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  • Minecraft Style Chunk building problem

    - by David Torrey
    I'm having some problems with speed in my chunk engine. I timed it out, and in its current state it takes a total ~5 seconds per chunk to fill each face's list. I have a check to see if each face of a block is visible and if it is not visible, it skips it and moves on. I'm using a dictionary (unordered map) because it makes sense memorywise to just not have an entry if there is no block. I've tracked my problem down to testing if there is an entry, and accessing an entry if it does exist. If I remove the tests to see if there is an entry in the dictionary for an adjacent block, or if the block type itself is seethrough, it runs within about 2-4 milliseconds. so here's my question: Is there a faster way to check for an entry in a dictionary than .ContainsKey()? As an aside, I tried TryGetValue() and it doesn't really help with the speed that much. If I remove the ContainsKey() and keep the test where it does the IsSeeThrough for each block, it halves the time, but it's still about 2-3 seconds. It only drops to 2-4ms if I remove BOTH checks. Here is my code: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Runtime.InteropServices; using OpenTK; using OpenTK.Graphics.OpenGL; using System.Drawing; namespace Anabelle_Lee { public enum BlockEnum { air = 0, dirt = 1, } [StructLayout(LayoutKind.Sequential,Pack=1)] public struct Coordinates<T1> { public T1 x; public T1 y; public T1 z; public override string ToString() { return "(" + x + "," + y + "," + z + ") : " + typeof(T1); } } public struct Sides<T1> { public T1 left; public T1 right; public T1 top; public T1 bottom; public T1 front; public T1 back; } public class Block { public int blockType; public bool SeeThrough() { switch (blockType) { case 0: return true; } return false ; } public override string ToString() { return ((BlockEnum)(blockType)).ToString(); } } class Chunk { private Dictionary<Coordinates<byte>, Block> mChunkData; //stores the block data private Sides<List<Coordinates<byte>>> mVBOVertexBuffer; private Sides<int> mVBOHandle; //private bool mIsChanged; private const byte mCHUNKSIZE = 16; public Chunk() { } public void InitializeChunk() { //create VBO references #if DEBUG Console.WriteLine ("Initializing Chunk"); #endif mChunkData = new Dictionary<Coordinates<byte> , Block>(); //mIsChanged = true; GL.GenBuffers(1, out mVBOHandle.left); GL.GenBuffers(1, out mVBOHandle.right); GL.GenBuffers(1, out mVBOHandle.top); GL.GenBuffers(1, out mVBOHandle.bottom); GL.GenBuffers(1, out mVBOHandle.front); GL.GenBuffers(1, out mVBOHandle.back); //make new list of vertexes for each face mVBOVertexBuffer.top = new List<Coordinates<byte>>(); mVBOVertexBuffer.bottom = new List<Coordinates<byte>>(); mVBOVertexBuffer.left = new List<Coordinates<byte>>(); mVBOVertexBuffer.right = new List<Coordinates<byte>>(); mVBOVertexBuffer.front = new List<Coordinates<byte>>(); mVBOVertexBuffer.back = new List<Coordinates<byte>>(); #if DEBUG Console.WriteLine("Chunk Initialized"); #endif } public void GenerateChunk() { #if DEBUG Console.WriteLine("Generating Chunk"); #endif for (byte i = 0; i < mCHUNKSIZE; i++) { for (byte j = 0; j < mCHUNKSIZE; j++) { for (byte k = 0; k < mCHUNKSIZE; k++) { Random blockLoc = new Random(); Coordinates<byte> randChunk = new Coordinates<byte> { x = i, y = j, z = k }; mChunkData.Add(randChunk, new Block()); mChunkData[randChunk].blockType = blockLoc.Next(0, 1); } } } #if DEBUG Console.WriteLine("Chunk Generated"); #endif } public void DeleteChunk() { //delete VBO references #if DEBUG Console.WriteLine("Deleting Chunk"); #endif GL.DeleteBuffers(1, ref mVBOHandle.left); GL.DeleteBuffers(1, ref mVBOHandle.right); GL.DeleteBuffers(1, ref mVBOHandle.top); GL.DeleteBuffers(1, ref mVBOHandle.bottom); GL.DeleteBuffers(1, ref mVBOHandle.front); GL.DeleteBuffers(1, ref mVBOHandle.back); //clear all vertex buffers ClearPolyLists(); #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void UpdateChunk() { #if DEBUG Console.WriteLine("Updating Chunk"); #endif ClearPolyLists(); //prepare buffers //for every entry in mChunkData map foreach(KeyValuePair<Coordinates<byte>,Block> feBlockData in mChunkData) { Coordinates<byte> checkBlock = new Coordinates<byte> { x = feBlockData.Key.x, y = feBlockData.Key.y, z = feBlockData.Key.z }; //check for polygonson the left side of the cube if (checkBlock.x > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x - 1, checkBlock.y, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.left); } //check for polygons on the right side of the cube if (checkBlock.x < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x + 1, checkBlock.y, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.right); } if (checkBlock.y > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y - 1, checkBlock.z)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.bottom); } //check for polygons on the right side of the cube if (checkBlock.y < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y + 1, checkBlock.z)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.top); } if (checkBlock.z > 0) { //check to see if there is a key for current x - 1. if not, add the vector if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z - 1)) { //add polygon AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } } else { //polygon is far left and should be added AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.back); } //check for polygons on the right side of the cube if (checkBlock.z < mCHUNKSIZE - 1) { if (!IsVisible(checkBlock.x, checkBlock.y, checkBlock.z + 1)) { //add poly AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } else { //poly for right add AddPoly(checkBlock.x, checkBlock.y, checkBlock.z, mVBOHandle.front); } } BuildBuffers(); #if DEBUG Console.WriteLine("Chunk Updated"); #endif } public void RenderChunk() { } public void LoadChunk() { #if DEBUG Console.WriteLine("Loading Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Deleted"); #endif } public void SaveChunk() { #if DEBUG Console.WriteLine("Saving Chunk"); #endif #if DEBUG Console.WriteLine("Chunk Saved"); #endif } private bool IsVisible(int pX,int pY,int pZ) { Block testBlock; Coordinates<byte> checkBlock = new Coordinates<byte> { x = Convert.ToByte(pX), y = Convert.ToByte(pY), z = Convert.ToByte(pZ) }; if (mChunkData.TryGetValue(checkBlock,out testBlock )) //if data exists { if (testBlock.SeeThrough() == true) //if existing data is not seethrough { return true; } } return true; } private void AddPoly(byte pX, byte pY, byte pZ, int BufferSide) { //create temp array GL.BindBuffer(BufferTarget.ArrayBuffer, BufferSide); if (BufferSide == mVBOHandle.front) { //front face mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.front.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.right) { //back face mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.back.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.top) { //left face mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.left.Add(new Coordinates<byte> { x = (byte)(pX), y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.bottom) { //right face mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ + 1) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY) , z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.right.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); } else if (BufferSide == mVBOHandle.front) { //top face mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ + 1) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY + 1), z = (byte)(pZ) }); mVBOVertexBuffer.top.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY + 1), z = (byte)(pZ) }); } else if (BufferSide == mVBOHandle.back) { //bottom face mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX + 1), y = (byte)(pY), z = (byte)(pZ + 1) }); mVBOVertexBuffer.bottom.Add(new Coordinates<byte> { x = (byte)(pX) , y = (byte)(pY), z = (byte)(pZ + 1) }); } } private void BuildBuffers() { #if DEBUG Console.WriteLine("Building Chunk Buffers"); #endif GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.front); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.front.Count), mVBOVertexBuffer.front.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.back); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.back.Count), mVBOVertexBuffer.back.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.left); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.left.Count), mVBOVertexBuffer.left.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.right); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.right.Count), mVBOVertexBuffer.right.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.top); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.top.Count), mVBOVertexBuffer.top.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer, mVBOHandle.bottom); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(Marshal.SizeOf(new Coordinates<byte>()) * mVBOVertexBuffer.bottom.Count), mVBOVertexBuffer.bottom.ToArray(), BufferUsageHint.StaticDraw); GL.BindBuffer(BufferTarget.ArrayBuffer,0); #if DEBUG Console.WriteLine("Chunk Buffers Built"); #endif } private void ClearPolyLists() { #if DEBUG Console.WriteLine("Clearing Polygon Lists"); #endif mVBOVertexBuffer.top.Clear(); mVBOVertexBuffer.bottom.Clear(); mVBOVertexBuffer.left.Clear(); mVBOVertexBuffer.right.Clear(); mVBOVertexBuffer.front.Clear(); mVBOVertexBuffer.back.Clear(); #if DEBUG Console.WriteLine("Polygon Lists Cleared"); #endif } }//END CLASS }//END NAMESPACE

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  • Type casting needed for byte = byte - byte?

    - by Vaccano
    I have the following code: foreach (byte b in bytes) { byte inv = byte.MaxValue - b; // Add the new value to a list.... } When I do this I get the following error: Cannot implicitly convert type 'int' to 'byte'. An explicit conversion exists (are you missing a cast?) Each part of this statement is a byte. Why does C# want to convert the byte.MaxValue - b to an int? Shouldn't you be able to do this some how without casting? (i.e. I don't want to have to do this: byte inv = (byte) (byte.MaxValue - b);)

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  • EnOcean -> USB Serial Communication (C++)

    - by regorianer
    I guess it is not the right place to ask here for enocean specific details, but maybe I am doing something wrong by using serial connections and you can help me no matter if there is knowledge about this technology or not. I have a problem to communicate with the RCM152 Module. I have written a C++ program to communicate with the RCM152 by emulating packets of the PTM 200. I teach the RCM152 to listen to the following packets: [06/19/12 04:21:44.546] INFO: SENDING BYTE : 55 <-- start byte [06/19/12 04:21:44.546] INFO: SENDING BYTE : 00 <-- head begin [06/19/12 04:21:44.546] INFO: SENDING BYTE : 07 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 07 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 01 <-- head end [06/19/12 04:21:44.546] INFO: SENDING BYTE : 7a <-- CRC Check [06/19/12 04:21:44.546] INFO: SENDING BYTE : f6 <-- packet type [06/19/12 04:21:44.546] INFO: SENDING BYTE : 20 <-- My action (00 and 10 -> OFF, 20 and 30 -> ON) [06/19/12 04:21:44.546] INFO: SENDING BYTE : 00 <-- serial.byte 3 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 24 <-- serial.byte 2 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 21 <-- serial.byte 1 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 87 <-- serial.byte 0 [06/19/12 04:21:44.546] INFO: SENDING BYTE : 30 <-- status [06/19/12 04:21:44.546] INFO: SENDING BYTE : 03 <-- 03 for send, 01 for receiver [06/19/12 04:21:44.546] INFO: SENDING BYTE : ff <-- begin destination [06/19/12 04:21:44.546] INFO: SENDING BYTE : ff [06/19/12 04:21:44.546] INFO: SENDING BYTE : ff [06/19/12 04:21:44.546] INFO: SENDING BYTE : ff <-- end destination [06/19/12 04:21:44.546] INFO: SENDING BYTE : ff <-- Transmission quality (sender ff) [06/19/12 04:21:44.546] INFO: SENDING BYTE : 00 [06/19/12 04:21:44.547] INFO: SENDING BYTE : 10 <-- CRC Check A PTM200 Device or a SG-FUS-24-230 Device are sending equivalent packets like: [06/19/12 04:30:31.106] INFO: Received Byte: 55 [06/19/12 04:30:31.106] INFO: Received Byte: 00 [06/19/12 04:30:31.106] INFO: Received Byte: 07 [06/19/12 04:30:31.106] INFO: Received Byte: 07 [06/19/12 04:30:31.106] INFO: Received Byte: 01 [06/19/12 04:30:31.106] INFO: Received Byte: 7a [06/19/12 04:30:31.106] INFO: Received Byte: f6 [06/19/12 04:30:31.106] INFO: Received Byte: 40 [06/19/12 04:30:31.106] INFO: Received Byte: 00 [06/19/12 04:30:31.106] INFO: Received Byte: 24 [06/19/12 04:30:31.106] INFO: Received Byte: 6c [06/19/12 04:30:31.106] INFO: Received Byte: 2f [06/19/12 04:30:31.106] INFO: Received Byte: 30 [06/19/12 04:30:31.106] INFO: Received Byte: 01 [06/19/12 04:30:31.106] INFO: Received Byte: ff [06/19/12 04:30:31.106] INFO: Received Byte: ff [06/19/12 04:30:31.108] INFO: Received Byte: ff [06/19/12 04:30:31.108] INFO: Received Byte: ff [06/19/12 04:30:31.108] INFO: Received Byte: 37 [06/19/12 04:30:31.108] INFO: Received Byte: 00 [06/19/12 04:30:31.108] INFO: Received Byte: d1 I can control the device connected to the RCM152 like I want to with my sending packets (thats a good fact and means that the RCM152 has learned my packets and can use them. Also the actions (0x10 - ON, 0x30 - OFF) are working fine), but the problem is, that no matter which serial I choose, the RCM152 reacts to these packets. I only want to have actions if the teached-in serial is send and all other packets with different serials to be ignored. The RCM152 is not reacting to the packets sent by the PTM200 nor by the SG-FUS-24-230 because these are not teached-in. Thats exactly what I want to have with the packets created myself. What am I doing wrong? The libraries I am using are these for C++ http://pvbrowser.de/pvbrowser/sf/manual/rllib/html/ The enocean EEP says: For this purpose of a determined relationship between transmitter and receiver each transmitting device has a unique Sender-ID which is part of each radio telegram. The receiving device detects from the Sender-ID whether the device is known, i.e., was already learned, or unknown. A telegram with unknown Sender-ID is disregarded.

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  • Converting 3 dimension byte array to a single byte array [on hold]

    - by Andrew Simpson
    I have a 3 dimensional byte array. The 3-d array represents a jpeg image. Each channel/array represents part of the RGB spectrum. I am not interested in retaining black pixels. A black pixel is represented by this atypical arrangement: myarray[0,0,0] =0; myarray[0,0,1] =0; myarray[0,0,2] =0; So, I have flattened this 3d array out to a 1d array by doing this byte[] AFlatArray = new byte[width x height x 3] and then assigning values respective to the coordinate. But like I said I do not want black pixels. So this array has to only contain color pixels with the x,y coordinate. The result I want is to re-represent the image from the i dimension byte array that only contains non-black pixels. How do I do that? It looks like I have to store black pixels as well because of the xy coordinate system. I have tried writing to a binary file but the size of that file is greater than the jpeg file as the jpeg file is compressed. I am using c#.

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  • C# (4): double minus double giving precision problems

    - by thermal7
    I have come across a precision issue with double in .NET I thought this only applied to floats but now I see that double is a float. double test = 278.97 - 90.46; Debug.WriteLine(test) //188.51000000000005 //correct answer is 188.51 What is the correct way to handle this? Round? Lop off the unneeded decimal places?

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  • Using delegates in C# (Part 2)

    - by rajbk
    Part 1 of this post can be read here. We are now about to see the different syntaxes for invoking a delegate and some c# syntactic sugar which allows you to code faster. We have the following console application. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: Operation op1 = new Operation(Division); 9: double result = op1.Invoke(10, 5); 10: 11: Console.WriteLine(result); 12: Console.ReadLine(); 13: } 14: 15: static double Division(double x, double y) { 16: return x / y; 17: } 18: } Line 1 defines a delegate type called Operation with input parameters (double x, double y) and a return type of double. On Line 8, we create an instance of this delegate and set the target to be a static method called Division (Line 15) On Line 9, we invoke the delegate (one entry in the invocation list). The program outputs 5 when run. The language provides shortcuts for creating a delegate and invoking it (see line 9 and 11). Line 9 is a syntactical shortcut for creating an instance of the Delegate. The C# compiler will infer on its own what the delegate type is and produces intermediate language that creates a new instance of that delegate. Line 11 uses a a syntactical shortcut for invoking the delegate by removing the Invoke method. The compiler sees the line and generates intermediate language which invokes the delegate. When this code is compiled, the generated IL will look exactly like the IL of the compiled code above. 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //shortcut constructor syntax 9: Operation op1 = Division; 10: //shortcut invoke syntax 11: double result = op1(10, 2); 12: 13: Console.WriteLine(result); 14: Console.ReadLine(); 15: } 16: 17: static double Division(double x, double y) { 18: return x / y; 19: } 20: } C# 2.0 introduced Anonymous Methods. Anonymous methods avoid the need to create a separate method that contains the same signature as the delegate type. Instead you write the method body in-line. There is an interesting fact about Anonymous methods and closures which won’t be covered here. Use your favorite search engine ;-)We rewrite our code to use anonymous methods (see line 9): 1: public delegate double Operation(double x, double y); 2:  3: public class Program 4: { 5: [STAThread] 6: static void Main(string[] args) 7: { 8: //Anonymous method 9: Operation op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } We could rewrite our delegate to be of a generic type like so (see line 2 and line 9). You will see why soon. 1: //Generic delegate 2: public delegate T Operation<T>(T x, T y); 3:  4: public class Program 5: { 6: [STAThread] 7: static void Main(string[] args) 8: { 9: Operation<double> op1 = delegate(double x, double y) { 10: return x / y; 11: }; 12: double result = op1(10, 2); 13: 14: Console.WriteLine(result); 15: Console.ReadLine(); 16: } 17: 18: static double Division(double x, double y) { 19: return x / y; 20: } 21: } The .NET 3.5 framework introduced a whole set of predefined delegates for us including public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2); Our code can be modified to use this delegate instead of the one we declared. Our delegate declaration has been removed and line 7 has been changed to use the Func delegate type. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //Func is a delegate defined in the .NET 3.5 framework 7: Func<double, double, double> op1 = delegate (double x, double y) { 8: return x / y; 9: }; 10: double result = op1(10, 2); 11: 12: Console.WriteLine(result); 13: Console.ReadLine(); 14: } 15: 16: static double Division(double x, double y) { 17: return x / y; 18: } 19: } .NET 3.5 also introduced lambda expressions. A lambda expression is an anonymous function that can contain expressions and statements, and can be used to create delegates or expression tree types. We change our code to use lambda expressions. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //lambda expression 7: Func<double, double, double> op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } C# 3.0 introduced the keyword var (implicitly typed local variable) where the type of the variable is inferred based on the type of the associated initializer expression. We can rewrite our code to use var as shown below (line 7).  The implicitly typed local variable op1 is inferred to be a delegate of type Func<double, double, double> at compile time. 1: public class Program 2: { 3: [STAThread] 4: static void Main(string[] args) 5: { 6: //implicitly typed local variable 7: var op1 = (x, y) => x / y; 8: double result = op1(10, 2); 9: 10: Console.WriteLine(result); 11: Console.ReadLine(); 12: } 13: 14: static double Division(double x, double y) { 15: return x / y; 16: } 17: } You have seen how we can write code in fewer lines by using a combination of the Func delegate type, implicitly typed local variables and lambda expressions.

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  • Adding multiple byte arrays in c# [migrated]

    - by James P. Wright
    I'm working on a legacy system that uses byte arrays for permission levels. Example: 00 00 00 00 00 00 00 01 means they have "Full Control" 00 00 00 00 00 00 00 02 means they have "Add Control" 00 00 00 00 00 00 00 04 means they have "Delete Control" So, if a User has "00 00 00 00 00 00 00 07" that means they have all 3 (as far as it has been explained to me). Now, my question is that I need to know how to get to "0x07" when creating/checking records. I don't know the syntax for actually combining 0x01, 0x02 and 0x04 so that I come out with 0x07.

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  • How to rotate a set of points on z = 0 plane in 3-D, preserving pairwise distances?

    - by cagirici
    I have a set of points double n[] on the plane z = 0. And I have another set of points double[] m on the plane ax + by + cz + d = 0. Length of n is equal to length of m. Also, euclidean distance between n[i] and n[j] is equal to euclidean distance between m[i] and m[j]. I want to rotate n[] in 3-D, such that for all i, n[i] = m[i] would be true. In other words, I want to turn a plane into another plane, preserving the pairwise distances. Here's my code in java. But it does not help so much: double[] rotate(double[] point, double[] currentEquation, double[] targetEquation) { double[] currentNormal = new double[]{currentEquation[0], currentEquation[1], currentEquation[2]}; double[] targetNormal = new double[]{targetEquation[0], targetEquation[1], targetEquation[2]}; targetNormal = normalize(targetNormal); double angle = angleBetween(currentNormal, targetNormal); double[] axis = cross(targetNormal, currentNormal); double[][] R = getRotationMatrix(axis, angle); return rotated; } double[][] getRotationMatrix(double[] axis, double angle) { axis = normalize(axis); double cA = (float)Math.cos(angle); double sA = (float)Math.sin(angle); Matrix I = Matrix.identity(3, 3); Matrix a = new Matrix(axis, 3); Matrix aT = a.transpose(); Matrix a2 = a.times(aT); double[][] B = { {0, axis[2], -1*axis[1]}, {-1*axis[2], 0, axis[0]}, {axis[1], -1*axis[0], 0} }; Matrix A = new Matrix(B); Matrix R = I.minus(a2); R = R.times(cA); R = R.plus(a2); R = R.plus(A.times(sA)); return R.getArray(); } This is what I get. The point set on the right side is actually part of a point set on the left side. But they are on another plane. Here's a 2-D representation of what I try to do: There are two lines. The line on the bottom is the line I have. The line on the top is the target line. The distances are preserved (a, b and c). Edit: I have tried both methods written in answers. They both fail (I guess). Method of Martijn Courteaux public static double[][] getRotationMatrix(double[] v0, double[] v1, double[] v2, double[] u0, double[] u1, double[] u2) { RealMatrix M1 = new Array2DRowRealMatrix(new double[][]{ {1,0,0,-1*v0[0]}, {0,1,0,-1*v0[1]}, {0,0,1,0}, {0,0,0,1} }); RealMatrix M2 = new Array2DRowRealMatrix(new double[][]{ {1,0,0,-1*u0[0]}, {0,1,0,-1*u0[1]}, {0,0,1,-1*u0[2]}, {0,0,0,1} }); Vector3D imX = new Vector3D((v0[1] - v1[1])*(u2[0] - u0[0]) - (v0[1] - v2[1])*(u1[0] - u0[0]), (v0[1] - v1[1])*(u2[1] - u0[1]) - (v0[1] - v2[1])*(u1[1] - u0[1]), (v0[1] - v1[1])*(u2[2] - u0[2]) - (v0[1] - v2[1])*(u1[2] - u0[2]) ).scalarMultiply(1/((v0[0]*v1[1])-(v0[0]*v2[1])-(v1[0]*v0[1])+(v1[0]*v2[1])+(v2[0]*v0[1])-(v2[0]*v1[1]))); Vector3D imZ = new Vector3D(findEquation(u0, u1, u2)); Vector3D imY = Vector3D.crossProduct(imZ, imX); double[] imXn = imX.normalize().toArray(); double[] imYn = imY.normalize().toArray(); double[] imZn = imZ.normalize().toArray(); RealMatrix M = new Array2DRowRealMatrix(new double[][]{ {imXn[0], imXn[1], imXn[2], 0}, {imYn[0], imYn[1], imYn[2], 0}, {imZn[0], imZn[1], imZn[2], 0}, {0, 0, 0, 1} }); RealMatrix rotationMatrix = MatrixUtils.inverse(M2).multiply(M).multiply(M1); return rotationMatrix.getData(); } Method of Sam Hocevar static double[][] makeMatrix(double[] p1, double[] p2, double[] p3) { double[] v1 = normalize(difference(p2,p1)); double[] v2 = normalize(cross(difference(p3,p1), difference(p2,p1))); double[] v3 = cross(v1, v2); double[][] M = { { v1[0], v2[0], v3[0], p1[0] }, { v1[1], v2[1], v3[1], p1[1] }, { v1[2], v2[2], v3[2], p1[2] }, { 0.0, 0.0, 0.0, 1.0 } }; return M; } static double[][] createTransform(double[] A, double[] B, double[] C, double[] P, double[] Q, double[] R) { RealMatrix c = new Array2DRowRealMatrix(makeMatrix(A,B,C)); RealMatrix t = new Array2DRowRealMatrix(makeMatrix(P,Q,R)); return MatrixUtils.inverse(c).multiply(t).getData(); } The blue points are the calculated points. The black lines indicate the offset from the real position.

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  • dividing double by double gives weird results - Java

    - by Aly
    Hi, I am trying to do the following 33.33333333333333/100.0 to get 0.333333333333333 however when I run System.out.println(33.33333333333333/100.0); I get 0.33333333333333326 as the output, similarly when I run System.out.println(33.33333333333333/1000.0); I get 0.033333333333333326 as the output. Does anyone know why, and how I can get the correct value (without loss of decimal places). Thanks

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  • Java Conversion of byte[] into a srting and then back to a byte[]

    - by Sid
    I am working on a proxy server. I am getting data in byte[] which i convert into a string to perform certain operations. Now when i convert this new string back into a byte [] it causes unkonw problems. So mainly its like i need to know how to correctly convert a byte[] into a string and then back into a byte[] again. I tried to just convert the byte[] to string and then back to byte[] again (to make sure thats its not my operations that are causing problems). So its like: // where reply is a byte[] String str= new String(reply,0, bytesRead); streamToClient.write(str.getBytes(), 0, bytesRead); is not equivalent to streamToClient.write(reply, 0, bytesRead); my proxy works fine when i just send the byte[] without any conversion but when i convert it from byte[] to a string and then back to a byte[] its causes problems. can some one please help? =]

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  • Why do you need float/double?

    - by acidzombie24
    I was watching http://www.joelonsoftware.com/items/2011/06/27.html and laughed at Jon Skeet joke about 0.3 not being 0.3. I personally never had problems with floats/decimals/doubles but then I remember I learned 6502 very early and never needed floats in most of my programs. The only time I used it was for graphics and math where inaccurate numbers were ok and the output was for the screen and not to be stored (in a db, file) or dependent on. My question is, where are places were you typically use floats/decimals/double? So I know to watch out for these gotchas. With money I use longs and store values by the cent, for speed of an object in a game I add ints and divide (or bitshift) the value to know if I need to move a pixel or not. (I made object move in the 6502 days, we had no divide nor floats but had shifts). So I was mostly curious.

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  • how to double buffer in multiple classes with java

    - by kdavis8
    I am creating a Java 2D video game. I can load graphics just fine, but when it gets into double buffering I have issues. My source code package myPackage; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class GameView extends JFrame { private BufferedImage backbuffer; private Graphics2D g2d; public GameView() { setBounds(0, 0, 500, 500); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); backbuffer = new BufferedImage(getHeight(), getWidth(), BufferedImage.TYPE_INT_BGR); g2d = backbuffer.createGraphics(); Toolkit tk = Toolkit.getDefaultToolkit(); Image img = tk.getImage(this.getClass().getResource("cage.png")); g2d.setColor(Color.red); //g2d.drawString("Hello",100,100); g2d.drawImage(img, 100, 100, this); repaint(); } public static void main(String args[]) { new GameView(); } public void paint(Graphics g) { g2d = (Graphics2D)g; g2d.drawImage(backbuffer, 0, 0, this); } }

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  • Thread safe double buffering

    - by kdavis8
    I am trying to implement a draw map method that will draw the tiled image across the surface of the component. I'm having issue with this code. The double buffering does not seem to be working, because the sprite flickers like crazy; my source code: package myPackage; import java.awt.Color; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import javax.swing.JFrame; public class GameView extends JFrame implements Runnable { public BufferedImage backbuffer; public Graphics2D g2d; public Image img; Thread gameloop; Scene scene; public GameView() { super("Game View"); setSize(600, 600); setVisible(true); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); backbuffer = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_RGB); g2d = backbuffer.createGraphics(); Toolkit tk = Toolkit.getDefaultToolkit(); img = tk.getImage(this.getClass().getResource("cage.png")); scene = new Scene(g2d, this); gameloop = new Thread(this); gameloop.start(); } public static void main(String args[]) { new GameView(); } public void paint(Graphics g) { g.drawImage(backbuffer, 0, 0, this); repaint(); } @Override public void run() { // TODO Auto-generated method stub Thread t = Thread.currentThread(); while (t == gameloop) { scene.getScene("dirtmap"); g2d.drawImage(img, 80, 80,this![enter image description here][1]); } } private void drawScene(String string) { // TODO Auto-generated method stub // g2d.setColor(Color.white); // g2d.fillRect(0, 0, getWidth(), getHeight()); scene.getScene(string); } } package myPackage; import java.awt.Color; import java.awt.Component; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Image; import java.awt.Toolkit; public class Scene { Graphics g2d; Component c; boolean loaded = false; public Scene(Graphics2D gr, Component co) { g2d = gr; c = co; } public void getScene(String mapName) { Toolkit tk = Toolkit.getDefaultToolkit(); Image tile = tk.getImage(this.getClass().getResource("dirt.png")); // g2d.setColor(Color.red); for (int y = 0; y <= 18; y++) { for (int x = 0; x <= 18; x += 1) { g2d.drawImage(tile, x * 32, y * 32, c); } } loaded = true; } }

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  • BinaryFormatter with MemoryStream Question

    - by Changeling
    I am testing BinaryFormatter to see how it will work for me and I have a simple question: When using it with the string HELLO, and I convert the MemoryStream to an array, it gives me 29 dimensions, with five of them being the actual data towards the end of the dimensions: BinaryFormatter bf = new BinaryFormatter(); MemoryStream ms = new MemoryStream(); byte[] bytes; string originalData = "HELLO"; bf.Serialize(ms, originalData); ms.Seek(0, 0); bytes = ms.ToArray(); returns - bytes {Dimensions:[29]} byte[] [0] 0 byte [1] 1 byte [2] 0 byte [3] 0 byte [4] 0 byte [5] 255 byte [6] 255 byte [7] 255 byte [8] 255 byte [9] 1 byte [10] 0 byte [11] 0 byte [12] 0 byte [13] 0 byte [14] 0 byte [15] 0 byte [16] 0 byte [17] 6 byte [18] 1 byte [19] 0 byte [20] 0 byte [21] 0 byte [22] 5 byte [23] 72 byte [24] 69 byte [25] 76 byte [26] 76 byte [27] 79 byte [28] 11 byte Is there a way to only return the data encoded as bytes without all the extraneous information?

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  • Find First Specific Byte in a Byte[] Array c#

    - by divinci
    Hi there, I have a byte array and wish to find the first occurance (if any) of a specific byte. Can you guys help me with a nice, elegant and efficient way to do it? /// Summary /// Finds the first occurance of a specific byte in a byte array. /// If not found, returns -1. public int GetFirstOccurance(byte byteToFind, byte[] byteArray) { }

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  • Is there a Math.atan2 substitute for j2ME? Blackberry development

    - by Kai
    I have a wide variety of locations stored in my persistent object that contain latitudes and longitudes in double(43.7389, 7.42577) format. I need to be able to grab the user's latitude and longitude and select all items within, say 1 mile. Walking distance. I have done this in PHP so I snagged my PHP code and transferred it to Java, where everything plugged in fine until I figured out J2ME doesn't support atan2(double, double). So, after some searching, I find a small snippet of code that is supposed to be a substitute for atan2. Here is the code: public double atan2(double y, double x) { double coeff_1 = Math.PI / 4d; double coeff_2 = 3d * coeff_1; double abs_y = Math.abs(y)+ 1e-10f; double r, angle; if (x >= 0d) { r = (x - abs_y) / (x + abs_y); angle = coeff_1; } else { r = (x + abs_y) / (abs_y - x); angle = coeff_2; } angle += (0.1963f * r * r - 0.9817f) * r; return y < 0.0f ? -angle : angle; } I am getting odd results from this. My min and max latitude and longitudes are coming back as incredibly low numbers that can't possibly be right. Like 0.003785746 when I am expecting something closer to the original lat and long values (43.7389, 7.42577). Since I am no master of advanced math, I don't really know what to look for here. Perhaps someone else may have an answer. Here is my complete code: package store_finder; import java.util.Vector; import javax.microedition.location.Criteria; import javax.microedition.location.Location; import javax.microedition.location.LocationException; import javax.microedition.location.LocationListener; import javax.microedition.location.LocationProvider; import javax.microedition.location.QualifiedCoordinates; import net.rim.blackberry.api.invoke.Invoke; import net.rim.blackberry.api.invoke.MapsArguments; import net.rim.device.api.system.Bitmap; import net.rim.device.api.system.Display; import net.rim.device.api.ui.Color; import net.rim.device.api.ui.Field; import net.rim.device.api.ui.Graphics; import net.rim.device.api.ui.Manager; import net.rim.device.api.ui.component.BitmapField; import net.rim.device.api.ui.component.RichTextField; import net.rim.device.api.ui.component.SeparatorField; import net.rim.device.api.ui.container.HorizontalFieldManager; import net.rim.device.api.ui.container.MainScreen; import net.rim.device.api.ui.container.VerticalFieldManager; public class nearBy extends MainScreen { private HorizontalFieldManager _top; private VerticalFieldManager _middle; private int horizontalOffset; private final static long animationTime = 300; private long animationStart = 0; private double latitude = 43.7389; private double longitude = 7.42577; private int _interval = -1; private double max_lat; private double min_lat; private double max_lon; private double min_lon; private double latitude_in_degrees; private double longitude_in_degrees; public nearBy() { super(); horizontalOffset = Display.getWidth(); _top = new HorizontalFieldManager(Manager.USE_ALL_WIDTH | Field.FIELD_HCENTER) { public void paint(Graphics gr) { Bitmap bg = Bitmap.getBitmapResource("bg.png"); gr.drawBitmap(0, 0, Display.getWidth(), Display.getHeight(), bg, 0, 0); subpaint(gr); } }; _middle = new VerticalFieldManager() { public void paint(Graphics graphics) { graphics.setBackgroundColor(0xFFFFFF); graphics.setColor(Color.BLACK); graphics.clear(); super.paint(graphics); } protected void sublayout(int maxWidth, int maxHeight) { int displayWidth = Display.getWidth(); int displayHeight = Display.getHeight(); super.sublayout( displayWidth, displayHeight); setExtent( displayWidth, displayHeight); } }; add(_top); add(_middle); Bitmap lol = Bitmap.getBitmapResource("logo.png"); BitmapField lolfield = new BitmapField(lol); _top.add(lolfield); Criteria cr= new Criteria(); cr.setCostAllowed(true); cr.setPreferredResponseTime(60); cr.setHorizontalAccuracy(5000); cr.setVerticalAccuracy(5000); cr.setAltitudeRequired(true); cr.isSpeedAndCourseRequired(); cr.isAddressInfoRequired(); try{ LocationProvider lp = LocationProvider.getInstance(cr); if( lp!=null ){ lp.setLocationListener(new LocationListenerImpl(), _interval, 1, 1); } } catch(LocationException le) { add(new RichTextField("Location exception "+le)); } //_middle.add(new RichTextField("this is a map " + Double.toString(latitude) + " " + Double.toString(longitude))); int lat = (int) (latitude * 100000); int lon = (int) (longitude * 100000); String document = "<location-document>" + "<location lon='" + lon + "' lat='" + lat + "' label='You are here' description='You' zoom='0' />" + "<location lon='742733' lat='4373930' label='Hotel de Paris' description='Hotel de Paris' address='Palace du Casino' postalCode='98000' phone='37798063000' zoom='0' />" + "</location-document>"; // Invoke.invokeApplication(Invoke.APP_TYPE_MAPS, new MapsArguments( MapsArguments.ARG_LOCATION_DOCUMENT, document)); _middle.add(new SeparatorField()); surroundingVenues(); _middle.add(new RichTextField("max lat: " + max_lat)); _middle.add(new RichTextField("min lat: " + min_lat)); _middle.add(new RichTextField("max lon: " + max_lon)); _middle.add(new RichTextField("min lon: " + min_lon)); } private void surroundingVenues() { double point_1_latitude_in_degrees = latitude; double point_1_longitude_in_degrees= longitude; // diagonal distance + error margin double distance_in_miles = (5 * 1.90359441) + 10; getCords (point_1_latitude_in_degrees, point_1_longitude_in_degrees, distance_in_miles, 45); double lat_limit_1 = latitude_in_degrees; double lon_limit_1 = longitude_in_degrees; getCords (point_1_latitude_in_degrees, point_1_longitude_in_degrees, distance_in_miles, 135); double lat_limit_2 = latitude_in_degrees; double lon_limit_2 = longitude_in_degrees; getCords (point_1_latitude_in_degrees, point_1_longitude_in_degrees, distance_in_miles, -135); double lat_limit_3 = latitude_in_degrees; double lon_limit_3 = longitude_in_degrees; getCords (point_1_latitude_in_degrees, point_1_longitude_in_degrees, distance_in_miles, -45); double lat_limit_4 = latitude_in_degrees; double lon_limit_4 = longitude_in_degrees; double mx1 = Math.max(lat_limit_1, lat_limit_2); double mx2 = Math.max(lat_limit_3, lat_limit_4); max_lat = Math.max(mx1, mx2); double mm1 = Math.min(lat_limit_1, lat_limit_2); double mm2 = Math.min(lat_limit_3, lat_limit_4); min_lat = Math.max(mm1, mm2); double mlon1 = Math.max(lon_limit_1, lon_limit_2); double mlon2 = Math.max(lon_limit_3, lon_limit_4); max_lon = Math.max(mlon1, mlon2); double minl1 = Math.min(lon_limit_1, lon_limit_2); double minl2 = Math.min(lon_limit_3, lon_limit_4); min_lon = Math.max(minl1, minl2); //$qry = "SELECT DISTINCT zip.zipcode, zip.latitude, zip.longitude, sg_stores.* FROM zip JOIN store_finder AS sg_stores ON sg_stores.zip=zip.zipcode WHERE zip.latitude<=$lat_limit_max AND zip.latitude>=$lat_limit_min AND zip.longitude<=$lon_limit_max AND zip.longitude>=$lon_limit_min"; } private void getCords(double point_1_latitude, double point_1_longitude, double distance, int degs) { double m_EquatorialRadiusInMeters = 6366564.86; double m_Flattening=0; double distance_in_meters = distance * 1609.344 ; double direction_in_radians = Math.toRadians( degs ); double eps = 0.000000000000005; double r = 1.0 - m_Flattening; double point_1_latitude_in_radians = Math.toRadians( point_1_latitude ); double point_1_longitude_in_radians = Math.toRadians( point_1_longitude ); double tangent_u = (r * Math.sin( point_1_latitude_in_radians ) ) / Math.cos( point_1_latitude_in_radians ); double sine_of_direction = Math.sin( direction_in_radians ); double cosine_of_direction = Math.cos( direction_in_radians ); double heading_from_point_2_to_point_1_in_radians = 0.0; if ( cosine_of_direction != 0.0 ) { heading_from_point_2_to_point_1_in_radians = atan2( tangent_u, cosine_of_direction ) * 2.0; } double cu = 1.0 / Math.sqrt( ( tangent_u * tangent_u ) + 1.0 ); double su = tangent_u * cu; double sa = cu * sine_of_direction; double c2a = ( (-sa) * sa ) + 1.0; double x= Math.sqrt( ( ( ( 1.0 /r /r ) - 1.0 ) * c2a ) + 1.0 ) + 1.0; x= (x- 2.0 ) / x; double c= 1.0 - x; c= ( ( (x * x) / 4.0 ) + 1.0 ) / c; double d= ( ( 0.375 * (x * x) ) -1.0 ) * x; tangent_u = distance_in_meters /r / m_EquatorialRadiusInMeters /c; double y= tangent_u; boolean exit_loop = false; double cosine_of_y = 0.0; double cz = 0.0; double e = 0.0; double term_1 = 0.0; double term_2 = 0.0; double term_3 = 0.0; double sine_of_y = 0.0; while( exit_loop != true ) { sine_of_y = Math.sin(y); cosine_of_y = Math.cos(y); cz = Math.cos( heading_from_point_2_to_point_1_in_radians + y); e = (cz * cz * 2.0 ) - 1.0; c = y; x = e * cosine_of_y; y = (e + e) - 1.0; term_1 = ( sine_of_y * sine_of_y * 4.0 ) - 3.0; term_2 = ( ( term_1 * y * cz * d) / 6.0 ) + x; term_3 = ( ( term_2 * d) / 4.0 ) -cz; y= ( term_3 * sine_of_y * d) + tangent_u; if ( Math.abs(y - c) > eps ) { exit_loop = false; } else { exit_loop = true; } } heading_from_point_2_to_point_1_in_radians = ( cu * cosine_of_y * cosine_of_direction ) - ( su * sine_of_y ); c = r * Math.sqrt( ( sa * sa ) + ( heading_from_point_2_to_point_1_in_radians * heading_from_point_2_to_point_1_in_radians ) ); d = ( su * cosine_of_y ) + ( cu * sine_of_y * cosine_of_direction ); double point_2_latitude_in_radians = atan2(d, c); c = ( cu * cosine_of_y ) - ( su * sine_of_y * cosine_of_direction ); x = atan2( sine_of_y * sine_of_direction, c); c = ( ( ( ( ( -3.0 * c2a ) + 4.0 ) * m_Flattening ) + 4.0 ) * c2a * m_Flattening ) / 16.0; d = ( ( ( (e * cosine_of_y * c) + cz ) * sine_of_y * c) + y) * sa; double point_2_longitude_in_radians = ( point_1_longitude_in_radians + x) - ( ( 1.0 - c) * d * m_Flattening ); heading_from_point_2_to_point_1_in_radians = atan2( sa, heading_from_point_2_to_point_1_in_radians ) + Math.PI; latitude_in_degrees = Math.toRadians( point_2_latitude_in_radians ); longitude_in_degrees = Math.toRadians( point_2_longitude_in_radians ); } public double atan2(double y, double x) { double coeff_1 = Math.PI / 4d; double coeff_2 = 3d * coeff_1; double abs_y = Math.abs(y)+ 1e-10f; double r, angle; if (x >= 0d) { r = (x - abs_y) / (x + abs_y); angle = coeff_1; } else { r = (x + abs_y) / (abs_y - x); angle = coeff_2; } angle += (0.1963f * r * r - 0.9817f) * r; return y < 0.0f ? -angle : angle; } private Vector fetchVenues(double max_lat, double min_lat, double max_lon, double min_lon) { return new Vector(); } private class LocationListenerImpl implements LocationListener { public void locationUpdated(LocationProvider provider, Location location) { if(location.isValid()) { nearBy.this.longitude = location.getQualifiedCoordinates().getLongitude(); nearBy.this.latitude = location.getQualifiedCoordinates().getLatitude(); //double altitude = location.getQualifiedCoordinates().getAltitude(); //float speed = location.getSpeed(); } } public void providerStateChanged(LocationProvider provider, int newState) { // MUST implement this. Should probably do something useful with it as well. } } } please excuse the mess. I have the user lat long hard coded since I do not have GPS functional yet. You can see the SQL query commented out to know how I plan on using the min and max lat and long values. Any help is appreciated. Thanks

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  • Why does multiplying a double by -1 not give the negative of the current answer

    - by Ankur
    I am trying to multiply a double value by -1 to get the negative value. It continues to give me a positive value double man = Double.parseDouble(mantissa); double exp; if(sign.equals("plus")){ exp = Double.parseDouble(exponent); } else { exp = Double.parseDouble(exponent); exp = exp*-1; } System.out.println(man+" - "+sign+" - "+exp); The printed result is 13.93 - minus - 2.0 which is correct except that 2.0 should be -2.0

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  • Inserting bits into byte

    - by JB_SO
    I was looking at an example of reading bits from a byte and the implementation looked simple and easy to understand. I was wondering if anyone has a similar example of how to insert bits into a byte or byte array, that is easier to understand and also implement like the example below. Here is the example I found of reading bits from a byte (http://bytes.com/topic/c-sharp/answers/505085-reading-bits-byte-file): static int GetBits3(byte b, int offset, int count) { return (b >> offset) & ((1 << count) - 1); } Here is what i'm trying to do....and this is my current implementation.....just a little confused with the bit-masking/shifting, etc, that's why I'm trying to find out if there is an easier way to do what i'm doing BYTE Msg[2]; Msg_Id = 3; Msg_Event = 1; Msg_Ready = 2; Msg[0] = ( ( Msg_Event << 4 ) & 0xF0 ) | ( Msg_Id & 0x0F ) ; Msg[1] = Msg_Ready & 0x0F; //MsgReady & Unused Thanks for your help!

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  • AES Key encoded byte[] to String and back to byte[]

    - by Tom Brito
    In the similar question "Conversion of byte[] into a String and then back to a byte[]" is said to not to do the byte[] to String and back conversion, what looks like apply to most cases, mainly when you don't know the encoding used. But, in my case I'm trying to save to a DB the javax.crypto.SecretKey data, and recoverd it after. The interface provide a method getEncoded() which returns the key data encoded as byte[], and with another class I can use this byte[] to recover the key. So, the question is, how do I write the key bytes as String, and later get back the byte[] to regenerate the key?

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  • How to read a file byte by byte in Python?

    - by zaplec
    Hi, I'm trying to read a file byte by byte, but I'm not sure how to do that. I'm trying to do it like that: file = open(filename, 'rb') while 1: byte = file.read(8) # Do something... So does that make the variable byte to contain 8 next bits at the beginning of every loop? It doesn't matter what those bytes really are. The only thing that matters is that I need to read a file in 8-bit stacks.

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  • C# Read Byte [] to Image

    - by LucasGuitar
    I have an application which I'm adding pictures and these are automatically converted to binary and stored in a single file. how can I save several images, I keep in an XML file start and size of each set of refente to an image byte. But it has several images in bytes, whenever I try to select a different set of bytes just opening the same image. I would like your help to be able to fix this and open different images. Code //Add Image private void btAddImage_Click(object sender, RoutedEventArgs e) { OpenFileDialog op = new OpenFileDialog(); op.Title = "Selecione a Imagem"; op.Filter = "All supported graphics|*.jpg;*.jpeg;*.png|" + "JPEG (*.jpg;*.jpeg)|*.jpg;*.jpeg|" + "Portable Network Graphic (*.png)|*.png"; if (op.ShowDialog() == true) { imgPatch.Source = new BitmapImage(new Uri(op.FileName)); txtName.Focus(); } } //Convert Image private void btConvertImage_Click(object sender, RoutedEventArgs e) { if (String.IsNullOrEmpty(txtName.Text)) { txtName.Focus(); MessageBox.Show("Preencha o Nome", "Error"); } else { save(ConvertFileToByteArray(op.FileName), txtName.Text); } } //Image to Byte Array private static byte[] ConvertFileToByteArray(String FilePath) { return File.ReadAllBytes(FilePath); } //Save Binary File and XML File public void save(byte[] img, string nome) { FileStream f; long ini, fin = img.Length; if (!File.Exists("Escudos.bcf")) { f = new FileStream("Escudos.bcf", FileMode.Create); ini = 0; } else { f = new FileStream("Escudos.bcf", FileMode.Append); ini = f.Length + 1; bin = new TestBinarySegment(); } bin.LoadAddSave("Escudos.xml", "Brasileiro", nome, ini, fin); BinaryWriter b = new BinaryWriter(f); b.Write(img); b.Close(); f.Dispose(); } //Load Image from Byte private void btLoad_Click(object sender, RoutedEventArgs e) { getImageFromByte(); } //Byte to Image public void getImageFromByte(int start, int length) { using (FileStream fs = new FileStream("Escudos.bcf", FileMode.Open)) { byte[] iba = new byte[fs.Length+1]; fs.Read(iba, start, length); Image image = new Image(); image.Source = BitmapFrame.Create(fs, BitmapCreateOptions.None, BitmapCacheOption.OnLoad); imgPatch2.Source = image.Source; } }

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  • Why is Double.Parse so slow?

    - by alexhildyard
    I was recently investigating a bottleneck in one of my applications, which read a CSV file from disk using a TextReader a line at a time, split the tokens, called Double.Parse on each one, then shunted the results into an object list. I was surprised to find it was actually the Double.Parse which seemed to be taking up most of the time.Googling turned up this, which is a little unfocused in places but throws out some excellent ideas:It makes more sense to work with binary format directly, rather than coerce strings into doublesThere is a significant performance improvement in composing doubles directly from the byte stream via long intermediariesString.Split is inefficient on fixed length recordsIn fact it turned out that my problem was more insidious and also more mundane -- a simple case of bad data in, bad data out. Since I had been serialising my Doubles as strings, when I inadvertently divided by zero and produced a "NaN", this of course was serialised as well without error. And because I was reading in using Double.Parse, these "NaN" fields were also (correctly) populating real Double objects without error. The issue is that Double.Parse("NaN") is incredibly slow. In fact, it is of the order of 2000x slower than parsing a valid double. For example, the code below gave me results of 357ms to parse 1000 NaNs, versus 15ms to parse 100,000 valid doubles.            const int invalid_iterations = 1000;            const int valid_iterations = invalid_iterations * 100;            const string invalid_string = "NaN";            const string valid_string = "3.14159265";            DateTime start = DateTime.Now;                        for (int i = 0; i < invalid_iterations; i++)            {                double invalid_double = Double.Parse(invalid_string);            }            Console.WriteLine(String.Format("{0} iterations of invalid double, time taken (ms): {1}",                invalid_iterations,                ((TimeSpan)DateTime.Now.Subtract(start)).Milliseconds            ));            start = DateTime.Now;            for (int i = 0; i < valid_iterations; i++)            {                double valid_double = Double.Parse(valid_string);            }            Console.WriteLine(String.Format("{0} iterations of valid double, time taken (ms): {1}",                valid_iterations,                ((TimeSpan)DateTime.Now.Subtract(start)).Milliseconds            )); I think the moral is to look at the context -- specifically the data -- as well as the code itself. Once I had corrected my data, the performance of Double.Parse was perfectly acceptable, and while clearly it could have been improved, it was now sufficient to my needs.

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