[Issue 1190] Reference becoming null (page 2)

September 05, 2007
[Issue 1190] Reference becoming null
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http://d.puremagic.com/issues/show_bug.cgi?id=1190


davidl@126.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID




------- Comment #10 from davidl@126.com  2007-09-05 03:06 -------
The Simpler test case just should access violation as Bill said in his last
comment. Kill the ref keyword, the simpler test case goes fine.
But without inout the original code fails at an assertion.

And I'm kind enough to illustrate the new problem for you. :)

Here is the code with a little bit correction, and illustrate the new assertion fail reason:

import std.string;
import std.stream;
import std.math;

alias std.string.toString strfy;
alias std.stdio.writefln Log;
int staticc;

private static const ubyte PatchSize=64; //must be power of 2
//const ubyte MAX_DEPTH=cast(ubyte)(2*sqrt(PatchSize)+1);
private static const MaxDepth=4;//17

private struct CamInfo
{
    uint x, y, z;
}

private CamInfo camInfo;

/**
The Terrain engine class.
*/
public final class Terrain
{
    ///The TreeNode class is used to store information about the patch tree
    private final class TreeNode
    {
        private TreeNode lChild, rChild, bNeigh, lNeigh, rNeigh;

        public this()
        {
            reset();
        }

        public void reset()
        {
            lChild=rChild=bNeigh=lNeigh=rNeigh=null;
        }
    }

    ///Patch Class. A terrain is composed of several patches
    private final class Patch
    {
        this (ushort x, ushort y)
        {
            this.x=x; this.y=y;
            visible=true;
            rNode=new TreeNode(); //these never get reassigned
            lNode=new TreeNode(); //they're const, remmember?
            assert(rNode !is null);
            assert(lNode !is null);
            //nodes come already clean
            rNode.bNeigh=lNode;
            lNode.bNeigh=rNode;
            calcError();
        }

        ///Resets the patch. It becomes undivided and ready for the next
tesselation.
        void reset()
        {
            rNode.reset();
            lNode.reset();
            rNode.bNeigh=lNode;
            lNode.bNeigh=rNode;
            //TODO: check visibility here
            visible=true;
        }

        ///Tesselates this patch and it becomes ready for rendering
        void update()
        {
            std.gc.disable();
            cError[]=lError;
            tesselate(lNode, x, cast(ushort)(y+PatchSize),
cast(ushort)(x+PatchSize), y, x, y, 1);
            cError[]=rError;
            tesselate(rNode, cast(ushort)(x+PatchSize), y, x,
cast(ushort)(y+PatchSize),
                cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1);
            std.gc.enable();
        }

        ///This patch's error measure is updated from the data on hData.
        void calcError()
        {
            Calculate(x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize),
y, x, y, 1);
            lError[]=cError; //copy the error data
            Calculate(cast(ushort)(x+PatchSize), y, x,
cast(ushort)(y+PatchSize),
                cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1);
            rError[]=cError;
            return;
        }

        ~this()
        {
            delete rNode;
            delete lNode;
        }

        //no need to protect this vars because this class won't be accessed
from the exterior
        const ushort x, y; //coordinates aren't expected to change
        bool visible; ///Result of lastest cull check
        ushort[MaxDepth] lError, rError;
        const TreeNode rNode, lNode;
    }

    public:
    this(in File file, float detail)
    in
    {
        assert(file !is null);
        assert(detail>=0); //negative error values make no sense. 0 values are
purely debugging technices
    }
    body
    {
        debug Log("Creating terrain object");
        this.detail=detail;
        file.read(sizeX);
        file.read(sizeY);
        assert((sizeX>0)&&(sizeY>0));
        HMult=1; //TODO: Replace with resolution from file
        hData=new ushort[][](sizeX, sizeY); //initialize data
        debug Log(" * Loading terrain data...");
        foreach (stripe; hData)
            foreach (inout vertex; stripe)
            {
                file.read(vertex);
                vertex*=HMult;
            }
        maxH=0; //Maximum height present on the map. Used somewhere in debug
code
        foreach (stripe; hData)
            foreach (vertex; stripe)
                if (vertex>maxH) maxH=vertex;
        xPatch=cast(ubyte)(sizeX/PatchSize);
        yPatch=cast(ubyte)(sizeY/PatchSize);
        nodes.length=(sizeX*sizeY/PatchSize);
        debug Log(" * Creating terrain nodes ("~strfy(nodes.length)~")...");
        foreach(inout node; nodes) node=new TreeNode;

        debug Log(" * Creating patches...");
        patches.length=xPatch;//how many columns will we have? Patch[col][row]
        foreach (size_t row, inout Patch[] strip; patches)
        {
            assert(strip.length==0, "Oups! Redefining a length of a strip");
            strip.length=yPatch; //How many rows?
            foreach (size_t col, inout Patch patch; strip)
                patch=new Patch(cast(ushort)(col*PatchSize),
cast(ushort)(row*PatchSize));
        }
        debug Log("Terrain creation complete");
    }

    public float heightAt(in float x, in float y)
    out(result)
    {
        assert((result>=0.0f)||(result==float.nan));
    }
    body
    {
        if ((x<0.0)||(y<0.0f)) return float.nan;
        //triangulate height at the given point
        return 0.0f;
    }

    ///Makes the terrain ready for rendering. Tesselates all the patches.
    void update()
    body
    {
        //reset the engine first
        currNode=0; //reset current node
        foreach (size_t row, inout Patch[] strip; patches)
            foreach (size_t col, inout Patch patch; strip)
            {
                patch.reset(); //Recalculate the visibility flag
                if (patch.visible) //bail on non-visible patches
                {
                    if (col>0) patch.lNode.lNeigh=patches[col-1][row].rNode;
                    else patch.lNode.lNeigh=null;
                    if (col<(xPatch-1))
patch.rNode.lNeigh=patches[col+1][row].lNode;
                    else patch.rNode.lNeigh=null;
                    if (row>0) patch.lNode.rNeigh=patches[col][row-1].rNode;
                    else patch.lNode.rNeigh=null;
                    if (row<(yPatch-1))
patch.rNode.rNeigh=patches[col][row+1].lNode;
                    else patch.rNode.rNeigh=null;
                }
            }
        //Unfloatize camera information. Remember the case in which the coords
are <0
        foreach (Patch[] strip; patches)
            foreach (Patch patch; strip)
                if (patch.visible) patch.update();
        return;
    }

    ~this()
    {
        /*Since the terrain is the last thing to be deleted when a game is
over, a gc.fullCollect()
        will be preformed sometime soon, so it is not necessary to clean up
manually*/
        foreach (inout stripe; hData)
        {
            stripe.length=0; delete stripe;
        }
        hData.length=0;
        foreach (inout Patch[] strip; patches)
            foreach (inout Patch patch; strip)
                delete patch;
        foreach(inout node; nodes) delete node;
        nodes.length=0;
    }

    private:
    ///Returns the next available TreeNode. Creates a new one if there are no
more available.
    TreeNode newNode()
    out(result)
    {
        assert(result !is null, "newNode() attempted to return a null
TreeNode.");
    }
    body
    {
        assert(currNode<=nodes.length, "currNode advanced too much");
        if (currNode==nodes.length)
        {
            nodes~=new TreeNode; //no more nodes available, create another one
            debug Log("Insufficient TreeNodes for current tesselation
(detail="~strfy(detail)~"). Increasing TreeNode pool
(currNode="~strfy(currNode)~").");
        }
        TreeNode ret=nodes[currNode]; //get a new node
        ret.reset(); //clear new node's affiliations
        currNode++;
        return ret;
    }

    ///To be used by functions of the class, returns raw height value.
    ushort heightAt(ushort x, ushort y)
    {
        if ((x==sizeX)||(y==sizeY)) return 0; //Out of bounds values are not
drawn (taken has void in game)
        assert(x<sizeX, "Out of bounds value requested");
        assert(y<sizeY, "Out of bounds value requested");
        return hData[x][y];
    }

    ushort Calculate(ushort lX, ushort lY, ushort rX, ushort rY, ushort aX,
ushort aY, ushort node)
    {
        //Calculate hipotenuse
        ushort cX=cast(ushort)((rX+lX)/2);
        ushort cY=cast(ushort)((rY+lY)/2);
        ushort cZ=heightAt(cX, cY);
        ushort rZ=heightAt(rX, rY);
        ushort lZ=heightAt(lX, lY);
        ushort errRatio=cast(ushort)abs(cZ-((lZ+rZ)/2)); //this iteraction's
primary error ratio
        if (errRatio==0) return 0; //reached perfectness
        if ((abs((rX-lX))>=2)||(abs(rY-lY))>=2) //smaller than 2x2
        {
            //calculate the error of one of the child triangles
            ushort tempErrRatio=Calculate(aX, aY, lX, lY, cX, cY,
cast(ushort)(node*2));
            if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is
greater, adopt it
            //and then try the other child
            tempErrRatio=Calculate(rX, rY, aX, aY, cX, cY,
cast(ushort)(node*2+1));
            if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is
greater, adopt it
        }
        //TODO: this "if" may not need to be here: required for range check,
nothing else
        if (node<MaxDepth) cError[node]=errRatio; //store error ratio as we
descend on the tree
        return errRatio; //return this levels error ratio
    }

    ///Splits a TreeNode, used by Patch sub-class
    void split(TreeNode myNode)
    in
    {
                if (myNode.rNeigh !is null)
//              assert(myNode.rNeigh.bNeigh !is myNode);
        assert(myNode !is null, "Attempted to split a null node");
    }
    body
    {
        if (myNode.lChild !is null) return; //already split
        //Check to see if current triangle is diamond with bNeigh
        if ((myNode.bNeigh !is null)&&(myNode.bNeigh.bNeigh !is myNode))
        {
                        TreeNode v=myNode.bNeigh;
            split(myNode.bNeigh); //it has to be split, so that current
triangle can be a diamond with it's bNeigh
                        if (myNode.bNeigh !is v){
                                printf("oh my god!");
                        }
            assert(myNode.bNeigh.lChild !is null, "Split failed!");
        }

        //asserts that I am a diamond with my bNeigh, or I'm a border node
        assert ((myNode.bNeigh is null)||(myNode.bNeigh.bNeigh is myNode),
"Attempted to split a node that is not part of a diamond");

        myNode.lChild=newNode();
        myNode.rChild=newNode();
        //with (myNode) //in this block, all the relations of myNode are
updated
        {
            myNode.lChild.bNeigh=myNode.lNeigh;
myNode.lChild.lNeigh=myNode.rChild;
            myNode.rChild.bNeigh=myNode.rNeigh;
myNode.rChild.rNeigh=myNode.lChild;

            if (myNode.lNeigh !is null) //I have a left neigh
            {
                if (myNode.lNeigh.bNeigh is myNode)
myNode.lNeigh.bNeigh=myNode.lChild;
                else
                {
                    if (myNode.lNeigh.lNeigh is myNode)
myNode.lNeigh.lNeigh=myNode.lChild;
                    else if (myNode.lNeigh.rNeigh is myNode)
myNode.lNeigh.rNeigh=myNode.lChild;
                }
            }

            assert((myNode.lChild !is null)&&(myNode.rChild !is null),
"Children died at lNeigh update");

            //The following if block causes the children to become null
            if (myNode.rNeigh !is null) //I have a right neigh
            {
                if (myNode.rNeigh.bNeigh is myNode)
                {
                    assert(myNode.lChild !is null);
                    assert(myNode.rChild !is null);
                    assert(myNode.rNeigh.bNeigh !is null);
//                                      assert(myNode.rNeigh.bNeigh !is
myNode);
                        myNode.rNeigh.bNeigh=myNode.rChild; //This causes the
children (both) to die
                                        assert(myNode.lChild !is
myNode.rNeigh.bNeigh);
                    assert(myNode.lChild !is null); //crash here
                    assert(myNode.rChild !is null);
                }
                else
                {
                    if (myNode.rNeigh.rNeigh is myNode)
myNode.rNeigh.rNeigh=myNode.rChild;
                    else if (myNode.rNeigh.lNeigh is myNode)
myNode.rNeigh.lNeigh=myNode.rChild;
                }
            }
            assert((myNode.lChild !is null)&&(myNode.rChild !is null),
"Children died at rNeigh update");

            if (myNode.bNeigh !is null) //I have a base neigh
            {
                if (myNode.bNeigh.lChild !is null) //My bNeigh is already split
                {
                    assert(myNode.bNeigh.rChild !is null, "bNeigh is only
partially split, cannot update relations.");
                    myNode.bNeigh.lChild.rNeigh=myNode.rChild;
                    myNode.bNeigh.rChild.lNeigh=myNode.lChild;
                    myNode.lChild.rNeigh=myNode.bNeigh.rChild;
                    myNode.rChild.lNeigh=myNode.bNeigh.lChild;
                }
                else split(myNode.bNeigh); //Split my base. He'll take care of
Neigh relations
            }
            else //I don't have bNeigh
            {
                myNode.lChild.rNeigh=null;
                myNode.rChild.lNeigh=null;
            }
            assert((myNode.lChild !is null)&&(myNode.rChild !is null),
"Children died at bNeigh update");
        } //updates to myNode are over
        assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Node
children have been lost!");      // this assertion doesn't test the problem
actually , in this scope testing myNode is useless
                                                         // you should test the
copy of myNode
        return;
    }

    void tesselate (TreeNode myNode, ushort lX, ushort lY, ushort rX, ushort
rY, ushort aX, ushort aY, ushort node)
    in
    {
                if (myNode.rNeigh !is null)
                assert(myNode.rNeigh.bNeigh !is myNode);
        assert(myNode !is null, "Attempted to tesselate a null node");
    }
    body
    {
        //Calculate hipotenuse
        ushort cX=cast(ushort)((rX+lX)/2);
        ushort cY=cast(ushort)((rY+lY)/2);
        ushort cZ=heightAt(cX, cY);
        ulong
distance=(cX-camInfo.x)*(cX-camInfo.x)+(cY-camInfo.y)*(cY-camInfo.y)+(cZ-camInfo.z)*(cZ-camInfo.z);
        ulong threshold=cError[node]*cError[node];

        if ((threshold*detail)>distance) //should this triangle be split?
        {
            split(myNode); //won't fail because TreeNodes will not go out
            //I have children and they aren't too small,
            //TODO: Unnecessary check: split never fails: (myNode.lChild !is
null)&&(myNode.rChild !is null)&&
            if
((node<cast(ushort)(MaxDepth/2))&&((abs(lX-rX)>=2)||(abs(lY-rY)>=2)))
            {
                tesselate(myNode.lChild, aX, aY, lX, lY, cX, cY,
cast(ushort)(node*2));
                tesselate(myNode.rChild, rX, rY, aX, aY, cX, cY,
cast(ushort)(node*2+1));
            }
        }
    }

    const ushort maxH;
    float detail; ///Detail Threshold
    TreeNode nodes[]; ///Node pool
    size_t currNode; ///Current node being assigned
    const ushort sizeX, sizeY;
    const ubyte xPatch, yPatch;
    ushort hData[][]; ///The Height Data
    static ushort[MaxDepth] cError; //error buffer
    const ubyte HMult; ///Height multiplier, determines the resolution of the
terrain
    const Patch patches[][]; ///The pathes that compose the terrain.
}

void main()
{
        File este=new File("novomapa.raw", FileMode.In);
        Terrain terrain=new Terrain(este, 2500);
        delete este;
        std.stdio.writefln("Preparing for rendering...");
        terrain.update();

        delete terrain;
}


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