VM

Virtual Memory. More...

Data Structures
struct	T_vmDataBlock
struct	T_vmEntry
struct	T_vmFileInfo
struct	T_vmHeader
struct	T_vmIndex

Macros
#define	VM_BLOCK_ID
#define	VM_ENTRY_GROW_SIZE   2000
#define	VM_FLAG_DIRTY   0x40
#define	VM_FLAG_IN_MEMORY   0x80
#define	VM_SEMAPHORE_READ   0x20
#define	VM_SEMAPHORE_WRITE   0x10
#define	VM_SHIFT_BLOCK_SIZE   4000

Typedefs
typedef T_byte8	F_vmFlags

Functions
T_word32	IVMAppendEntry (T_vmFile file)
T_void	IVMCreate (T_vmFileInfo *p_fileInfo)
T_vmBlock	IVMCreateBlockAtEnd (T_vmFile file, T_word32 size)
T_vmBlock	IVMFindFreeBlockOfSize (T_vmFile file, T_word32 size)
T_vmBlock	IVMFindLowestBlock (T_vmFile file, T_word32 place)
T_void	IVMFree (T_vmFile file, T_vmBlock block)
T_void	IVMRelease (T_vmFile file, T_vmBlock block)
T_void	IVMSaveIfDirty (T_vmFileInfo *p_fileInfo, T_vmEntry *p_entry)
T_void	IVMSaveIndex (T_vmFileInfo *p_fileInfo)
T_void	IVMShiftBlockDown (T_vmFile file, T_vmBlock block, T_word32 *place)
T_void	IVMTruncate (T_vmFile file, T_word32 place)
T_void	IVMUpdate (T_vmFileInfo *p_fileInfo)
T_vmBlock	VMAlloc (T_vmFile file, T_word32 size)
T_void	VMCleanUp (T_byte8 *p_filename)
T_void	VMClose (T_vmFile file)
T_void	VMDecRefCount (T_vmFile file, T_vmBlock block)
T_void	VMDirty (T_vmFile file, T_vmBlock block)
T_word16	VMGetRefCount (T_vmFile file, T_vmBlock block)
T_void	VMIncRefCount (T_vmFile file, T_vmBlock block)
void *	VMLock (T_vmFile file, T_vmBlock block)
T_vmFile	VMOpen (T_byte8 *p_filename)
T_void	VMUnlock (void *block)

Detailed Description

Virtual Memory.

Virtual Memory System – NOT USED!

See Also

http://www.amuletsandarmor.com/AALicense.txt

Macro Definition Documentation

#define VM_BLOCK_ID

Value:

((((T_word32)'V')<<0) | \
                    (((T_word32)'m')<<8) | \
                    (((T_word32)'B')<<16))

#define VM_ENTRY_GROW_SIZE   2000

#define VM_FLAG_DIRTY   0x40

#define VM_FLAG_IN_MEMORY   0x80

#define VM_SEMAPHORE_READ   0x20

#define VM_SEMAPHORE_WRITE   0x10

#define VM_SHIFT_BLOCK_SIZE   4000

Typedef Documentation

typedef T_byte8 F_vmFlags

Function Documentation

T_word32 IVMAppendEntry

(

T_vmFile

file)

IVMAppendEntry adds another entry at the bottom of the index.

Parameters

file	– File to append an entry.

T_void IVMCreate

(

T_vmFileInfo *

p_fileInfo)

IVMCreate opens up a new vm file and vm records file. Any previous data is lost.

Parameters

p_fileInfo

– Pointer to file info structure to create.

T_vmBlock IVMCreateBlockAtEnd	(	T_vmFile	file,
		T_word32	size
	)

IVMCreateBlockAtEnd assumes that the best place for a new block is at the end of the records file (and at the end of the index). A new block is created there.

Parameters

file	– File to append block to
size	– Size of block

T_vmBlock IVMFindFreeBlockOfSize	(	T_vmFile	file,
		T_word32	size
	)

IVMFindFreeBlockOfSize searches for the first block that meets the given size requirement. In addition, it splits the blocks accordingly.

NOTE: Based on the way this routine works, it is fast, but causes alot of fragmentation.

Parameters

file	– File to search for block within
size	– Size to find

T_vmBlock IVMFindLowestBlock	(	T_vmFile	file,
		T_word32	place
	)

IVMFindLowestBlock searches the index to find the lowest block that is above the given file offset. If none is found, a zero is returned.

Parameters

file	– File to release block within
place	– Place in VM

T_void IVMFree	(	T_vmFile	file,
		T_vmBlock	block
	)

IVMFree takes a originally reference allocated block and frees it and puts it on the linked list of free blocks.

NOTE: Obviously you should not call this on an already freed block.

Parameters

file	– File to free block within
block	– Block that is being freed

T_void IVMRelease	(	T_vmFile	file,
		T_vmBlock	block
	)

IVMRelease makes a block that was in memory be released to disk (and saves if necessary).

NOTE: Obviously you should not call this on an already freed block.

Parameters

file	– File to release block within
block	– Block that is being released

T_void IVMSaveIfDirty	(	T_vmFileInfo *	p_fileInfo,
		T_vmEntry *	p_entry
	)

IVMSaveIfDirty checks the given block if is dirty, and if so, saves it to disk. Otherwise, nothing happens.

Parameters

p_fileInfo	– Pointer to the file information struct
p_entry	– Pointer to entry to check to save

T_void IVMSaveIndex

(

T_vmFileInfo *

p_fileInfo)

IVMSaveIndex saves the index file.

Parameters

p_fileInfo

– Pointer to the file information struct

T_void IVMShiftBlockDown	(	T_vmFile	file,
		T_vmBlock	block,
		T_word32 *	place
	)

IVMShiftBlockDown moves a vm block within the records file to the given place. The byte after the block is also returned.

Parameters

file	– File to shift block within
block	– Block to shift
place	– Place to shift down to (and variable to record end of block).

T_void IVMTruncate	(	T_vmFile	file,
		T_word32	place
	)

IVMTruncate clips the end of the vm file so that the file takes up less disk space.

Parameters

file	– File to truncate
place	– where to truncate the file

T_void IVMUpdate

(

T_vmFileInfo *

p_fileInfo)

IVMUpdate saves all dirty records, mark them as clean, and then saves the whole index.

Parameters

p_fileInfo

– Pointer to file info structure to update.

T_vmBlock VMAlloc	(	T_vmFile	file,
		T_word32	size
	)

VMAlloc does all the work of finding a block of the given size in the current virtual memory file. If no space can be found, a VM_BLOCK_BAD is returned.

Parameters

file	– File to allocate vm block within
size	– Size to make the vm block

Returns

block handle to block, or VM_BLOCK_BAD

T_void VMCleanUp

(

T_byte8 *

p_filename)

From time to time, files will become 'pitted' with free blocks that nothing will use. When this happens, all the free spots need to be compressed and expulged. All free spots are removed and everything is relocated correctly. Major files should have this routine called on them at least once a day. Note that this routine should only be called on FULLY CLOSED vm files. If you don't the file will be destroyed since two versions will exist (one in memory, one on disk).

NOTE: The VM file that is being cleaned-up should NOT be opened at this time. No checks are made to confirm this.

Parameters

p_filename

– Name of file to clean-up

T_void VMClose

(

T_vmFile

file)

VMClose closes out all of the records opened (but waiting to be written). All corresponding junk that is not needed is cleared from memory.

Parameters

file	– File that is to be closed.

T_void VMDecRefCount	(	T_vmFile	file,
		T_vmBlock	block
	)

VMDecRefCount decrements the count of references to this block. This number is very important since it tells whether or not the block is free. Accurate reference counts is a must. Note that newly VMAlloc'd blocks start with a reference count of 1. A reference count of 0 is a free block.

NOTE: VMDecRefCount may destroy all data related to the block if the reference count goes to zero. Make VMDecRefCount the last action performed on any block.

Parameters

file	– File containing vm block to decrement
block	– Block to decrement in vm file.

T_void VMDirty	(	T_vmFile	file,
		T_vmBlock	block
	)

VMDirty marks a block dirty so the block is saved to disk. Otherwise, the block is never saved and any changes are lost.

Parameters

file	– File containing newly dirty block
block	– Block in file to mark dirty

T_word16 VMGetRefCount	(	T_vmFile	file,
		T_vmBlock	block
	)

VMGetRefCount returns the number of references to this block.

Parameters

file	– File containing vm block to decrement
block	– Block to decrement in vm file.

T_void VMIncRefCount	(	T_vmFile	file,
		T_vmBlock	block
	)

VMIncRefCount increments the count of references to this block. This number is very important since it tells whether or not the block is free. Accurate reference counts is a must. Note that newly VMAlloc'd blocks start with a reference count of 1.

Parameters

file	– File containing vm block to increment
block	– Block to increment in vm file.

void* VMLock	(	T_vmFile	file,
		T_vmBlock	block
	)

VMLock is used to retrieve a block from the vm file. In addition, semaphoring is done to check for read/write access priviledges. A block can be locked with a semaphore on reading or writing. If locked for writing semaphore, no other locking actions for write access are allowed. If the lock requests read priviledge, but the block is locked with read semaphored, then the lock is stopped. In addition, a flag is added to allow for thread blocking. If TRUE, the calling will wait until the block is free. If FALSE, the calling process will not wait and will not return with a block pointer.

NOTE: In this current version, the routine does not make memory write protected even though the semaphores may request read only. It is up to the programmer to make sure read and writes are appropriate to the semaphore accesses.

Parameters

file	– File containing vm block to decrement
block	– Block to decrement in vm file.

Returns

Pointer to data block, or NULL

T_vmFile VMOpen

(

T_byte8 *

p_filename)

VMOpen opens a file for VM file access. If the file does not exist, it is created. Minimal setup is used when first created. Pass to this routine the filename WITHOUT an extension. A .idx postfix is added for the index and A .rec postfix is added for the records file.

Parameters

p_filename

– File to open for VM access.

Returns

File that was opened.

T_void VMUnlock

(

void *

block)

VMUnlock releases the vm block from memory. If multiple locks have been executed, an equal number of unlocks must be performed to remove the block from memory.

Parameters

block

– Pointer to block previously locked