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Control Flow

2 (2.2%)

Arrays, Strings, Pointers, and References

8 (9%)

Functions

4 (4.5%)

Basic object-oriented programming

30 (33.7%)

A bit more advanced OOP (Composition, Operator overloading, Inheritance, Virtual Functions)

18 (20.2%)

Templates

8 (9%)

Other (Explain)

4 (4.5%)

Working with files?  (Streams)

15 (16.9%)

Total Members Voted: 89

[TolyK]

I have very little experience with any sort of net-based coding

You want to look at 0MQ, this is actually true for anyone interested in multi-threaded programming too.

CLICK CLICK CLICK CLICK CLICK

[Derekristow]

Mouse collision can actually be quite easy, depending on the amount of support your library is giving. In the case of a 3D game you can draw a ray from the camera through the front of the camera's frustum (a truncated pyramid that determines what should and should not be drawn) till the back of it. Then you can do a ray intersection check to find the object the player is clicking on. (both ray drawing and intersection checking tends to be available in most engines.
That is of course, assuming you're doing 3D. If it's 2D you need size bounds for your object so that you can just plug in the x and y coordinates of the mouse and get the object the mouse is hovering over.

I'm doing it in 2D, but the mouse needs to collide with non-rectangular objects, namely the tiles in the picture.  It's proving more complicated than necessary because I don't always know where the tiles are in the window (I designed it so they would always be centered-ish, and the number of tiles displayed can be changed).

[ILikePie]

I seem to have forgotten how pass by ref works in c.

Code: [Select]

$ cat temp.c
#include <stdio.h>

void change(char *i)
{
     char *d = "hello, world";
     i = d;
}

int main ()
{
    char *d = "world, hello";
    change(d);
    puts(d);

    return 0;
}

$ gcc -o temp temp.c
$ ./temp
world, hello
iirc, that should change d to "hello, world".

[lordnincompoop]

I seem to have forgotten how pass by ref works in c.

iirc, that should change d to "hello, world".

Code: [Select]

void change(char *&i)
{
     char *d = "hello, world";
     i = d;
}

int main ()
{
    char *d = "world, hello";
    change(d);
    puts(d);

    return 0;
}
There. References are ampersands, and the parameter needs to be *&i to work.

[ILikePie]

C++ uses ampersands in function parameters, I'm using C.

[lordnincompoop]

 

Nevermind, then.

[olemars]

change(&d);

[ILikePie]

Tried that too, it doesn't work. iirc d is a pointer pointing to d[0].
Anyway, I dropped the pass by reference, now I'm having trouble getting it to read 16 bytes.

Code: [Select]

$ cat libdib.c
#include  <stdio.h>
#include <stdlib.h>

char *extract_data (FILE *in)
{
     int pos;       // data offset
     long int size; // data size
     size_t len;    // length of data read
     char *d;       // the data

     fseek(in, 0xA, SEEK_SET);
     len = fread(&pos, sizeof(int), 1, in);

     if (len != 1) {
         fputs("read error", stderr);
         return NULL;
     }
     
     fseek(in, 0, SEEK_END);
     size = ftell(in) - pos;
     
     d = (char *)malloc (sizeof(char)*size);
     fseek(in, pos, SEEK_SET);
     len = fread(d, 1, size, in);

     if (len != size) {
         fputs("read error", stderr);
         return NULL;
     }
     return d;
}

int main ()
{
     FILE *f = fopen("./bitmap.dib", "r");
     char *d;
     if (f == NULL) {
         puts("io error");
         return 1;
     }
     d = extract_data(f);
     fclose(f);
     (d != NULL) ? puts(d):puts("");

     return 0;
}
$ gcc -o libdib libdib.c
$ ./libdib && echo "" && ./libdib | hexdump
ÿÿÿÿÿÿ

0000000 ffff ffff ffff 000a                   
0000007
According to hexdump, it reads only 8 bytes.

[SolarShado]

haven't read your entire prog, but are you sure that sizeof(int) returns 16 on your system? that's what it looks like you're using for your length, but IIRC 8 bytes is the standard length of an int (i know it varies, but i believe that's the most common)

[Virex]

int should be 32 or 64 unless you're working on a very old computer or an IC or something. A char is conventionally 8 bits, but an int is usually the length of a word.

[Blank Expression]

int should be 32 or 64 unless you're working on a very old computer or an IC or something. A char is conventionally 8 bits, but an int is usually the length of a word.

This. Under no architecture with which I am familiar is sizeof(int) = 16 (which would be 128-bit). As it's almost certainly an x64 system, a fread of 8 bytes makes sense.

Understand your inputs before you assume your code is wrong. (Better still is to understand your inputs before you start writing code.)

[TolyK]

try using unsigned ints longs.

[olemars]

EDIT: nm

[ILikePie]

It's a 32 bit machine, an old P4.
The first fread, the one using sizeof(int), is supposed to read an int from the header of the file. The second fread (fread(d, 1, size, in)), is what's causing problems. I know that size = 16, and yet it still reads only 8 bytes.

[olemars]

Dangerous assumptions there. sizeof(int) on your computer does not have to be the same as the computer that wrote the file. When dealing with file headers, always know the byte count of each data element and read that amount explicitly.

Edit: Would help to know the (hex) contents of the file.