/**

  * $Id$

  *

  * Texture cache. Responsible for maintaining a working set of OpenGL 

  * textures. 

  *

  *

  * Copyright (c) 2005 Nathan Keynes.

  *

  * This program is free software; you can redistribute it and/or modify

  * it under the terms of the GNU General Public License as published by

  * the Free Software Foundation; either version 2 of the License, or

  * (at your option) any later version.

  *

  * This program is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

  * GNU General Public License for more details.

  */

 #include <assert.h>

 #include <string.h>

 #include "pvr2/pvr2.h"

 #include "pvr2/pvr2mmio.h"

 /** Specifies the maximum number of OpenGL

  * textures we're willing to have open at a time. If more are

  * needed, textures will be evicted in LRU order.

  */

 #define MAX_TEXTURES 256

 /**

  * Data structure:

  *

  * Main operations:

  *    find entry by texture_addr

  *    add new entry

  *    move entry to tail of lru list

  *    remove entry

  */

 typedef signed short texcache_entry_index;

 #define EMPTY_ENTRY -1

 static texcache_entry_index texcache_free_ptr = 0;

 static GLuint texcache_free_list[MAX_TEXTURES];

 typedef struct texcache_entry {

     uint32_t texture_addr;

     int width, height, mode;

     GLuint texture_id;

     render_buffer_t buffer;

     texcache_entry_index next;

     uint32_t lru_count;

 } *texcache_entry_t;

 static texcache_entry_index texcache_page_lookup[PVR2_RAM_PAGES];

 static uint32_t texcache_ref_counter;

 static struct texcache_entry texcache_active_list[MAX_TEXTURES];

 /**

  * Initialize the texture cache.

  */

 void texcache_init( )

 {

     int i;

     for( i=0; i<PVR2_RAM_PAGES; i++ ) {

         texcache_page_lookup[i] = EMPTY_ENTRY;

     }

     for( i=0; i<MAX_TEXTURES; i++ ) {

         texcache_free_list[i] = i;

         texcache_active_list[i].texture_addr = -1;

         texcache_active_list[i].buffer = NULL;

         texcache_active_list[i].next = EMPTY_ENTRY;

     }

     texcache_free_ptr = 0;

     texcache_ref_counter = 0;

 }

 /**

  * Setup the initial texture ids (must be called after the GL context is

  * prepared)

  */

 void texcache_gl_init( )

 {

     int i;

     GLuint texids[MAX_TEXTURES];

     glGenTextures( MAX_TEXTURES, texids );

     for( i=0; i<MAX_TEXTURES; i++ ) {

         texcache_active_list[i].texture_id = texids[i];

     }

 }

 void texcache_release_render_buffer( render_buffer_t buffer )

 {

     if( !buffer->flushed ) 

         pvr2_render_buffer_copy_to_sh4(buffer);

     pvr2_destroy_render_buffer(buffer);

 }

 /**

  * Flush all textures from the cache, returning them to the free list.

  */

 void texcache_flush( )

 {

     int i;

     /* clear structures */

     for( i=0; i<PVR2_RAM_PAGES; i++ ) {

         texcache_page_lookup[i] = EMPTY_ENTRY;

     }

     for( i=0; i<MAX_TEXTURES; i++ ) {

         texcache_free_list[i] = i;

         texcache_active_list[i].next = EMPTY_ENTRY;

         if( texcache_active_list[i].buffer != NULL ) {

             texcache_release_render_buffer(texcache_active_list[i].buffer);

             texcache_active_list[i].buffer = NULL;

         }

     }

     texcache_free_ptr = 0;

     texcache_ref_counter = 0;

 }

 /**

  * Flush all textures and delete. The cache will be non-functional until

  * the next call to texcache_init(). This would typically be done if

  * switching GL targets.

  */    

 void texcache_shutdown( )

 {

     GLuint texids[MAX_TEXTURES];

     int i;

     texcache_flush();

     for( i=0; i<MAX_TEXTURES; i++ ) {

         texids[i] = texcache_active_list[i].texture_id;

     }

     glDeleteTextures( MAX_TEXTURES, texids );

 }

 static void texcache_evict( int slot )

 {

     /* Remove the selected slot from the lookup table */

     assert( texcache_active_list[slot].texture_addr != -1 );

     uint32_t evict_page = texcache_active_list[slot].texture_addr >> 12;

     texcache_entry_index replace_next = texcache_active_list[slot].next;

     texcache_active_list[slot].texture_addr = -1;

     texcache_active_list[slot].next = EMPTY_ENTRY; /* Just for safety */

     if( texcache_active_list[slot].buffer != NULL ) {

         texcache_release_render_buffer(texcache_active_list[slot].buffer);

         texcache_active_list[slot].buffer = NULL;

     }

     if( texcache_page_lookup[evict_page] == slot ) {

         texcache_page_lookup[evict_page] = replace_next;

     } else {

         texcache_entry_index idx = texcache_page_lookup[evict_page];

         texcache_entry_index next;

         do {

             next = texcache_active_list[idx].next;

             if( next == slot ) {

                 assert( idx != replace_next );

                 texcache_active_list[idx].next = replace_next;

                 break;

             }

             idx = next;

         } while( next != EMPTY_ENTRY );

     }

 }

 /**

  * Evict a single texture from the cache.

  * @return the slot of the evicted texture.

  */

 static texcache_entry_index texcache_evict_lru( void )

 {

     /* Full table scan - take over the entry with the lowest lru value */

     texcache_entry_index slot = 0;

     int lru_value = texcache_active_list[0].lru_count;

     int i;

     for( i=1; i<MAX_TEXTURES; i++ ) {

         /* FIXME: account for rollover */

         if( texcache_active_list[i].lru_count < lru_value ) {

             slot = i;

             lru_value = texcache_active_list[i].lru_count;

         }

     }

     texcache_evict(slot);

     return slot;

 }

 /**

  * Evict all textures contained in the page identified by a texture address.

  */

 void texcache_invalidate_page( uint32_t texture_addr ) {

     uint32_t texture_page = texture_addr >> 12;

     texcache_entry_index idx = texcache_page_lookup[texture_page];

     if( idx == EMPTY_ENTRY )

         return;

     assert( texcache_free_ptr >= 0 );

     do {

         texcache_entry_t entry = &texcache_active_list[idx];

         entry->texture_addr = -1;

         if( entry->buffer != NULL ) {

             texcache_release_render_buffer(entry->buffer);

             entry->buffer = NULL;

         }

         /* release entry */

         texcache_free_ptr--;

         texcache_free_list[texcache_free_ptr] = idx;

         idx = entry->next;

         entry->next = EMPTY_ENTRY;

     } while( idx != EMPTY_ENTRY );

     texcache_page_lookup[texture_page] = EMPTY_ENTRY;

 }

 /**

  * Mark all textures that use the palette table as needing a re-read (ie 

  * for when the palette is changed. We could track exactly which ones are 

  * affected, but it's not clear that the extra maintanence overhead is 

  * worthwhile.

  */

 void texcache_invalidate_palette( )

 {

     int i;

     for( i=0; i<MAX_TEXTURES; i++ ) {

         if( texcache_active_list[i].texture_addr != -1 &&

                 PVR2_TEX_IS_PALETTE(texcache_active_list[i].mode) ) {

             texcache_evict( i );

             texcache_free_ptr--;

             texcache_free_list[texcache_free_ptr] = i;

         }

     }

 }

 static void decode_pal8_to_32( uint32_t *out, uint8_t *in, int inbytes, uint32_t *pal )

 {

     int i;

     for( i=0; i<inbytes; i++ ) {

         *out++ = pal[*in++];

     }

 }

 static void decode_pal8_to_16( uint16_t *out, uint8_t *in, int inbytes, uint32_t *pal )

 {

     int i;

     for( i=0; i<inbytes; i++ ) {

         *out++ = (uint16_t)pal[*in++];

     }

 }

 static void decode_pal4_to_32( uint32_t *out, uint8_t *in, int inbytes, uint32_t *pal )

 {

     int i;

     for( i=0; i<inbytes; i++ ) {

         *out++ = pal[*in & 0x0F];

         *out++ = pal[(*in >> 4)];

         in++;

     }

 }

 static void decode_pal4_to_16( uint16_t *out, uint8_t *in, int inbytes, uint32_t *pal )

 {

     int i;

     for( i=0; i<inbytes; i++ ) {

         *out++ = (uint16_t)pal[*in & 0x0F];

         *out++ = (uint16_t)pal[(*in >> 4)];

         in++;

     }

 }

 #define VQ_CODEBOOK_SIZE 2048 /* 256 entries * 4 pixels per quad * 2 byte pixels */

 struct vq_codebook {

     uint16_t quad[256][4];

 };

 static void vq_get_codebook( struct vq_codebook *codebook, 

                              uint16_t *input )

 {

     /* Detwiddle the codebook, for the sake of my own sanity if nothing else */

     uint16_t *p = (uint16_t *)input;

     int i;

     for( i=0; i<256; i++ ) {

         codebook->quad[i][0] = *p++;

         codebook->quad[i][2] = *p++;

         codebook->quad[i][1] = *p++;

         codebook->quad[i][3] = *p++;

     }

 }    

 static void vq_decode( uint16_t *output, unsigned char *input, int width, int height, 

                        struct vq_codebook *codebook ) {

     int i,j;

     uint8_t *c = (uint8_t *)input;

     for( j=0; j<height; j+=2 ) {

         for( i=0; i<width; i+=2 ) {

             uint8_t code = *c++;

             output[i + j*width] = codebook->quad[code][0];

             output[i + 1 + j*width] = codebook->quad[code][1];

             output[i + (j+1)*width] = codebook->quad[code][2];

             output[i + 1 + (j+1)*width] = codebook->quad[code][3];

         }

     }

 }

 static inline uint32_t yuv_to_rgb32( float y, float u, float v )

 {

     u -= 128;

     v -= 128;

     int r = (int)(y + v*1.375);

     int g = (int)(y - u*0.34375 - v*0.6875);

     int b = (int)(y + u*1.71875);

     if( r > 255 ) { r = 255; } else if( r < 0 ) { r = 0; }

     if( g > 255 ) { g = 255; } else if( g < 0 ) { g = 0; }

     if( b > 255 ) { b = 255; } else if( b < 0 ) { b = 0; }

     return 0xFF000000 | (r<<16) | (g<<8) | (b);

 }

 /**

  * Convert raster YUV texture data into RGB32 data - most GL implementations don't

  * directly support this format unfortunately. The input data is formatted as

  * 32 bits = 2 horizontal pixels, UYVY. This is currently done rather inefficiently

  * in floating point.

  */

 static void yuv_decode( uint32_t *output, uint32_t *input, int width, int height )

 {

     int x, y;

     uint32_t *p = input;

     for( y=0; y<height; y++ ) {

         for( x=0; x<width; x+=2 ) {

             float u = (float)(*p & 0xFF);

             float y0 = (float)( (*p>>8)&0xFF );

             float v = (float)( (*p>>16)&0xFF );

             float y1 = (float)( (*p>>24)&0xFF );

             *output++ = yuv_to_rgb32( y0, u, v ); 

             *output++ = yuv_to_rgb32( y1, u, v );

             p++;

         }

     }

 }

 static gboolean is_npot_texture( int width )

 {

     while( width != 0 ) {

         if( width & 1 ) 

             return width != 1;

         width >>= 1;

     }

     return TRUE;

 }

 /**

  * Load texture data from the given address and parameters into the currently

  * bound OpenGL texture.

  */

 static void texcache_load_texture( uint32_t texture_addr, int width, int height,

                                    int mode ) {

     int bpp_shift = 1; /* bytes per (output) pixel as a power of 2 */

     GLint intFormat = GL_RGBA, format, type;

     int tex_format = mode & PVR2_TEX_FORMAT_MASK;

     struct vq_codebook codebook;

     GLint filter = GL_LINEAR;

     glPixelStorei( GL_UNPACK_ROW_LENGTH, 0 );

     /* Decode the format parameters */

     switch( tex_format ) {

     case PVR2_TEX_FORMAT_IDX4:

     case PVR2_TEX_FORMAT_IDX8:

         /* For indexed-colour modes, we need to lookup the palette control

          * word to determine the de-indexed texture format.

          */

         switch( MMIO_READ( PVR2, RENDER_PALETTE ) & 0x03 ) {

         case 0: /* ARGB1555 */

             format = GL_BGRA;

             type = GL_UNSIGNED_SHORT_1_5_5_5_REV;

             break;

         case 1:  /* RGB565 */

             intFormat = GL_RGB;

             format = GL_RGB;

             type = GL_UNSIGNED_SHORT_5_6_5;

             break;

         case 2: /* ARGB4444 */

             format = GL_BGRA;

             type = GL_UNSIGNED_SHORT_4_4_4_4_REV;

             break;

         case 3: /* ARGB8888 */

             format = GL_BGRA;

             type = GL_UNSIGNED_BYTE;

             bpp_shift = 2;

             break;

         default:

             return; /* Can't happen, but it makes gcc stop complaining */

         }

         break;

         default:

         case PVR2_TEX_FORMAT_ARGB1555:

             format = GL_BGRA;

             type = GL_UNSIGNED_SHORT_1_5_5_5_REV;

             break;

         case PVR2_TEX_FORMAT_RGB565:

             intFormat = GL_RGB;

             format = GL_RGB;

             type = GL_UNSIGNED_SHORT_5_6_5;

             break;

         case PVR2_TEX_FORMAT_ARGB4444:

             format = GL_BGRA;

             type = GL_UNSIGNED_SHORT_4_4_4_4_REV;

             break;

         case PVR2_TEX_FORMAT_YUV422:

             /* YUV422 isn't directly supported by most implementations, so decode

              * it to a (reasonably) standard ARGB32.

              */

             bpp_shift = 2;

             format = GL_BGRA;

             type = GL_UNSIGNED_BYTE;

             break;

         case PVR2_TEX_FORMAT_BUMPMAP:

             WARN( "Bumpmap not supported" );

             return;

     }

     if( PVR2_TEX_IS_STRIDE(mode) && tex_format != PVR2_TEX_FORMAT_IDX4 &&

             tex_format != PVR2_TEX_FORMAT_IDX8 ) {

         /* Stride textures cannot be mip-mapped, compressed, indexed or twiddled */

         uint32_t stride = (MMIO_READ( PVR2, RENDER_TEXSIZE ) & 0x003F) << 5;

         unsigned char data[(width*height) << bpp_shift];

         if( tex_format == PVR2_TEX_FORMAT_YUV422 ) {

             unsigned char tmp[(width*height)<<1];

             pvr2_vram64_read_stride( tmp, width<<1, texture_addr, stride<<1, height );

             yuv_decode( (uint32_t *)data, (uint32_t *)tmp, width, height );

         } else {

             pvr2_vram64_read_stride( data, width<<bpp_shift, texture_addr, stride<<bpp_shift, height );

         }

         glTexImage2D( GL_TEXTURE_2D, 0, intFormat, width, height, 0, format, type, data );

         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);

         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

         return;

     } 

     if( PVR2_TEX_IS_COMPRESSED(mode) ) {

         uint16_t tmp[VQ_CODEBOOK_SIZE];

         pvr2_vram64_read( (unsigned char *)tmp, texture_addr, VQ_CODEBOOK_SIZE );

         texture_addr += VQ_CODEBOOK_SIZE;

         vq_get_codebook( &codebook, tmp );

     }

     int level=0, last_level = 0, mip_width = width, mip_height = height, src_bytes, dest_bytes;

     if( PVR2_TEX_IS_MIPMAPPED(mode) ) {

         uint32_t src_offset = 0;

         filter = GL_LINEAR_MIPMAP_LINEAR;

         mip_height = height = width;

         while( (1<<last_level) < width ) {

             last_level++;

             src_offset += ((width>>last_level)*(width>>last_level));

         }

         if( width != 1 ) {

             src_offset += 3;

         }

         if( PVR2_TEX_IS_COMPRESSED(mode) ) {

             src_offset >>= 2;

         } else if( tex_format == PVR2_TEX_FORMAT_IDX4 ) {

             src_offset >>= 1;

         } else if( tex_format == PVR2_TEX_FORMAT_YUV422 ) {

             src_offset <<= 1;

         } else if( tex_format != PVR2_TEX_FORMAT_IDX8 ) {

             src_offset <<= bpp_shift;

         }

         texture_addr += src_offset;

     }

     dest_bytes = (mip_width * mip_height) << bpp_shift;

     src_bytes = dest_bytes; // Modes will change this (below)

     for( level=0; level<= last_level; level++ ) {

         unsigned char data[dest_bytes];

         /* load data from image, detwiddling/uncompressing as required */

         if( tex_format == PVR2_TEX_FORMAT_IDX8 ) {

             src_bytes = (mip_width * mip_height);

             int bank = (mode >> 25) &0x03;

             uint32_t *palette = ((uint32_t *)mmio_region_PVR2PAL.mem) + (bank<<8);

             unsigned char tmp[src_bytes];

             pvr2_vram64_read_twiddled_8( tmp, texture_addr, mip_width, mip_height );

             if( bpp_shift == 2 ) {

                 decode_pal8_to_32( (uint32_t *)data, tmp, src_bytes, palette );

             } else {

                 decode_pal8_to_16( (uint16_t *)data, tmp, src_bytes, palette );

             }

         } else if( tex_format == PVR2_TEX_FORMAT_IDX4 ) {

             src_bytes = (mip_width * mip_height) >> 1;

             int bank = (mode >>21 ) & 0x3F;

             uint32_t *palette = ((uint32_t *)mmio_region_PVR2PAL.mem) + (bank<<4);

             unsigned char tmp[src_bytes];

             pvr2_vram64_read_twiddled_4( tmp, texture_addr, mip_width, mip_height );

             if( bpp_shift == 2 ) {

                 decode_pal4_to_32( (uint32_t *)data, tmp, src_bytes, palette );

             } else {

                 decode_pal4_to_16( (uint16_t *)data, tmp, src_bytes, palette );

             }

         } else if( tex_format == PVR2_TEX_FORMAT_YUV422 ) {

             src_bytes = ((mip_width*mip_height)<<1);

             unsigned char tmp[src_bytes];

             if( PVR2_TEX_IS_TWIDDLED(mode) ) {

                 pvr2_vram64_read_twiddled_16( tmp, texture_addr, mip_width, mip_height );

             } else {

                 pvr2_vram64_read( tmp, texture_addr, src_bytes );

             }

             yuv_decode( (uint32_t *)data, (uint32_t *)tmp, mip_width, mip_height );

         } else if( PVR2_TEX_IS_COMPRESSED(mode) ) {

             src_bytes = ((mip_width*mip_height) >> 2);

             unsigned char tmp[src_bytes];

             if( PVR2_TEX_IS_TWIDDLED(mode) ) {

                 pvr2_vram64_read_twiddled_8( tmp, texture_addr, mip_width>>1, mip_height>>1 );

             } else {

                 pvr2_vram64_read( tmp, texture_addr, src_bytes );

             }

             vq_decode( (uint16_t *)data, tmp, mip_width, mip_height, &codebook );

         } else if( PVR2_TEX_IS_TWIDDLED(mode) ) {

             pvr2_vram64_read_twiddled_16( data, texture_addr, mip_width, mip_height );

         } else {

             pvr2_vram64_read( data, texture_addr, src_bytes );

         }

         /* Pass to GL */

         if( level == last_level && level != 0 ) { /* 1x1 stored within a 2x2 */

             glTexImage2D( GL_TEXTURE_2D, level, intFormat, 1, 1, 0, format, type,

                     data + (3 << bpp_shift) );

         } else {

             glTexImage2D( GL_TEXTURE_2D, level, intFormat, mip_width, mip_height, 0, format, type,

                     data );

             if( mip_width > 2 ) {

                 mip_width >>= 1;

                 mip_height >>= 1;

                 dest_bytes >>= 2;

                 src_bytes >>= 2;

             }

             texture_addr -= src_bytes;

         }

     }

     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);

     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

 }

 static int texcache_find_texture_slot( uint32_t texture_word, int width, int height )

 {

     uint32_t texture_addr = (texture_word & 0x000FFFFF)<<3;

     uint32_t texture_page = texture_addr >> 12;

     texcache_entry_index next;

     texcache_entry_index idx = texcache_page_lookup[texture_page];

     while( idx != EMPTY_ENTRY ) {

         texcache_entry_t entry = &texcache_active_list[idx];

         if( entry->texture_addr == texture_addr &&

                 entry->mode == texture_word &&

                 entry->width == width &&

                 entry->height == height ) {

             entry->lru_count = texcache_ref_counter++;

             return idx;

         }

         idx = entry->next;

     }

     return -1;

 }

 static int texcache_alloc_texture_slot( uint32_t texture_word, int width, int height )

 {

     uint32_t texture_addr = (texture_word & 0x000FFFFF)<<3;

     uint32_t texture_page = texture_addr >> 12;

     texcache_entry_index slot = 0;

     if( texcache_free_ptr < MAX_TEXTURES ) {

         slot = texcache_free_list[texcache_free_ptr++];

     } else {

         slot = texcache_evict_lru();

     }

     /* Construct new entry */

     texcache_active_list[slot].texture_addr = texture_addr;

     texcache_active_list[slot].width = width;

     texcache_active_list[slot].height = height;

     texcache_active_list[slot].mode = texture_word;

     texcache_active_list[slot].lru_count = texcache_ref_counter++;

     /* Add entry to the lookup table */

     int next = texcache_page_lookup[texture_page];

     if( next == slot ) {

         int i;

         fprintf( stderr, "Active list: " );

         for( i=0; i<MAX_TEXTURES; i++ ) {

             fprintf( stderr, "%d, ", texcache_active_list[i].next );

         }

         fprintf( stderr, "\n" );

         assert( next != slot );

     }

     assert( next != slot );

     texcache_active_list[slot].next = next;

     texcache_page_lookup[texture_page] = slot;

     return slot;

 }

 /**

  * Return a texture ID for the texture specified at the supplied address

  * and given parameters (the same sequence of bytes could in theory have

  * multiple interpretations). We use the texture address as the primary

  * index, but allow for multiple instances at each address. The texture

  * will be bound to the GL_TEXTURE_2D target before being returned.

  * 

  * If the texture has already been bound, return the ID to which it was

  * bound. Otherwise obtain an unused texture ID and set it up appropriately.

  */

 GLuint texcache_get_texture( uint32_t texture_word, int width, int height )

 {

     int slot = texcache_find_texture_slot( texture_word, width, height );

     if( slot == -1 ) {

         /* Not found - check the free list */

         slot = texcache_alloc_texture_slot( texture_word, width, height );

         /* Construct the GL texture */

         uint32_t texture_addr = (texture_word & 0x000FFFFF)<<3;

         glBindTexture( GL_TEXTURE_2D, texcache_active_list[slot].texture_id );

         texcache_load_texture( texture_addr, width, height, texture_word );

     }

     return texcache_active_list[slot].texture_id;

 }

 render_buffer_t texcache_get_render_buffer( uint32_t texture_addr, int mode, int width, int height )

 {

     INFO( "Rendering to texture!" );

     uint32_t texture_word = ((texture_addr >> 3) & 0x000FFFFF) | PVR2_TEX_UNTWIDDLED;

     switch( mode ) {

     case COLFMT_BGRA1555: texture_word |= PVR2_TEX_FORMAT_ARGB1555; break;

     case COLFMT_RGB565:   texture_word |= PVR2_TEX_FORMAT_RGB565; break;

     case COLFMT_BGRA4444: texture_word |= PVR2_TEX_FORMAT_ARGB4444; break;

     default:

         WARN( "Rendering to non-texture colour format" );

     }

     if( is_npot_texture(width) )

         texture_word |= PVR2_TEX_STRIDE;

     int slot = texcache_find_texture_slot( texture_word, width, height );

     if( slot == -1 ) {

         slot = texcache_alloc_texture_slot( texture_word, width, height );

     }

     texcache_entry_t entry = &texcache_active_list[slot];

     if( entry->buffer == NULL ) {

         entry->buffer = pvr2_create_render_buffer( texture_addr, width, height, entry->texture_id );

     } else if( entry->buffer->width != width || entry->buffer->height != height ) {        

         texcache_release_render_buffer(entry->buffer);

         entry->buffer = pvr2_create_render_buffer( texture_addr, width, height, entry->texture_id );

     }

     return entry->buffer;

 }

 /**

  * Check the integrity of the texcache. Verifies that every cache slot

  * appears exactly once on either the free list or one page list. For 

  * active slots, the texture address must also match the page it appears on.

  * 

  */

 void texcache_integrity_check()

 {

     int i;

     int slot_found[MAX_TEXTURES];

     memset( slot_found, 0, sizeof(slot_found) );

     /* Check entries on the free list */

     for( i= texcache_free_ptr; i< MAX_TEXTURES; i++ ) {

         int slot = texcache_free_list[i];

         assert( slot_found[slot] == 0 );

         assert( texcache_active_list[slot].next == EMPTY_ENTRY );

         slot_found[slot] = 1;

     }

     /* Check entries on the active lists */

     for( i=0; i< PVR2_RAM_PAGES; i++ ) {

         int slot = texcache_page_lookup[i];

         while( slot != EMPTY_ENTRY ) {

             assert( slot_found[slot] == 0 );

             assert( (texcache_active_list[slot].texture_addr >> 12) == i );

             slot_found[slot] = 2;

             slot = texcache_active_list[slot].next;

         }

     }

     /* Make sure we didn't miss any entries */

     for( i=0; i<MAX_TEXTURES; i++ ) {

         assert( slot_found[i] != 0 );

     }

 }