Automatic VRAM tile allocation functions

[Moon-Watcher]

Here is a little code I've been using for a short time. Haven't tested it a lot but I feel it *works*. Title pretends to be self explanatory; it looks for room in the VRAM table and returns a position. That simple.

Works with SGDK and hope it'll be useful for someone (newbies like me, I'm talking to you). Use it on your own way.

Code: Select all

#include <genesis.h>


typedef struct _vram
{
	u32 pos;
	u32 tiles;
	struct _vram *next;
}
VRAM;


static VRAM *vram;



void vram_init ( )
{
	VRAM *aux;

	while ( vram != NULL )
	{
		aux = vram->next;
		MEM_free ( vram );
		vram = aux;
	}

	vram = NULL;
}


u16 vram_new ( u16 nb_tiles )
{
	u16 pos      = 1; // VRAM_BASE_POS;

	VRAM *repeat = vram;
	VRAM *new    = MEM_alloc ( sizeof ( VRAM ) );
	VRAM *next   = NULL;


	if ( !repeat )
	{
		vram = new;
	}

	while ( repeat )
	{
		pos  = repeat->pos + repeat->tiles;
		next = repeat->next;

		if ( next->pos > pos + nb_tiles )
		{
			break;
		}

		repeat = next;
	}

	new->pos   = pos;
	new->tiles = nb_tiles;
	new->next  = next;

	repeat->next = new;


	return pos;
}


void vram_delete ( u16 pos )
{
	VRAM *repeat = vram;
	VRAM *prev   = NULL;

	while ( repeat )
	{
		if ( repeat->pos == pos )
		{
			prev->next = repeat->next;
			MEM_free ( repeat );

			return;
		}

		prev   = repeat;
		repeat = repeat->next;
	}
}


void vram_sample ( void )
{
	vram_init();

	vram_new(7);
	u16 x = vram_new(20);
	vram_new(5);
	vram_delete ( x );
	u16 y = vram_new(5);
	vram_new(1);
	vram_new(8);
	vram_delete ( y );
	vram_new(3);

	vram_info();
}


void vram_info ()
{
	VRAM *aux = vram;


	u8 i = 3;
	u8 str[10];

	VDP_drawText ( " Nb  Pos Tiles", 1, 0 );
	VDP_drawText ( "--- ---- -----", 1, 1 );

	while ( aux )
	{
		uintToStr(i-2, str, 1);
		VDP_drawText(str, 1, i);

		uintToStr(aux->pos, str, 1);
		VDP_drawText(str, 5, i);

		uintToStr(aux->tiles, str, 1);
		VDP_drawText(str, 11, i);

		aux = aux->next;
		i++;
	}
}

[Moon-Watcher]

May you noticed the single linked list uses u32 instead u16. Well, that's because it is the only way I did it work and can't understand why.

Code: Select all

typedef struct _vram 
{ 
   u16 pos;                      // u16 !!!
   u16 tiles;                     // u16 !!!
   struct _vram *next; 
} 
VRAM; 

vram_new(246);  // works
vram_new(247);  // 247 or higher fails

Don't think it's related to MEM_alloc() itself.