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Classes | Functions
vram.h File Reference

SGDK VRAM (Video Memory) management unit. More...

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Go to the source code of this file.

Classes

struct  VRAMRegion
 VRAM region structure. More...
 

Functions

void VRAM_createRegion (VRAMRegion *region, u16 startIndex, u16 size)
 Initialize a new VRAM region structure.
 
void VRAM_releaseRegion (VRAMRegion *region)
 Release the VRAM region structure.
 
void VRAM_clearRegion (VRAMRegion *region)
 Release all allocations from specified VRAM region.
 
u16 VRAM_getFree (VRAMRegion *region)
 Return the number of free tile remaining in the specified VRAM region.
 
u16 VRAM_getAllocated (VRAMRegion *region)
 Return the number of allocated tile in the specified VRAM region.
 
u16 VRAM_getLargestFreeBlock (VRAMRegion *region)
 Return the largest free block size (in tile) in the specified VRAM region.
 
s16 VRAM_alloc (VRAMRegion *region, u16 size)
 Try to allocate the specified number of tile in the given VRAM region and return its index.
 
void VRAM_free (VRAMRegion *region, u16 index)
 Release the previously allocated VRAM block at specified index in the given VRAM region.

 

Detailed Description

SGDK VRAM (Video Memory) management unit.

Author
Stephane Dallongeville
Date
11/2015

Video Memory management unit.
It offerts methods to manage dynamic VRAM allocation for tile data.
Tile data should always be located before tilemap in VRAM (0000-XXXX = tile data, XXXX-FFFF = tilemaps).

  VRAMRegion structure define a VRAM region where we want to use dynamic allocation.
  'vram' field is a buffer representing the VRAM region usage. For each entry:
   b14-b0 = size of the bloc (in tile)
   b15    = 1:used, 0:free

   address           value

                   +-------------------+
   free = 0        | cacheSize  (free) |
                   |                   |
                   |                   |
   cacheSize - 1   |                   |
                   +-------------------+
   cacheSize       | 0                 |
                   +-------------------+


   1. Before allocation (with cacheSize = 1000)

                   +-------------------+
   free = 0        | 1000       (free) |
                   |                   |
                   |                   |
   999             |                   |
                   +-------------------+
   1000            | 0                 |
                   +-------------------+

   cache = ???
   free = cache            *free = cacheSize
   end = cache+cacheSize   *end = 0


   2. After allocation of 32 tiles

                   +------------------------+
   0               | 32              (used) |
   free = 32       | 968             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+

   cache = ???
   free = cache + 32       *free = cacheSize - 32


   3. After allocation of 128 tiles

                   +------------------------+
   0               | 32              (used) |
   32              | 128             (used) |
   free = 32+128   | 840             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+


   4. After allocation of 64, 500, 100 tiles

                   +------------------------+
   0               | 32              (used) |
   32              | 128             (used) |
   160             | 64              (used) |
   224             | 500             (used) |
   724             | 100             (used) |
   free = 824      | 176             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+


   5. After release of allocation #3 (64 tiles)

                   +------------------------+
   0               | 32              (used) |
   32              | 128             (used) |
   160             | 64              (free) |
   224             | 500             (used) |
   724             | 100             (used) |
   free = 824      | 176             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+


   6. After release of allocation #4 (500 tiles)

                   +------------------------+
   0               | 32              (used) |
   32              | 128             (used) |
   160             | 64              (free) |
   224             | 500             (free) |
   724             | 100             (used) |
   free = 824      | 176             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+


   7. After allocation of 400 tiles

                   +------------------------+
   0               | 32              (used) |
   32              | 128             (used) |
   160             | 400             (used) |
   560             | 164             (free) |
   724             | 100             (used) |
   free = 824      | 176             (free) |
                   |                        |
                   |                        |
   999             |                        |
                   +------------------------+
   1000            | 0                      |
                   +------------------------+
*

Function Documentation

◆ VRAM_alloc()

s16 VRAM_alloc ( VRAMRegion * region,
u16 size )

Try to allocate the specified number of tile in the given VRAM region and return its index.

Parameters
regionVRAM region
sizeNumber of tile we want to allocate in VRAM (need to be > 0).
Returns
the index in VRAM where we allocated the bloc of tile.
-1 if there is no enough available VRAM in the region.
See also
VRAM_free(..)

◆ VRAM_clearRegion()

void VRAM_clearRegion ( VRAMRegion * region)

Release all allocations from specified VRAM region.

Parameters
regionVRAM region we want to clear.

◆ VRAM_createRegion()

void VRAM_createRegion ( VRAMRegion * region,
u16 startIndex,
u16 size )

Initialize a new VRAM region structure.

Parameters
regionRegion to initialize.
startIndexTile start index in VRAM.
sizeSize in tile of the region.

Set parameters and allocate memory for the VRAM region structure.

See also
VRAM_releaseRegion(..)

◆ VRAM_free()

void VRAM_free ( VRAMRegion * region,
u16 index )

Release the previously allocated VRAM block at specified index in the given VRAM region.

Parameters
regionVRAM region
indexThe index of the VRAM block we want to release
See also
VRAM_alloc(..)

◆ VRAM_getAllocated()

u16 VRAM_getAllocated ( VRAMRegion * region)

Return the number of allocated tile in the specified VRAM region.

Parameters
regionVRAM region
Returns
the number of allocated tile in the specified VRAM region.

◆ VRAM_getFree()

u16 VRAM_getFree ( VRAMRegion * region)

Return the number of free tile remaining in the specified VRAM region.

Parameters
regionVRAM region
Returns
the number of free tile in the specified VRAM region

◆ VRAM_getLargestFreeBlock()

u16 VRAM_getLargestFreeBlock ( VRAMRegion * region)

Return the largest free block size (in tile) in the specified VRAM region.

Parameters
regionVRAM region
Returns
the largest free block size (in tile) in the specified VRAM region.

◆ VRAM_releaseRegion()

void VRAM_releaseRegion ( VRAMRegion * region)

Release the VRAM region structure.

Parameters
regionVRAMRegion we want to release.

Release memory used by the VRAM region structure.

See also
VRAM_createRegion(..)