I am consuming a web service that return an XML of data, how can i convert a string containing lexical representation xsd:hexBinary not base64 format to Uint8List, coming from java i can do this by :
import javax.xml.bind.DatatypeConverter;
....
byte[] decoder = DatatypeConverter.parseHexBinary(hexStringXls);
or
public static byte[] hexStringToByteArray(String s) {
int len = s.length();
byte[] data = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4)
+ Character.digit(s.charAt(i+1), 16));
}
return data;
}
Is this what you want?
final s = "somestring";
final List<int> bytes = s.codeUnits;
https://api.dart.dev/stable/2.8.4/dart-core/String/codeUnits.html
Related
I am converting an IBrowserfile to a stream of 6gig. I am trying to hash the file in chunks but getting the Out Of Memory exception,
public static async Task<byte[]> hashmultiblock(Stream stream)
{
int chunckSize = 30000000;
int totalChunks = (int)(stream.Length / chunckSize);
if (stream.Length % chunckSize != 0)
totalChunks++;
using (SHA256 hashAlgorithm = SHA256.Create())
{
int offset = 0;
for (int i = 0; i < totalChunks; i++)
{
long position = (i * (long)chunckSize);
int toRead = (int)Math.Min(stream.Length - position + 1, chunckSize);
byte[] buffer = new byte[toRead];
if (i == totalChunks)
hashAlgorithm.TransformFinalBlock(buffer.ToArray(), 0, toRead);
else
hashAlgorithm.TransformBlock(buffer.ToArray(), 0, toRead, null, -1);
}
return hashAlgorithm.Hash;
}
}
I am having an issue with my merge sort, when I print out my sortedArray it only returns [ 0.0, 0.0.....] Im not sure if there is an error in my sort code or in my print line or if it has to do with doubles. The code I am us posted below.
By calling System.out.println(toString(sortedArray) I get an even more obscure answer.
Thanks for any help.
package mergesort;
import java.util.Arrays;
import java.util.Random;
public class mergesort {
public static void main(String[] args) {
double[] array = getIntArray();
long before = System.nanoTime();
double[] sortedArray= mergeSort(array);
System.out.println("Sorting took "+ (System.nanoTime() - before) +" nanoseconds ");
System.out.println(toString(array) + "\n\n" + toString(sortedArray) + "\n main method completed in: " + (System.nanoTime() - before) + " nanoseconds.");
}
private static String toString(double[] array) {
StringBuilder sb = new StringBuilder("[ ");
double len = array.length;
for(int i = 0; i < len - 1; i++) {
sb.append(array[i] + ", ");
}
sb.append(array[(int) (len - 1)] + " ]");
return sb.toString();
}
public static double[] mergeSort(double[] array) {
if (array.length <= 1) {
return array;
}
int half = array.length / 2;
return merge(mergeSort(Arrays.copyOfRange(array, 0, half)),
mergeSort(Arrays.copyOfRange(array, half, array.length)));
}
private static double[] merge(double[] ds, double[] ds2) {
int len1 = ds.length, len2 = ds2.length;
int totalLength = len1 + len2;
double[] result = new double[totalLength];
int counterForLeft =0,counterForRight=0,resultIndex=0;
while(counterForLeft<len1 || counterForRight < len2){
if(counterForLeft<len1 && counterForRight < len2){
if(ds[counterForLeft]<= ds2[counterForRight]){
result[resultIndex++] =(int) ds[counterForLeft++];
} else {
result[resultIndex++] =(int) ds2[counterForRight++];
}
}else if(counterForLeft<len1){
result[resultIndex++] = (int) ds[counterForLeft++];
}else if (counterForRight <len2){
result[resultIndex++] =(int) ds2[counterForRight++];
}
}
return result;
}
private static double[] getIntArray() {
double[] array = new double[10000];
Random random = new Random();
for(int i = 0; i < 10000; i++) {
array[i] = (random.nextDouble() * .99999);
}
return array;
}
}
In the merge method, when copying from one of the input arrays to the results, you cast to int. For example:
result[resultIndex++] =(int) ds[counterForLeft++];
All your doubles are in the range [0...1), so the result of casting any of them to int is zero. Just get rid of those casts, and you will keep your numbers in the merge result.
As an additional tip, it is much easier to debug small problems than large ones. It failed for any size greater than 2, so you should have been debugging with size 2, not 10000.
I need to encode and decode BER data. .NET has the class System.DirectoryServices.Protocols.BerConverter
The static method requires me to enter a string in the first parameter as shown below
byte[] oid = { 0x30, 0xD, 0x6, 0x9, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0xD, 0x1, 0x1, 0x1, 0x5, 0x0 }; // Object ID for RSA
var result2 = System.DirectoryServices.Protocols.BerConverter.Decoding("?what goes here?", oid);
BER encoding is used in LDAP, Certificates, and is commonplace in many other formats.
I'll be happy with information telling me how to Encode or Decode on this class. There is nothing on Stack Overflow or the first few pages of Google (or Bing) regarding this.
Question
How do I convert the byte array above to the corresponding OID using BER decoding?
How can I parse (or attempt to parse) SubjectPublicKeyInfo ASN.1 data in DER or BER format?
It seems the DER encoding\decoding classes are internal to the .NET framework. If so, where are they? (I'd like to ask connect.microsoft.com to make these members public)
How do I convert the byte array above to the corresponding OID using BER decoding?
After you have extracted the OID byte array, you can convert it to an OID string using OidByteArrayToString(). I have included the code below, since I couldn't find a similar function in the .NET libraries.
How can I parse (or attempt to parse) SubjectPublicKeyInfo ASN.1 data in DER or BER format?
I was not able to find a TLV parser in the .NET SDK either. Below is an implementation of a BER TLV parser, BerTlv. Since DER is a subset of BER, parsing will work the same way. Given a BER-TLV byte[] array, it will return a list of BerTlv objects that support access of sub TLVs.
It seems the DER encoding\decoding classes are internal to the .NET framework. If so, where are they? (I'd like to ask connect.microsoft.com to make these members public)
Maybe somebody else can answer this question.
Summary
Here is an example of how you can use the code provided below. I have used the public key data you provided in your previous post. The BerTlv should probably be augmented to support querying like BerTlv.getValue(rootTlvs, '/30/30/06');.
public static void Main(string[] args)
{
string pubkey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDrEee0Ri4Juz+QfiWYui/E9UGSXau/2P8LjnTD8V4Unn+2FAZVGE3kL23bzeoULYv4PeleB3gfmJiDJOKU3Ns5L4KJAUUHjFwDebt0NP+sBK0VKeTATL2Yr/S3bT/xhy+1xtj4RkdV7fVxTn56Lb4udUnwuxK4V5b5PdOKj/+XcwIDAQAB";
byte[] pubkeyByteArray = Convert.FromBase64String(pubkey);
List<BerTlv> rootTlvs = BerTlv.parseTlv(pubkeyByteArray);
BerTlv firstTlv = rootTlvs.Where(tlv => tlv.Tag == 0x30).First();//first sequence (tag 30)
BerTlv secondTlv = firstTlv.SubTlv.Where(tlv => tlv.Tag == 0x30).First();//second sequence (tag 30)
BerTlv oid = secondTlv.SubTlv.Where(tlv => tlv.Tag == 0x06).First();//OID tag (tag 30)
string strOid = OidByteArrayToString(oid.Value);
Console.WriteLine(strOid);
}
Output:
1.2.840.113549.1.1.1
OID Encode/Decode
public static byte[] OidStringToByteArray(string oid)
{
string[] split = oid.Split('.');
List<byte> retVal = new List<byte>();
//root arc
if (split.Length > 0)
retVal.Add((byte)(Convert.ToInt32(split[0])*40));
//first arc
if (split.Length > 1)
retVal[0] += Convert.ToByte(split[1]);
//subsequent arcs
for (int i = 2; i < split.Length; i++)
{
int arc_value = Convert.ToInt32(split[i]);
Stack<byte> bytes = new Stack<byte>();
while (arc_value != 0)
{
byte val = (byte) ((arc_value & 0x7F) | (bytes.Count == 0 ? 0x0:0x80));
arc_value >>= 7;
bytes.Push(val);
}
retVal.AddRange(bytes);
}
return retVal.ToArray();
}
public static string OidByteArrayToString(byte[] oid)
{
StringBuilder retVal = new StringBuilder();
//first byte
if (oid.Length > 0)
retVal.Append(String.Format("{0}.{1}", oid[0] / 40, oid[0] % 40));
// subsequent bytes
int current_arc = 0;
for (int i = 1; i < oid.Length; i++)
{
current_arc = (current_arc <<= 7) | oid[i] & 0x7F;
//check if last byte of arc value
if ((oid[i] & 0x80) == 0)
{
retVal.Append('.');
retVal.Append(Convert.ToString(current_arc));
current_arc = 0;
}
}
return retVal.ToString();
}
BER-TLV Parser
class BerTlv
{
private int tag;
private int length;
private int valueOffset;
private byte[] rawData;
private List<BerTlv> subTlv;
private BerTlv(int tag, int length, int valueOffset, byte[] rawData)
{
this.tag = tag;
this.length = length;
this.valueOffset = valueOffset;
this.rawData = rawData;
this.subTlv = new List<BerTlv>();
}
public int Tag
{
get { return tag; }
}
public byte[] RawData
{
get { return rawData; }
}
public byte[] Value
{
get
{
byte[] result = new byte[length];
Array.Copy(rawData, valueOffset, result, 0, length);
return result;
}
}
public List<BerTlv> SubTlv
{
get { return subTlv; }
}
public static List<BerTlv> parseTlv(byte[] rawTlv)
{
List<BerTlv> result = new List<BerTlv>();
parseTlv(rawTlv, result);
return result;
}
private static void parseTlv(byte[] rawTlv, List<BerTlv> result)
{
for (int i = 0, start=0; i < rawTlv.Length; start=i)
{
//parse Tag
bool constructed_tlv = (rawTlv[i] & 0x20) != 0;
bool more_bytes = (rawTlv[i] & 0x1F) == 0x1F;
while (more_bytes && (rawTlv[++i] & 0x80) != 0) ;
i++;
int tag = Util.getInt(rawTlv, start, i-start);
//parse Length
bool multiByte_Length = (rawTlv[i] & 0x80) != 0;
int length = multiByte_Length ? Util.getInt(rawTlv, i+1, rawTlv[i] & 0x1F) : rawTlv[i];
i = multiByte_Length ? i + (rawTlv[i] & 0x1F) + 1: i + 1;
i += length;
byte[] rawData = new byte[i - start];
Array.Copy(rawTlv, start, rawData, 0, i - start);
BerTlv tlv = new BerTlv(tag, length, i - length, rawData);
result.Add(tlv);
if (constructed_tlv)
parseTlv(tlv.Value, tlv.subTlv);
}
}
}
Here is a utility class that contains some functions used in the class above. It is included for the sake of clarity how it works.
class Util
{
public static string getHexString(byte[] arr)
{
StringBuilder sb = new StringBuilder(arr.Length * 2);
foreach (byte b in arr)
{
sb.AppendFormat("{0:X2}", b);
}
return sb.ToString();
}
public static byte[] getBytes(String str)
{
byte[] result = new byte[str.Length >> 1];
for (int i = 0; i < result.Length; i++)
{
result[i] = (byte)Convert.ToInt32(str.Substring(i * 2, 2), 16);
}
return result;
}
public static int getInt(byte[] data, int offset, int length)
{
int result = 0;
for (int i = 0; i < length; i++)
{
result = (result << 8) | data[offset + i];
}
return result;
}
}
I'm planning to use (Handwritten Number Recognition by Yan Cheng, Cheok) for a project I'm working on it,I should use their database for number recognition but the files are not on their website, I should use a file called "LRTBHVtrainingdata.txtI=96H=200LR=0.9M=0.1C=2000.snet" as they say in their tutorial,But what I found on their website (http://yann.lecun.com/exdb/mnist/) is four files and I don't know how to use them ? so any help on where to get their database or where or the files to use them ?
The files you're looking at are the correct files. They are normalized grey-scale images (0-white, 255-black) centered in a 20x20 box. The page explains the structure of the files (just scroll down towards the bottom).
Here's some code I wrote a while back in Java, that reads in the MNIST image and label files:
import net.vivin.digit.DigitImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/**
* Created by IntelliJ IDEA.
* User: vivin
* Date: 11/11/11
* Time: 10:07 AM
*/
public class DigitImageLoadingService {
private String labelFileName;
private String imageFileName;
/** the following constants are defined as per the values described at http://yann.lecun.com/exdb/mnist/ **/
private static final int MAGIC_OFFSET = 0;
private static final int OFFSET_SIZE = 4; //in bytes
private static final int LABEL_MAGIC = 2049;
private static final int IMAGE_MAGIC = 2051;
private static final int NUMBER_ITEMS_OFFSET = 4;
private static final int ITEMS_SIZE = 4;
private static final int NUMBER_OF_ROWS_OFFSET = 8;
private static final int ROWS_SIZE = 4;
public static final int ROWS = 28;
private static final int NUMBER_OF_COLUMNS_OFFSET = 12;
private static final int COLUMNS_SIZE = 4;
public static final int COLUMNS = 28;
private static final int IMAGE_OFFSET = 16;
private static final int IMAGE_SIZE = ROWS * COLUMNS;
public DigitImageLoadingService(String labelFileName, String imageFileName) {
this.labelFileName = labelFileName;
this.imageFileName = imageFileName;
}
public List<DigitImage> loadDigitImages() throws IOException {
List<DigitImage> images = new ArrayList<DigitImage>();
ByteArrayOutputStream labelBuffer = new ByteArrayOutputStream();
ByteArrayOutputStream imageBuffer = new ByteArrayOutputStream();
InputStream labelInputStream = this.getClass().getResourceAsStream(labelFileName);
InputStream imageInputStream = this.getClass().getResourceAsStream(imageFileName);
int read;
byte[] buffer = new byte[16384];
while((read = labelInputStream.read(buffer, 0, buffer.length)) != -1) {
labelBuffer.write(buffer, 0, read);
}
labelBuffer.flush();
while((read = imageInputStream.read(buffer, 0, buffer.length)) != -1) {
imageBuffer.write(buffer, 0, read);
}
imageBuffer.flush();
byte[] labelBytes = labelBuffer.toByteArray();
byte[] imageBytes = imageBuffer.toByteArray();
byte[] labelMagic = Arrays.copyOfRange(labelBytes, 0, OFFSET_SIZE);
byte[] imageMagic = Arrays.copyOfRange(imageBytes, 0, OFFSET_SIZE);
if(ByteBuffer.wrap(labelMagic).getInt() != LABEL_MAGIC) {
throw new IOException("Bad magic number in label file!");
}
if(ByteBuffer.wrap(imageMagic).getInt() != IMAGE_MAGIC) {
throw new IOException("Bad magic number in image file!");
}
int numberOfLabels = ByteBuffer.wrap(Arrays.copyOfRange(labelBytes, NUMBER_ITEMS_OFFSET, NUMBER_ITEMS_OFFSET + ITEMS_SIZE)).getInt();
int numberOfImages = ByteBuffer.wrap(Arrays.copyOfRange(imageBytes, NUMBER_ITEMS_OFFSET, NUMBER_ITEMS_OFFSET + ITEMS_SIZE)).getInt();
if(numberOfImages != numberOfLabels) {
throw new IOException("The number of labels and images do not match!");
}
int numRows = ByteBuffer.wrap(Arrays.copyOfRange(imageBytes, NUMBER_OF_ROWS_OFFSET, NUMBER_OF_ROWS_OFFSET + ROWS_SIZE)).getInt();
int numCols = ByteBuffer.wrap(Arrays.copyOfRange(imageBytes, NUMBER_OF_COLUMNS_OFFSET, NUMBER_OF_COLUMNS_OFFSET + COLUMNS_SIZE)).getInt();
if(numRows != ROWS && numRows != COLUMNS) {
throw new IOException("Bad image. Rows and columns do not equal " + ROWS + "x" + COLUMNS);
}
for(int i = 0; i < numberOfLabels; i++) {
int label = labelBytes[OFFSET_SIZE + ITEMS_SIZE + i];
byte[] imageData = Arrays.copyOfRange(imageBytes, (i * IMAGE_SIZE) + IMAGE_OFFSET, (i * IMAGE_SIZE) + IMAGE_OFFSET + IMAGE_SIZE);
images.add(new DigitImage(label, imageData));
}
return images;
}
}
I want to split a file ( a docx file) and use the individual fragments of the file to encode a QRCode such that when the qrcodes are read in sequence, it reproduces the original file.
I was able to split the file and create a bunch of QRCodes but when attempted to recreate the file, the Decoder throws the following Error Message.
"Invalid number of finder pattern detected"
I am using http://www.codeproject.com/KB/cs/qrcode.aspx library.
My encoder code
private List Encode(String content, Encoding encoding, int
System.Drawing.Color qrCodeBackgroundColor,
QRCodeCapacity,System.Drawing.Color qrCodeBackgroundColor,System.Drawing.Color
qrCodeForegroundColor,int qrCodeScale, int NoOfQRcodes)
{
List<Bitmap> _qrcodesImages = new List<Bitmap>();
byte[] _filebytearray = encoding.GetBytes(content);
for (int k = 0,l=0; k < NoOfQRcodes; k++)
{
byte[] _tempByteArray = _filebytearray.Skip(l).Take(QRCodeCapacity).ToArray();
bool[][] matrix = calQrcode(_tempByteArray);
SolidBrush brush = new SolidBrush(qrCodeBackgroundColor);
Bitmap image = new Bitmap((matrix.Length * qrCodeScale) + 1, (matrix.Length * qrCodeScale) + 1);
Graphics g = Graphics.FromImage(image);
g.FillRectangle(brush, new Rectangle(0, 0, image.Width, image.Height));
brush.Color = qrCodeForegroundColor;
for (int i = 0; i < matrix.Length; i++)
{
for (int j = 0; j < matrix.Length; j++)
{
if (matrix[j][i])
{
g.FillRectangle(brush, j * qrCodeScale, i * qrCodeScale, qrCodeScale, qrCodeScale);
}
}
}
_qrcodesImages.Add(image);
l += QRCodeCapacity;
}
return _qrcodesImages;
}