org.iq80.leveldb.env

Interface Env

All Known Implementing Classes:

EnvImpl, MemEnv

public interface Env

Method Summary

Modifier and Type	Method and Description
File	createTempDir(String prefix) Create a temporary directory in filesystem
WritableFile	newAppendableFile(File file) Create an WritableFile that either appends to an existing file, or writes to a new file (if the file does not exist to begin with).
Logger	newLogger(File loggerFile) Create and return a log file for storing informational messages.
RandomInputFile	newRandomAccessFile(File file) Create a brand new random access read-only file with the specified file name.
SequentialFile	newSequentialFile(File file) Create a brand new sequentially-readable file with the specified file name.
WritableFile	newWritableFile(File file) Create an object that writes to a new file with the specified name.
long	nowMicros()
String	readFileToString(File file) Read full file content to string
File	toFile(String filename) Transform a file name into a File instance scoped to this Env instance
DbLock	tryLock(File lockFile) Attempts to acquire an exclusive lock on lock file
void	writeStringToFileSync(File file, String content) Write content to file.

Method Detail

nowMicros

long nowMicros()

toFile

File toFile(String filename)

Transform a file name into a File instance scoped to this Env instance

Parameters:

filename - full file name

Returns:

File instance

createTempDir

File createTempDir(String prefix)

Create a temporary directory in filesystem

Parameters:

prefix - prefix to use as name

Returns:

newly created directory

newSequentialFile

SequentialFile newSequentialFile(File file)
                          throws IOException

Create a brand new sequentially-readable file with the specified file name.

Returns:

new file that can only be accessed by one thread at a time.

Throws:

IOException - If the file does not exist or inaccessible.

newRandomAccessFile

RandomInputFile newRandomAccessFile(File file)
                             throws IOException

Create a brand new random access read-only file with the specified file name.

Returns:

new file that may be concurrently accessed by multiple threads.

Throws:

IOException - If the file does not exist or inaccessible.

newWritableFile

WritableFile newWritableFile(File file)
                      throws IOException

Create an object that writes to a new file with the specified name. Deletes any existing file with the same name and creates a new file.

Returns:

new file that can be accessed by one thread at a time.

Throws:

IOException - If the file not writable.

newAppendableFile

WritableFile newAppendableFile(File file)
                        throws IOException

Create an WritableFile that either appends to an existing file, or writes to a new file (if the file does not exist to begin with).

May return an IsNotSupportedError error if this Env does not allow appending to an existing file. Users of Env (including the leveldb implementation) must be prepared to deal with an Env that does not support appending. TODO

Returns:

new or existing writable file only accessible by one thread at a time.

Throws:

IOException - If the file is inaccessible.

writeStringToFileSync

void writeStringToFileSync(File file,
                           String content)
                    throws IOException

Write content to file. Replace existing content.

Parameters:

file - file location

content - new content

Throws:

IOException - If the file not writable.

readFileToString

String readFileToString(File file)
                 throws IOException

Read full file content to string

Parameters:

file - file location

Throws:

IOException - If the file not readable.

newLogger

Logger newLogger(File loggerFile)
          throws IOException

Create and return a log file for storing informational messages.

Parameters:

loggerFile - logger file

Returns:

logger instance if file is writable, null otherwise

Throws:

IOException

tryLock

DbLock tryLock(File lockFile)
        throws IOException

Attempts to acquire an exclusive lock on lock file

Parameters:

lockFile - lock file

Returns:

releasable db lock

Throws:

IOException - If lock is already held or some other I/O error occurs