Interleave two or more files

Build:
    g++ -mno-cygwin -o interleave interleave.cpp

FILE *fo = fopen(argv[1], "wb");
if (!fo) { fprintf(stderr, "Error opening output file!n"); return 1; }

int bufsize = strtoul(argv[2],0,0);
unsigned char *buffer = new unsigned char[bufsize];

FILE *fi[32];
int files = 0;
for (int a=3; argv[a]; a++)
{
    fi[files] = fopen(argv[a], "rb");
    if (!fi[files]) { fprintf(stderr, "Error opening input file!n"); return 1; }
    files++;
}

int files_active = files;
for (int f=0; files_active; f++)
{
    if (f == files) f = 0;
    int read = 0;
    if (fi[f])
    {
        read = fread(buffer, 1, bufsize, fi[f]);
        if (read <= 0) { fclose(fi[f]); fi[f] = 0; files_active--; continue; }
        fwrite(buffer, 1, read, fo);
    }
    //if (bufsize > read)
    {
        memset(buffer, 0, bufsize - read);
        fwrite(buffer, 1, bufsize - read, fo);
    }
}

fclose(fo);

delete [] buffer;

return 0;