer sb = StringBuffer();
for (var i = 0; i < length; i++) {
sb.write(_random.nextInt(16).toRadixString(16));
}
return sb.toString();
}
Related
Is there any editor for dart.
I was trying to run my dart program at vscode it runs but did not print anything.
I was trying to take input from user and add it into a list of numbers and then show the list on console.
It takes the input but did not shown any list.
// Importing dart:io file
import 'dart:io';
void main() {
List<int> list = [5];
// Scanning number
for (var i = 0; i < list.length; i++) {
int? n = int.parse(stdin.readLineSync()!);
list.add(n);
}
// Here ? and ! are for null safety
// Printing that number
print("Your list $list");
}
I have an EmguCV.Image<Brg, Byte>() instance and another 3rd party API, that requires Stream that represents the image data.
I was able to convert the EmguCV image to the stream and pass it to the 3rd party API using System.Drawing.Bitmap.Save but that is not very efficient.
How to get the stream as afficietnly as possible?
This code works:
var image = new Image<Rgb, byte>("photo.jpg");
var bitmap = image.Bitmap// System.Drawing - this takes 108ms!
using (var ms = new MemoryStream())
{
bitmap.Save(ms, ImageFormat.Bmp); //not very efficient either
ms.Position = 0;
return ImageUtils.load(ms); //the 3rd party API
}
I have tried to create UnmanagedMemoryStream directly from the image:
byte* pointer = (byte*)image.Ptr.ToPointer();
int length = image.Height*image.Width*3;
var unmanagedMemoryStream = new UnmanagedMemoryStream(pointer, length);
but when i try to read from it, it throws an AccessViolationException: Attempted to read or write protected memory.
for (int i = 0; i < length; i++)
{
//throw AccessViolationException at random interation, e.g i==82240, 79936, etc
unmanagedMemoryStream.ReadByte();
}
the length is 90419328 in this case and it shoudl be correct, because it has the same value as image.ManagedArray.Length;
How to get the stream without copying the data?
Ok, there is Bytes property of type byte[] on the Image() so the answer is very easy:
new MemoryStream(image.Bytes)
I looking for the equivalent of
java.io.DataInputStream.readDouble() for Vala.
Is it even possible?
Currently I have :
public double data;
public override void load (DataInputStream dis) throws IOError {
data = dis.read_int64 ();
}
But it just converting a int64 to a double which is not what I want.
I've tried all sort of casting and de-referencing, but nothing seems to work.
This worked for me:
int main()
{
int64 foo = 0; // Whatever value you have
double data = *(double*)(&foo); // This is where the "magic" happens
stdout.printf("%f", data);
return 0;
}
Mind you, you may have to set the correct byte order for the conversion to succeed.
I need to see some example code in java so that i can figure out the proper functioning of the various methods defined in the library.Also how to pass various necessary parameters.
some of them are
svm_predict
svm_node
svm_problem etc.
I have done a lot of googling and i still haven't found something substantial. And the documentation for java is another major disappointment. please help me out!!
here is some code that i have written so far.
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import libsvm.*;
import libsvm.svm_node;
import java.io.IOException;
import java.io.InputStream;
public class trial {
public static void main(String[] args) throws IOException {
svm temp = new svm();
svm_model model;
model = svm.svm_load_model("C:\\Users\\sidharth\\Desktop\\libsvm-3.18\\windows\\svm- m.model");
svm_problem prob = new svm_problem();
prob.l = trial.countLines("C:\\Users\\sidharth\\Desktop\\libsvm-3.18\\windows\\svm-ml.test");
prob.y = new double[prob.l];
int i;
for(i=0;i<prob.l;i++)
{
prob.y[i]=0.0;
}
prob.x = new svm_node[prob.l][];
temp.svm_predict(model, /*what to put here*/);
}
public static int countLines(String filename) throws IOException {
InputStream is = new BufferedInputStream(new FileInputStream(filename));
try {
byte[] c = new byte[1024];
int count = 0;
int readChars = 0;
boolean empty = true;
while ((readChars = is.read(c)) != -1) {
empty = false;
for (int i = 0; i < readChars; ++i) {
if (c[i] == '\n') {
++count;
}
}
}
return (count == 0 && !empty) ? 1 : count;
} finally {
is.close();
}
}
}
I already have a model file created and i want to predict a sample data using this model file. I have given prob.y[] a label of 0 .
Any example code that has been written by you will be of great help.
P.S. I am supposed to make an SVM based POS tagger. that is why i have tagged nlp.
Its pretty straightforward.
For training you could write something of the form:
svm_train training = new svm_train();
String[] options = new String[7];
options [0] = "-c";
options [1] = "1";
options [2] = "-t";
options [3] = "0"; //linear kernel
options [4] = "-v";
options [5] = "10"; //10 fold cross-validation
options [6] = your_training_filename;
training.run(options);
If you choose to save the model. Then you can retrieve it by
libsvm.svm_model model = training.getModel();
If you wish to test the model on test data, you could write something of the form:
BufferedReader input = new BufferedReader(new FileReader(test_file));
DataOutputStream output = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(prediction_output_file)));
svm_predict.predict(input, output, model, 0);
Hope this helps !
How i can do a simple pattern matching in blackberry OS 6.0. The purpose is to check whether the user name entered to the UserName edit field contains special characters.... plz help me
thanks jibysthomas
A better solution would be to control the user input by adding an appropriate TextFilter to your edit field. That has the added benefit of modifying the on-screen keyboard to match your filter on those devices so equipped.
Here is an example combining the action of two built in text filters to make one that only allows upper letters and numbers:
import net.rim.device.api.ui.text.TextFilter;
import net.rim.device.api.system.Characters;
/**
* A TextFilter class to filter for station identifiers
*/
private static class StationFilter extends TextFilter {
// Order of the supporting filters is important, NUMERIC will convert
// letters to numbers if it gets them first.
private static TextFilter[] _tf = {
TextFilter.get(TextFilter.NUMERIC),
TextFilter.get(TextFilter.UPPERCASE)
};
// Convert using the first supporting filter that has a conversion
public char convert( char character, int status) {
char c = 0;
for (int i = _tf.length - 1; i >= 0; i--) {
c = _tf[i].convert(character, status);
if (c != 0) {
return c;
}
}
return 0;
}
// Validate a space for separator, then by supporting filter
public boolean validate(char character) {
if (character == Characters.SPACE) {
return true;
}
for (int i = _tf.length - 1; i >= 0; i--) {
boolean b = _tf[i].validate(character);
if (b) {
return true;
}
}
return false;
}
}