void * CachePermRead( file_list *list, unsigned long pos, unsigned len )
/*****************************************************************************/
{
char * buf;
char * result;
buf = CacheRead( list, pos, len );
if( list->file->flags & INSTAT_FULL_CACHE ) return buf;
if( Multipage ) {
_LnkReAlloc( result, buf, len );
_ChkAlloc( TokBuff, TokSize );
Multipage = FALSE; // indicate that last read is permanent.
} else {
_ChkAlloc( result, len );
memcpy( result, buf, len );
}
return result;
}
void *CacheRead( file_list *list, unsigned long pos, unsigned len )
/**************************************************************************/
/* read len bytes out of the cache. */
{
unsigned bufnum;
unsigned startnum;
unsigned offset;
unsigned amtread;
char *result;
char **cache;
unsigned long newpos;
infilelist *file;
if( list->file->flags & INSTAT_FULL_CACHE ) {
if( pos + len > list->file->len )
return( NULL );
return( (char *)list->file->cache + pos );
}
Multipage = FALSE;
file = list->file;
offset = pos % CACHE_PAGE_SIZE;
amtread = CACHE_PAGE_SIZE - offset;
startnum = pos / CACHE_PAGE_SIZE;
bufnum = startnum;
cache = file->cache;
for( ;; ) {
if( cache[ bufnum ] == NULL ) { // make sure page is in.
_ChkAlloc( cache[ bufnum ], CACHE_PAGE_SIZE );
newpos = (unsigned long)bufnum * CACHE_PAGE_SIZE;
if( file->currpos != newpos ) {
QSeek( file->handle, newpos, file->name );
}
file->currpos = newpos + CACHE_PAGE_SIZE;
QRead( file->handle, cache[ bufnum ], CACHE_PAGE_SIZE, file->name );
}
if( amtread >= len )
break;
amtread += CACHE_PAGE_SIZE; // it spans pages.
bufnum++;
Multipage = TRUE;
}
if( !Multipage ) {
result = cache[ startnum ] + offset;
} else {
if( len > TokSize ) {
TokSize = ROUND_UP( len, SECTOR_SIZE );
_LnkReAlloc( TokBuff, TokBuff, TokSize );
}
amtread = CACHE_PAGE_SIZE - offset;
memcpy( TokBuff, cache[ startnum ] + offset, amtread );
len -= amtread;
result = TokBuff + amtread;
for( ;; ) {
startnum++;
if( len <= CACHE_PAGE_SIZE ) {
memcpy( result, cache[ startnum ], len );
break;
} else {
memcpy( result, cache[ startnum ], CACHE_PAGE_SIZE );
len -= CACHE_PAGE_SIZE;
result += CACHE_PAGE_SIZE;
}
}
result = TokBuff;
}
return( result );
}
