All Known Implementing Classes:

SqlJetFile, SqlJetMemJournal
```
public interface ISqlJetFile
```
OS Interface Open File Handle. An ISqlJetFile object represents an open file in the OS interface layer. Individual OS interface implementations will want to subclass this object by appending additional fields for their own use.

Field Summary

Fields
Modifier and Type Field Description

static long PENDING_BYTE

static long RESERVED_BYTE

static long SHARED_FIRST

static long SHARED_SIZE

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`boolean`	`checkReservedLock()`	This routine checks if there is a RESERVED lock held on the specified file by this or any other process.
`void`	`close()`	Close a file.
`java.util.Set<SqlJetDeviceCharacteristics>`	`deviceCharacteristics()`	Return the device characteristics for the file.
`long`	`fileSize()`	Determine the current size of a file in bytes
`SqlJetFileType`	`getFileType()`	Returns file type.
`SqlJetLockType`	`getLockType()`	Returns lock type of file.
`java.util.Set<SqlJetFileOpenPermission>`	`getPermissions()`	Returns assiciated permissions.
`boolean`	`isMemJournal()`	Return true if the file-handle passed as an argument is an in-memory journal
`boolean`	`lock(SqlJetLockType lockType)`	Lock the file with the lock specified by parameter locktype - one of the following: (1) SHARED (2) RESERVED (3) PENDING (4) EXCLUSIVE Sometimes when requesting one lock state, additional lock states are inserted in between.
`int`	`read(ISqlJetMemoryPointer buffer, int amount, long offset)`	Read data from a file into a buffer.
`int`	`sectorSize()`	Return the sector size in bytes of the underlying block device for the specified file.
`void`	`sync(java.util.Set<SqlJetSyncFlags> syncFlags)`	Make sure all writes to a particular file are committed to disk.
`void`	`truncate(long size)`	Truncate an open file to a specified size
`boolean`	`unlock(SqlJetLockType lockType)`	Lower the locking level on file descriptor pFile to locktype.
`void`	`write(ISqlJetMemoryPointer buffer, int amount, long offset)`	Write data from a buffer into a file.

- Field Detail
  - PENDING_BYTE
```
static final long PENDING_BYTE
```
    See Also:
    
    Constant Field Values
  - RESERVED_BYTE
```
static final long RESERVED_BYTE
```
    See Also:
    
    Constant Field Values
  - SHARED_FIRST
```
static final long SHARED_FIRST
```
    See Also:
    
    Constant Field Values
  - SHARED_SIZE
```
static final long SHARED_SIZE
```
    See Also:
    
    Constant Field Values
- Method Detail
  - getFileType
```
SqlJetFileType getFileType()
```
    Returns file type.
    
    Returns:
    
    SqlJetFileType
  - getPermissions
```
java.util.Set<SqlJetFileOpenPermission> getPermissions()
```
    Returns assiciated permissions.
    
    Returns:
    
    SqlJetFileOpenPermission
  - close
```
void close()
    throws SqlJetException
```
    Close a file.
    
    Throws:
    
    SqlJetException
  - read
```
int read(ISqlJetMemoryPointer buffer,
         int amount,
         long offset)
  throws SqlJetIOException
```
    Read data from a file into a buffer.
    
    Parameters:
    
    buffer -
    
    amount -
    
    offset -
    
    Returns:
    
    Throws:
    
    SqlJetIOException
  - write
```
void write(ISqlJetMemoryPointer buffer,
           int amount,
           long offset)
    throws SqlJetIOException
```
    Write data from a buffer into a file.
    
    Parameters:
    
    buffer -
    
    amount -
    
    offset -
    
    Throws:
    
    SqlJetIOException
  - truncate
```
void truncate(long size)
       throws SqlJetIOException
```
    Truncate an open file to a specified size
    
    Parameters:
    
    size -
    
    Throws:
    
    SqlJetIOException
  - sync
```
void sync(java.util.Set<SqlJetSyncFlags> syncFlags)
   throws SqlJetIOException
```
    Make sure all writes to a particular file are committed to disk. If dataOnly==false then both the file itself and its metadata (file size, access time, etc) are synced. If dataOnly==true then only the file data is synced. Also make sure that the directory entry for the file has been created by fsync-ing the directory that contains the file. If we do not do this and we encounter a power failure, the directory entry for the journal might not exist after we reboot. The next SqlJet to access the file will not know that the journal exists (because the directory entry for the journal was never created) and the transaction will not roll back - possibly leading to database corruption.
    
    Parameters:
    
    dataOnly -
    
    full -
    
    Throws:
    
    SqlJetIOException
  - fileSize
```
long fileSize()
       throws SqlJetException
```
    Determine the current size of a file in bytes
    
    Returns:
    
    Throws:
    
    SqlJetException
  - lock
```
boolean lock(SqlJetLockType lockType)
      throws SqlJetIOException
```
    Lock the file with the lock specified by parameter locktype - one of the following: (1) SHARED (2) RESERVED (3) PENDING (4) EXCLUSIVE Sometimes when requesting one lock state, additional lock states are inserted in between. The locking might fail on one of the later transitions leaving the lock state different from what it started but still short of its goal. The following chart shows the allowed transitions and the inserted intermediate states: UNLOCKED -> SHARED SHARED -> RESERVED SHARED -> (PENDING) -> EXCLUSIVE RESERVED -> (PENDING) -> EXCLUSIVE PENDING -> EXCLUSIVE This routine will only increase a lock.
    
    Parameters:
    
    lockType -
    
    Returns:
    
    Throws:
    
    SqlJetIOException
  - unlock
```
boolean unlock(SqlJetLockType lockType)
        throws SqlJetIOException
```
    Lower the locking level on file descriptor pFile to locktype. locktype must be either NONE or SHARED. If the locking level of the file descriptor is already at or below the requested locking level, this routine is a no-op.
    
    Parameters:
    
    lockType -
    
    Returns:
    
    Throws:
    
    SqlJetIOException
  - checkReservedLock
```
boolean checkReservedLock()
```
    This routine checks if there is a RESERVED lock held on the specified file by this or any other process. The return value is set unless an I/O error occurs during lock checking.
    
    Returns:
  - getLockType
```
SqlJetLockType getLockType()
```
    Returns lock type of file.
    
    Returns:
  - sectorSize
```
int sectorSize()
```
    Return the sector size in bytes of the underlying block device for the specified file. This is almost always 512 bytes, but may be larger for some devices. SqlJet code assumes this function cannot fail. It also assumes that if two files are created in the same file-system directory (i.e. a database and its journal file) that the sector size will be the same for both.
    
    Returns:
  - deviceCharacteristics
```
java.util.Set<SqlJetDeviceCharacteristics> deviceCharacteristics()
```
    Return the device characteristics for the file.
    
    Returns:
  - isMemJournal
```
boolean isMemJournal()
```
    Return true if the file-handle passed as an argument is an in-memory journal

Modifier and Type	Field	Description
`static long`	`PENDING_BYTE`
`static long`	`RESERVED_BYTE`
`static long`	`SHARED_FIRST`
`static long`	`SHARED_SIZE`

Interface ISqlJetFile

Field Summary

Method Summary

Field Detail

PENDING_BYTE

RESERVED_BYTE

SHARED_FIRST

SHARED_SIZE

Method Detail

getFileType

getPermissions

close

read

write

truncate

sync

fileSize

lock

unlock

checkReservedLock

getLockType

sectorSize

deviceCharacteristics

isMemJournal